Ultrasensitive and Visible Detection of Influenza A Virus Based on Enzymatic Properties of Layered Gold Nanoparticles

Considering the urgent demand for reliable and rapid detection of infectious respiratory viruses during unpredictable pandemics, an innovative ultrasensitive colorimetric immunoassay for influenza A (H1N1) virus detection is developed herein. The proposed approach leverages dual amplification by combining layer‐by‐layer interactions with the nanozyme effect of biotinylated gold nanoparticles (BGNPs). BGNPs assemble around the target via repeated incubation cycles under optimized conditions, resulting in a layered structure that increases optical density, producing a more intense signal proportional to the viral titer. Additionally, the nanozyme effect of the layered BGNPs induces oxidation of 3,3',5,5'‐tetramethylbenzidine, which further enhances the visible signal detectable by the naked eye. This synergetic nanoprobe‐based system demonstrates remarkable sensitivity, with a limit of detection of 10^1.29 EID₅₀ mL⁻¹, which is 2500‐fold higher than that of commercial rapid kits and conventional enzyme‐linked immunosorbent assays, within a rapid 55 min timeframe. Furthermore, the anti‐interference capability and portability of the developed system reinforce its practicality, making it a promising tool for field diagnostic tests that offers advanced, ultrasensitive, and early detection of respiratory viruses.