A Compact Surface Plasmon Resonance Biosensor for Sensitive Detection of Exosomal Proteins for Cancer Diagnosis.

Exosomes are nanosized (50-150 nm) extracellular vesicles released by all types of cells in the body. They transport various biological molecules, such as DNAs, RNAs, proteins, and lipids from parent cells to recipient cells for intercellular communication. Exosomes, especially those from tumor cells, are actively involved in caner development, metastasis, and drug resistance. Recently, many studies have shown that exosomal proteins are promising biomarkers for cancer screening, early detection and prognosis. Among many detection techniques, surface plasmon resonance (SPR) is a highly sensitive, label-free, and real-time optical detection method. Commercial prism-based wavelength/angular-modulated SPR sensors afford high sensitivity and resolution, but their large footprint and high cost limit their adaptability for clinical settings. We have developed an intensity-modulated, compact SPR biosensor (25 cm × 10 cm × 25 cm) for the detection of exosomal proteins. We have demonstrated the potential application of the compact SPR biosensor in lung cancer diagnosis using exosomal epidermal growth factor receptor (EGFR) and programmed death-ligand 1 (PD-L1) as biomarkers. The compact SPR biosensor offers sensitive, simple, fast, user-friendly, and cost-effective detection of exosomal proteins, which may serve as an in vitro diagnostic test for cancer.