Quantification of multiple microRNAs by microchip electrophoresis assisted by strand displacement amplification

MicroRNAs (miRNAs) are increasingly recognized as potential biomarkers for the early diagnosis of cancer. However, the concurrent detection of multiple miRNAs in biological samples presents a significant challenge due to their high homogeneity and low abundance. This study introduced a novel approach combining strand displacement amplification (SDA) with microchip electrophoresis (MCE) for the simultaneous quantitation of trace levels of three miRNAs associated with cancer: miRNA-21, miRNA-145, and miRNA-221. Specifically designed probes were utilized to selectively capture the target miRNAs, thereby initiating the SDA process in a single solution without cross-interference. Under optimized conditions, the SDA-MCE method achieved the limit of detection (LOD) as low as 0.02 fM (S/N = 3) and the limit of quantitation (LOQ) as low as 0.1 fM across a broad linear range spanning from 0.1 fM to 1 pM. The SDA reaction was completed in approximately 1.5 h, and all target products were separated within 135 s through MCE. Application of this method for the simultaneous detection of these three miRNAs in human lung cancer cell samples yielded satisfactory results. Featuring high sensitivity, rapid analysis, minimal reagent consumption, and straightforward operation, the proposed MCE-SDA strategy holds considerable promise for multi-miRNAs detection applications.