Characterization of protein release through glucose-sensitive hydrogel membranes

Glucose-sensitive phase-reversible hydrogels have been prepared based on the specific interaction between polymer-bound glucose and concanavalin A (Con-A). The main goal of this study was to characterize the release of model proteins (insulin and lysozyme) through the hydrogel membrane as the free glucose concentration in the environment was changed. The diffusion of the model proteins through the hydrogel membrane was examined using a diffusion cell. Porous poly(hydroxyethyl methacrylate) (PHEMA) membranes were used to sandwich the mixture of glucose-containing polymers and Con-A in between the donor and receptor chambers. The porous PHEMA membranes allowed diffusion of glucose, insulin and lysozyme, while preventing loss of glucose-containing polymers and Con-A in the sol state. The release rate of model proteins through the glucose-sensitive hydrogel membrane was dependent on the concentration of free glucose. The release rate of the proteins did not remain constant, however, due to the change in free glucose concentration resulting from diffusion of glucose from the receptor chamber to the donor chamber. This study demonstrated the possibility that the glucose-sensitive phase-reversible hydrogels can be used to regulate the insulin release as a function of the free glucose concentration in the environment. (C) 1997 Elsevier Science Limited.