Quantum dots-based glucose sensing through fluorescence quenching by bienzyme-catalyzed chromogenic substrate oxidation

In this paper, a novel and sensitive assembled quantum dots (QDs)-bienzyme (glucose oxidase (GOD) and horseradish peroxidise (HRP)) hybrid system was designed for the direct determination of glucose. Using o-phenylenediamine (OPD) or 3,3'-diaminobenzidine (DAB) as substrate of HRP, whose corresponding oxidation product (oxDPD or oxDAB) effectively quenched the fluorescence of thioglycollic acid (TGA)capped CdS QDs. The fluorescence quenching of the CdS QDs was proportional to the concentration of glucose and a detection limit of 0.1 mu mol/L (or 20 nmol/L) was achieved under the optimum conditions when using OPD (or DAB) as the substrate of HRP. The sensing system was also applied to the determination of glucose in human serum with satisfactory results without any need for complicated sample pretreatments. Other sugars such as fructose, sucrose and lactose hardly interfered on the detection of glucose. The developed method manifested several advantages of high sensitivity, short analysis time, low cost and easy of operation. Moreover, it had great potential in the direct detection of real samples in clinical diagnostics of various diseases. (C) 2014 Elsevier B.V. All rights reserved.