Detection of small extracellular vesicles as biomarkers in tear enabled by shear-horizontal surface acoustic wave...

Small extracellular vesicles (sEVs) are promising disease biomarkers present in various biofluids. However, their quantification requires a tedious, complex, and time-consuming isolation process, which limits access to these valuable biomarkers for disease monitoring. In this study, we introduce a shear-horizontal surface acoustic wave (SH-SAW) biosensor for the isolation-free, sensitive, and real-time detection of sEVs in human tears. The SH-SAW biosensor detects a wide range of cell-secreted sEVs from cancerous and non-cancerous cell lines. Specificity is confirmed using four control proteins, demonstrating high selectivity. The device achieves a detection limit of 1.26 × 10⁸ particles/mL with a turnaround time of 80 min and a sample volume of 5 μL. It exhibits a 7.9-fold higher sensitivity and a 3.5-fold faster assay time compared to the gold-standard enzyme-linked immunosorbent assay. Furthermore, the selective identification of Glypican-1 in sEVs derived from pancreatic ductal adenocarcinoma cells validates device's potential for marker-based detection of specific cancer-derived sEVs. The biosensor successfully detects sEVs based on their two surface markers, CD63 and CD9, in four unprocessed tear samples from healthy individuals. Liquid cell transmission electron microscopy and nanoparticle tracking analysis further characterize the abundance of tear-derived sEVs. These results demonstrate that the SH-SAW biosensor provides a rapid, non-invasive, and real-time approach for detecting intact sEVs in human tears, offering significant potential for clinical applications. In the future, we aim to integrate the SH-SAW biosensor into a microfluidic chip to develop a fully integrated point-of-care platform for the detection of tear exosomes.