Rapid antigen test based on gold nanoparticles embedded with highly sensitive surface-enhanced Raman scattering probes for detecting antigen concentrations below the visual detection limit.

The COVID-19 pandemic has proven that people expect medically high accuracy, sensitivity, and rapid testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection. These needs have led to developing various testing methods and platforms to replace reverse transcription polymerase chain reaction (RT-PCR), the golden standard in diagnostics. Rapid antigen testing (RAT) using gold nanoparticles (AuNPs) has been developed to compensate for the shortcomings of RT-PCR. However, RAT still shows less sensitive results because it is judged by sight only. Here, we applied gold-nanobridged nanogap particles (Au-NNPs) to conventional lateral flow assay (LFA) technology for high-sensitivity testing of samples containing antigen concentration below the visual detection limit through surface-enhanced Raman scattering (SERS) signal detection. By using Raman dye-embedded Au-NNPs showing susceptible Raman signals instead of simply using gold nanoparticles, the sensitivity of the conventional RAT has been significantly increased. Therefore, it was possible to increase the sensitivity of RAT combined with simplicity and rapidity of the approach. These developments will lead to characterization applications of bio-nanotechnology and nanoparticles for health and social issues.