Circular dichroism glucose biosensor based on chiral cadmium sulfide quantum dots

A new approach to the fabrication of a glucose biosensor based on circular dichroism spectroscopy (CD) using cadmium sulfide quantum dots (CdS QDs) as a sensor probe was successfully developed and showed excellent selectivity and sensitivity. The chiral CdS QDs (DPA/Cys-CdS QDs) can be simply prepared by mixing cysteamine-capped CdS QDs (Cys-CdS QDs; achiral QDs) with D-penicillamine (DPA). The as-prepared DPA/Cys-CdS QDs are active in circular dichroism spectroscopy due to the chirality of DPA. The principle of glucose detection is based on the destruction of chiral QDs by the H2O2 generated in situ from the enzymatic reaction of glucose oxidase (GOx) and glucose in the presence of dissolved oxygen. In the presence of the generated H2O2, the DPA/ Cys-CdS QDs were etched, and the CD signal decreased as a linear function of the glucose concentration. This sensor provided excellent selectivity for the detection of glucose over other possible interfering compounds because of the combination of the enzymatic reaction and the circular dichroism measurement. Parameters that might affect the detection sensitivity of the sensor were investigated and optimized. Under the optimized conditions, the linear working concentration range was found to be 50-250 mu M with a limit of detection (LOD) of 31 mu M.