Veröffentlichungen im März 2009
Auch im März stellen wir Ihnen die neuesten Veröffentlichungen rund um Chitin und Chitosan vor.
1: J Biomed Mater Res A 2009 Apr;
Peripheral nerve regeneration by transplantation of BMSC-derived Schwann cells as chitosan gel sponge scaffolds
Ishikawa, N, Suzuki, Y, Dezawa, M, Kataoka, K, Ohta, M, Cho, H, Ide, C
Department of Plastic and Reconstructive Surgery, Johoku Hospital, Kyoto, Japan.
It is said that bone marrow stromal cells (BMSCs) are able to differentiate into different kinds of cells, including Schwann cells, under relevant conditions (Dezawa et al., Eur J Neurosci 2001;14:1771-1776). In the previous paper, we demonstrated that chitosan gel sponge is one of the effective scaffolds for regenerating axons of the rat sciatic nerve (Ishikawa et al., J Biomed Mater Res A 2007;83:33-40). In the present study, we examined whether BMSC-derived Schwann cells with chitosan gel sponges were one of the effective scaffolds for peripheral nerve regeneration in rats. ... This study indicates that chitosan gel sponges containing BMSC-derived Schwann cells have strong potentiality as a graft that can be used for peripheral nerve regeneration. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 2009.
PMID: 19343770 [found with GoPubMed]
2: J Drug Target 2009 Apr;:1-8
Enhanced cellular uptake of chlorine e6 mediated by stearic acid-grafted chitosan oligosaccharide micelles
Hu, F Q, Jiang, X H, Huang, X, Wu, X L, Yuan, H, Wei, X H, Du, Y Z, College of Pharmaceutical Science, Zhejiang University, Hangzhou, People's Republic of China
Chlorines are attractive compounds for photodynamic therapy because of their high absorption in the red wavelength region. The stearic acid-grafted chitosan oligosaccharide (CSO-SA) micelles have been presented as potential candidates for intracellular drug delivery carrier because of their special structure. In this study, CSO-SA micelles were prepared to encapsulate chlorine e6 (Ce6). ...
PMID: 19343607 [found with GoPubMed]
3: Acta Biomater 2009 Mar;
Accelerated wound closure of pressure ulcers in aged mice by chitosan scaffolds with and without bFGF
Park, C J, Clark, S G, Lichtensteiger, C A, Jamison, R D, Johnson, A J
Department of Materials Science & Engineering, University of Illinois at Urbana-Champaign, 1304 W Green St., Urbana, IL 61801, USA; College of Medicine, University of Illinois at Urbana-Champaign, 506 S Matthews Ave., Urbana, IL 61801, USA
Pressure ulcers are a significant healthcare concern, especially for elderly populations. Our work served to ameliorate the chronicity of these ulcers by addressing ischemia-reperfusion injury mediated by neutrophils and the concomitant loss of vasculature in these wounds. To this end, chitosan scaffolds loaded with basic fibroblast growth factor (bFGF) contained in gelatin microparticles were developed and tested for clinical relevance in an aged mouse model. ... These results suggest that chitosan is an effective material for growth factor delivery and can help to heal chronic ulcers. Collectively, our data show that chitosan-bFGF scaffolds are effective in accelerating wound closure of pressure ulcers in aged animals.
PMID: 19342320 [found with GoPubMed]
4: Med Hypotheses 2009 Mar;
Mechanism of anti-angiogenic activities of chitooligosaccharides may be through inhibiting heparanase activity
Quan, H, Zhu, F, Han, X, Xu, Z, Zhao, Y, Miao, Z, Key Laboratory for Molecular Animal Nutrition of Ministry of Education, Feed Animal Sciences Institute, Zhejiang University, Qiutao North Road 164, Zhejiang, Hangzhou 310029, China. Tel.: +86 571 86971075; fax: +86 571 86994963
Metastatic disease is the primary cause of death for most cancer patients. Angiogenesis is the formation of a new capillary network from pre-existing vessels and required for tumor vasculature. Heparanase, a beta-endoglucuronidase, assistants tumor invasion, metastasis and angiogenesis. Chitooligosaccharides (COS) is obtained by hydrolysis of chitosan. COS has been proved to be anti-angiogenesis activity. The mechanism of COS inhibits angiogenesis is not very clear, COS is hypothesized by author to be an inhibitor of heparanase.
PMID: 19342181 [found with GoPubMed]
5: J Hazard Mater 2009 Mar;
Adsorption of uranium (VI) from aqueous solution onto cross-linked chitosan
Wang, G, Liu, J, Wang, X, Xie, Z, Deng, N, Department of Civil and Environmental Engineering, East China Institute of Technology, Fuzhou, 344000, Jiangxi, PR China
Cross-linked chitosan (CCTS) was synthesized by the reaction of chitosan with epichlorohydrin under alkaline conditions. Adsorption of uranium (VI) from aqueous solution onto cross-linked chitosan was investigated in a batch system. Adsorption isotherm and adsorption kinetic studies of uranium (VI) onto cross-linked chitosan were carried out. ... Kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Results also showed that cross-linked chitosan was favourable adsorbent.
PMID: 19342166 [found with GoPubMed]
6: J Plant Physiol 2009 Mar;
Accumulation of p-hydroxybenzoic acid in hairy roots of Daucus carota 2: Confirming biosynthetic steps through feeding of inhibitors and precursors
Sircar, D, Mitra, A, Natural Product Biotechnology Group, Agricultural & Food Engineering Department, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India
Biosynthesis of hydroxybenzoates even at enzymatic level is poorly understood. In this report, effect of feeding of putative biosynthetic precursors and pathway-specific enzyme inhibitors of early phenylpropanoid pathway on p-hydroxybenzoic acid accumulation in chitosan-elicited hairy roots of Daucus carota was studied. ....
PMID: 19342120 [found with GoPubMed]
7: Nanomedicine 2009 Mar;
Enhanced Delivery and Expression of a Nanoencapsulated DNA Vaccine Vector for RSV
Boyoglu, S, Vig, K, Pillai, S, Rangari, V, Dennis, V A, Khazi, F, Singh, S R, Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL
This study evaluated the efficiency of chitosan encapsulated DNA based RSV vaccine. Antigenic regions of RSV F, M2, and G genes were cloned into the phCMV1 vector resulting in a DNA vaccine vector named DR-FM2G. This vector was used to formulate DNA/Chitosan nanoparticles (DCNP) using a complex coacervation process that yielded an encapsulation efficiency of 94.7%. The DCNP sizes ranged from 80-150 nm with uniform size distribution and spherical shape. DNA release was between 50-60% when DCNP was incubated with Similar Gastrointestinal Fluid (SGF), while 21-25% of DNA was released from DCNP in 30 min at pH 10. Differential Scanning Calorimetry (DSC) showed DCNP to be more stable than naked DNA or chitosan, offering protection of DNA degradation by nucleases. DCNP was not toxic to cells when used at concentrations <!--=400 mug/ml. Immunohistochemical and real-time PCR results showed a higher level of RSV protein expression in mice tissues given when DCNP was injected via i.v.as compared to naked DNA.
PMID: 19341819 [found with GoPubMed]
8: Mol Pharm 2009 Apr;
Nanospheres Formulated from L-Tyrosine Polyphosphate Exhibiting Sustained Release of Polyplexes and In Vitro Controlled Transfection Properties
Ditto, A J, Shah, P N, Gump, L R, Yun, Y H
Currently, viruses are utilized as vectors for gene therapy, since they transport across cellular membranes, escape endosomes, and effectively deliver genes to the nucleus. The disadvantage of using viruses for gene therapy is their immune response. Therefore, nanospheres have been formulated as a non-viral gene vector by blending L-tyrosine-polyphosphate (LTP) with polyethylene glycol grafted to chitosan (PEG-g-CHN) and linear polyethylenimine (LPEI) conjugated to plasmid DNA (pDNA). PEG-g-CHN stabilizes the emulsion and prevents nanosphere coalescence. ... This result is sustained longer than pDNA-LPEI and pDNA-FuGENE(R) 6 complexes. Therefore, LTP-pDNA nanospheres exhibit controlled transfection and can be used as a non-viral gene delivery vector.
PMID: 19341289 [found with GoPubMed]
9: Macromol Biosci 2009 Apr;
Self Assembling and Crosslinking of Polyelectrolyte Multilayer Films of Chitosan and Alginate Studied by QCM and IR Spectroscopy
Alves, N M, Picart, C, Mano, J F, 3B's Research Group, Biomaterials, Biodegradables and Biomimetics, Dept. of Polymer Engineering, University of Minho, AvePark, Zona Industrial da Gandra, S. Cláudio do Barco, 4806-909 Caldas das Taipas, Guimarães, Portugal.
The formation of novel biocompatible multilayer films based on the alternate deposition of CHI and ALG was investigated for the first time by QCM-D and FTIR-ATR. A linear increase of the thickness was found during the film build-up. GLUT was used to crosslink the films terminated with either CHI or ALG. A change in the QCM-D signal was observed just in the first case, indicating that crosslinking only takes place in the top CHI layer. The evolution of the dissipation factor during crosslinking was modelled with a first-order kinetics; this reaction was found to be faster for chitosan terminated films with a lower number of multilayers. It was also found that more robust films could be produced by crosslinking the intermediate CHI layers during the build-up.
PMID: 19340816 [found with GoPubMed]
10: Int J Food Microbiol 2009 Mar;
Changes in microbial flora of Pacific oysters (Crassostrea gigas) during refrigerated storage and its shelf-life extension by chitosan
Cao, R, Xue, C H, Liu, Q, College of Food Science and Engineering, Ocean university of China, Qingdao, Shandong Province, 266003, PR China
Changes in microbial flora of Pacific oysters (Crassostrea gigas) during storage at 5+/-1 degrees C were analyzed and the antimicrobial activity of chitosan was studied to identify its potential in shelf-life extension. The dominant microorganisms were found to be Pseudomonas (22%) and Vibrionaceae (20%) in raw oysters. During storage, proportion of Pseudomonas increased significantly and reached 73% at the end of storage, while Vibrionaceae preserved a level of approximate 20%. Wide-spectrum antibacterial property of chitosan against the bacteria isolated from oysters was discovered, and chitosan concentration of 5.0 g/L was eventually determined for application in oyster preservation. Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-life of oysters stored at 5+/-1 degrees C was determined. Data showed that chitosan treatment extended the shelf-life of oysters from 8-9 days to 14-15 days.
PMID: 19339074 [found with GoPubMed]
11: Biomaterials 2009 Mar;
Influence of the degree of acetylation on the enzymatic degradation and in vitro biological properties of trimethylated chitosans
Verheul, R J, Amidi, M, van Steenbergen, M J, van Riet, E, Jiskoot, W, Hennink, W E, Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, Sorbonnelaan 16, PO Box 80082, 3508 TB Utrecht, The Netherlands
Chitosan derivatives such as N,N,N-trimethylated chitosan (TMC) are currently being investigated for the delivery of drugs, vaccines and genes. However, the influence of the extent of N-acetylation of these polymers on their enzymatic degradability and biological properties is unknown. In this study, TMCs with a degree of acetylation (DA) ranging from 11 to 55% were synthesized by using a three-step method. First, chitosan was partially re-acetylated using acetic anhydride followed by quantitative dimethylation using formaldehyde and sodium borohydrate. Then, in presence of an excess amount of iodomethane, TMC was synthesized. The TMCs obtained by this method showed neither detectable O-methylation nor loss in acetyl groups ((1)H NMR) and a slight increase in molecular weight (GPC) with increasing degree of substitution, implying that no chain scission occurred during synthesis. The extent of lysozyme-catalyzed degradation of TMC, and that of its precursors chitosan and dimethyl chitosan, was highly dependent on the DA and polymers with the highest DA showed the largest decrease in molecular weight. On Caco-2 cells, TMCs with a high DA ( approximately 50%), a DQ of around 44% and with or without O-methylated groups, were not able to open tight junctions in the trans-epithelial electrical resistance (TEER) assay, in contrast with TMCs (both O-methylated and O-methyl free; concentration 2.5mg/ml) with a similar DQ but a lower DA which were able to reduce the TEER with 30 and 70%, respectively. Additionally, TMCs with a high DA ( approximately 50%) demonstrated no cell toxicity (MTT, LDH release) up to a concentration of 10mg/ml.
PMID: 19339046 [found with GoPubMed]
12: Yakugaku Zasshi 2009 Apr;129(4):475-84
Evaluation of the Binding Affinity and RNA Interference of Low-molecular-weight Chitosan/siRNA Complexes Using an Imaging System
Kawaguchi, Yasuhisa, Okuda, Tomoyuki, Ban, Tatsunori, Danjo, Kazumi, Okamoto, Hirokazu, Faculty of Pharmacy, Meijo University
Chitosan is one of the attractive non-viral carriers for gene delivery including siRNA. However, common chitosan, which has a relatively high molecular weight, is insoluble in water, which might make it difficult to apply clinically. In this study, we investigated the efficacy of low-molecular-weight chitosan (LMWC), which is soluble in water, as a carrier for siRNA delivery. To evaluate the binding affinity and RNA interference (RNAi) of LMWC/siRNA complexes, a multi-well imaging system (IVIS((R))) was adapted. CT26 cells stably expressing firefly luciferase (CT26/Luc cells) were established to evaluate RNAi. Evaluation of RNAi using lipofectamine(TM) 2000 was carried out by employing a luminometer with cell lysis and IVIS((R)) without cell lysis. The results were closely correlated, suggesting the advantages of the multi-well imaging system regarding screening, the visualization of results, and nondestructive evaluation. Fluorescence generated by ethidium bromide intercalated in the double strand of siRNA was markedly quenched at a higher ratio of LMWC to siRNA (N/P) and lower pH. Evaluation of the particle size and zeta potential of LMWC/siRNA complexes also indicated the higher binding affinity of LMWC with siRNA. At N/P=300 and pH 6.5, which satisfied the high-level binding affinity of LMWC with siRNA, significantly lower luminescence was detected in CT26/Luc cells treated with LMWC/siRNA compared with those treated with LMWC alone, suggesting the presence of RNAi. These results suggested that LMWC may be an effective carrier for siRNA delivery, and that the multi-well imaging system may be a powerful tool to evaluate the binding affinity and RNAi.
PMID: 19337002 [found with GoPubMed]
13: Biol Pharm Bull 2009 Apr;32(4):706-10
N/P Ratio Significantly Influences the Transfection Efficiency and Cytotoxicity of a Polyethylenimine/Chitosan/DNA Complex
Zhao, Qing-Qing, Chen, Jin-Liang, Lv, Teng-Fei, He, Cai-Xia, Tang, Gu-Ping, Liang, Wen-Quan, Tabata, Yasuhiko, Gao, Jian-Qing, College of Pharmaceutical Sciences, Zhejiang University
For designing a complex vector that has the advantages of both polyethylenimine (PEI) and chitosan for gene delivery, a PEI/chitosan/DNA complex was constructed at various N/P ratios (the ratios of moles of the amine groups of cationic polymers to those of the phosphate ones of DNA) and both the cytotoxicity and the transfection efficiency of the vector were evaluated. The results demonstrated that the chitosan/DNA binding degree was depended on the N/P ratio. The mean size of the complex vector was between 100 nm and 150 nm. Compared with PEI/DNA, the complex vector (PEI/chitosan/DNA with chitosan/DNA N/P=4, PEI/DNA N/P=10) appeared to have low cytotoxicity, which maintained the cell survival rate at greater than 80%, and showed higher transfection efficiency of nearly 1000 fold compared with that using chitosan/DNA alone. Furthermore, the expression efficiency of the complex vector carrying enhanced green fluorescent protein was not inhibited in the presence of serum in both HeLa cells and A549 cells. The PEI/chitosan complex may be a promising gene carrier that has high transfection efficiency as well as low cytotoxicity.
PMID: 19336909 [found with GoPubMed]
14: Appl Biochem Biotechnol 2009 Mar;
Depolymerization of Chitosan with a Crude Cellulase Preparation from Aspergillus Niger
Xie, Y, Wei, Y, Hu, J, College of Environment and Chemical Engineering, Nanchang Hangkong University, No.696 Fenghe Southern Road, Nanchang, Jiangxi, 330063, People's Republic of China,
A crude cellulase preparation from Aspergillus niger was used to depolymerize chitosan. The depolymerization process was followed by measuring the apparent viscocity and the intrinsic viscosity. The optimum conditions for enzymatic hydrolysis were investigated. On the selected optimum conditions (pH 5.0, temperature 50 degrees C, and an enzyme to substrate ratio of 1:5), chitosan was hydrolyzed for 1, 4, 8, and 24 h, its viscosity-average molecular weights were 3.49 x 10(4), 1.18 x 10(4), 5.83 x 10(3), and 1.13 x 10(3), respectively. Compared with chitosan having viscosity-average molecular weight of 5.18 x 10(5) before enzymatic hydrolysis, the crude cellulase preparation had rather apparent effect on depolymerization of chitosan. Through the comparison of different origin of cellulases, the prepared cellulase has good ability of enzymatic hydrolysis. The reproducibility and reversibility for enzymatic hydrolysis was appraised. The data are of value for the production of low-molecular weight chitosans and chitooligomers of medical and biotechnological interest.
PMID: 19333566 [found with GoPubMed]
15: Bioresour Technol 2009 Mar;
In situ preparation of magnetic Fe(3)O(4)-chitosan nanoparticles for lipase immobilization by cross-linking and oxidation in aqueous solution
Wu, Y, Wang, Y, Luo, G, Dai, Y, State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
A new and simple method has been proposed to prepare magnetic Fe(3)O(4)-chitosan (CS) nanoparticles by cross-linking with sodium tripolyphosphate (TPP), precipitation with NaOH and oxidation with O(2) in hydrochloric acid aqueous phase containing CS and Fe(OH)(2), and these magnetic CS nanoparticles were used to immobilize lipase. The effects on the sequence of adding NaOH and TPP, the reaction temperature, and the ratio of CS/Fe(OH)(2) were studied. TEM showed that the diameter of composite nanoparticles was about 80nm, and that the magnetic Fe(3)O(4) nanoparticles with a diameter of 20nm were evenly dispersed in the CS materials. Magnetic measurement revealed that the saturated magnetisation of the Fe(3)O(4)-CS nanoparticles could reach 35.54emu/g. The adsorption capacity of lipase onto nanoparticles could reach 129mg/g; and the maximal enzyme activity was 20.02mumolmin(-1)mg(-1) (protein), and activity retention was as high as 55.6% at a certain loading amount.
PMID: 19329306 [found with GoPubMed]
16: Carbohydr Res 2009 Mar;
Chitosan-LiOH-urea aqueous solution-a novel water-based system for chitosan processing
Fan, M, Hu, Q, Department of Polymer Science and Engineering, Zhejiang University, Key Laboratory of Macromolecule Synthesis and Functionalization, Ministry of Education, Hangzhou 310027, People's Republic of China
A solution of partially N-deacetylated chitosan in aqueous lithium hydroxide (LiOH)/urea was prepared successfully through a freeze-thawing process and the dissolution behavior was studied. The results indicated that chitosan can directly dissolve in LiOH/urea aqueous solution. LiOH mainly contributed to the breakage of intramolecular and intermolecular hydrogen bonds in chitosan. Urea, LiOH, and chitosan formed inclusion compound (IC) with urea as the IC host, and the LiOH-chitosan complex as the guest. Aqueous 4.8wt% LiOH/8.0wt% urea was verified to be the optimal solvent for chitosan. The results of rheology and viscosity characterizations revealed that chitosan/4.8wt% LiOH/8.0wt% urea aqueous solution was pseudoplastic fluid, and was more stable than the solution of chitosan in acetic acid at ambient temperature.
PMID: 19329109 [found with GoPubMed]
17: Bioorg Med Chem Lett 2009 Mar;
Novel synthesis and in vitro drug release of polymeric prodrug: Chitosan-O-isopropyl-5'-O-d4T monophosphate conjugate
Yang, L, Zeng, R, Li, C, Li, G, Qiao, R, Hu, L, Li, Z, State Key Laboratory of Chemical Resource Engineering, Department of Pharmaceutical Engineering, Beijing University of Chemical Technology, Beijing 100029, PR China
A novel approach to synthesize chitosan-O-isopropyl-5'-O-d4T monophosphate conjugate was developed. Chitosan-d4T monophosphate prodrug with a phosphoramidate linkage was efficiently synthesized through Atherton-Todd reaction. In vitro drug release studies in pH 1.1 and 7.4 indicated that chitosan-O-isopropyl-5'-O-d4T monophosphate conjugate prefers to release the d4T 5'-(O-isopropyl)monophosphate than free d4T for a prolonged period. The results suggested that chitosan-O-isopropyl-5'-O-d4T monophosphate conjugate may be used as a sustained polymeric prodrug for improving therapy efficacy and reducing side effects in antiretroviral treatment.
PMID: 19328686 [found with GoPubMed]
18: Biosens Bioelectron 2009 Mar;
Electrochemically deposited nanocomposite film of CS-Fc/Au NPs/GOx for glucose biosensor application
Qiu, J D, Wang, R, Liang, R P, Xia, X H, Department of Chemistry, Nanchang University, Nanchang 330031, China
A simple and controllable electrodeposition method is described to fabricate a homogeneous chitosan-ferrocene/Au nanoparticles/glucose oxidase (CS-Fc/Au NPs/GOx) nanocomposite film. The morphologies and electrochemistry of the nanocomposite film were investigated by using scanning electron microscopy (SEM) and electrochemical techniques including electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. The ferrocene group (Fc) covalently bounded chitosan hybrid (CS-Fc) can effectively avoid the leakage of Fc and retain its electrochemical activity. Further immobilization of Au NPs into the CS-Fc matrix enhances both the charge-transport properties of the composite and bioaffinity to enzyme. Biosensor based on this CS-Fc/Au NPs/GOx film has advantages of fast response, excellent reproducibility and high stability. This biosensor shows a linear response to glucose in the concentration range from 0.02 to 8.66mM with a detection limit of 5.6muM at a signal-to-noise ratio of 3. The present method offers a facile way to fabricate biosensors and bioelectronic devices.
PMID: 19327978 [found with GoPubMed]
19: Biomacromolecules 2009 Mar;
Mechanisms Involved During the Ultrasonically Induced Depolymerization of Chitosan: Characterization and Control
Popa-Nita, S, Lucas, J M, Ladavière, C, David, L, Domard, A, Universite de Lyon, Universite Lyon 1, UMR CNRS 5223 IMP, Laboratoire des Materiaux Polymeres et des Biomateriaux, Bat. ISTIL, 15, bd. A. Latarjet, F-69622 Villeurbanne Cedex, France
The existence of two mechanisms involved in the ultrasonically induced depolymerization of chitosan is evidenced. The first leads to a rapid scission of polymer chains and a lowering of the polydispersity, and the second is responsible for obtaining short polymer chains and oligomers with a polydispersity increase. A systematic experimental study allowed us to identify and quantify the main parameters influencing the chain scission kinetics. Consequently, using a "master curve" approach, a general law of variation of the molecular weight during the depolymerization is proposed. This law can be used in various experimental conditions to easily control the production of chitosan chains of precise length and low polydispersity or a collection of chito-oligosaccharides (COS). Characterization of the latter by (1)H NMR and MALDI-TOF mass spectrometry shows their high purity and an unchanged primary structure.
PMID: 19323509 [found with GoPubMed]
20: World J Gastroenterol 2009 Mar;15(12):1512-7
Lung tissue flap repairs esophagus defection with an inner chitosan tube stent
Chen, Gang, Shi, Wen-Jun, Department of Thoracic Surgery, Shengjing Hospital, China Medical University, Shenyang 110004, Liaoning Province, China
AIM: To repair the partial esophagus defect with a chitosan stent, a new esophageal prosthesis made of pulmonary tissue with vascular pedicle. METHODS: Fifteen Japanese big ear white rabbits were divided into experimental group (n = 10) and control group (n = 5). Esophagus defect in rabbits of experimental group was repaired using lung tissue flap with a chitosan tube stent, gross and histological appearance was observed at week 2, 4 and 8 after operation, and barium sulphate X-ray screen was performed at week 10 after operation. Esophagus defect of rabbits in control group was repaired using lung tissue flap with no chitosan tube stent, gross and histological appearance was observed at week 2, 4 and 8 after operation, and barium sulphate X-ray screen was performed at week 10 after operation. RESULTS: In the experimental group, 6 rabbits survived for over two weeks, the lung tissue flap healed esophageal defection, and squamous metaplasia occurred on the surface of lung tissue flap. At week 10 after operation, barium sulphate examination found that barium was fluent through the esophagus with no stricture or back stream, the creeping was good. In the control group, 4 rabbits survived for two weeks, the lung tissue flap healed esophageal defection with fibrous tissue hyperplasia, barium sulphate examination found that barium was fluent through the esophagus with a slight stricture or back stream, and the creeping was not good at week 10 after operation. CONCLUSION: Esophagus defect can be repaired using lung tissue flap with an inner chitosan tube stent.
PMID: 19322927 [found with GoPubMed]
21: J Biomed Mater Res A 2009 Mar;
Development of new chitosan/carrageenan nanoparticles for drug delivery applications
Grenha, A, Gomes, M E, Rodrigues, M, Santo, V E, Mano, J F, Neves, N M, Reis, R L, Department of Polymer Engineering, University of Minho, 3Bs Research Group, Biomaterials, Biodegradables and Biomimetics, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, IBB Institute for Biotechnology and Bioengineering, PT Government Associated Laboratory, Portugal
The use of polymeric nanoparticles, especially those composed of natural polymers, has become a very interesting approach in drug delivery, mainly because of the advantages offered by their small dimensions. The aim of this work was to develop a novel formulation of nanoparticles comprised of two natural marine-derived polymers, namely chitosan and carrageenan, and to evaluate their potential for the association and controlled release of macromolecules. Nanoparticles were obtained in a hydrophilic environment, under very mild conditions, avoiding the use of organic solvents or other aggressive technologies for their preparation. The developed nanocarriers presented sizes within 350-650 nm and positive zeta potentials of 50-60 mV. Polymeric interactions between nanoparticles' components were evaluated by Fourier transform infrared spectroscopy. Using ovalbumin as model protein, nanoparticles evidenced loading capacity varying from 4% to 17% and demonstrated excellent capacity to provide a controlled release for up to 3 weeks. Furthermore, nanoparticles have demonstrated to exhibit a noncytotoxic behavior in biological in vitro tests performed using L929 fibroblasts, which is critical regarding the biocompatibility of those carriers. In summary, the developed chitosan-carrageenan nanoparticles have shown promising properties to be used as carriers of therapeutic macromolecules, with potential application not only strictly in drug delivery, but also in broader areas, such as tissue engineering and regenerative medicine. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009.
PMID: 19322874 [found with GoPubMed]
22: J Mater Sci Mater Med 2009 Mar;
Injectable thermosensitive hydrogel based on chitosan and quaternized chitosan and the biomedical properties
Ji, Q X, Chen, X G, Zhao, Q S, Liu, C S, Cheng, X J, Wang, L C, College of Marine Life Science, Ocean University of China, 5# Yushan Road, Qingdao, Shandong Province, 266003, People's Republic of China
A novel injectable thermosensitive hydrogel (CS-HTCC/alpha beta-GP) was successfully designed and prepared using chitosan (CS), quaternized chitosan (HTCC) and alpha,beta-glycerophosphate (alpha,beta-GP) without any additional chemical stimulus. The gelation point of CS-HTCC/alpha beta-GP can be set at a temperature close to normal body temperature or other temperature above 25 degrees C. The transition process can be controlled by adjusting the weight ratio of CS to HTCC, or different final concentration of alpha,beta-GP. The optimum formulation is (CS + HTCC) (2% w/v), CS/HTCC (5/1 w/w) and alpha,beta-GP 8.33% or 9.09% (w/v), where the sol-gel transition time was 3 min at 37 degrees C. The drug released over 3 h from the CS-HTCC/alpha,beta-GP thermosensitive hydrogel in artificial saliva pH 6.8. In addition, CS-HTCC/alpha,beta-GP thermosensitive hydrogel exhibited stronger antibacterial activity towards two periodontal pathogens (Porphyromonas gingivalis, P.g and Prevotella intermedia, P.i). CS-HTCC/alpha, beta-GP thermosensitive hydrogel was a considerable candidate as a local drug delivery system for periodontal treatment.
PMID: 19322644 [found with GoPubMed]
23: Ann Emerg Med 2009 Mar;
Hemostatic Efficacy of Modified Chitosan Powder in a Lethal Porcine Model of Extremity Arterial Injury
Kilbourne, M, Keledjian, K, Hess, J R, Scalea, T, Bochicchio, G V, Department of Surgery, Division of Clinical and Outcomes Research, R. Adams Cowley Shock Trauma Center, Baltimore, MD
STUDY OBJECTIVE: Rapid hemostasis is crucial in controlling severe extremity hemorrhage. Our objective is to evaluate the hemostatic efficacy of a newly modified chitosan powder in a model of severe extremity arterial hemorrhage. METHODS: Anesthetized pigs underwent severe, reproducible femoral artery injuries. Animals were randomized (nonblinded) to either modified chitosan powder (n=10) or standard gauze application (n=6). Each hemostatic agent was applied through a pool of blood with manual compression for 3-minute intervals until hemostasis was achieved. Fluid resuscitation was infused as necessary to reestablish a mean arterial pressure within at least 80% of the preinjury mean arterial pressure if possible. The primary measured outcome was total blood loss. Secondary endpoints were survival, time to hemostasis, resuscitation mean arterial pressure, and resuscitation volume. RESULTS: Pretreatment blood losses were similar in both groups. Median (absolute average deviation of the median) posttreatment blood loss was significantly less in the modified chitosan powder group than in the gauze group, 275 (108) mL versus 1,312 (171) mL. Resuscitation mean arterial pressure at 180 minutes after injury was 68% of preinjury mean arterial pressure in the modified chitosan powder group and undetectable in all control animals. Fluid volume required for resuscitation was 1,962 (258) mL in the modified chitosan powder group and 2,875 (150) mL in the gauze group. Time to hemostasis was 9.0 (2.1) minutes in the modified chitosan powder group. Hemostasis was not achieved in any animal in the gauze group. Survival was 100% in the modified chitosan powder group, whereas no animals survived in the gauze group. CONCLUSION: Modified chitosan powder demonstrates the ability to control major vascular bleeding in a lethal arterial injury model during a 3-hour period.
PMID: 19321227 [found with GoPubMed]
24: Tissue Eng Part A 2009 Mar;
Composite Chitosan/Nano-Hydroxyapatite Scaffolds Induce Osteocalcin Production by Osteoblasts In Vitro and Support Bone Formation In Vivo
Chesnutt, B M, Yuan, Y, Buddington, K, Haggard, W O, Bumgardner, J D, 1 Department of Biomedical Engineering, University of Memphis , Memphis, Tennessee
There is a significant clinical need to develop alternatives to autografts and allografts for bone grafting procedures. Porous, biodegradable scaffolds based on the biopolymer chitosan have been investigated as bone graft substitutes, and the addition of calcium phosphate to these scaffolds has been shown to improve the mechanical properties of the scaffold and may increase osteoconductivity. In this study, in vitro mineralization was examined for osteoblasts seeded in a porous scaffold composed of fused chitosan/nano-hydroxyapatite microspheres. Human fetal osteoblasts were cultured on composite and chitosan scaffolds for 21 days. On days 1, 4, 7, 14, and 21, total dsDNA, alkaline phosphatase, type I collagen, and osteocalcin production were measured. Total cellularity (measured by dsDNA), alkaline phosphatase, and type I collagen production were similar between the two scaffold groups. However, osteocalcin production occurred significantly earlier (day 7 vs. day 21) and was more than three times greater (0.0022 vs. 0.0068 ng/mL/ng DNA) on day 21 when osteoblasts were cultured on composite scaffolds. Osteocalcin is a marker of late osteoblastic differentiation and mineralized bone matrix formation. Therefore, the increase in osteocalcin production seen when cells were cultured on composite scaffolds may indicate that these scaffolds were superior to chitosan-only scaffolds in facilitating osteoblast mineralization. Composite scaffolds were also shown to be biocompatible and osteoconductive in a preliminary critical size rat calvarial defect study. These results demonstrate the potential of composite chitosan/nano-hydroxyapatite scaffolds to be used in bone tissue engineering.
PMID: 19309240 [found with GoPubMed]
25: Anal Bioanal Chem 2009 Mar;
Disposable DNA biosensor with the carbon nanotubes-polyethyleneimine interface at a screen-printed carbon electrode for tests of DNA layer damage by quinazolines
Galandová, J, Ovádeková, R, Ferancová, A, Labuda, J, Institute of Analytical Chemistry, Slovak University of Technology in Bratislava, Radlinského 9, 812 37, Bratislava, Slovakia
A screen-printed carbon working electrode within a commercially available screen-printed three-electrode assembly was modified by using a composite of multiwalled carbon nanotubes (MWCNT) dispersed in polyethylenimine (PEI) followed by covering with the calf thymus dsDNA layer. Several electrochemical methods were used to characterize the biosensor and to evaluate damage to the surface-attached DNA: square wave voltammetry of the [Ru(bpy)(3)](2+) redox indicator and mediator of the guanine moiety oxidation, cyclic voltammetry and electrochemical impedance spectroscopy in the presence of the [Fe(CN)(6)](3-/4-) indicator in solution. Due to high electroconductivity and large surface area of MWCNT and positive charge of PEI, the MWCNT-PEI composite is an advantageous platform for the DNA immobilization by the polyelectrolyte complexation and its voltammetric and impedimetric detection. In this respect, the MWCNT-PEI interface exhibited better properties than the MWCNT-chitosan one reported from our laboratory previously. A deep DNA layer damage at incubation of the biosensor in quinazoline solution was found, which depends on the quinazoline concentration and incubation time.
PMID: 19306115 [found with GoPubMed]
26: J Control Release 2009 Mar;
Chitosan based oligoamine polymers: Synthesis, characterization, and gene delivery
Lu, B, Wang, C F, Wu, D Q, Li, C, Zhang, X Z, Zhuo, R X, Key Laboratory of Biomedical Polymers of Ministry of Education & Department of Chemistry, Wuhan University, Wuhan 430072, P. R. China
A series of chitosan-based oligoamine polymers were synthesized from N-maleated chitosan (NMC) via Michael addition with diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and linear polyethylenimine (M(n) 423), respectively. The resulted polymers exhibited well binding ability to condense plasmid DNA to form complexes with size ranging from 200 to 600 nm when the polymer/DNA weight ratio was above 7. The polymer/DNA complexes observed by scanning electron microscopy (SEM) exhibited a compact and spherical morphology. The cytotoxicity assay showed that the synthesized polymers were less toxic than that of PEI (25 K). The gene transfection effect of resulted polymers was evaluated in 293T and HeLa cells, and the results showed that the gene transfection efficiency of these polymers was better than that of chitosan. Moreover, the transfection efficiency was dependent on the length of the oligoamine side chains and the molecular weight of the chitosan derivatives.
PMID: 19303039 [found with GoPubMed]
27: Biomacromolecules 2009 Mar;
Improvement of Chitosan Adsorption onto Cellulosic Fabrics by Plasma Treatment
Fras Zemljič, L, Peršin, Z, Stenius, P, Laboratory for Characterization and Processing of Polymers, Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, 2000 Maribor, Slovenia, and Laboratory of Forest Products Chemistry, Helsinki University of Technology, P.O. Box 6300, 02015 HUT, Finland
Oxygen plasma treatment was applied in order to improve the adsorption of chitosan onto viscose fabric. Modification of the surface and adsorption of chitosan was monitored by determination of XPS spectra, determination of contact angles from rates of water imbibition, and conductometric titration. The plasma treatment resulted in hydrophilization of the surfaces through oxidation. The hydrophilic surfaces were stable for at least 24 h. The treatment also yielded binding sites that resulted in over 20% increase of the amount of chitosan adsorbed over that adsorbed on nontreated fabric. Layers of chitosan adsorbed after plasma treatment were substantially more active as antimicrobial agents than those on nontreated surfaces.
PMID: 19301906 [found with GoPubMed]
28: Biomacromolecules 2009 Mar;
PH-Controlled Self-Assembling of meso-Tetrakis(4-sulfonatophenyl)porphyrin-Chitosan Complexes
Synytsya, A, Synytsya, A, Blafková, P, Ederová, J, Spěvaček, J, Slepička, P, Král, V, Volka, K, Department of Analytical Chemistry, Department of Carbohydrate Chemistry and Technology, Central Laboratories, Department of Solid State Engineering, Institute of Chemical Technology, Prague 16628, Czech Republic, and Institute of Macromolecular Chemistry, Academy of Science of the Czech Republic, Prague 16206, Czech Republic
Solid meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS(4))-chitosan supramolecular complexes were prepared by addition of porphyrin to an aqueous solution of chitosan at pH values. The precipitates obtained were assigned as 1 (pH 6.8) and 2 (pH 2.5) and characterized by spectroscopic, thermal, and microscopic methods. Spectroscopic investigation confirmed the presence of TPPS(4) and chitosan in both products and that the porphyrin is highly self-associated. H-type (stacked) of TPPS(4) aggregation was proposed for 1 and J-type (tilted) for 2. Thermal analysis revealed different pyrolysis routes of the complexes depending on their structural diversity. Light microscopic analysis indicated fibrous and lamellar microstructures, respectively, for 1 and 2. SEM and AFM analysis showed that both complexes consist of compact nanostructures; their size and interconnection is different for 1 and 2. Based on structural inferences, self-assembling hierarchy models were proposed for both of the TPPS(4)-chitosan supramolecular complexes.
PMID: 19301895 [found with GoPubMed]
29: J Mater Sci Mater Med 2009 Mar;
In vitro biocompatibility of chitosan-based materials to primary culture of hippocampal neurons
He, Q, Zhang, T, Yang, Y, Ding, F, Jiangsu Key Laboratory of Neuroregeneration, Nantong University, 19 Qixiu Road, Nantong, Jiangsu Province, 226001, People's Republic of China
The natural biomaterial chitosan has been widely used as a promising nerve guidance conduit material for peripheral nerve repair. This study aimed to investigate in vitro biocompatibility of chitosan to primarily cultured hippocampal neurons, one type of central nervous system (CNS) cells. The substrate made up of chitosan fibers or membranes was found to support the survival and growth of the attached hippocampal neurons by using light and electron microscopy as well as immunocytochemistry for neurofilament 200, growth-associated protein-43, microtubule-associated protein 2, beta-tubulin III and synaptophysin. MTT assay indicated that the cell viability of hippocampal neurons in chitosan fiber or membrane extract was not significantly different from that in hydroxyapatite extract or plain neuronal medium, but significantly higher than that in organotin extract after culture for different times. Western analysis revealed that no significant difference in the protein level of growth-associated protein-43 and beta-tubulin III was detected between hippocampal neurons cultured in chitosan extract and in plain neuronal culture medium. The results collectively demonstrate that chitosan is biocompatible to primary culture of hippocampal neurons without cytotoxic effects on cell phenotype and functions, raising a potential possibility of using chitosan for CNS therapy.
PMID: 19301107 [found with GoPubMed]
30: J Mater Sci Mater Med 2009 Mar;
A novel composite membrane of chitosan-carboxymethyl cellulose polyelectrolyte complex membrane filled with nano-hydroxyapatite I. Preparation and properties
Liuyun, J, Yubao, L, Chengdong, X, Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu, 610041, China,
A novel tri-component composite membranes of chitosan/carboxymethyl cellulose (CS/CMC) polyelectrolyte complex membranes filled with different weight ratios of nano-hydroxyapatite (n-HA)(0, 20, 40 and 60 wt%), namely, n-HA/CS/CMC composite membrane, were prepared by self-assembly of static electricity. The structure and the properties of the composite membranes were investigated by Fourier transformed infrared spectroscopy(IR), X-ray diffraction(XRD), Scanning electron microscopy(SEM), mechanical performance measurement, swelling behavior test, and soaking behavior study in phosphate buffered saline (PBS) and simulate body fluid (SBF). The results showed that the n-HA/CS/CMC composite membrane was formed though superficial static electricity interaction among n-HA, CS and CMC. For the n-HA/CS/CMC composite membrane, the microstructure compatibility, mechanical property, swelling behavior, the degradation and bioactivity in vitro of the composite membrane were improved by the addition of n-HA, compared with CS/CMC polyelectrolyte complex membrane. Moreover, the n-HA/CS/CMC composite membrane with 40 wt% n-HA had the most highest mechanical property, which suggested that the novel n-HA/CS/CMC composite membrane with 40 wt% n-HA was more suitable to be used as guided bone tissue regeneration membrane than CS/CMC polyelectrolyte complex membrane.
PMID: 19301105 [found with GoPubMed]
31: J Biomed Biotechnol 2009;2009:149254
Cationic polybutyl cyanoacrylate nanoparticles for DNA delivery
Duan, Jinghua, Zhang, Yangde, Chen, Wei, Shen, Chengrong, Liao, Mingmei, Pan, Yifeng, Wang, Jiwei, Deng, Xingming, Zhao, Jinfeng, Key Laboratory of Nanobiological Technology, Ministry of Health National Hepatobiliary and Enteric Surgery Research Center, Central South University, Changsha, Hunan 410008, China
To enhance the intracellular delivery potential of plasmid DNA using nonviral vectors, we used polybutyl cyanoacrylate (PBCA) and chitosan to prepare PBCA nanoparticles (NPs) by emulsion polymerization and prepared NP/DNA complexes through the complex coacervation of nanoparticles with the DNA. The object of our work is to evaluate the characterization and transfection efficiency of PBCA-NPs. The NPs have a zeta potential of 25.53 mV at pH 7.4 and size about 200 nm. Electrophoretic analysis suggested that the NPs with positive charges could protect the DNA from nuclease degradation and cell viability assay showed that the NPs exhibit a low cytotoxicity to human hepatocellular carcinoma (HepG2) cells. Qualitative and quantitative analysis of transfection in HepG2 cells by the nanoparticles carrying plasmid DNA encoding for enhanced green fluorescent protein (EGFP-N1) was done by digital fluorescence imaging microscopy system and fluorescence-activated cell sorting (FACS). Qualitative results showed highly efficient expression of GFP that remained stable for up to 96 hours. Quantitative results from FACS showed that PBCA-NPs were significantly more effective in transfecting HepG2 cells after 72 hours postincubation. The results of this study suggested that PBCA-NPs have favorable properties for nonviral delivery.
PMID: 19300519 [found with GoPubMed]
32: Biomaterials 2009 Mar;
Development of pH-responsive chitosan/heparin nanoparticles for stomach-specific anti-Helicobacter pylori therapy
Lin, Y H, Chang, C H, Wu, Y S, Hsu, Y M, Chiou, S F, Chen, Y J, Department of Biological Science and Technology, China Medical University, Taichung 40402, Taiwan, ROC
The microorganism now known as Helicobacter pylori is considered to be an important factor in the etiology of peptic ulcers. It can secrete urease enzyme and buffer gastric acids to survive in the stomach. H. pylori can colonize the gastric mucosa and preferentially adheres near the cell-cell junctions of the gastric mucous cells. In this study, pH-responsive nanoparticles were produced instantaneously upon the addition of heparin solution to a chitosan solution with magnetic stirring at room temperature. The nanoparticles appeared to have a particle size of 130-300nm, with a positive surface charge, and were stable at pH 1.2-2.5, allowing them to protect an incorporated drug from destructive gastric acids. We also demonstrated that the prepared nanoparticles can adhere to and infiltrate cell-cell junctions and interact locally with H. pylori infection sites in intercellular spaces.
PMID: 19299008 [found with GoPubMed]
33: Proteomics 2009 Mar;
Plasma proteome analysis for anti-obesity and anti-diabetic potentials of chitosan oligosaccharides in ob/ob mice
Kumar, S G, Rahman, M A, Lee, S H, Hwang, H S, Kim, H A, Yun, J W, Department of Biotechnology, Daegu University, Kyungsan, Kyungbuk, Republic of Korea
Altered levels of adipokines, derived as a result of distorted adipocytes, are the major factors responsible for changing biochemical parameters in obesity that leads to the development of metabolic disorders such as insulin resistance and atherosclerosis. In our previous reports, chitosan oligosaccharides (CO) were proved to inhibit the differentiation of 3T3-L1 adipocytes. In the present study, an attempt was made to investigate the anti-obesity and anti-diabetic effect of CO on ob/ob mice, by means of differential proteomic analysis of plasma. This was followed by immunoblotting, and gene expression in adipose tissue to clarify the molecular mechanism. CO treatment showed reduced diet intake (13%), body weight gain (12%), lipid (29%) and glucose levels (35%). 2-DE results showed differential levels of five proteins namely RBP4, apoE, and apoA-IV by >2-fold down-regulation and by >2-fold of apoA-I and glutathione peroxidase (GPx) up-regulation after CO treatment. Immunoblotting studies of adiponectin and resistin showed amelioration in their levels in plasma. Furthermore, the results of gene expressions for adipose tissue specific TNF-alpha, and IL-6 secretary molecules were also down-regulated by CO treatment. Gene expressions of PPARgamma in adipose tissue were in good agreement with the ameliorated levels of adipokines, thereby improving the pathological state. Taken together, CO might act as a potent down-regulator of obesity-related gene expression in ob/ob mice that may normalize altered plasma proteins to overcome metabolic disorders of obesity.
PMID: 19296549 [found with GoPubMed]
34: Drug Dev Ind Pharm 2009 Mar;:1-10
Effect of chitosan glutamate, carbomer 974P, and EDTA on the in vitro Caco-2 permeability and oral pharmacokinetic profile of acyclovir in rats
Merzlikine, A, Rotter, C, Rago, B, Poe, J, Christoffersen, C, Thomas, V H, Troutman, M, El-Kattan, A, Department of Pharmaceutical Sciences, Pfizer Global Research and Development, Eastern Point Road, Groton, CT, USA
Background: Chitosan glutamate and polyacrylic acid (e.g., carbomer 974P) are known to modulate the tight junctions in the intestinal wall and increase permeability and blood exposure of drugs absorbed orally by the paracellular route. Aim: To assess the impact of chitosan glutamate and carbomer 974P on the absorption of paracellularly absorbed model drug, acyclovir, in vitro and in rat in vivo. Methods: The influence of chitosan glutamate and carbomer 974P (alone and in combination with EDTA-Na2) on the in vitro Caco-2 permeability and oral pharmacokinetic profile in the rat of acyclovir was investigated. Results: In the presence of chitosan glutamate, the apparent permeability of acyclovir across Caco2 monolayer increased 4.1 times relative to control. This increase was accompanied by a significant ( approximately 60%) decrease in transepithelial electrical resistance values indicating opening of the tight junctions in the cell monolayer. In rat, chitosan glutamate doubled oral bioavailability of acyclovir and tripled the amount of acyclovir excreted unchanged into urine. In contrast, the effect of carbomer 974P was not statistically significant at 5% level. Conclusions: In conclusion, chitosan glutamate (1-3%) and chitosan glutamate (1%)/EDTA-Na2 (0.01%) are effective excipients to increase permeability of acyclovir across Caco-2 cell monolayers and the oral absorption in the rat in vivo.
PMID: 19294548 [found with GoPubMed]
35: Tissue Eng Part A 2009 Mar;
Formation of Keratocyte Spheroids on Chitosan-Coated Surface Can Maintain Keratocyte Phenotypes
Chen, Y H, Wang, I J, Young, T H, 1 Institute of Polymer Science and Engineering, College of Engineering, National Taiwan University , Taipei, Taiwan
Corneal keratocytes have been reported to be able to form spheroids that can preserve their phenotypes after being seeded back onto tissue culture plate in specific culture media. In this study, we found that keratocytes could also form spheroids on a bioengineered material, chitosan-coated surface, with 10% horse serum and Dulbecco's modified Eagle's medium. Under scanning electron microscopy observation, the cells in the spheroids were found to adhere each other tightly, and the cellular boundary could not be distinguished. They could return to a dendritic (keratocyte) morphology and proliferate after they were seeded back onto tissue culture plate. Immunocytochemistry was used to characterize these cells. Reverse transcription-polymerase chain reaction revealed that keratocytes in the spheroids were not from the PAX-6-positive progenitor cells. Further, the results of the seeding density and the number of spheroids formation, cell viability (MTT) assays, negative staining of Ki-67, and Live/Dead assay suggested that the spheroids were from cell aggregation instead of cell proliferation. Cells in the spheroids maintained phenotypes and functions characteristic of keratocytes, as seen by reverse transcription-polymerase chain reaction, collagen gel contraction assay, and challenges of keratocytes with transforming growth factor-beta1. Our results showed that corneal keratocytes could form spheroids on a chitosan-coated surface and maintain a keratocyte phenotype. However, such keratocyte spheroids do not proliferate and cannot withstand transforming growth factor-beta from myofibroblast differentiation.
PMID: 19292684 [found with GoPubMed]
36: Biomacromolecules 2009 Mar
Preparation, Characterization, and Oral Delivery of Insulin Loaded Carboxylated Chitosan Grafted Poly(methyl methacrylate) Nanoparticles
Cui, F, Qian, F, Zhao, Z, Yin, L, Tang, C, Yin, C, State Key Laboratory of Genetic Engineering, Department of Pharmaceutical Sciences, School of Life Sciences, Fudan University, Shanghai 200433, China, and Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai 200433, China
To improve the efficiency of insulin via oral administration, pH-sensitive carboxylated chitosan grafted poly(methyl methacrylate) nanoparticles (CCGN) were prepared. CCGN were characterized by (1)H NMR, dynamic light scattering, zeta potential, and transmission electron microscopy, and the hypoglycemic effect of insulin loaded CCGN via the oral route was evaluated in normal and diabetic rats. CCGN exhibited a homogeneous morphology and a spherical shape with core-shell structure. They were aggregated in simulated gastric fluid while separated in simulated intestinal fluid. Insulin was mainly located in the shell of the CCGN via hydrogen bonding, electrostatic interaction, and Van der Waals force. Insulin release from the CCGN exhibited a pH-sensitive property in that it had a slow release rate at pH 2.0 and a fast release rate at pH 6.8 and 7.4. The pharmacological bioavailability after oral administration of insulin loaded CCGN at a dose of 25 IU/kg was found to be 9.7%. Besides, CCGN showed desirable tissue and blood compatibility. Therefore, the CCGN would be a promising delivery carrier for protein drugs via the oral route.
PMID: 19292439 [found with GoPubMed]
37: J Biomed Mater Res A 2009 Mar;
bFGF-loaded HA-chitosan: A promising scaffold for periodontal tissue engineering
Akman, A C, Tığlı, R S, Gümüşderelioğlu, M, Nohutcu, R M, Department of Periodontology, Faculty of Dentistry, Hacettepe University, Sihhiye, Ankara 06100, Turkey
A scaffold containing growth factors promoting regeneration may be a useful device to maintain periodontal regeneration when applied with appropriate cells. The aim of this study is to evaluate the convenience of chitosan and hydroxyapatite (HA)-chitosan scaffolds loaded with basic fibroblast growth factor (bFGF) for periodontal tissue engineering applications. Scaffolds were fabricated by freeze-drying technique using 2 and 3% chitosan gel in the absence or presence of HA particles. Addition of HA beads to chitosan gels produced a novel scaffold in which the pore sizes and interconnectivity were preserved. The scaffolds were loaded with 100 ng bFGF by embedding technique. HA-chitosan scaffolds provide better controlled release kinetics for bFGF compared with chitosan scaffolds and total release continued up to 168 h. Cell culture studies were carried out with periodontal ligament (PDL) cells and cementoblasts. Both 3-[4,5-dimethylthiazol-2-yl]-diphenyltetrazolium bromide (MTT) assay and confocal laser scanning microscope analysis revealed cells proliferating inside the scaffolds. The results demonstrated that bFGF-loaded HA-chitosan scaffolds provide a suitable three-dimensional environment supporting the cellular structure, proliferation, and mineralization. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009.
PMID: 19291690 [found with GoPubMed]
38: J Biomed Mater Res A 2009 Mar;
Preparation and evaluation of thiolated chitosan scaffolds for tissue engineering
Li, Z, Cen, L, Zhao, L, Cui, L, Liu, W, Cao, Y, National Tissue Engineering Center of China, Third Floor, Building 1, No. 100, Qin Zhou Road, Shanghai 200235, China
Thiolated chitosan (TCS) was proposed as a promising candidate as scaffold material for tissue engineering. However, a continuous exploration of such material as a three-dimensional (3D) scaffold with controllable design of microstructure as well as mechanical strength was necessitated. The current study was thus carried out to substantiate such potential of TCS. Thioglycolic acid (TGA) was first introduced on the side chain of chitosan (CS) via the amide bond formation between COOH groups of TGA and NH(2) groups of CS. Composite TCS/CS scaffolds with different ratios were prepared via freeze-drying under different temperatures to optimize the structural properties. The microstructure of the scaffolds was observed by scanning electron microscopy (SEM), and tensile strength of scaffolds was measured. Both the TCS/CS proportion and freezing temperature affected the microstructure and mechanical property of scaffolds, which in turn rendered effects on the growth of cultured fibroblasts. Scaffolds obtained from the TCS/CS proportion of 7:3 and a freezing temperature of -20 degrees C had the maximum tensile strength with a pore distribution ranging from a few to several hundred micrometers. The preferential growth of fibroblasts on this scaffold was also demonstrated. Hence, results in this study would offer valuable information on the preparation of suitable TCS scaffolds for tissue engineering. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009.
PMID: 19291689 [found with GoPubMed]
39: Appl Biochem Biotechnol 2009 Mar;
Immobilization of beta-Galactosidase onto Magnetic Beads
Zhang, S, Gao, S, Gao, G, Lanzhou Industry Research Institute, Gansu, Lanzhou, 730050, People's Republic of China
A study of the cross-linking of beta-galactosidase on magnetic beads is reported here. The magnetic beads were prepared from artemisia seed gum, chitosan, and magnetic fluid in the presence of a cross-linking regent (i.e., glutaraldehyde). The reactive aldehyde groups of the magnetic beads allowed the reaction of the amino groups of the enzymes. The animated magnetic beads were used for the covalent immobilization of beta-galactosidase. The effect of various preparation conditions on the activity of the immobilized beta-galactosidase, such as immobilizing time, amount of enzyme, and the concentration of glutaraldehyde, were investigated. The influence of pH and temperature on the activity and the stability of the enzyme, both free and immobilized, have been studied. And o-nitrophenyl-beta-D: -galactopyranoside (ONPG) was chosen as a substrate. The beta-galactosidase immobilized on the magnetic beads resulted in an increase in enzyme stability. Optimum operational temperature for immobilized enzyme was 10 degrees C higher than that of free enzyme and was significantly broader.
PMID: 19288068 [found with GoPubMed]
40: Science 2009 Mar;323(5920):1458-60
Self-repairing oxetane-substituted chitosan polyurethane networks
Ghosh, Biswajit, Urban, Marek W, School of Polymers and High Performance Materials, Shelby F. Thames Polymer Science Research Center, University of Southern Mississippi, Hattiesburg, MS 39406, USA
Polyurethanes have many properties that qualify them as high-performance polymeric materials, but they still suffer from mechanical damage. We report the development of polyurethane networks that exhibit self-repairing characteristics upon exposure to ultraviolet light. The network consists of an oxetane-substituted chitosan precursor incorporated into a two-component polyurethane. Upon mechanical damage of the network, four-member oxetane rings open to create two reactive ends. When exposed to ultraviolet light, chitosan chain scission occurs, which forms crosslinks with the reactive oxetane ends, thus repairing the network. These materials are capable of repairing themselves in less than an hour and can be used in many coatings applications, ranging from transportation to packaging or fashion and biomedical industries.
PMID: 19286550 [found with GoPubMed]
41: Int Immunopharmacol 2009 Mar;
Dietary supplementation with chitosan derived from mushrooms changes adipocytokine profile in diet-induced obese mice, a phenomenon linked to its lipid-lowering action
Neyrinck, A M, Bindels, L B, De Backer, F, Pachikian, B D, Cani, P D, Delzenne, N M, Unit of Pharmacokinetics, Metabolism, Nutrition and Toxicology, Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium
Recent data reported that chitosan reduces high-fat (HF) diet-induced obesity in mice without describing the metabolic consequences of such an effect. The aim of this study was to investigate the capacity of chitosan derived from edible mushrooms to modify adipocytokine levels and to assess the relevance of this effect on the development of fat mass, and on glucose and lipid metabolism in obese mice. Mice were fed a HF diet or a HF diet supplemented with 5% fungal chitosan for ten weeks. HF-induced hypertriglyceridaemia, fasting hyperinsulinaemia and fat accumulation in liver, muscle and white adipose tissue (WAT) were reduced after chitosan treatment. The higher lipid content in the caecum following treatment with chitosan suggested that this dietary fiber reduced lipid absorption. We postulated that the lower triglyceridaemia observed upon chitosan treatment could also be the result of the lower FIAF (fasting-induced adipose factor) expression observed in visceral adipose tissue. IL-6, resistin and leptin levels decreased in the serum after chitosan supplementation. We conclude that fungal chitosan counteracts some inflammatory disorders and metabolic alterations occurring in diet-induced obese mice since it decreases feed efficiency, fat mass, adipocytokine secretion and ectopic fat deposition in the liver and the muscle.
PMID: 19286482 [found with GoPubMed]
42: J Tissue Eng Regen Med 2009 Mar;
Electrostatic binding of nanoparticles to mesenchymal stem cells via high molecular weight polyelectrolyte chains
Heng, B C, Cowan, C M, Davalian, D, Stankus, J, Duong-Hong, D, Ehrenreich, K, Basu, S, Abbott Vascular Inc., 3200 Lakeside Drive, Santa Clara, CA 95054, USA
Combining stem cell transplantation with nanoparticle-mediated delivery of drugs and pharmaceuticals is envisioned to be one of the next major developmental steps in regenerative medicine. However, a major challenge would be to keep nanoparticles co-localized with stem cells upon transplantation or transfusion in situ. Since nanoparticles are physically much smaller in size than cells and would not specifically bind to extracellular matrix, it is easier for them to disperse from the transplantation site via the blood circulation. Conjugating nanoparticles directly to the cell membrane can potentially interfere with cellular function by physically obstructing cell surface receptors from interacting with the extracellular matrix, various growth factors and cytokines and other cells. Moreover, drug-loaded nanoparticles may be internalized into the cytoplasm via endocytosis or phagocytosis, which may wreak damage on the cellular machinery, leading to impaired physiological function or cell death. A novel solution may be to utilize high molecular weight polyelectrolyte chains to electrostatically bind nanoparticles to cells. For this purpose, hyaluronan, poly-L-lysine and chitosan are of special interest, because these molecules are generally recognized to be biocompatible for application in various pharmaceutical and surgical products. This study investigated the use of these molecules to bind nanoparticles to mesenchymal stem cells (MSCs), and a novel technique of conjugating half the cell surface with nanoparticles through the use of polyelectrolyte chains was also developed. This would avoid blocking MSC interaction with cytokines, growth factors, extracellular matrix and other cells within the recipient tissue/organ upon delivery in situ. Copyright (c) 2009 John Wiley & Sons, Ltd.
PMID: 19283725 [found with GoPubMed]
43: Bioorg Med Chem 2009 Apr;17(7):2718-23
Binary and ternary inclusion complexes of finasteride in HPbetaCD and polymers: Preparation and characterization
Asbahr, Ana Carolina C, Franco, Luzia, Barison, Andersson, Silva, Caroline W P, Ferraz, Humberto G, Rodrigues, Letícia N C, Departamento de Farmácia, Universidade Federal do Paraná, Av. Lothario Meissner, 632, Curitiba, PR 80210-170, Brazil
The aim of this study was to determine whether inclusion complexes between 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) and finasteride (FIN) are formed, and to characterize these. Equimolar FIN/HPbetaCD solid systems in the presence or absence of 0.1% (w/v) of polyvinylpyrrolidone K30 (PVP K30) or 0.3% of chitosan were prepared by coevaporation and freeze-drying methods. The systems were characterized by phase solubility, NMR, DSC, and XRD analysis. The results suggest that true binary and ternary inclusion complexes were formed.
PMID: 19282187 [found with GoPubMed]
44: J Agric Food Chem 2009 Mar;
Optimization of the Film-Forming and Storage Conditions of Chitosan as an Antimicrobial Agent
Fernandez-Saiz, P, Lagarón, J M, Ocio, M J, Novel Materials and Nanotechnology Laboratory, Instituto de Agroquimica y Tecnologia de Alimentos (IATA), CSIC, Apartado de correos 73, 46100 Burjassot, Valencia, Spain, and Departamento Medicina Preventiva, Facultad de Farmacia, Universidad de Valencia, Vicente Andres Estelles s/n, 46100 Burjassot, Valencia, Spain
The aim of this work was to assess the antimicrobial capacity of chitosan-based films obtained by a dissolution and solvent evaporation (solvent casting) method at various temperatures (i.e., 37, 80, and 120 degrees C) on the growth of Staphylococcus aureus and Salmonella spp. bacteria. The effect of temperature (4, 23, 37 degrees C) and relative humidity (RH; 0, 75%) during storage on the biocide performance was also investigated. Color parameters and ATR-FTIR spectra were analyzed for each sample to investigate the relationship between structural and/or chemical alterations in the films during storage and biocide performance. The results indicated that films formed at 37 and 80 degrees C presented a significant inhibitory effect for both types of bacteria; however, when cast at 120 degrees C, the films ceased to exhibit antimicrobial properties. Curiously, chitosonium acetate films were seen to diminish to a large extent their biocide properties when stored at 23 degrees C and 75% RH for 2 months or alternatively when stored and 37 degrees C and 0% RH over the same period of time. In good agreement with this behavior the FTIR results indicated that under the previous conditions a significant fraction of the biocide carboxylate chemistry remained in the polymer after contact with the bacterial solution due to a strong reduction in cast film solubility. Because biopolymer active species migration from the film to the culture media is needed for the biomaterial to exhibit measurable antimicrobial effect, proper control of temperature and humidity during film formation and storage is necessary to design the optimum performance of chitosan as a biocide.
PMID: 19281273 [found with GoPubMed]
45: J Biomed Mater Res A 2009 Mar;
Culture of human mesenchymal stem cells using electrosprayed porous chitosan microbeads
Maeng, Y J, Choi, S W, Kim, H O, Kim, J H, Department of Chemical Engineering, Yonsei University, 134 Shinchon-dong, Sudaemoon-ku, Seoul, Korea
The aim of this study was to fabricate porous chitosan microbeads using an electrospraying method into liquid nitrogen, then thawing and refreezing. The microbeads were then used to evaluate their potential for tissue engineering of human mesenchymal stem cells (hMSCs). Scanning electron microscopy (SEM) and a mercury porosimeter were used to show the morphology of the scaffolds formed and to determine their pore size and porosity. As the chitosan concentration increased (0.5, 1, 1.5, and 2 wt %), the diameter of the porous microbead increased from 350 to 890 mum, and the average pore size and the porosity decreased from 65 to 21 mum and 95 to 38%, respectively. The hMSCs were cultured onto the porous microbeads in a spinner flask. SEM images and methyl tetrazolium salt assays at 3, 7, 14, and 21 days of culture revealed that hMSCs had successfully attached and proliferated inside the porous microbeads. This study demonstrated that electrosprayed porous chitosan microbeads can be used as three-dimensional scaffolds for tissue engineering. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2009.
PMID: 19280627 [found with GoPubMed]
46: Mol Cell Proteomics 2009 Mar;
From secretome analysis to immunology: Chitosan induces major alterations in the activation of dendritic cells via a TLR4-dependent mechanism
Villiers, C, Chevallet, M, Diemer, H, Couderc, R, Freitas, H, Van Dorsselaer, A, Marche, P N, Rabilloud, T, iRTSV/LBBSI, CNRS UMR 5092, CEA Grenoble, Grenoble 38054
Dendritic cells are known to be activated by a wide range of microbial products, leading to cytokine production, and increased levels of membrane markers such as MHC Class II molecules. Such activated dendritic cells possess the capacity to activate naïve T cells. We demonstrate here that immature dendritic cells secrete both the YM1 lectin and lipocalin2. By testing the ligands of these two poteins, respectively chitosan and siderophores, we also demonstrate that chitosan, a degradation product of various fungal and protozoal cell walls, induce an activation of dendritic cells at the membrane level, as shown by the upregulation of membrane proteins such as class II molecules, CD80 and CD86, via a TLR4-dependent mechanism, but is not able to induce cytokine production. This leads to the production of activated dendritic cells unable to stimulate T cells. However, costimulation with other microbial products overcomes this partial activation and restore the capacity of these activated dendritic cells to stimulate T cells. In addition, successive stimulation with chitosan and then by LPS induced a dose-dependent change in the cytokinic IL-12/IL-10 balance produced by the dendritic cells.
PMID: 19279042 [found with GoPubMed]
47: Cancer Genet Cytogenet 2009 Apr;190(1):8-14
Selection of optimal sites for TGFB1 gene silencing by chitosan-TPP nanoparticle-mediated delivery of shRNA
Wang, So-Ly, Yao, Hui-Hua, Guo, Ling-Ling, Dong, Liang, Li, Shi-Gang, Gu, Yong-Ping, Qin, Zheng-Hong, Department of Pathology, Soochow University School of Medicine, Suzhou, China
Most human tumors produce high levels of TGF-beta1, whose autocrine and paracrine actions promote tumor cell invasiveness and metastasis. Currently, many experimental therapies that target TGFB1 have utilized antisense DNA or RNA interference (RNAi). Despite the great potential of RNAi, the selection of effective target sites and proper delivery systems for short hairpin RNA (shRNA) remains a significant issue. Here, we used chitosan nanoparticle-mediated delivery of a shRNA-expressing vector to inhibit TGFB1 expression in the human rhabdomyosarcoma cell line RD. Knockdown of TGFB1 by shRNA resulted in a decrease in RD cell growth in vitro and tumorigenicity in nude mice. The efficiency of TGFB1 gene silencing varied with the selection of targeting sites. These data suggest that chitosan nanoparticle-mediated delivery of an shRNA produces efficient TGFB1 knockdown in rhabdomyosarcoma cells and may be a method of choice for shRNA delivery for gene therapy.
PMID: 19264227 [found with GoPubMed]
48: Carbohydr Res 2009 Mar;344(5):699-706
Synthesis and characterization of chitosan-based pH-sensitive semi-interpenetrating network microspheres for controlled release of diclofenac sodium
Al-Kahtani Ahmed, A, Bhojya Naik, H S, Sherigara, B S, Department of Industrial Chemistry, Kuvempu University, School of Chemical Science, Jnana Sahyadri, Shankaraghatta 577 451, Karnataka, India
pH-Sensitive semi-interpenetrating networks (IPNs) based on chitosan (Cs) and acrylamide-grafted hydroxyethylcellulose (AAm-g-HEC) were prepared in the form of microspheres (MPs) by emulsion-crosslinking technique using glutaraldehyde (GA) as a crosslinker. Diclofenac sodium (DS) drug was successfully encapsulated into IPN microspheres by varying the ratio of Cs and AAm-g-HEC, % drug loading, and amount of GA. DS encapsulation of up to 83% was obtained as measured by UV spectroscopy. MPs with average particle sizes in the range of 188-310microm were obtained. MPs were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Differential scanning calorimetry (DSC). Diffusion coefficients (D) of water transport through the microspheres were determined using an empirical equation. In vitro release of DS from these matrices has been investigated in pH 1.2 and 7.4 media.
PMID: 19246032 [found with GoPubMed]
49: FEMS Microbiol Lett 2009 Apr;293(1):79-84
Molecular characterization and antifungal activity of a family 46 chitosanase from Amycolatopsis sp. CsO-2
Saito, Akihiro, Ooya, Takaaki, Miyatsuchi, Daisuke, Fuchigami, Hiroko, Terakado, Kanako, Nakayama, Shin-ya, Watanabe, Takeshi, Nagata, Yoshiho, Ando, Akikazu, Department of Bioresource Chemistry, Faculty of Horticulture, Chiba University, Matsudo, Chiba, Japan
An actinomycete strain, Amycolatopsis sp. CsO-2, produces a 27-kDa chitosanase. To reveal the molecular characteristics of the enzyme, its corresponding gene ctoA was cloned by a reverse genetic technique, based on the N-terminal amino acid sequence of the protein. The encoded CtoA protein was deduced to be composed of 286 amino acids, including a putative signal peptide (1-48), and exhibited 83% identity in the amino acid sequence with the family 46 chitosanases from Streptomyces sp. N174 or Nocardioides sp. N106. The active recombinant CtoA protein was successfully overproduced in Escherichia coli. The mutant protein E22Q, in which the glutamic acid residue 22 was replaced with glutamine, abolished the chitosanase activity, showing that the Glu22 residue is required for the enzymatic activity. CtoA exhibited antifungal activity against Rhizopus oryzae, which is known to produce chitosan probably as a cell wall component. In contrast, E22Q did not inhibit the growth of the fungus, suggesting that chitosan-hydrolyzing activity is essential for the antifungal activity. It is noteworthy that the antifungal effect of CtoA against R. oryzae was drastically enhanced by the simultaneous addition of the family 19 chitinase ChiC from Streptomyces griseus.
PMID: 19236484 [found with GoPubMed]
50: Carbohydr Res 2009 Mar;344(5):679-82
A novel supramolecular compound 2,2'-bipyridyl-phosphotungstic acid: synthesis and catalysis
Wang, Qiong-Sheng, Wang, Shi-Ming, Lin, Shan, College of Chemistry and Materials Science, Fujian Normal University, Fuzhou, China
A new supramolecular compound (C(10)H(8)N(2))(3.2).H(3)PW(12)O(40).25.6H(2)O (Bipy-PW(12)) was synthesized by self-assembly design, and characterized by elemental analysis, Fourier-transform infrared spectra (FTIR), and (31)P NMR spectra. Bipy-PW(12) can effectively catalyze oxidative degradation of chitosan with H(2)O(2) in heterogeneous phase. To obtain water-soluble chitosan with an average molecular weight of 5000, the optimum reaction conditions were determined as follows: reaction temperature, 80 degrees C; reaction time, 13min; H(2)O(2) concentration, 2.7mol/L; and mass ratio of Bipy-PW(12) to chitosan, 0.01.
PMID: 19217082 [found with GoPubMed]
51: Bioelectrochemistry 2009 Apr;75(1):77-82
A microbial biosensor based on bacterial cells immobilized on chitosan matrix
Odaci, Dilek, Timur, Suna, Telefoncu, Azmi, Ege University, Faculty of Science, Biochemistry Department, 35100 Bornova-Izmir, Turkey
A bio-electrochemical system consisting of Gluconobacter oxydans DSM 2343 cells as a biological material and carbon nanotube (CNT)-free and CNT-modified chitosan as immobilizing matrices has been developed. The measurement was based on the respiratory activity of the cells estimated by the oxygen consumption at -0.7 V (versus the Ag|AgCl reference electrode) due to the metabolic activity in the presence of substrates. The system was calibrated and dependence of signal amplitude on the measuring conditions and cell amount was studied as well as the substrate specificity, pH, temperature and working potential. The biosensors (CNT-modified and unmodified) were demonstrated for the quantification of glucose in the range of 0.05-1.0 mM, at 30 degrees C and pH 7.0 with the 40 s of response time. The linear relationships between sensor response (y; microA/cm(2)) and substrate concentration (x; mM) were defined by the equations of y=1.160x+0.151 (R(2)=0.990) and y=1.261x+0.197 (R(2)=0.982), respectively. All other data were also given as comparison of two systems one with CNT-modified and CNT-free.
PMID: 19196553 [found with GoPubMed]
52: Appl Biochem Biotechnol 2009 Apr;157(1):23-35
Purification and characterization of thermostable chitinase from Bacillus licheniformis SK-1
Kudan, Sanya, Pichyangkura, Rath, Biochemistry Department, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
Chitinase was purified from the culture medium of Bacillus licheniformis SK-1 by colloidal chitin affinity adsorption followed by diethylamino ethanol-cellulose column chromatography. The purified enzyme showed a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular size and pI of chitinase 72 (Chi72) were 72 kDa and 4.62 (Chi72) kDa, respectively. The purified chitinase revealed two activity optima at pH 6 and 8 when colloidal chitin was used as substrate. The enzyme exhibited activity in broad temperature range, from 40 to 70 degrees C, with optimum at 55 degrees C. It was stable for 2 h at temperatures below 60 degrees C and stable over a broad pH range of 4.0-9.0 for 24 h. The apparent K (m) and V (max) of Chi72 for colloidal chitin were 0.23 mg ml(-1) and 7.03 U/mg, respectively. The chitinase activity was high on colloidal chitin, regenerated chitin, partially N-acetylated chitin, and chitosan. N-bromosuccinamide completely inhibited the enzyme activity. This enzyme should be a good candidate for applications in the recycling of chitin waste.
PMID: 19190863 [found with GoPubMed]
53: Biomaterials 2009 Apr;30(12):2329-39
In vivo evaluation of safety and efficacy of self-assembled nanoparticles for oral insulin delivery
Sonaje, Kiran, Lin, Yu-Hsin, Juang, Jyuhn-Huarng, Wey, Shiaw-Pyng, Chen, Chiung-Tong, Sung, Hsing-Wen, Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, ROC
A variety of approaches have been studied in the past to overcome the problems encountered with the oral delivery of insulin, but with little success. In this study, self-assembled nanoparticles (NPs) with a pH-sensitive characteristic were prepared by mixing the anionic poly-gamma-glutamic acid solution with the cationic chitosan solution in the presence of MgSO(4) and sodium tripolyphosphate. The in vitro results found that the transport of insulin across Caco-2 cell monolayers by NPs appeared to be pH-dependent; with increasing pH, the amount of insulin transported decreased significantly. An in vivo toxicity study was performed to establish the safety of the prepared NPs after oral administration. Additionally, the impact of orally administered NPs on the pharmacodynamics (PD) and pharmacokinetics (PK) of insulin was evaluated in a diabetic rat model. The in vivo results indicated that the prepared NPs could effectively adhere on the mucosal surface and their constituted components were able to infiltrate into the mucosal cell membrane. The toxicity study indicated that the NPs were well tolerated even at a dose 18 times higher than that used in the PD/PK study. Oral administration of insulin-loaded NPs demonstrated a significant hypoglycemic action for at least 10h in diabetic rats and the corresponding relative bioavailability of insulin was found to be 15.1+/-0.9%. These findings suggest that the NPs prepared in the study are a promising vehicle for oral delivery of insulin.
PMID: 19176244 [found with GoPubMed]
54: Food Microbiol 2009 Apr;26(2):151-6
Use of natural compounds to improve the microbial stability of Amaranth-based homemade fresh pasta
Del Nobile, M A, Di Benedetto, N, Suriano, N, Conte, A, Lamacchia, C, Corbo, M R, Sinigaglia, M, Department of Food Science, University of Foggia, Via Napoli 25, 71100 Foggia, Italy.
A study on the use of natural antimicrobial compounds to improve the microbiological stability of refrigerated amaranth-based homemade fresh pasta is presented in this work. In particular, the antimicrobial activity of thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) has been tested against mesophilic and psychrotrophic bacteria, total coliforms, Staphylococcus spp., yeasts and moulds. A sensory analysis on both fresh and cooked pasta was also run. Results suggest that chitosan and GFSE strongly increase the microbial acceptability limit of the investigated spoilage microorganisms, being the former the most effective. Thymol efficiently reduces the growth of mesophilic bacteria, psychrotrophic bacteria and Staphylococcus spp., whereas it does not affect, substantially, the growth cycle of total coliforms. Lemon extract is the less effective in preventing microbial growth. In fact, it is able to delay only total mesophilic and psychrotrophic bacterial evolution. From a sensorial point of view no significant differences were recorded between the control samples and all the types of loaded amaranth-based pasta.
PMID: 19171256 [found with GoPubMed]
55: Biomaterials 2009 Apr;30(12):2276-83
The effect of a layer-by-layer chitosan-heparin coating on the endothelialization and coagulation properties of a coronary stent system
Meng, Sheng, Liu, Zongjun, Shen, Li, Guo, Zhang, Chou, Laisheng L, Zhong, Wei, Du, Qiangguo, Ge, Junbo, Department of Macromolecular Science and The Key Laboratory of Molecular Engineering of Polymers, Ministry of Education, Fudan University, Shanghai 200433, People's Republic of China
A biomacromolecular layer-by-layer coating process of chitosan/heparin onto a coronary stent is designed for the acceleration of the re-endothelialization and healing process after coronary stent deployment. The results of in vitro culturing of porcine iliac artery endothelial cells as well as the measurements of the APTT, PT and TT supported the rationale that the combination of chitosan and heparin could bring both endothelial cell compatibility and haemocompatibility to the stent surface. A porcine coronary injury model and arteriovenous shunt model were used for the further evaluation of the application of this kind of surface-modified stainless steel stent in vivo. The final results proved that this facile coating approach could significantly promote re-endothelialization and was safer compared with bare metal stents for its much improved anticoagulation property.
PMID: 19168214 [found with GoPubMed]
56: Biosens Bioelectron 2009 Mar;24(7):2211-7
Development of a stable cholesterol biosensor based on multi-walled carbon nanotubes-gold nanoparticles composite covered with a layer of chitosan-room-temperature ionic liquid network
Gopalan, Anantha Iyengar, Lee, Kwang-Pill, Ragupathy, Dhanusuraman, Department of Chemistry Graduate School, Kyungpook National University, Daegu 702-701, South Korea
A novel amperometric biosensor was fabricated based on the immobilization of cholesterol oxidase (ChOx) into a cross-linked matrix of chitosan (Chi)-room-temperature ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate). Initially, the surface of bare electrode (indium tin oxide coated glass) was modified with the electrodeposition of Au particles onto thiol (-SH) functionalized multi-walled carbon nanotubes (MWNTs). The biosensor electrode is designated as MWNT(SH)-Au/Chi-IL/ChOx. Scanning electron microscopy image of MWNT(SH)-Au/Chi-IL/ChOx reveals that Chi-IL exists as the interconnected wires covering the Au particles on the surface of MWNT(SH)-Au. Cyclic voltammetry and chronoamperometry were used for the electrochemical determination of cholesterol at the biosensor electrode, MWNT(SH)-Au/Chi-IL/ChOx. The presence of Au particles in the matrix of CNTs provides an environment for the enhanced electrocatalytic activities. The MWNT(SH)-Au/Chi-IL/ChOx biosensor exhibited a linear response to cholesterol in the concentration range of 0.5-5mM with a correlation coefficient of 0.998, good sensitivity (200 microAM(-1)), a low response time ( approximately 7s), repeatability (R.S.D value of 1.9%) and long term stability (20 days with a decrease of 5% response). The synergistic influence of MWNT(SH), Au particles, Chi and IL contributes to the excellent performance for the biosensor.
PMID: 19167880 [found with GoPubMed]
57: J Pharm Biomed Anal 2009 Apr;49(3):655-9
Evaluation of surface and microstructure of differently plasticized chitosan films
Bajdik, János, Marciello, Marzia, Caramella, Carla, Domján, Attila, Süvegh, Károly, Marek, Tamás, Pintye-Hódi, Klára, Department of Pharmaceutical Technology, University of Szeged, Eötvös u. 6, H-6720 Szeged, Hungary
Surface and structural investigations of natural biopolymer (chitosan) films containing various conventionally applied hydrophilic plasticizers (glycerol and poly(ethylene glycol) 400) were performed and the results were compared, with the aim of acquiring new information concerning the formation of these plasticized films. The surface tests revealed that the water uptake, the water-binding properties (moisture content) and the polarity were higher for the film containing glycerol as plasticizer. Positronium lifetime measurements and NMR studies performed to evaluate the effects of the plasticizer on the polymer structure demonstrated relevant differences in the effects of the plasticizers. The influence of glycerol on the structure of the film formed was more intensive than that of PEG 400. It can be concluded that the surface properties of the films, which are very important for their storage and application, cannot be established exactly by means of structural tests. Both surface and structural tests must be performed before the formulation of this type of plasticized mucoadhesive films.
PMID: 19162425 [found with GoPubMed]
58: Talanta 2009 Mar;77(5):1647-53
Deoxyribonucleic acid modified poly(dimethylsiloxane) microfluidic channels for the enhancement of microchip electrophoresis
Liang, Ruping, Hu, Pengfei, Gan, Guihua, Qiu, Jianding, Department of Chemistry, Nanchang University, Xue fu Road 999, Nanchang 330031, PR China
In this paper, deoxyribonucleic acid (DNA) was employed to construct a functional film on the PDMS microfluidic channel surface and apply to perform electrophoresis coupled with electrochemical detection. The functional film was formed by sequentially immobilizing chitosan and DNA to the PDMS microfluidic channel surface using the layer-by-layer assembly. The polysaccharide backbone of chitosan can be strongly adsorbed onto the hydrophobic PDMS surface through electrostatic interaction in the acidic media, meanwhile, chitosan contains one protonatable functional moiety resulting in a strong electrostatic interactions between the surface amine group of chitosan and the charged phosphate backbone of DNA at low pH, which generates a hydrophilic microchannel surface and reveals perfect resistance to nonspecific adsorption of analytes. Aminophenol isomers (p-, o-, and m-aminophenol) served as a separation model to evaluate the effect of the functional PDMS microfluidic chips. The results clearly showed that these analytes were efficiently separated within 60s in a 3.7 cm long separation channel and successfully detected on the modified microchip coupled with in-channel amperometric detection mode at a single carbon fiber electrode. The theoretical plate numbers were 74,021, 92,658 and 60,552 Nm(-1) at the separation voltage of 900 V with the detection limits of 1.6, 4.7 and 2.5 microM (S/N=3) for p-, o-, and m-aminophenol, respectively. In addition, this report offered an effective means for preparing hydrophilic and biocompatible PDMS microchannel surface, which would facilitate the use of microfluidic devices for more widespread applications.
PMID: 19159778 [found with GoPubMed]
59: Biosens Bioelectron 2009 Mar;24(7):2225-31
Biofuel cell and phenolic biosensor based on acid-resistant laccase-glutaraldehyde functionalized chitosan-multiwalled carbon nanotubes nanocomposite film
Tan, Yueming, Deng, Wenfang, Ge, Bin, Xie, Qingji, Huang, Jinhua, Yao, Shouzhuo, Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, China
To immobilize laccase (Lac) from Trametes versicolor that shows its maximum enzymatic activity in acidic aqueous solutions, the biopolymer chitosan (CS) was chemically modified with glutaraldehyde (GA) to form GA functionalized CS (GAfCS), which was then allowed to react with Lac to form a Lac-GAfCS composite that is robust in weakly acidic solutions (two-step protocol), as confirmed by quartz crystal microbalance and durability tests. The Lac-GAfCS-multiwalled carbon nanotubes (MWCNTs)/glassy carbon (GC) electrode exhibited good catalytic activity towards O(2) reduction in the presence of 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS), and the pH-dependent enzymatic activity of the immobilized Lac towards O(2) reduction was examined. A glucose/air biofuel cell was fabricated, with the Lac-GAfCS-MWCNTs/GC electrode as the biocathode and a glucose oxidase (GOx)-GAfCS-MWCNTs/GC electrode as the bioanode in a Nafion membrane-separated acetate buffer solution (pH 5.0). The biofuel cell output a maximum power density of 9.6 microW/cm(2), an open-circuit cell voltage of 0.19V, and a short-circuit current density of 114 microA/cm(2), respectively, as measured with an electrochemical noise (ECN) apparatus. Furthermore, the Lac-GAfCS-MWCNTs/GC electrode was applied to determine catechol in Britton-Robinson buffer solution (pH 3.0), with a linear range of 0.1-50 microM and a limit of detection of 20 nM. In comparison with the direct use of GA for one-pot Lac-GA-CS or Lac-GA crosslinking to immobilize Lac, the use of macromolecular GAfCS in the proposed two-step protocol was proven to be less harmful to the enzymatic activity and thus more suitable for immobilizing the enzyme to construct the biofuel cell and biosensor. This work may be helpful for exploiting the popular biocompatible CS as an acid-resistant film matrix for many other biotechnology applications, and the proposed two-step crosslinking protocol is recommended for high-activity immobilization of other biomolecules.
PMID: 19153037 [found with GoPubMed]
60: Biomaterials 2009 Apr;30(12):2340-8
Long-circulating polymeric nanoparticles bearing a combinatorial coating of PEG and water-soluble chitosan
Sheng, Yan, Liu, Changsheng, Yuan, Yuan, Tao, Xinyi, Yang, Fan, Shan, Xiaoqian, Zhou, Huanjun, Xu, Feng, The State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China
A major obstacle in the development of polymeric nanoparticles (NPs) as effective drug delivery vesicles is the rapid clearance from blood. In order to realize a significant prolongation in blood circulation, a combinatorial design, covalent attachment of polyethylene glycol (PEG) to polylactic acid (PLA) and physical adsorption of water-soluble chitosan (WSC) to particle surface, has been developed for surface modification of PLA NPs. Two types of WSC, cationic partially deacetylated chitin (PDC) and anionic N-carboxy propionyl chitosan sodium (CPCTS) were investigated. All the NPs formulated in the size range of 100-200nm were prepared by a modified w/o/w technique and physicochemically characterized. In vitro phagocytosis by mouse peritoneal macrophage (MPM), in vivo blood clearance and biodistribution following intravenous administration in mice, of these NPs labeled with 6-coumarin, were evaluated. The presence of WSC, whether alone or with PEG, highly improved the surface hydrophilicity as well as suspension stability of NPs. Their surface charge was greatly affected by the WSC coating, being close to neutrality for PEG/PDC NPs and highly negative in the case of PEG/CPCTS NPs. In comparison to NPs treated with PEG or WSC alone, the synergistic action of PEG and WSC strongly inhibited the macrophage uptake and extended the circulation half-life (t(1/2)) with concomitant reduced liver sequestration. Particularly, PEG/PDC NPs showed the most striking result with regard to their performance in vitro and in vivo. Calculated t(1/2) of PEG/PDC NPs and PEG/CPCTS NPs was 63.5h and 7.1h, respectively, much longer than that of control PEG/PVA NPs (1.1h). More WSC materials need to be evaluated, but the present data suggest that, a combinatorial coating of PEG and PDC greatly prolongs the systemic circulation of NPs and represents a significant step in the development of long-circulating drug delivery carriers.
PMID: 19150737 [found with GoPubMed]
61: Int J Biol Macromol 2009 Apr;44(3):249-56
Synthesis of novel pH-sensitive chitosan graft copolymers and micellar solubilization of paclitaxel
Li, Hongxia, Liu, Jia, Ding, Song, Zhang, Can, Shen, Wenbin, You, Qidong, Centre for Drug Discovery, China Pharmaceutical University, Nanjing, PR China
Herein, highly pH-sensitive graft copolymers, N-octyl-N-(2-carboxylbenzoyl) chitosan derivatives, were synthesized and characterized by FTIR, (1)H NMR, (13)C NMR, differential scanning calorimetry and X-ray diffraction spectrometry. The polymers can form micelles solublizing paclitaxel, with critical micellar concentrations ranged from 0.07 to 0.32mg/ml, drug-loading rate ranged from 30.7% to 65.3% and entrapment efficiency ranged from 44.2% to 61.4%. Additionally, the result shows that the micelles display highly sensitivity to mildly acidic pH while reasonably stable at physiologic pH, which might pave the way for building pharmaceutical nanocarriers specifically releasing cargo at certain pathological sites of body.
PMID: 19150369 [found with GoPubMed]
62: Int J Biol Macromol 2009 Apr;44(3):229-35
Photopolymerization of methacrylated chitosan/PNIPAAm hybrid dual-sensitive hydrogels as carrier for drug delivery
Han, Jing, Wang, Kemin, Yang, Dongzhi, Nie, Jun, Beijing University of Chemical Technology, PR China
A series of hybrid hydrogels based on glycidyl methacrylated chitosan (CS-GMA) and N-isopropylacrylamide (NIPAAm) were designed and prepared via photopolymerization technology. The hydrogels were characterized by Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC) and optical transmittance. The interior morphology of hydrogels was investigated by scanning electron microscopy (SEM). The swelling experiment results revealed that hybrid hydrogel exhibited combined pH and temperature sensitivities. Acid orange 8 (AO8) and 5-flurouracil (5-Fu) were selected as model drugs for examining their release from hydrogels. The results suggested that hydrogel composition and pH value of buffer solution had great influences on release profiles.
PMID: 19146871 [found with GoPubMed]
63: Biomaterials 2009 Apr;30(11):2102-11
A nanoscale drug-entrapment strategy for hydrogel-based systems for the delivery of poorly soluble drugs
Chen, Mei-Chin, Tsai, Hung-Wen, Liu, Chin-Tang, Peng, Shu-Fen, Lai, Wei-Yun, Chen, Shiang-Jiuun, Chang, Yen, Sung, Hsing-Wen, Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, ROC
The hydrophilic nature of hydrogel matrices makes them disadvantageous to entrap poorly soluble therapeutic agents and greatly restricts their applications as drug-delivery systems. In this study, we demonstrated that sustained delivery of lipophilic drugs in hydrogel-based devices can be readily achieved by enhancing retention of drugs within micelles. This nanoscale drug-entrapment strategy was applied to develop a polymeric drug-eluting stent. Sirolimus, a lipophilic anti-proliferative/immunosuppressive drug, was entrapped into the hydrophobic core of Pluronic L121 micelles and then blended in a chitosan-based strip and crosslinked by an epoxy compound to fabricate test stents. It was found that the use of such a nanoscale drug-entrapment strategy was able to significantly increase the loading efficiency of lipophilic drugs, prevent the drug from aggregation and beneficially reduce its initial burst release; thus, the duration of drug release was extended considerably. When implanting the stent in rabbit infrarenal abdominal aortas, in-stent restenosis was markedly reduced and less inflammatory reaction was observed, while unfavorable effects such as delayed endothelial healing caused by the overdose of sirolimus could be significantly evaded.
PMID: 19135720 [found with GoPubMed]
64: Biomaterials 2009 Apr;30(10):1910-7
Formation of a human-derived fat tissue layer in P(DL)LGA hollow fibre scaffolds for adipocyte tissue engineering
Morgan, Suzanne M, Ainsworth, Ben J, Kanczler, Janos M, Babister, Jodie C, Chaudhuri, Julian B, Oreffo, Richard O C, Bone and Joint Research Group, Centre for Human Development, Stem Cells and Regeneration, Institute of Developmental Sciences, University of Southampton, Southampton SO166YD, UK
Development of adipose tissue-engineering strategies, where human bone marrow stromal cells (HBMSC) are combined with three-dimensional scaffolds, is likely to prove valuable for soft tissue restoration. In this study, we assessed the function of poly(DL-lactide-co-glycolide) (P(DL)LGA) hollow fibres in facilitating the development of HBMSC-derived adipocytes for advancement of an associated adipocyte layer. The large surface area of 75:25 P(DL)LGA fibres facilitated the rapid generation of extensive adipocyte aggregates from an undifferentiated HBMSC monolayer, where the fat-laden cells stained positive with Oil Red O and expressed the adipocyte marker, fatty acid binding protein 3 (FABP3). Following implantation subcutaneously in severely compromised immunodeficient mice, the adipogenic phenotype of the PLGA-adipocyte graft was maintained for up to 56 days. Confocal microscopy showed associated LipidTOX Deep Red neutral lipid staining in an (FL)P(DL)LGA fibre-adipocyte graft after 56 days, critical evidence demonstrating maintenance of the adipocyte phenotype in the subcutaneous graft. To support adipose tissue advancement in a defined volume, the P(DL)LGA-adipocyte scaffold was encapsulated within alginate/chitosan hydrogel capsules (typical diameters, 4.0 mm). In a 28-day in vivo trial in immunodeficient mice, clusters of the capsules were maintained at the subcutaneous site. An adipocyte tissue layer advancing within the surrounding hydrogel was demonstrated.
PMID: 19135718 [found with GoPubMed]
65: Biosens Bioelectron 2009 Mar;24(7):2165-70
Synergistically improved sensitivity for the detection of specific DNA sequences using polyaniline nanofibers and multi-walled carbon nanotubes composites
Yang, Tao, Zhou, Na, Zhang, Yongchun, Zhang, Wei, Jiao, Kui, Li, Guicun, Key Laboratory of Eco-Chemical Engineering (Ministry of Education), College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, No. 53 Zhengzhou Road, Qingdao 266042, China
A sensitive electrochemical DNA biosensor was successfully realized on polyaniline nanofibers (PANI), multi-walled carbon nanotubes (MWNT) and chitosan (CHIT) modified carbon paste electrode (CPE) based on the synergistic effect between PANI and MWNT nanoparticles in chitosan film. PANI and MWNT nanocomposites resulted in highly enhanced electron conductive and biocompatible nanostructured film, which was examined by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The immobilization of the probe DNA on the surface of electrode was largely improved due to the unique synergistic effect of PANI and MWNT. The DNA hybridization events were monitored with an EIS label-free detection strategy. Under the optimal conditions, the dynamic detection range of this DNA electrochemical biosensor was from 1.0 x 10(-13) to 1.0 x 10(-7)mol/L and a detection limit of 2.7 x 10(-14)mol/L for the detection of DNA specific sequence of the phosphinothricin acetyltransferase gene (PAT, one of the important screening detection genes for the transgenic plants). Simultaneously, the polymerase chain reaction (PCR) amplification of the terminator of nopaline synthase gene (NOS) from the sample of one kind of genetically modified soybean was also detected satisfactorily.
PMID: 19131238 [found with GoPubMed]
66: J Control Release 2009 Mar;134(3):158-68
Nucleic acid delivery with chitosan and its derivatives
Lai, Wing-Fu, Lin, Marie Chia-Mi, Department of Chemistry, Faculty of Science, University of Hong Kong, Pokfulam, Hong Kong.
Chitosan is a naturally occurring cationic mucopolysaccharide. It is generally biocompatible, biodegradable, mucoadhesive, non-immunogenic and non-toxic. Although chitosan is able to condense nucleic acids (NA) (both DNA and RNA) and protect them from nuclease degradation, its poor water solubility and low transfection efficacy have impeded its use as an NA carrier. In order to overcome such limitations, a multitude of strategies for chitosan modification and formulation have been proposed. In this article, we will first give a brief overview of the physical and biological properties of chitosan. Then, with a special focus on plasmid DNA delivery, we will have a detailed discussion of the latest advances in chitosan-mediated NA transfer. For future research, the following three important areas will be discussed: chitosan-mediated therapeutic small RNA transfer, structure-activity relationships (SAR) in chitosan vector design, and chitosan-mediated oral/nasal NA therapy.
PMID: 19100795 [found with GoPubMed]
67: J Mater Sci Mater Med 2009 Apr;20(4):991-9
Investigation of polymeric amphiphilic nanoparticles as antitumor drug carriers
Zhang, Jing, Chen, Xi Guang, Liu, Cheng Sheng, Park, Hyun Jin, College of Marine Life Science, Ocean University of China, 5# Yushan Road, Qingdao, 266003, People's Republic of China
In this paper, polymeric amphiphilic nanoparticles based on oleoyl-chitosan (OCH) with different degrees of substitution (DS, 5%, 11% and 27%) were prepared by Oil/Water emulsification method. Mean diameters of the nanoparticles were 327.4 nm, 255.3 nm and 192.6 nm, respectively. Doxorubicin (DOX) was efficiently loaded into OCH nanoparticles and provided a sustained released after a burst release in PBS. These nanoparticles showed no cytotoxicity to mouse embryo fibroblasts (MEF) and low hemolysis rates (<5%). The results of SDS-PAGE indicated that bovine calf serum (BCS) adsorption on OCH nanoparticles was inhibited by smaller particle size. Cellular uptake was evaluated by incubating fluorescence labeled OCH nanoparticles with human lung carcinoma cells (A549) and mouse macrophages (RAW264.7). Cellular uptake of OCH nanoparticles was time--and concentration--dependent. Finding the appropriate incubation time and concentration of OCH nanoparticles used as drug carriers might decrease phagocytic uptake, increase cancer cell uptake and ultimately improve therapeutic efficiency of antitumor therapeutic agents.
PMID: 19083084 [found with GoPubMed]
68: Int J Pharm 2009 Mar;370(1-2):26-32
Chitosan-aprotinin coated liposomes for oral peptide delivery: Development, characterisation and in vivo evaluation
Werle, Martin, Takeuchi, Hirofumi, Gifu Pharmaceutical University, Laboratory of Pharmaceutical Engineering, 5-6-1 Mitahora Higashi, 502-8585 Gifu, Japan
In order to improve the systemic uptake of therapeutic peptides/proteins after oral administration, the polymer-protease inhibitor conjugate chitosan-aprotinin was synthesised and polyelectrolyte complexes between negatively charged multilamellar vesicles (MLV) and positively charged chitosan-aprotinin conjugate were prepared. It could be demonstrated that chitosan-aprotinin was capable of significantly inhibiting Trypsin in vitro in concentrations of 0.05% and 0.1%, whereas no inhibition was observed in the presence of 0.1% chitosan. The size range of the prepared MLV was between 3 and 4.5microm and the initially negative zeta potential (ca. -90mV) of the core liposomes switched to a positive value after polymer coating (ca. +40mV). Confocal laser microscopy studies showed comparable mucoadhesive properties of chitosan-aprotinin coated MLV and chitosan coated MLV. In comparison to calcitonin in solution, the area above the blood calcium concentration-time curve (AAC) after oral administration of calcitonin loaded chitosan coated MLV to rats increased around 11-fold, and around 15-fold in the case of calcitonin loaded chitosan-aprotinin coated MLV. Data gained in the current study are believed to contribute to the development of novel polymer-protease inhibitor based delivery systems.
PMID: 19073243 [found with GoPubMed]
69: J Mater Sci Mater Med 2009 Apr;20(4):935-41
Fabrication of calcium phosphate-calcium sulfate injectable bone substitute using chitosan and citric acid
Song, Ho-Yeon, Esfakur Rahman, A H M, Lee, Byong-Taek, Department of Microbiology, School of Medicine, Soonchunhyang University, 366-1 Ssangyoung-dong, Cheonan City, Chungnam, 330-090, South Korea
In this study, an injectable bone substitute (IBS) consisting of citric acid, chitosan solution as the liquid phase and tetra calcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and calcium sulfate hemihydrate (CSH) powders as the solid phase was prepared. Four groups containing different percentages (0-30%) of calcium sulfate hemihydrate (CSH, CaSO(4) . 0.5H(2)O) were investigated. Initial setting times for IBS with CSH were longer than those without CSH. The setting times for all compositions were in the range of 25-45 min. The injectability was improved by the addition of CSH in the present system. Scanning electron microscopy images showed that fiber-like crystallization appeared in the cements. The enhancement of crystallinity was confirmed by XRD profiles where the peak intensity of HAp increased with incubation time and the addition of CSH. Also, the compressive strength increased with the addition of CSH. The maximum compressive strength obtained for IBS was with 20% CSH after 28-day incubation in 100% humidity at 37 degrees C.
PMID: 19052849 [found with GoPubMed]
70: Int J Pharm 2009 Mar;369(1-2):64-71
Chitosan formulations improve the immunogenicity of a GnRH-I peptide-based vaccine
Sáenz, Leonardo, Neira-Carrillo, Andrónico, Paredes, Rodolfo, Cortés, Marlies, Bucarey, Sergio, Arias, José L, Veterinary Biotechnological Center (BIOVETEC), Chile.
Peptide vaccines using specific antigens with poor immunogenicity like GnRH-I are unable to develop an effective adaptive immune response and require the presence of adjuvants, essential to lymphocytic activation. Three chitosan formulations were evaluated for their ability as adjuvant of a poor immunogenic peptide vaccine against GnRH-I. Male Sprague-Dawley rats were immunized subcutaneously with recombinant His-GnRH-tandem-repeat peptide in high, low and phosphorylated high molecular weight chitosan solution at 0.5% (w/v). Freund's complete adjuvant was used as a positive control of immune response. Our results suggest that different chitosan formulations as adjuvant, with high or low viscosity degree allow inducing a high and persistent immune response against a poor immunogenic recombinant peptide. We found that the immune response was mediated by a increasing of IgG isotype 1, which were significantly greater than levels presented by the animals immunized with Freund's complete adjuvant. Nevertheless, chitosan with low molecular weight and highest acetylation degree was able to induce an immune response mediated by IgG isotype 2a. Additionally, high molecular weight phosphorylated chitosan, in which the phosphate groups were linked to N-acetyl-d-glucosamine unit, the immune response was reduced. All the immune responses obtained with chitosan as adjuvant were able to neutralize effectively the GnRH hormone proves by reducing of animal steroidogenesis and spermatogenesis demonstrating its capacity to improve immunogenicity in peptide vaccine.
PMID: 19041932 [found with GoPubMed]
71: J Neurosci Methods 2009 Mar;177(2):427-33
Significant delivery of tacrine into the brain using magnetic chitosan microparticles for treating Alzheimer's disease
Wilson, Barnabas, Samanta, Malay Kumar, Santhi, Kumaraswamy, Sampath Kumar, Kokilampal Perumal, Ramasamy, Muthu, Suresh, Bhojraj, Department of Pharmaceutics, J.S.S College of Pharmacy, Rocklands, Ootacamund, Tamil Nadu 643001, India.
Alzheimer's disease (AD) is a progressive degenerative disorder of the brain characterized by a slow, progressive decline in cognitive function and behavior. As the disease advances, persons have a tough time with daily tasks like using the phone, cooking, handling money or driving the car. AD affects 15 million people worldwide and it has been estimated that AD affects 4.5 million Americans. Tacrine is a reversible cholinesterase inhibitor used for treating mild to moderate AD. In the present study, an attempt was made to target the anti-Alzheimer's drug tacrine in the brain by using magnetic chitosan microparticles. The magnetic chitosan microparticles were prepared by emulsion cross-linking. The formulated microparticles were characterized for process yield, drug loading capacity, particle size, in vitro release, release kinetics and magnetite content. The particle size was analyzed by scanning electron microscope. The magnetite content of the microparticles was determined by atomic absorption spectroscopy. For animal testing, the microparticles were injected intravenously after keeping a suitable magnet at the target region. The concentrations of tacrine at the target and non-target organs were analyzed by HPLC. The magnetic chitosan microparticles significantly increased the concentration of tacrine in the brain in comparison with the free drug.
PMID: 19041670 [found with GoPubMed]
72: J Mater Sci Mater Med 2009 Apr;20(4):917-23
Novel electrohydrodynamic preparation of porous chitosan particles for drug delivery
Pancholi, Ketan, Ahras, Nassim, Stride, Eleanor, Edirisinghe, Mohan, Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK
Uniform spherical chitosan particles of size 10 mum diameter. In this study, by reducing surface tension of a high viscosity chitosan suspension, it was found that smaller diameter particles could be prepared. Chitosan solutions were electrosprayed in the stable cone-jet mode to systematically study the relationship between particle diameter, viscosity and surface tension. Increasing viscosity resulted in larger diameter particles with a broad size distribution, but decreasing surface tension had the opposite effect. Results show that a chitosan solution having a viscosity of ~80 mPa s can be used to prepare chitosan particles of diameter ~2.5 mum which on drying reduced to particles of 500 nm.
PMID: 19034624 [found with GoPubMed]
73: J Mater Sci Mater Med 2009 Apr;20(4):897-907
Multilayer coatings on biomaterials for control of MG-63 osteoblast adhesion and growth
Kirchhof, Kristin, Hristova, Kamelia, Krasteva, Natalia, Altankov, George, Groth, Thomas, Biomedical Materials Group, Department of Pharmaceutics and Biopharmaceutics, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Heinrich-Damerow-Strasse 4, 06120, Halle (Saale), Germany
Here, the layer-by-layer technique (LbL) was used to modify glass as model biomaterial with multilayers of chitosan and heparin to control the interaction with MG-63 osteoblast-like cells. Different pH values during multilayer formation were applied to control their physico-chemical properties. In the absence of adhesive proteins like plasma fibronectin (pFN) both plain layers were rather cytophobic. Hence, the preadsorption of pFN was used to enhance cell adhesion which was strongly dependent on pH. Comparing the adhesion promoting effects of pFN with an engineered repeat of the FN III fragment and collagen I which both lack a heparin binding domain it was found that multilayers could bind pFN specifically because only this protein was capable of promoting cell adhesion. Multilayer surfaces that inhibited MG-63 adhesion did also cause a decreased cell growth in the presence of serum, while an enhanced adhesion of cells was connected to an improved cell growth.
PMID: 19034623 [found with GoPubMed]
74: J Mater Sci Mater Med 2009 Apr;20(4):949-57
Preparation and HL-7702 cell functionality of titania/chitosan composite scaffolds
Zhao, Li, Chang, Jiang, Zhai, Wanyin, Shanghai Tissue Engineering Research and Development Center, Shanghai, China,
Titania/chitosan composite scaffolds were prepared through a freeze-drying technique. The composite scaffolds were highly porous with the average pore size of 120-300 mum, and the titania (TiO(2)) powders were uniformly dispersed on the surface of the pore walls. The compressive strength of the composite scaffolds was significantly improved compared to that of pure chitosan scaffolds. Composite scaffold with 0.3 of TiO(2)/chitosan weight ratio showed the maximum compressive strength of 159.7 +/- 21 kPa. Hepatic immortal cell line HL-7702 was used as seeding cells on the scaffolds, and after different culture periods, cell attachment and function was analyzed. HL-7702 cells attached on the pore walls of the scaffolds with the spheroid shape after 1 day of culture, but more cell aggregations formed within the TiO(2)/chitosan composite scaffolds as compared to pure chitosan scaffolds. Liver-specific functions, albumin secretion and urea synthesis were detected using a spectrometric method. The results showed that albumin secretion and urea synthesis rate of HL-7702 cells slightly decreased with the culture time, and there was no significant difference between composite scaffolds and pure chitosan scaffolds. In conclusion, the TiO(2)/chitosan composite scaffolds possessed an improved mechanical strength compared to pure chitosan scaffolds and supported the attachment and functional expression of hepatocyte, implying their potential application in liver tissue engineering.
PMID: 19034620 [found with GoPubMed]
75: J Mater Sci Mater Med 2009 Apr;20(4):943-8
Effects of alkylated-chitosan-DNA nanoparticles on the function of macrophages
Liu, L X, Song, C N, Song, L P, Zhang, H L, Dong, X, Leng, X G, Tianjin Key Laboratory of Biomedical materials, Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, China
Chitosan could form nanoparticles with DNA through electrostatic interaction, and hence protect the DNA from enzymatic degradation. Numerous studies have been working on modifying chitosan aiming at improving its transgenic efficacy. While the modification of chitosan with alkyl group has been shown to significantly improve the cell transfection efficiency, little is known about its impact on its biocompatibility. The current study was performed to investigate the impact of alkylated-chitosan/DNA nanoparticles on the function of the murine macrophage through observing its phagocytic activity and production of pro-inflammatory cytokines (IL-1beta, IL-6, IL-10, IL-12 and TNF-alpha). Our results demonstrated that the alkylated-chitosan/DNA nanoparticles at the concentration of 20 mug/ml DNA content had no significant impact on the production of cytokines and phagocytic activity of the macrophages as compared with the unmodified chitosan/DNA nanoparticles and negative control even after 24 h co-incubation. It suggested that the modification of chitosan with alkyl group should not have negative impact on the function of the macrophages.
PMID: 19020960 [found with GoPubMed]
76: Drug Dev Ind Pharm 2009 Apr;35(4):387-95
Formulation and characterization of nanoemulsion-based drug delivery system of risperidone
Kumar, Mukesh, Pathak, Kamla, Misra, Ambikanandan, Department of Pharmaceutics Rajiv Academy for Pharmacy, Mathura, Uttar Pradesh, India
Risperidone nanoemulsion (NE) and mucoadhesive NE formulations were successfully prepared by the spontaneous emulsification method (titration method) using Capmul MCM as the oily phase on the basis of solubility studies. The NE formulation containing 8% oil, 44% S(mix), 48% (wt/wt) aqueous phase that displayed an optical transparency of 99.82%, globule size of 15.5 +/- 2.12 nm, and polydispersity of 0.172 +/- 0.02 was selected for the incorporation of mucoadhesive components. The mucoadhesive formulation that contained 0.5% by weight of chitosan displayed highest diffusion coefficient that followed Higuchi model was free from nasal ciliotoxicity and stable for 3 months.
PMID: 19016058 [found with GoPubMed]
77: Int J Parasitol 2009 Apr;39(5):599-606
Mucosal delivery of native and recombinant protein vaccines against Trichostrongylus colubriformis
McClure, S J, CSIRO Livestock Industries, F.D. McMaster Laboratory, Locked Bag 1, Armidale DC, NSW 2350, Australia.
This paper describes a series of five pilot trials to test the feasibility of inducing a protective mucosal immune response against a non-blood-feeding intestinal nematode by delivery of antigens across the mucosal epithelium. A number of antigen preparations from Trichostrongylus colubriformis (viable larvae, larval homogenate and recombinant 17kDa excretory-secretory protein) were delivered to the luminal surface of the mucosal epithelium overlying jejunal or rectal lymphoid tissue in cellulose or chitosan formulations. Significant protection was induced following delivery of viable larvae, larval homogenate or recombinant protein to the epithelium overlying rectal Peyer's patches, and recombinant protein to the epithelium overlying jejunal Peyer's patches. Viable larvae were associated with a jejunal IgE/IgG1 response, while the 17kDa antigen was associated with a jejunal IgA response. The results demonstrate that delivery of Trichostrongylus native and recombinant antigens across the epithelium overlying rectal lymphoid patches can result in significant protective immunity even in the absence of adjuvant. They warrant the further investigation of appropriate mucosal delivery methods and adjuvants for induction of protective mucosal responses to stages and species of gastrointestinal helminths which do not ingest serum antibodies.
PMID: 18952092 [found with GoPubMed]
78: Bioprocess Biosyst Eng 2009 Apr;32(3):407-14
Study on immunosensor based on gold nanoparticles/chitosan and MnO2 nanoparticles composite membrane/Prussian blue modified gold electrode
Ling, Shujuan, Yuan, Ruo, Chai, Yaqin, Zhang, Tingting, Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest China University, 400715, Chongqing, People's Republic of China.
A novel and convenient immunosensor, based on the electrostatic adsorption characteristics between the positively charged MnO(2) nanoparticles (nano-MnO(2)) and chitosan (CS) composite membrane (nano-MnO(2) + CS) and the negatively charged prussian blue (PB), was prepared for the detection of carcinoembryonic antigen (CEA). Firstly, PB was electro-deposited on the surface of the gold electrode in the constant potential, and then nano-MnO(2) + CS was adsorbed onto PB-modified electrode surface. Subsequently, Gold nanoparticles (nano-Au) were electro-deposited on the nano-MnO(2) + CS-modified electrode to immobilize antibody CEA (anti-CEA). Finally, bovine serum albumin (BSA) was employed to block sites against nonspecific binding. In our study, cyclic voltammetry (CV) and scanning electron microscopy (SEM) were used to characterize the fabricated process of the immunosensor. The immunosensor put up a rapid response time, high sensitivity and stability. Under the optimized conditions, cyclic voltammograms(CVs) determination of CEA displayed a broader linear response to CEA in two ranges, from 0.25 to 8.0 ng/mL, and from 8.0 to 100 ng/mL, with a relative low-detection limit of 0.083 ng/mL at three times the background and noise. The originality of the preparation of the immunosensor lies in not only using the synergistic effect of two kinds of nanomaterials (nano-MnO(2) and nano-Au) to immobilize anti-CEA, but also using nano-MnO(2) + CS to furnish a media transferring electron path. What is more, the researched methodology was efficient and potentially attractive for clinical immunoassays.
PMID: 18923847 [found with GoPubMed]
79: Macromol Biosci 2009 Mar;9(3):268-78
Layer-by-layer buildup of poly(L-glutamic acid)/chitosan film for biologically active coating
Song, Zhijiang, Yin, Jingbo, Luo, Kun, Zheng, Yanzhen, Yang, Yan, Li, Qiong, Yan, Shifeng, Chen, Xuesi, Department of Polymer Materials, Shanghai University, 20 Chengzhong Street, Jiading, Shanghai 201800, China
A new biocompatible film based on chitosan and poly(L-glutamic acid) (CS/PGA), created by alternate deposition of CS and PGA, was investigated. FT-IR spectroscopy, UV-vis spectroscopy and QCM were used to analyze the build-up process. The growth of CS and PGA deposition are both exponential to the deposition steps at first. After about 9 (CS/PGA) depositions, the exponential to linear transition takes place. QCM measurements combined with UV-vis spectra revealed the increase in the multilayer film growth at different pH (4.4, 5.0 and 5.5). The build-up of the multilayer stops after a few depositions at pH = 6.5. A muscle myoblast cell (C2C12) assay showed that (CS/PGA)(n) multilayer films obviously promote C2C12 attachment and growth.
PMID: 18855946 [found with GoPubMed]
80: Macromol Biosci 2009 Mar;9(3):256-61
A facile route for regioselective conjugation of organo-soluble polymers onto chitosan
Cai, Guoqiang, Jiang, Hongliang, Tu, Kehua, Wang, Liqun, Zhu, Kangjie, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China
A facile route is described for the regioselective conjugation of organo-soluble polymers onto chitosan under very mild conditions, using SCC as intermediates. SCC could be prepared simply by mixing chitosan acidic aqueous solution with SDS. PEG or PCL were then grafted to SCC using the NHS/DCC coupling method. In addition, the polymers were found to be linked to chitosan through the hydroxyl groups of chitosan when stoichiometric SCC was used as a precursor. SDS could be removed simply by either precipitating the solution of SCC-graft-polymer in DMSO into Tris aqueous solution or dialyzing against Tris solution.
PMID: 18855945 [found with GoPubMed]
81: J Biomed Mater Res B Appl Biomater 2009 Apr;89(1):65-76
Poly(methyl methacrylate)-grafted chitosan microspheres for controlled release of ampicillin
Changerath, Radhakumary, Nair, Prabha D, Mathew, Suresh, Nair, C P Reghunadhan, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, India.
Microspheres of 50-500 microm diameter were prepared from a blend of chitosan and chitosan-g-PMMA. Environmental scanning electron microscopic and SEM studies revealed that the microspheres are porous and the pores extend toward the inner core of the microspheres. The microspheres were also found to be hemocompatible and cytocompatible. A model drug ampicillin was used to evaluate the drug loading capacity and the controlled release properties of the microspheres. The system maintained a sustained release of ampicillin for a period of more than 8 days. The drug-loaded chitosan/chitosan-g-PMMA microspheres exhibited higher antibacterial activity for both the gram positive (ATCC 25923 S. aureus) and gram negative (ATCC 25922 E. coli) bacteria than the drug-loaded virgin chitosan microspheres. The percentage release and bioactivity of ampicillin was found to be higher for the chitosan/chitosan-g-PMMA microspheres than the virgin chitosan microspheres. Potential applications such as oral drug delivery, wound dressings, tissue engineering, and so forth, are envisaged from these microspheres.
PMID: 18720417 [found with GoPubMed]
82: J Biomed Mater Res B Appl Biomater 2009 Apr;89(1):1-8
Nonwoven supported temperature-sensitive poly(N-isopropylacrylamide)/polyurethane copolymer hydrogel with antibacterial activity
Liu, Baohua, Hu, Jinlian, Meng, Qinghao, Institute of Textile and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China
This article is focused on the study of the antibacterial activity of temperature sensitive poly(N-isopropylacrylamide/polyurethane (PNIPAAm/PU) hydrogel grafted nonwoven fabrics with chitosan modification. A series of temperature sensitive hydrogel grafted nonwoven fabrics with different N-isopropylacrylamide/polyurethane (NIPAAm/PU) feeding ratios have been synthesized by using ammonium persulfate (APS) as initiator and N,N,N',N'-tetramethyl-ethane-1,2-diamine (TEMED) as accelerator. FTIR and XPS were used to examine the surface modification of chitosan. The phase transition temperature of hydrogel grafted nonwoven fabrics was about 32 degrees C by DSC. S. aureus and E. coli were used to evaluate the antibacterial efficiency of the fabric composite. After chitosan modification, the hydrogel grafted nonwoven cellulose fabrics demonstrates an antibacterial activity to S. aureus. and E. coli and the antibacterial efficiency is about 80%.
PMID: 18688797 [found with GoPubMed]
83: Am J Surg 2009 Apr;197(4):510-4
Laparoscopic repair of inferior vena caval injury using a chitosan-based hemostatic dressing
Xie, Hua, Teach, Jeffrey S, Burke, Allen P, Lucchesi, Lisa D, Wu, Ping-Cheng, Sarao, Rebecca C, Oregon Medical Laser Center, Providence St. Vincent Medical Center, 9205 SW Barnes Rd., Portland, OR 97225, USA
BACKGROUND: Vena caval injury is a rare but serious complication of laparoscopic surgery, and often requires conversion to an open procedure. The current study investigated whether a vena caval injury could be repaired with a chitosan dressing laparoscopically. METHODS: Six domestic swine were studied. A 4- to 5-mm circumferential incision was created in the inferior vena cava (IVC) and repaired laparoscopically with a chitosan dressing. Neither suture nor additional hemostatic techniques were used. The animals were killed at 30 minutes (n = 2) and at 1 week (n = 4) postoperatively for histopathological analysis. RESULTS: All IVC injuries were successfully repaired laparoscopically using a single chitosan dressing application without recurrent hemorrhaging. Mean operative time was 6 minutes and the blood loss was approximately 55 mL. There was no evidence of clot formation in the repaired vessels. Histology showed that the chitosan dressing had partially degenerated into small particles with moderate chronic inflammatory response 1 week after repair. CONCLUSION: Use of the chitosan-based hemostatic dressing is a simple and reliable technique to control serious hemorrhage from IVC injury during laparoscopic surgery.
PMID: 18585679 [found with GoPubMed]
84: J Biomed Mater Res A 2009 Mar;88(4):1058-68
Poly(ethylene imine)-g-chitosan using EX-810 as a spacer for nonviral gene delivery vectors
Lou, Yu-Lun, Peng, Yu-Shiang, Chen, Bing-Hung, Wang, Li-Fang, Leong, Kam W, Faculty of Medicinal and Applied Chemistry, School of Life Science, Kaohsiung Medical University, Kaohsiung, Taiwan 80708, Republic of China
Polyelectrolyte complexes have been widely studied as gene carriers in recent years. In this study, poly (ethylene imine) was grafted onto chitosan (PEI-g-CHI) as a nonviral gene carrier in order to improve the water solubility as well as the inherent transfection efficiency of chitosan. We present a novel method to conjugate the amine or hydroxyl groups of chitosan (CHI) and the amine groups of PEI through opening the epoxide rings of ethylene glycol diglycidyl ether (EX-810), which also brings the merits as mentioned in PEGylation chemistry. The degree of substitution of PEI onto CHI was characterized by NMR. The preliminarily cellular mechanisms, from the cellular entry to the endosomal release, were investigated by the correlations among the physicochemical properties of the DNA-polymer complexes, the buffering capacity of the modified polymer, the cytotoxicity, and the efficiency of the transgene expression. The cytotoxicity assayed by MTT shows that cell viability of PEI-g-CHI is higher than CHI especially noticeable at high concentrations using human kidney 293T cells. The efficiency of transgene expression and the amount of intracellular plasmid were monitored using green fluorescent protein (GFP) and visualized by fluorescence microscopy. The transfection efficiency of PEI-g-CHI/DNA polyplex is significantly better than CHI/DNA polyplex when using the weight ratios higher than 2.5.
PMID: 18404706 [found with GoPubMed]
85: J Biomed Mater Res A 2009 Mar;88(4):916-22
Rheological, microstructural, and in vitro characterization of hybrid chitosan-polylactic acid/hydroxyapatite composites
Araújo, A B A, Lemos, A F, Ferreira, J M F, Department of Ceramics and Glass Engineering, University of Aveiro, CICECO, Aveiro 3810-193, Portugal
In this work, hybrid chitosan/hydroxyapatite composites material were developed and characterized. The polymer matrix was first dissolved in polylactic acid, and then hydroxyapatite (HA) was added as filler material. The effects of the added amounts of a crosslinking agent (genipin) and of the concentrations of lactic acid, and of the presence of HA powder on the evolution of rheological properties were evaluated. A significant decrease of gelation time with increasing amounts of crosslinking agent was observed, the effect being even more pronounced in the presence of HA. The chitosan matrix and the composites with a chitosan/HA weight ratio of 2/5 were characterized using microstructural analysis and in vitro tests. The formation of large pore sizes in the chitosan-based scaffolds was favored by low concentrations of lactic acid and genipin. The in vitro tests in synthetic body fluid revealed an extensive formation of an apatitic layer onto the surface of the chitosan/HA composite scaffolds crosslinked with genipin.
PMID: 18384164 [found with GoPubMed]