Fluorescence Resonance Energy Transfer(FRET) Between Quantum Dots Of Different Sizes For Glucose Sensing

The nanomaterials provide vast potentials for the development of biosensors. The analytical methods based on the fluorescence resonance energy transfer (FRET) between luminescence nanoparticals usually have high sensitivity and high selectivity and have been extensively used in biosensing systems. Fluorescence resonance energy transfer (FRET) between quantum dots of different sizes can cause fluorescence quench. The pre-binding of glucose on the donor or the acceptor occupies the binding sites and thus blocks resonance energy transfer between the two quantum dots, protecting the fluorescence from being quenched. A glucose biosensor is developed based on this binding site pre-blocking approach.In practice, thioglycolic acid (TGA) capped CdTe QDs are synthesized followed by modification with concanavalin A (Con A) and D-(+)-glucosamine hydrochloride (NH2-glu) via chemical bonding to form Gre QDs-Con A conjugates (green emission) and Red QDs-NH2-glu conjugates (red emission), and then the conjugates are characterized by UV-vis, CD and FT-IR.The glucose content is correlated with the fluorescence difference in the absence and in the presence of glucose. The inhibition of fluorescence quenching is then measured in the presence of glucose. A linear calibration graph is achieved within0.1～2.0mmol L-1, along with a detection limit of0.04mmol L-1and a RSD of2.4%(1.0mmol L-1). The sensing of glucose in serum and urine samples give rise to satisfactory recoveries from91%～105%. The FRET glucose sensing system also generates a fluorescence chromatic difference imaging, and the formative color display can clearly identify the glucose contents by visual detection with a distinguishing ability of ca.0.5mmol L-1.