Effects of thermoresponsive coacervation on the hydrolytic degradation amphipathic poly(γ-glutamate)s

Hydrolytic properties of thermoresponsive biopolymers with amphiphilic structures, gamma-PGA-P, were investigated. Hydrolysis was monitored in terms of molecular weight changes using GPC and spectroscopic measurements. The hydrolytic degradation of gamma-PGA-P was controlled by a change in the degree of propyl group conversion, reaction temperature, and/or reaction pH. The degradation was classified as the rapid elimination of propyl side and the moderate cleavage of peptide linkages in the back-bone. Furthermore, hydrophobic environments established by the thermoresponsive coacervation of gamma-PGA-P60 solutions inhibited hydrolytic degradation reactions. Inversely, hydrolytic degradations increased coacervation temperatures. Kinetic studies of hydrolytic reactions suggest that the degradation rate of gamma-PGA-P60 solutions can be controlled by their thermoresponsivity. The hydrolysis reported here represents the first degradation rate controlled by thermoresponsive coacervation.