Primer ExchangeReaction with Cascade RNA Transcriptionfor Highly Specific Detection of Exosomal miRNA and Liver Cancer Diagnosis

Exosomal microRNAs (miRNAs) serve as dependable and noninvasive biomarkers for early cancer diagnosis. However, the accurate and feasible detection of exosomal miRNAs is often hindered by their low abundance and the requirement of specialized equipment for miRNA detection. In this study, we present a novel approach, termed <b><u>p</u></b>rimer <b><u>e</u></b>xchange <b><u>r</u></b>eaction-based <b><u>f</u></b>luorescence <b><u>e</u></b>mission with <b><u>c</u></b>ascade RNA aptamers <b><u>t</u></b>ranscription (PERFECT) for the highly sensitive detection of exosomal miRNA. The design of this method involves the selective interaction of a DNA probe with the target miRNA, leading to its activation. Once activated, isothermal signal amplification and RNA aptamer transcription are initiated, resulting in an amplified fluorescent signal within 90 min. This method achieves a detection limit of 2.2 fM at 37 °C and 2.7 fM at room temperature (25 °C). We used the PERFECT technology to analyze miR-21 expression levels in cell extracts, cell-derived exosomes, and human plasma-derived exosomes, achieving a diagnostic accuracy of 93.6% in distinguishing hepatocellular carcinoma (HCC) patients. Overall, this study highlights its broad range of detection temperature, simplicity of the detection process, and strong potential for clinical application, rendering it a promising tool for early cancer diagnosis.