Biocompatible chitosan-based hydrogel with tunable mechanical and physical properties formed at body temperature.

Chemical crosslinking hydrogels provide irreversible matrices with reliable characteristics for wider medical applications. When hydrogels used for hosting bioactive substances, matrices have to be crosslinked at mild condition with high yield reaction and inactive to the biological molecules. In this work, chitosan was functionalized with active double bonds as a precursor to hydrogel that gels at body temperature. Free-radical crosslinking was conducted in the presence of maleic anhydride (MA) and potassium persulfate (KPS). The chemical structures of hydrogels were confirmed via spectral analysis. Mechanical and gelation characteristics of the hydrogels were tuned by using different molar ratios of MA and KPS. Pores size was controlled according to the crosslinking density in range of 313-866 µm that agrees proportionally with the swelling degree. Young's modulus values were tuned to span from 6 to 31 Pa with opposite relationship with the stress at break that varied from 6 to 17 Pa. Hydrogel release profiles were plotted representing varied releasing rates. Gels were obtained at 37 °C for 2 h using KPS (24-48 mM) and different concentration of MA (0.17, 0.35 and 0.5 M). The tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT), colorimetric, biological assay using skin fibroblast cells showed high biocompatibility of chitosan-based hydrogels.