Drug release kinetics from monolayer films of glucose-sensitive microgel

To study the drug release behaviors of glucose-sensitive poly(N-isopropylacrylamide-co-3-acrylamidophenylboronic acid) (P(NIPAM-PBA)) microgels, P(NIPAM-PBA) microgel monolayers were prepared by the modification of poly(N-isopropylacrylamide-co-acrylic acid) microgel monolayers with 3-aminophenylboronic acid under EDC catalysis. Alizarin Red S (ARS) and FITC-labeled insulin (FITC-insulin) were loaded in the monolayers respectively. Their release kinetics under various conditions were measured. For both drugs, at low temperature, the drug release can be described as passive diffusion of the drugs. At temperature higher than the phase transition temperature, however, the drugs are released via a “squeeze-out” mechanism. Glucose-regulated release for both drugs was observed. At all temperatures glucose enhances the release of ARS because it competes with ARS for binding with PBA groups. For FITC-insulin, glucose enhances its release at 4 °C, but retards at 37 °C. These results will guide the design of self-regulated insulin release systems based on P(NIPAM-PBA) microgels.