Novel Magnetic Fe3O4@CdSe Composite Quantum Dot-Based Electrochemiluminescence Detection of Thrombin by a Multiple DNA Cycle Amplification Strategy

A novel small magnetic electrochemiluminescent Fe3O4@CdSe composite quantum dot (QD) was facilely prepared and successfully applied to sensitive electrochemiluminescence (ECL) detection of thrombin by a multiple DNA cycle amplification strategy for the first time. The as-prepared composite QDs feature intense ECL, excellent magnetism, strong fluorescence, and favorable biocompatibility, which offers promising advantages for ECL biosensing. ECL of the composite QDs was efficiently quenched by gold nanoparticles (NPs). Taking advantages of the unique and attractive ECL and magnetic characteristics of the composite QDs, a novel DNA-amplified detection method based on ECL quenching was thus developed for a sensitive assay of thrombin. More importantly, the DNA devices by cleavage reaction were cycled multiple rounds, which greatly amplified the ECL signal and much improve the detection sensitivity. This flexible biosensing system exhibits not only high sensitivity and specificity but also excellent performance in real human serum assay. The present work opens a promising approach to develop magnetic quantum dot-based amplified ECL bioassays, which has wider potential application with more favorable analytical performances than other ECL reagent-based systems. Moreover, the composite QDs are suitable for long-term fluorescent cellular imaging, which also highlights the promising directions for further development of QD-based in vitro and in vivo imaging materials.