DNA Framework-Mediated Electrochemical Biosensing Platform for Amplification-Free MicroRNA Analysis.

MicroRNAs (miRNAs) have been explored as biomarkers for early diagnosis of diseases like cancers. However, it remains challenging to detect low-level miRNAs in the total RNA from real samples in a facile approach. In this work, we report a two-phase miRNA biosensing strategy based on a modular framework nucleic acid (FNA) platform, which combines the high efficiency of homogeneous reaction and the convenience of heterogeneous biosensing. In the first phase, free DNA probes bind target miRNAs in a homogeneous solution, forming a DNA-RNA complex with high base stacking energy. Then, at the second phase, the universal FNA interface on the electrode selectively mediated the transition of the complex from the solution onto the interface for electrochemical signal generating and transduction. By applying this method, we detected as few as 1 aM of miR-141, a cancer marker miRNA, without the need for nucleic acid amplification. The dynamic range spans 10 orders of magnitude. We demonstrate multiplex miRNA detection and discrimination of highly homologous miRNAs with mismatches as few as a single base. We also show that this system can detect miR-141 in only 50 ng of total RNA samples from real cells, which allows discrimination of prostate cancer cells with normal cells. We envision this platform may satisfy the need for facile and high-throughput screening of early cancer markers.