Sensing gastric cancer exosomes with MoS₂-based SERS aptasensor

Exosomes have been widely used in early cancer diagnosis as promising cancer biomarkers due to their abundant tumor-specific molecular information. In this study, we developed a sensitive and straightforward surface-enhanced Raman scattering (SERS) aptasensor to detect exosomes based on gold nanostars-decorated molybdenum disulfide (MoS₂) nanocomposites (MoS₂-AuNSs). ROX-labeled aptamers (ROX-Apt) were assembled on MoS₂-AuNSs surface as recognition probes that specifically bind with transmembrane protein CD63 (a representative surface marker on exosomes). Thus obvious ROX Raman signals were obtained through the synergistic Raman enhancement effect of AuNSs and MoS₂ nanosheet. In presence of exosomes, ROX-Apt is preferentially tethered onto exosomes and released from the surface of nanocomposites, resulting in a decrease of the SERS signal. Expectedly, the as-fabricated SERS aptasensor was capable of detecting exosomes in a wide range from 55 to 5.5 × 10⁵ particles μL^-1 with a detection limit of 17 particles μL^-1. Moreover, the aptasensor exhibited accepted stability and potential clinical applicability.