The use of microgels is one way of biomimetically mimicking tissue. In the presented study, chitosan microgels will be functionalized with Zn (II) and Cu (II) ions to improve their physicochemical properties.

Preparation and properties of bimetallic spherical chitosan microgels

Lončarević, A.; Ostojić, K.; Urlić, I.; Rogina, A. Preparation and Properties of Bimetallic Chitosan Spherical Microgels. Polymers 2023, 15, 1480. https://doi.org/10.3390/polym15061480

Small-scale tissue regeneration can be enhanced by implanted biomaterials, e.g. hydrogels, which have characteristics of an extracellular matrix (ECM). Hydrogels provide a good platform for tissue regeneration due to their high surface-to-volume ratio and high porosity. In addition, a high water content allows for a microclimate that can initiate tissue formation. 3D crosslinked hydrogels enable the encapsulation of biomolecules for further functionalization for tissue engineering and drug delivery. Physical crosslinking with weak bonds is advantageous here. This allows biomolecules to be transported without losing their structural integrity.

An alternative to hydrogels functionalized with biomolecules can be hydrogels based on natural polymers functionalized with metal ions. So-called therapeutic ions can enhance specific biological functions, such as angiogenesis, osteogenesis or antibacterial effects.

Chitosan-based hydrogels are particularly interesting for this purpose, as they are well suited for the complexation of metal ions due to the functional groups of the chitosan. They also form a structure similar to ECM, which makes them favored for applications in the field of tissue engineering.

Tissues in general are formed from small heterogeneous building blocks that form a hierarchy from a microscopic to macroscopic level. For this reason, microscale hydrogels, e.g. microgels, are considered a method to produce biomimetic tissues. The adhesion, agglomeration and integration with the surrounding tissue can be improved by additional surface modifications with special biomolecules.

In the presented study, chitosan-based microgels will be functionalized with Zn (II) and Cu (II) ions. The aim is to produce bimetallic CTS complex microgels with a narrow size distribution and a defined surface morphology. The influence of ion content and ion type on size, morphology, swelling behavior, biodegradability and biological properties of the microgel is investigated. In addition, the influence of the degree of deacetlyation (DDA) of the chitosan on the microgels was investigated. Chitosans from Heppe Medical Chitosan GmbH with a DDA of 83.2 % and a viscosity of 293 mPas (Chitosan 85/200) and with a DDA of 96.9 % and a viscosity of 324 mPas (Chitosan 95/200) were used.

RESULTS

• Successful production of bimetallic, highly spherical microgels with a narrow size distribution using the electrohydrodynamic atomization process
• Size distribution for bimetallic chitosan particles from 60-110 μm
• FTIR indicated physical interaction of chitosan and the metal ions → Formation of metal ion-chitosan complexes
• Swelling capacity of the bimetallic chitosan microgels decreases with increasing DDA and Cu (II) content → stronger complex formation of Zn (II) ions
• Good stability of the microgels during a four-week enzymatic degradation
• Bimetallic systems with a small amount of Cu (II) ions showed good cytocompatibility for both chitosans used

Conclusions: The physicochemical properties of chitosan-based microgels can be improved by the formation of physical interactions between the amino and hydroxyl groups of chitosan and therapeutic metal ions. The results generated in the presented study show the potential of bimetallic chitosan microgels as microscopic matrices for tissue engineering applications.

Your are interested in buying chitosan? Here is your direct link to both chitosans: Chitosan 85/200 and Chitosan 95/200

Link to article: https://www.mdpi.com/2073-4360/15/6/1480