(484e) Nanoplasmonic Quantification of Pathogen-Derived Extracellular Vesicles in Plasma Microsamples

Cancer-derived extracellular vesicles (EVs) are of increasing interest as a resource of diagnostic biomarkers. However, most EV assays are limited by large-sample needs, and are time-consuming, low-throughput and costly. Here, we describe a rapid, ultrasensitive and inexpensive nanoplasmon-enhanced scattering (nPES) assay that directly quantifies tumour-derived EVs from as little as 1 µL of unprocessed plasma. The assay uses the binding of antibody-conjugated gold nanospheres and nanorods to EVs captured by EV-specific antibodies on the surface of a sensor chip to produce a local plasmon effect that enhances tumour-derived EV detection sensitivity and specificity. We identified a pancreatic-cancer EV biomarker, ephrin type-A receptor 2 (EphA2), and demonstrate that the nPES assay for EphA2 EVs distinguishes pancreatic-cancer patients from pancreatitis patients and healthy subjects. EphA2 EVs were also informative in staging tumour progression and in detecting early responses to neoadjuvant therapy, with better performance than that of a conventional enzyme-linked immunosorbent assay. The nPES assay can be easily refined for clinical use, and be readily adapted for the diagnosis and monitoring of conditions with disease-specific EV biomarkers.