Cytocompatible hydrogels based on photocrosslinkable methacrylated O-carboxymethylchitosan with tunable charge: Synthesis and characterization

Ionic hydrogels are attractive for the protection, delivery and controlled release of charged biomacromolecules such as proteins, growth factors or DNA. We have prepared and characterized a series of photocrosslinked anionic hydrogels based on water soluble methacrylated (MA) O-carboxymethylchitosan (OCMCS) and polyethylene glycol (PEG) diacrylate. OCMCS samples with varying degree of substitution of carboxymethyl group ranging from 0.69 to 1.86 were prepared by reacting native chitosan with different amounts of monochloroacetic acid. The OCMCS products demonstrated differences in solubility, zeta potential (-52.7 to -12.8 mV) and thermal decomposition temperature (260 to 283°C). The OCMCS products were then reacted with glycidyl methacrylate to make ultra-violet (UV) crosslinkable OCMCS-MAs which were blended with PEG diacrylate, a photoinitiator and water and successfully photocrosslinked to create OCMCS-MA/PEG hydrogels. Water uptake of the hydrogels varied between 226% to 358% and the porous structures of the prepared OCMCS-MA/PEG hydrogels could be modulated by the degree of methacrylation. All the OCMCS-MA/PEG hydrogel substrates similarly supported attachment and proliferation of Smooth Muscle Cells (SMCs). The in vitro biodegradation of these hydrogels, in the presence of SMCs, could be controlled by the degree of methacrylation; weight loss after 9-week was (15±1) % and (19±2) % using OCMCS 4-MA (12.7% MA) and OCMCS 1-MA (4.6% MA), respectively. In addition, the hydrogel based on the most anionic OCMCS 1 showed higher adsorption of basic TGF-β₁ than similarly modified -agarose, -dextran, and -chondroitin sulfate hydrogels.