A telomerase-enhanced homogeneous cascade amplification strategy designed for highly sensitive electrochemical...

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.