Conducting Polymer Nanowires Technique for High-Sensitivity miRNA Expression Analysis

Abstract

The Conducting Polymer Nanowires technique is an ultrasensitive, nonlabeling approach for direct and RT–PCR-free miRNA expression profiling. A nanogapped microelectrode-based biosensor array is fabricated for ultrasensitive electrical detection of miRNAs. After peptide nucleic acid (PNA) capture probes are immobilized in the nanogaps of a pair of interdigitated microelectrodes and hybridization is performed with their complementary target miRNA, the deposition of conducting polymer nanowires, polyaniline nanowires, is carried out by an enzymatically catalyzed method, where the electrostatic interaction between anionic phosphate groups in miRNA and cationic aniline molecules is exploited to guide the formation of the polyaniline nanowires onto the hybridized target miRNA. The conductance of the deposited polyaniline nanowires correlates directly with the amount of hybridized miRNA. Under optimized conditions, the target miRNA can be quantified in a range from 10 fM to 20 pM with a detection limit of 5 fM. The biosensor array can be applied to the direct detection of miRNA in total RNA extracted from cell lines or tissues. This technique was initially developed by Gao’s group from the Institute of Microelectronics, Singapore (J Am Chem Soc 129:5437–5443, 2007).