Publications in November and December 2013

The jear 2013 was an outstanding year for chitosan research, as a new record of publications has been achieved. Throughout the year, 1845 articles about chitosan and chitosan derivatives have been published, which mainly focused on animal and human studies, nanoparticles, pharmaceutical preparations and evaluation studies. The leading scientists in the field of chitosan were Rui L. Reis (University of Minho, Portugal), Shantikumar V. Nair (Amrita Vishwa Vidyapeetham University, India) and Andreas Bernkop-Schnürch (University of Innsbruck, Austria).

Table: List of scientific journals, which published the highest number of chitosan-related articles in the year 2013.

In November and December, 281 reports were released about chitosan. Two interesting reports from R.L. Reis and S.V. Nair are presented below. Both articles address bone tissue engineering and examine novel chitosan-modified formulations to improve biocompatibility and mechanical performance of bone scaffolds.

Carboxymethylation of ulvan and chitosan and their use as polymeric components of bone cements.

Barros A.A., Alves A., Nunes C., Coimbra M.A., Pires R.A., Reis R.L.; Acta Biomater.  Vol.: 9(11):9086-97. November 2013

In the present study, conventional glass-ionomer cements (GIC) should be improved by incorporating natural marine polysaccharides like ulvan or chitosan. GICs can chemically bind to dental hard tissue, bone and prosthetic materials. They consist of a powder and a liquid component. The GIC powder is made of acid-soluble, aluminum-free glass particles. The liquid consists of polyacrylic acid (PAA) and tartaric acid. GICs are obtained upon mixing both components. Since PAA is cytotoxic it should be replaced by chitosan and ulvan. Both polymers were carboxymethylated to increase their acidity.

Results:

• Degree of carboxymethylation of ulvan (98 %; CMU) and chitosan (87%; CMC)
• Carboxymethylation is evidenced by increasing molecular weight of ulvan and chitosan
• Inclusion of CMC:CMU into the cement enhanced mechanical performance
  
  • compressive strength: 52 MPa
  • pore size < 67 µm
  • water uptake: 230%
• non-cytotoxic
• Ca- and P-based moieties diffuse from the surface into the cement bulk

Conclusion: The mechanical performance of conventional GICs is clearly improved by using carboxymethylated polysaccharides instead of PAA. The novel formulation is non-cytotoxic and displays a higher absorption capacity for Ca- and P-based moieties, which diffuse into the cement bulk. Thus, bone cements, supplemented with carboxymethylated chitosan and ulvan, could also be suitable for in vivo studies.

Biocompatible conducting chitosan/polypyrrole-alginate composite scaffold for bone tissue engineering.

Sajesh K.M., Jayakumar R., Nair S.V., Chennazhi K.P.; International journal of biological macro-molecules.  Vol.: 62:465-71. November 2013

In this study, a polypyrrole-modified scaffold for bone tissue engineering has been developed. Polypyrrole (PPy) is an organic polymer and a good electrical conductor. The conductive properties of PPy might improve bone regeneration, as bone tissue responds to external electric stimuli.

PPy was further blended with the biopolymers chitosan and alginate. Chitosan generates porous matrix structures and could enhance mechanical stability of the scaffold. Alginate was added to improve adhesion and penetration of cell into the matrix.

Results for chitosan/PPy-Alg scaffold:

• Stable scaffold formation: 1 wt% PPy–Alg in 3 wt% chitosan
• Increased surface conductivity
• Decreased porosity
• Swelling ability increased over 28 day
• Reduced degradation compared to chitosan scaffolds
• Improved biocompatibility and cell attachment
• Increased mineral deposition on the scaffold

Conclusion: Chitosan/PPy-Alg scaffolds possess advantageous physico-chemical properties, which promote attachment and distribution of MG-63 osteosarcoma cells. After 14 day of incubation a uniform apatite layer was deposited on the scaffold surface. The increased biomineralization and bioactivity of the scaffold might facilitate its integration into the site of implantation and could accelerate tissue regeneration.