Gold nanoparticle-based lateral flow immunoassays (AuNP LFIA) are widely used for point-of-care (POC) diagnostics, but their sensitivity limitations hinder the detection of trace biomarkers. This study investigates surface chemistry to enhance the sensitivity of AuNP LFIA. By modifying surface ligands, a surface chemistry strategy involving weakly ionized AuNPs is developed, achieving an ultrahigh sensitivity of ~100-fold compared to conventional methods. The approach modulates nanointerfacial bindings to promote antibody adsorption and higher activity of adsorbed antibodies. This method eliminates complex nanosynthesis, auxiliary devices, or additional reagents while maintaining simplicity, reproducibility, and reliability. The weakly ionized AuNPs represent a versatile approach for sensitizing POC sensors, demonstrating superior sensitivity in detecting various biomarkers and virus mutants.Gold nanoparticle-based lateral flow immunoassays (AuNP LFIA) are widely used for point-of-care (POC) diagnostics, but their sensitivity limitations hinder the detection of trace biomarkers. This study investigates surface chemistry to enhance the sensitivity of AuNP LFIA. By modifying surface ligands, a surface chemistry strategy involving weakly ionized AuNPs is developed, achieving an ultrahigh sensitivity of ~100-fold compared to conventional methods. The approach modulates nanointerfacial bindings to promote antibody adsorption and higher activity of adsorbed antibodies. This method eliminates complex nanosynthesis, auxiliary devices, or additional reagents while maintaining simplicity, reproducibility, and reliability. The weakly ionized AuNPs represent a versatile approach for sensitizing POC sensors, demonstrating superior sensitivity in detecting various biomarkers and virus mutants.