Bio-based biodegradable hydrogels prepared by crosslinking of microbial poly(γ-glutamic acid) with L-lysine in aqueous solution

Abstract

Bio-based biodegradable hydrogels were prepared by crosslinking microbial homo poly(amino acid), poly(γ-glutamic acid) (PGA), with L-lysine in a one-pot synthesis in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) at 25 °C. The crosslinking was carried out in aqueous solution and the yields of the gels prepared with DMT-MM were higher than those prepared with water-soluble carbodiimide. The water absorption of the PGA gels crosslinked with L-lysine ranged from 300 to 2100 g/g. The water absorption of the PGA gel was affected by the amount of crosslinker and DMT-MM, which had an effect on the crosslinking density of the PGA gel. It was confirmed in a hydrolysis test in a buffer of pH 9 at 37 °C that the obtained gel that was crosslinked with L-lysine by amide bonds was more resistant to hydrolysis than the gel crosslinked by ester bonds. biochemical oxygen demand-biodegradability of the PGA gel crosslinked with L-lysine reached 60% in activated sludge at 25 °C. Bio-based biodegradable hydrogels were prepared by crosslinking microbial poly(γ-glutamic acid) (PGA) with L-lysine in aqueous solution in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) in a one-pot synthesis. The crosslinking was carried out in aqueous solution in a high yield. The gels obtained in this study were readily biodegraded in the biochemical oxygen demand test. The PGA gel and the crosslinking method by DMT-MM in aqueous solution will be applicable to the development of functional bio-based materials. WSC, water-soluble carbodiimide.