Complex Core-Satellite Nanoparticles with Trench-Structured Shells and Cavities for Highly Sensitive SERS-Based Lateral Flow Assays

Abstract Herein, we report a multistep synthetic strategy for the fabrication of complex and multifunctional core-satellite nanoparticles with trench-structured shells and cavities (CSTs). Starting from cuboctahedral Au nanoparticles, Pt, Ag, and Au were sequentially deposited in a site-selective fashion to direct metal growth at specific crystallographic facets. This approach yielded nanoparticles featuring trench-like nanogaps on the outer shell along with internal cavities, producing strong and reproducible single-particle surface-enhanced Raman scattering (SERS) signals via enhanced near-field focusing at the nanogaps. The application of the CSTs in a SERS-based lateral flow assay resulted in enhanced SERS signals, efficient analyte quantification, and improved mobility within the membrane; these favorable properties derived from (i) strong and reproducible light–matter interactions at the nanogaps, (ii) buoyancy effects provided by the internal cavities acting as air pockets, and (iii) minimized contact with the nitrocellulose membrane, owing to the protruding satellite structures on the nanoparticle surfaces. As a result, we achieved a detection limit of 10 pg/mL for influenza A hemagglutinin proteins. These findings demonstrate that cavity-integrated plasmonic nanostructures with multifunctional properties and enhanced performance hold significant promise for advanced point-of-care diagnostic applications.