Enhancing chemical signal transformation in lateral flow assays using aptamer-architectured plasmonic nanozymes and para-phenylenediamine

The widespread adoption and commercialization of lateral flow assays (LFAs) for clinical diagnosis have been hindered by limitations in sensitivity, specificity, and the absence of quantitative data. To address these challenges, we developed aptamer-architectured gold nanoparticles as nanozymes that catalytically convert <i>para</i>-phenylenediamine (PPD) into Bandrowski's base (BB), thereby amplifying signal strength and sensitivity. The physiochemical properties of the nanozymes were characterized and their specific binding efficiency was demonstrated using experimental studies. The nanozymes and PPD-based LFA test strips were evaluated for the detection of the COVID-19 spike protein in both test and clinical samples. Notably, we achieved a significant visual detection limit of 168 pg mL^-1, with a signal quality enhancement of over 20-fold within 15-minute timeframe. Moreover, we rigorously tested 25 clinical samples to assess the transformative potential of the product, demonstrating a semi-quantitative analysis efficiency exceeding 90%. This performance outstripped commercially available LFA kits (87.5%). Notably, the colorimetric system exhibited an <i>R</i>² value of 0.9989, a critical factor for clinical testing and industry integration. The incorporation of nanozymes and PPD in LFAs offers a cost-effective solution with significantly improved sensitivity, enabling the detection of ultra-low concentrations (picograms) of spike protein. By addressing key challenges in LFA-based diagnostics, the current technique underscores the potential of this transformative biomedical sensor for industry integration. It also highlights its suitability for commercialization, positioning it as a universal platform for diagnostic applications.