Characterization of glucose dependent gel-sol phase transition of the polymeric glucose-concanavalin a hydrogel system

Abstract

Purpose. The main goal of this study was to synthesize and characterize hydrogels which undergo reversible gel-sol phase transformation in response to changes in glucose concentration in the surrounding environment. Methods. The glucose-sensitive hydrogels were made by mixing the appropriate concentrations of acrylamide-allyl glucose copolymer and concanavalin A (Con A). To examine their phase reversibility, hydrogels in dialysis membranes were cycled between glucose-free and glucose-containing buffers. The binding affinity of allyl glucose (AG) to Con A was examined by using an equilibrium dialysis technique. Results. The synthesized hydrogels underwent phase transition to sol in the presence of free glucose in the environment. The concentration of external free glucose (C(f)) had to be at least 4 times that of polymer-bound glucose (C(p)) to induce phase transition from gel to sol. The binding affinity study showed that binding of AG to Con A was four times stronger than that of free glucose. When C(p) in the gel was 0.42 mg/ml or higher, C(f) had to be much higher than 4 times C(p) to induce phase transition. Conclusions. The synthesized hydrogels underwent phase transition in the presence of free glucose in the environment, but the phase transition was not linearly dependent on the concentration of free glucose. This non-linear dependence was explained by the increased binding affinity of AG over native glucose to Con A, and the cooperative interactions between polymer-bound glucose and Con A.