Comprehensive studies to improve ultrasensitive detection of HIV-1 p24 antigen†

Early and accurate detection of HIV-1 p24 antigen is crucial for timely diagnosis and treatment, particularly in resource-limited settings where traditional methods often lack the necessary sensitivity for early-stage detection or is expensive. Here, we developed a layer-by-layer signal amplification platform employing fluorescent silica nanoparticles functionalized via bioorthogonal TCO/TZ chemistry. We evaluated nanoparticles of different sizes (25, 50, and 100 nm) and two dye-doped nanoparticle formulations to optimize signal intensity, detection limits, and nonspecific binding. The 25 nm RITC-doped nanoparticles demonstrated superior performance, achieving an ultra-low detection limit of 7 fg mL⁻¹ with a broad linear range up to 1 ng mL⁻¹. Compared to FITC-doped nanoparticles, RITC-doped nanoparticles provided enhanced brightness and signal strength. Further optimization revealed that using 50 μg of 25 nm nanoparticles yielded the best sensitivity while minimizing nonspecific binding. This nanoparticle-based assay significantly outperformed commercial ELISA kits, offering a broad dynamic range and improved sensitivity. Our platform presents a highly sensitive and adaptable approach for HIV-1 p24 antigen detection, with broad potential applications in point-of-care diagnostics and detection of other low-abundance biomarkers, ultimately enhancing early disease detection and treatment accessibility.