Development and Characterization of Borate-based Hydrogels for Controlled Delivery of Insulin Using Glucose Sensing

Background: Diabetes mellitus is a disease that is characterized by the inability of the body to completely and continuously metabolize glucose, thus resulting in poor regulation of blood sugar levels in the body. Poor control is associated by the decrease in insulin secretion from the beta cells. Aim: The aim of this work was to develop glucose-responsive hydrogels for the controlled delivery of insulin using chitosan and polyvinyl alcohol cross linked with boric acid as matrices for insulin delivery. Slight changes in glucose concentration under physiological conditions was detected by such hydrogels. Materials and methods: Hydrogels were prepared by cross-linking chitosan and polyvinyl alcohol using boric acid after loading the polymer mixtures with insulin under controlled conditions. The formulated hydrogels were further subjected to various tests such as organoleptic test, pH, viscosity, in vitro insulin release, in vitro glucose-dependent insulin release and in vivo pharmacodynamic study using rats. Results: The results obtained showed that the gel products were odorless, slightly thick and sticky with a pH range between 4.1 to 4.8, viscosity values were within 145.5 mPa/s to 259.5 mPa/s. Variation in the in vitro insulin release was obtained due to the proportion of the polymers, cross-linker and insulin in the product. The insulin hydrogels were sensitive to glucose because they showed time-dependent increase in percentage insulin release with increasing glucose concentration in the medium. There was a significant higher reduction (P < 0.05) in blood glucose levels in the rat after subcutaneous injection of the borate-based insulin hydrogels when compared to either insulin alone or the negative control. Conclusion: Controlled delivery and improved efficacy of insulin can be achieved by formulation as hydrogels with glucose sensing capacity.