Ultrasensitive detection of circulating exosomes with a 3D-nanopatterned microfluidic chip.

Abstract

The performance of current microfluidic methods for exosome detection is constrained by boundary conditions and by fundamental limits to microscale mass transfer and to interfacial exosome binding. Here, we show that a microfluidic chip designed with self-assembled 3D herringbone nanopatterns can detect low levels of tumour-associated exosomes in plasma (10 exosomes μL−1, or approximately 200 vesicles per 20-μL spiked sample) that would otherwise be undetectable by standard microfluidic systems for biosensing. The nanopatterns promote microscale mass transfer, increase surface area and probe density to enhance the efficiency and speed of exosome binding, and permit drainage of the boundary fluid to reduce near-surface hydrodynamic resistance, thus promoting particle–surface interactions for exosome binding. We used the device for the detection, in 2-μL plasma samples from 20 ovarian cancer patients and from 10 age-matched controls, of exosome subpopulations expressing CD24, EpCAM, and FRalpha proteins, and suggest exosomal FRalpha as a potential biomarker for the early detection and progression monitoring of ovarian cancer. The nanolithography-free nanopatterned device should facilitate the use of liquid biopsies for cancer diagnosis.