The growing emphasis on personalized medicine significantly increases the need to analyze key molecular markers. In comparison to tissue biopsies, circulating biomarkers (liquid biopsies) can be conveniently and repeatedly obtained from biofluids with minimal complications. In particular, exosomes have recently emerged as a promising circulating biomarker. Exosomes are nanometer-sized membrane vesicles actively shed off by cells and possess unique advantages: they abound in biofluids, readily cross the blood brain barrier and harbor diverse molecular contents. A sensor platform capable of sensitive and rapid detection of exosomes would thus be an invaluable tool in translating their clinical potential. In this talk, I will describe various systems that we have developed for quantitative analyses of circulating cancer exosomes. By enabling rapid, sensitive and cost-effective detection of circulating biomarkers, these platforms could significantly expand the reach of preclinical and clinical research, in informing therapy selection, rationally directing trials, and improving sequential monitoring to achieve better clinical outcomes.