Chitosan-gallic acid conjugate with enhanced functional properties and synergistic wound healing effect

Chitosan-gallic acid conjugates were synthesized by carbodiimide method and characterized by physicochemical methods (UV-vis, FTIR, ¹H NMR, TGA). The FTIR and NMR assays confirmed that the chemical interaction occurred solely due to the formation of an amide bond. It was established that by varying the ratio of the components during synthesis it is possible to obtain conjugates with desired conjugation ratio, grafting efficiency and gallic acid content up to 8.09 ± 1.72 %, 70.51 ± 9.45 % and 79.9 ± 2.4 μg gallic acid/mg chitosan, respectively. Chitosan-gallic acid conjugate with a 5 % conjugation ratio demonstrated excellent antioxidant properties: the IC50 value for ABTS radical scavenging activity was 0.0073 ± 0.0001 mg/mL. In vitro tests showed that conjugation of chitosan with gallic acid provided the antiglycemic activity of the material and its good biocompatibility. A low level of cytotoxicity was recorded in the HaCaT cell line model (IC50 was 1030.4 μg/mL). The received eco-friendly chitosan-gallic acid conjugate effectively inhibited the growth of thermophilic spore-forming bacteria G. thermodenitrificans and the resistant to classical antibiotics strain A. palidus. The results of an in vivo comparative analysis showed that chitosan-gallic acid conjugate had excellent wound healing properties due to the synergism of the polysaccharide and the natural antioxidant.