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

Bio-based biodegradable hydrogels were prepared by crosslinking microbial homo poly(amino acid), poly(gamma-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 degrees 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 degrees 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 degrees C. Polymer Journal (2011) 43, 414-420; doi:10.1038/pj.2010.142; published online 19 January 2011