The inhibition of fluorescence resonance energy transfer between quantum dots for glucose assay

Fluorescence resonance energy transfer (FRET) between two quantum dots of different sizes causes fluorescence quenching. Hereby a binding site pre-blocking approach is proposed to avoid this effect. Pre-binding of glucose on the donor occupies the binding sites and thus blocks resonance energy transfer between the two quantum dots, protecting the fluorescence from being quenched. A glucose assay is developed based on this approach. The glucose content is correlated with the fluorescence difference in the absence and in the presence of glucose. In practice, Green QDs–Con A conjugates are used as donors and Red QDs–NH2-glu conjugates as acceptors to form FRET system. The inhibition of fluorescence quenching is then measured in the presence of glucose. A linear calibration graph is achieved within 0.1–2.0 mmol L−1, along with a detection limit of 0.03 mmol L−1 and a RSD of 2.1% (1.0 mmol L−1). 91–105% of glucose in serum and urine samples is recovered. It is worth mentioning that the present glucose assay approach also generates a fluorescence chromatic difference imaging, and the color display clearly identifies the glucose contents by visual detection with a distinguishing ability of ca. 0.5 mmol L−1. The present approach can potentially be used for the clinical determination of glucose in biological samples which can be further developed into a glucose sensor.

► FRET between two quantum dots causes fluorescence quenching. A binding site pre-blocking assay approach for avoiding this phenomenon is proposed. ► Pre-binding of glucose on the donor occupies the binding sites and blocks resonance energy transfer between quantum dots, protecting the fluorescence from being quenched. ► A glucose assay approach is developed based on this approach. ► This system generates a fluorescence chromatic difference image, which can identify glucose contents by visual detection with a distinguishing ability of ca. 0.5 mM.