Ultrasensitive Electrochemical Detection of MicroRNA\nBased on an Arched Probe Mediated Isothermal Exponential Amplification

Abstract

In this work, a simple and label-free\nelectrochemical biosensor\nis developed for microRNA (miRNA) detection on the basis of an arched\nprobe mediated isothermal exponential amplification reaction (EXPAR).\nThe arched probe assembled on the electrode surface consists of two\nstrands that are partially complementary to each other at both ends.\nThe target can hybridize with the complementary sequence of the arched\nstructure, leading to the cleavage of the probe. The strand fixed\non the surface of the electrode self-assembles, in the presence of\nhemin, to G-quadruplex unit, yielding electrochemical signals. The\nother strand liberated into the solution triggers the EXPAR to recycle\nand regenerate targets. This method exhibits ultrahigh sensitivity\ntoward miRNA with detection limits of 5.36 fM and a detection range\nof 3 orders of magnitude. The biosensor is capable of discriminating\na single-nucleotide difference between concomitant miRNA and performs\nwell in analyzing crude extractions from cancer cell lines.