A portable system for isothermal amplification and detection of exosomal microRNAs

Exosomal microRNAs (miRNAs) play a key role in cell-cell communication to regulate gene expression in target cells and have great potential as biomarkers for disease diagnosis. This paper reports an on-chip exosomal miRNA amplification and detection system for rapid analysis of exosomal miRNAs. The compact system consists of two connected flow cells for processing exosomes and detecting miRNAs, respectively. The miRNAs extracted from exosomes were quantitatively measured using the on-chip exponential amplification reaction (EXPAR) assay. The sensor chip was designed to store multiple oligonucleotide templates for the EXPAR, mix sample and reagent, and simultaneously analyze multiple exosomal miRNAs of interest. To facilitate the miRNA analysis, a portable detection instrument was built on an IoT platform using a low-cost microcontroller to execute the EXPAR assay, collect fluorescent images, and analyze amplification curves. Here, we studied the miRNA profiles carried by exosomes derived from three different phenotypes of tissue macrophages. The affordable instrument, rapid assay, multiplexed analysis, as well as disposable sensor chip, would boost the development of point-of-care liquid biopsy tests using exosomal miRNAs.