Rapid exosomes concentration and in situ detection of exosomal microRNA on agarose-based microfluidic chip

Exosomes, together with their accompanying proteins and nucleic acids have been increasingly recognized as biomarkers for non-invasive tumor diagnostic and prognostic. However, rapid and efficient detection of exosomes remains challenging, due to their small size (30−150 nm), and low concentration. Thus, to guarantee, especially when cancer screening requires detection limits lower than exosome concentrations, it not only needs to isolate and purify exosomes, but it needs to preconcentrate them as well. Here, a low-cost, rapid, and portable agarose-based microfluidic chip for exosome concentration and in situ exosomal microRNA detection was developed, termed isExoCD (in situ exosome concentration and detection). The target exosomes loaded at the entrance will be automatically enriched at the closed end of the microchannel by leveraging the capillary effect and the strong water permeability of the agarose gel. To detect the exosomal microRNA, we integrated the catalyzed hairpin assembly (CHA) based strategy into the isExoCD, allowing high sensitive detection of exosomes with a limit of detection (LOD) of ∼103. Using our method, we can successfully distinguish cancer cell-derived exosomes from other exosomes that obtained other cell types. Thus, our platform paves a new avenue to early cancer detection, liquid biopsy, and point-of-care diagnosis.