A diboronic acid fluorescent sensor for selective recognition of d-ribose via fluorescence quenching

Boronic acids have been widely developed as fluorescent sensors for recognition of carbohydrates, especially D-glucose, ions, catechol compounds and so on. However, few D-ribose selective boronic acid sensors have been reported, and their poor water solubility brings a lot of inconvenience to their applications. Herein we report a novel water-soluble sensor, (4-(4-((3-boronobenzamido) propyl) carbamoyl)quinolin- 2-yl) boronic acid (sensor 6). The fluorescence of sensor 6 decreased by 50% when combined with 0.0146 M of D-ribose, while it increased when combined with D-mannose, D-galactose, D-fructose, D-glucosamine, sialic acid, D-sorbitol and D-arabinose, and fluorescence change was not obvious after binding to D-glucose. Therefore, this sensor may serve as a fluorescence quenching sensor for D-ribose. By processing the fluorescence binding data using the Benesi-Hildebrand equation, we found that the reciprocal of fluorescence intensity quenching showed a good linear relationship with the reciprocal of D-ribose concentration, indicating that the binding ratio of sensor 6 to D-ribose is 1 : 1. In pH titration experiments, the quenched fluorescence was most pronounced at pH 7.4, indicating that the sensor may serve to recognize D-ribose at physiological pH 7.4. Subsequently, D-ribose can also cause sensor fluorescence quenching in rabbit plasma and the rabbit plasma fluorescence interference can be excluded. These studies indicate that sensor 6 is a promising tool for detecting D-ribose.