Extracellular vesicles, including exosomes, are nanoscale vesicles that carry molecular information of parental cells. They are being pursued as biomarkers of cancers that are difficult to detect or serially follow. Here researchers from Massachusetts General Hospital present a compact sensor technology for rapid, on-site exosome screening. The sensor is based on an integrated magnetic-electrochemical assay: exosomes are immunomagnetically captured from patient samples, and profiled through electrochemical reaction. By combining magnetic enrichment and enzymatic amplification, the approach enables i) highly sensitive, cell-specific exosome detection, and ii) sensor miniaturization and scale-up for high throughput measurements. As a proof-of-concept, the researchers implemented a portable, eight-channel device, and applied it to screen extracellular vesicles in plasma samples from ovarian cancer patients. The sensor allowed for the profiling of multiple protein markers simultaneously within an hour, outperforming conventional methods in assay sensitivity and speed.
Integrated magnetic-electrochemical exosome (iMEX) platform.
(A) Sensor schematic. The sensor can simultaneously measure signals from eight electrodes. Small cylindrical magnets are located below the electrodes to concentrate immunomagnetically captured exosomes. (B) Circuit diagram. The sensor system has eight potentiostats, an 8-to-1 multiplexer, an analog-to-digital converter (ADC), a digitalto-analog converter (DAC), and a micro-controller unit (MCU). Each potentiostat has three electrodes: reference (R), counter (C), and working (W). (C) A packaged device. The device has a small form factor (9 × 6 × 2 cm3). (D) Schematic of iMEX assay. Exosomes are captured on magnetic beads directly in plasma and labeled with HRP enzyme for electrochemical detection. The magnetic beads were coated with antibodies against CD63, an enriched surface marker in exosomes. The working (W) and the counter (C) electrodes were made of gold (Au), and the reference electrode (R) was made of silver/silver chloride (Ag/AgCl). Eight channels are simultaneously monitored for high-throughput analysis. HRP, horseradish peroxidase; TMB, 3,3’,5,5’-tetramethylbenzidine.