Microfluidic exponential rolling circle amplification for sensitive microRNA detection directly from biological samples

Abstract There is an urgent need of sensitive bioanalytical platforms for sensitive and precise quantification of low-abundance microRNA targets in complex biological samples, including liquid biopsies of tumors. Many of current miRNA biosensing methods require laborious sample pretreatment procedures, including extraction of total RNA, which largely limits their biomedical and clinical applications. Herein we developed an integrated Microfluidic Exponential Rolling Circle Amplification (MERCA) platform for sensitive and specific detection of microRNAs directly in minimally processed samples. The MERCA system integrates and streamlines solid-phase miRNA isolation, miRNA-adapter ligation, and a dual-phase exponential rolling circle amplification (eRCA) assay in one analytical workflow. By marrying the advantages of microfluidics in leveraging bioassay performance with the high sensitivity of eRCA, our method affords a remarkably low limit of detection at 6 exosomes. Such analytical capability immediately addresses the unmet challenge in sample consumption, a key setback in clinical development of exosome-based liquid biopsies. Therefore, the MERCA would provide a useful platform to facilitate miRNA analysis in broad biological and clinical applications.