Exploiting the Anti-Aggregation of Gold Nanostars for Rapid Detection of Hand, Foot, and Mouth Disease Causing Enterovirus 71 Using Surface-Enhanced Raman Spectroscopy

Enterovirus 71 (EV71) is a major public health threat that requires rapid point-of-care detection. Here, we developed a surface-enhanced Raman spectroscopy (SERS)-based scheme that utilized protein-induced aggregation of colloidal gold nanostars (AuNS) to rapidly detect EV71 without the need for fabricating a solid substrate, Raman labels or complicated sample handling. We used AuNS (hydrodynamic diameter, D_H of 105.12 ± 1.13 nm) conjugated to recombinant scavenger receptor class B, member 2 (SCARB2) protein with known affinity to EV71. In the absence of EV71, AuNS-SCARB2 aggregated in biological media and produced four enhanced Raman peaks at 390, 510, 670, and 910 cm^-1. In the presence of EV71, the three peaks at 510, 670, and 910 cm^-1 disappeared, while the peak at 390 cm^-1 diminished in intensity as the virus bound to AuNS-SCARB2 and prevented them from aggregation. These three peaks (510, 670, and 910 cm^-1) were potential markers for specific detection of EV71 as their disappearance was not observable with a different dengue virus (DENV) as our control. Furthermore, the Raman measurements from colloidal SERS were more sensitive in probing the aggregation of AuNS-SCARB2 for detecting the presence of EV71 in protein-rich samples compared to UV-vis spectrum measurements. With this facile "anti-aggregation" approach, we were able to detect EV71 in protein-rich biological medium within 15 min with reasonable sensitivity of 10⁷ pfu/mL and minimal sample preparation, making this translatable for point-of-care applications.