A boronic acid based glucose assay based on the suppression of the inner filter effect of gold nanoparticles on the orange fluorescence of graphene oxide quantum dots

The authors describe a non-enzymatioc glucose assay that has three features: (a) The use of a boronic acid as the recognition element; (b) the aggregation of gold nanoparticles (AuNPs), and (c) the use of graphene oxide quantum dots (GOQD) whose fluorescence matches the absorption of the AuNPs and thereby results in an inner filter effect (IFE). The GOQD display an orange colored fluorescence that is filtered off by the AuNPs due to an IFE. In the presence of 3-aminobenzeneboronic acid, glucose is bound to form a cationic species that causes the aggregation of AuNPs to form large assemblies. This is accompanied by a color change from red to blue, and the IFE no longer does occur so that the orange fluorescence of the GOQD pops up again. These findings were used to design an assay witha linear response in the 2.5 to 75 mu mol L-1 glucose concentration range, with a detection limit of 0.65 mu mol L-1. The method was applied to the determination of glucose in spiked diluted serum and gave satisfactory results.