Visualization of the Specific Interaction of Sulfonylurea-Incorporated Polymer with Insulinoma Cell Line MIN 6

Abstract

A derivative of sulfonylurea (SU) that mimicks glibenclamide in chemical structure was synthesized and incorporated into a water-soluble polymeric backbone as a biospecific polymer for stimulating insulin secretion. In this study, a backbone polymer fluorescence-labeled with rodamine-B isothiocyanate was found to be strongly adsorbed onto MIN6 cells, probably due to its specific interaction mediated by SU receptors on the cell membrane. The intensity of fluorescence on the cells was significantly increased by increasing the incubation time and polymer concentration. To verify the specific interaction between the SU (K⁺ channel closer)-incorporated copolymer and MIN 6 cells, the cells were pretreated with diazoxide, an agonist of the ATP-sensitive K⁺ channel (K⁺ channel opener), before adding the polymer to the cell culture medium. This treatment suppressed the interaction between SU and MIN 6 cells. A confocal laser microscopic study confirmed this effect. The results of this study provide evidence that SU-incorporated copolymer stimulates insulin secretion through the specific interactions of SU moieties in the polymer with MIN 6 cells.