Exosomes derived from
cancer cells/tissues have great potential for early
cancer diagnostic use, but their clinical potential has not been fully explored because of a lack of cost-effective multiplex approaches capable of effectively isolating and identifying specific exosome populations and analyzing their content
biomarkers. This study was aimed at overcoming the technical barrier by developing a paper-based isotachophoresis (
ITP) technology capable of 1) rapid isolation and identification of exosomes from both malignant and healthy cells and 2) multiplex detection of selected exosomal
protein biomarkers of the target exosomes. The technology integrates the focusing power of
ITP and the multiplex capability of paper-based lateral flow to achieve on-board separation of target exosomes from large extracellular vesicles, followed by electrokinetic enrichment of the targets, leading to an ultrasensitive platform for comprehensive exosome analysis. For a proof of concept, the technology platform was tested with human serum samples spiked with exosomes derived from healthy human serum and a
prostate cancer cell line. Under an anionic
ITP condition, the device showed superior performance in simultaneous detection of the
cancer exosomes and normal exosomes at concentrations as low as 1.2-2.0 × 106 exosomes/mL, which is equivalent to 2.0-3.0 × 10-18 M. The observed limit of detection was more than 30-fold better than that of enhanced ELISA. More importantly, in a subsequent step the technology was capable of the rapid profiling of a selected
protein biomarker panel associated with the target exosomes. The results represent a significant step toward translating the detection of
tumor-derived exosomes to a medical use at a point of care.