Enzymatic hydrolysis of copoly(N-hydroxypropyl-L-glutamine/L-leucine) hydrogels in vitro

Two component random copolypeptide hydrogels consisting of N-hydroxyalkyl L-glutamine and L-leucine were prepared by carrying out aminolysis reactions with 3-amino-1-propanol(P) together with cross-linking reactors with 1,8-octamethylenediamine (OMDA) on hydrogels of the starting copolymers consisting of gamma-methyl-L-glutamate(M) and L-leucine(L). The relation between their bulk structure and properties was investigated with regard to the swelling ration in water, aqueous vapor permeability, tensile properties, and enzymatic degradation behavior in a pseudoextracellular fluid (PECF). The tensile property of the hydrogels was highly dependent on the swelling ratio in PECF, and on the hydrophobicity of the side chains, whose behavior was typical of an elastomer. It was shown that a common relation was obtained between the rate of water vapor permeabilities and the swelling ratio of hydrogels in PECF regardless of the difference of the nature of side chains. Biodegradation of the hydrogels in vitro by bromelain indicated that the degradation took place in bulk rather than on surface, and that the rate of degradation was also highly dependent on the swelling ratio of samples as well as on the hydrophobicity of the side chains of samples.