Surface-Enhanced Raman Scattering-Based Lateral Flow Assay Strips Using Highly Symmetric Gold Nanostars

The applications for lateral flow assay (LFA) strips in point-of-care testing have been significantly constrained by their insufficient sensitivity and reproducibility. To address these inherent issues, we developed surface-enhanced Raman scattering (SERS)-based LFA strips, in which highly symmetric Au nanostars (Sym-AuNS) were employed as the sensing element. Due to the uniform tip-sharp nanostructure and a certain number of branches on the surface of Sym-AuNS, it generates a uniform hotspot distribution, thus producing a strong and stable SERS signal. As a proof of concept, human IgG was chosen as the target to evaluate the performance of the proposed SERS-LFA strips. In human serum spiked samples, the limit of detection for human IgG detection was achieved as low as 38 ng/mL, which exhibited a 2-fold, 3-fold, and 13-fold sensitivity improvement compared with the SERS-LFA strips using conventional gold nanostars (AuNS), enzyme-linked immunosorbent assays (ELISA), and the conventional LFA strips, respectively. Furthermore, the SERS-LFA strips demonstrated high assay reproducibility, with a relative standard deviation of 7.75% for five repeated tests, much lower than those of SERS-LFA strips using AuNS (24.6%), ELISA (12.42%), and conventional LFA strips (31.32%). These results demonstrate that the construction of sensitive and reproducible SERS-LFA strips was obtained, and this platform using Sym-AuNS as SERS nanoparticles paves the way for a promising approach in immunoassay technology.