An integrated sample-to-answer SERS platform for multiplex phenotyping of extracellular vesicles

Tumor-derived extracellular vesicles (EVs) are emerging as a non-invasive liquid biopsy marker for cancer diagnosis and treatment monitoring. However, clinical detection techniques that can rapidly, sensitively, comprehensively profile the EV proteomic phenotypes are non-existent and thus desperately needed. Herein, an on-chip surface-enhanced Raman spectroscopy (SERS) platform was proposed to enable comprehensive characterization of tumor-derived EVs. The microfluidic chip with a serpentine microstructure was designed to enable automatic mixing and processing of samples without cumbersome manual operating processes. The multiplex SERS labeling strategy provided simultaneous characterization of three tumor-associated biomarkers on the EV surface. Our proposed method demonstrated a remarkably sensitive detection capability for lung cancer cell-derived EVs, with limits of detection of 4.46 × 10² to 5.46 × 10³ particles mL^‑1. Our platform also showcased the excellent capability in differentiating EVs derived from various cell lines. We envision that our platform could facilitate the understanding of EV biology and functions, as well as their clinical applications.