Glucose Recognition by a Supramolecular Complex of Boronic Acid Fluorophore with Boronic Acid-Modified Cyclodextrin in Water

A boronic acid fluorophore (C1-APB)/boronic acid-modified gamma-cyclodextrin (3-PB-gamma-CyD) complex as a supramolecular sensor has been designed for selective glucose recognition in water. The fluorescent response behavior of the C1-APB/3-PB-gamma-CyD complex under various pH conditions revealed that a C1-APB/3-PB-gamma-CyD complex solution containing glucose showed a large increase in the fluorescence intensity under alkaline pH conditions. In contrast, only small increases in the fluorescence intensity were noted for fructose and without sugar solutions. The observed response selectivity for the C1-APB/3-PB-gamma-CyD complex was on the order of glucose >> galactose, mannose > fructose. The evidence on a large value of the inclusion constant (K-L.CyD = 6.5 x 10(3) M-1), a marked broadening of the H-1 NMR spectra, and an enhancement of induced circular dichloism (ICD) intensity for the C1-APB/3-PB-gamma-CyD complex by glucose binding supported the multi-point interaction of the C1-APB/3-PB-gamma-CyD complex with glucose. These results demonstrated that the C1-APB/3-PB-gamma-CyD complex functioned as an efficient supramolecular sensor for selective glucose recognition in water.