Catalytic Self-Assembly of Quantum-Dot-Based MicroRNA Nanosensor Directed by Toehold-Mediated Strand Displacement Cascade

Semiconductor quantum dots (QDs) are highly attractive nanomaterials with wide biomedical applications owing to their unique photophysical properties. However, the adaptation of the nonenzymatic QD nanosensor assembly to sense low-abundance targets remains a great challenge. Herein, taking advantage of the dynamic DNA nanotechnology and single-molecule fluorescence detection, we demonstrate the catalytic self-assembly of a QD-based microRNA nanosensor directed by toehold-mediated strand displacement cascade for the simple and sensitive detection of microRNA at femtomolar concentration without the requirement of any enzymes. Moreover, this QD nanosensor is capable of detecting circulating microRNA in clinical serum samples and even imaging microRNA in living cells. This work may extend the use of an enzyme-free QD nanosensor assembly for low-abundance biomarker detection and offer a novel platform for fundamental biomedical research and clinical applications.