Swelling properties of phenylboronic acid containing hydrogels.

Abstract

Glucose-sensitive hydrogels have been of interest for developing a glucose sensor for management of diabetes. In this thesis, swelling behavior and mechanical properties of glucose-sensitive hydrogels containing phenylboronic acid (PBA) were investigated. Swelling studies were conducted at different pH values and at different sugar concentrations. At pH values lower than the pKa of PBA, the hydrogel swells with increased glucose concentration due to progressive charging of the polymer chains. At pH values higher than the pKa of PBA, extra reversible crosslinks form in the hydrogel due to complexation of PBA sidechains on separate polymer chains with glucose molecules, which causes hydrogel shrinking to occur. By incorporating a tertiary amine, reversible crosslinking by glucose occursat physiological pH,7.4. Modeling of pH and fructose effects on the swelling of MPBA-co-AAm hydrogels was also researched. Extended Flory-Rehner-Donnan-Langmuir (FRDL) models were applied to our data, and good fits were obtained. Auxiliary experiments to validate the models were carried out. Compression tests provided a value for crosslink density that was not consistent with that determined by the model fits to swelling data.. Osmotic deswelling experiments using poly(N-vinyl-pyrrolidone) (PVP) were also carried out to challenge the FRDL models. This work provides both experimental and theoretical input to the development of novel glucose sensors based on PBA-based hydrogel swelling.