Toward clinical translation of eLFIA: analytical tuning and serum application for PSA detection

In this follow-up to our previously developed electrochemical lateral flow immunoassay (eLFIA) for prostate-specific antigen (PSA) detection, we investigate the impact of gold nanoparticle (AuNP) optical properties on assay performance and demonstrate a serum proof-of-concept as a step toward clinical translation. While the original system employed spherical AuNPs with a surface plasmon resonance (SPR) peak at 525 nm, here we synthesized and tested three additional variants with SPR peaks at 529, 521 (spherical), and 618 nm (non-spherical). These AuNPs were compared under identical conditions in both conventional LFIA and hybrid eLFIA formats. Calibration curves in buffer were obtained for each variant, highlighting how nanoparticle morphology and plasmonic behavior affect sensitivity, visual detection limits, and reproducibility. Among the tested AuNPs, the 529 nm particles demonstrated the most balanced performance, achieving a LOD of 0.08 ng/mL and an RSD of 3 % in the eLFIA setup. This variant was then applied in PSA-spiked female serum samples, where the system maintained stable analytical behavior across a 0.01-100 ng/mL range, reaching a LOD of 0.06 ng/mL. These results confirm both the robustness of the eLFIA strategy and the importance of nanoparticle tuning for the fine-tuning of lateral flow-based biosensing platforms toward clinical translation.