Gold Nanorods Enable Rapid and Label-Free SARS-CoV‑2 Detection through LAMP Assay.

Nanoscale noble metals exhibit unique optical properties due to localized surface plasmon resonance (LSPR), which occurs within the visible range of the electromagnetic spectrum. This property has facilitated their extensive use as transducers in biosensor platforms. Among these, gold nanoparticlesparticularly gold nanorods (AuNRs)have gained significant attention owing to their superior plasmonic characteristics. Their anisotropic shape generates two distinct plasmonic bands, enhancing light absorption, scattering, and sensitivity to environmental changes. Here, we present a biosensing approach for detecting the SARS-CoV-2 genetic material amplified via loop-mediated isothermal amplification (LAMP), using AuNRs as transducers to generate dynamic light scattering signals captured by a custom-built depolarized dynamic light scattering (DDLS) apparatus. This strategy reduces the conventional LAMP reaction time to 20 min and allows direct detection of target amplicons, representing a substantial improvement over traditional indirect detection methods that are often prone to false results. Clear discrimination between negative and positive samples was achieved using both control reactions and clinical specimens, demonstrating the potential of integrating AuNR-based transducers with LAMP and DDLS into an efficient, rapid, and highly sensitive diagnostic platform.