Lighting-up RNA aptamer transcription synchronization amplification for ultrasensitive and label-free imaging of microRNA in single cells.

Sensitive imaging of intracellular microRNAs (miRNAs) in cells is of great significance in clinical diagnoses and disease treatments, and it remains a major challenge to achieve this goal. Herein, we report a new in situ rolling circle transcription synchronization machinery (RCTsm) of lighting-up RNA aptamer strategy for highly sensitive imaging and selective differentiation of miRNA expression levels in cells. Such a RCTsm approach utilizes a DNA promoter to recycle the target miRNAs to trigger the initiation of multiple RCT process for the yield of many lighting-up RNA aptamers. The malachite green dye further binds these aptamers to show significantly enhanced fluorescence for completely label-free detection of the target miRNAs with a high sensitivity in vitro with a low femtomolar detection limit. More importantly, sensitive detection of under-expressed miRNAs in cells and distinct differentiation of the miRNA expression variations in different cells can also be realized with this RCTsm approach in a washing-free format, making it a versatile and useful tool for imaging trace miRNAs in single cells with the great potential for early cancer diagnosis as well as biomedical research.