Graphene Quantum Dots and Enzyme-Coupled Biosensor for Highly Sensitive Determination of Hydrogen Peroxide and Glucose.

In this paper, a simple and specific graphene quantum dots (GQDs)-based fluorescent biosensor adopted for the determination of glucose based on the combination of the enzyme-coupled method and fluorescence quenching mechanism is demonstrated. Glucose was oxidized by the enzyme glucose oxidase (GOx), forming hydrogen peroxide (H 2 O 2 ) via the catalysis by horseradish peroxidase (HRP). H 2 O 2 was then employed to oxidize phenol to quinone, which led to effective quenching effect in the GQDs⁻GOx⁻HRP⁻phenol system. By optimizing the reaction conditions of the GQDs-enzyme system, a linear relationship between the concentration of glucose and the fluorescence intensity over a range of 0.2⁻10 μ mol/L was obtained. The limit of detection for glucose is 0.08 μ mol/L. The present biosensor for the determination of glucose showed satisfactory reproducibility and accuracy in human serum samples. Since the enzymes have high specificity and unique affinity to the certain substance, the enzyme-coupled system promises a sensitive way for further detection of those chemicals which could be oxidized by enzymes and generated H 2 O 2 or glucose. GQDs and other fluorescent materials coupled with several enzymes can be applied to extensive sensing field.