The selective detection of galactose based on boronic acid functionalized fluorescent carbon dots

Abstract

In this paper, we presented a galactose biosensing system based on boronic acid functionalized carbon dots (APBA-Cdots) as the fluorescent probe. Carbon dots were directly synthesized by chemical oxidation with strong acids, and then they were linked to m-aminophenylboronic acid to form the APBA-Cdot fluorescent probe. Boronic acid groups on APBA-Cdot surfaces could covalently react with cis-diol units in galactose to form five- or six-membered cyclic esters. Compared with the close isomeric cousins of galactose such as fructose and glucose, galactose molecules possess more cis-conformational diol units in both pyranose and furanose forms, and as a result, they could selectively lead to the assembly and fluorescence quenching of APBA-Cdots. The fluorescence intensity linearly decreased with increase of galactose concentration in the range of 0 to 500 μM, and a detection limit as low as 6.2 μM was achieved. The proposed sensing system has been successfully used for the assay of galactose in human urine.