A telomerase-enhanced homogeneous cascade amplification strategy designed for highly sensitive electrochemical detection of microRNA

Highly sensitive and specific detection of microRNAs (miRNAs) is vital for cancer early diagnosis. In this work, we have proposed a telomerase-enhanced homogeneous cascade amplification strategy for high-performance electrochemical detection of miRNA-21 (miR-21). The target miRNA is first transcribed and amplified into massive single-stranded output DNA fragments through the endonucleases-assisted primary amplification element. Then, the output DNAs can activate the telomerase-promoted entropy-driven DNA catalytic (EDC) circuit, which can significantly improve the amplification efficiency and release a mass of linker DNAs, achieving the secondary amplification of miR-21. Finally, the G-quadruplex loaded with plenty of electroactive substances can be captured on the electrode via the linker DNAs for highly sensitive detection of miR-21. The fabricated electrochemical biosensor exhibits a broad linear range from 1 aM to 1 nM with the detection limit of 0.36 aM. The exceptional sensitivity and specificity endow this biosensor with the ability to discriminate miR-21 from the interference miRNAs and proteins. In addition, the biosensor has been utilized to analyze miR-21 expression levels in human serum and diverse cell lysates, demonstrating its practicability in real sample analysis. Therefore, our designed electrochemical biosensor will have huge potential in analysis of cancer-related miRNA and early cancer diagnosis.