Highly sensitive visual detection of Avian Influenza A (H7N9) virus based on the enzyme-induced metallization

Development of convenient but sensitive method for influenza detection is highly important in immediate and effective clinical treatment. In this study, an ultrasensitive colorimetric approach combining the advantages of the convenience of the enzyme-induced metallization and the high specificity of enzyme-linked immunosorbent assay for the detection of influenza virus A (H7N9 as model) has been developed. Two rounds of amplification are utilized to enhance the detection sensitivity. The amplification of enzymatic reaction combines with the specific optical properties of gold nanoparticles causing the enhancing of the optical signal immensely. In addition, the increased surface area and the magnetic enrichment effect also enable the magnetic bead (MB) to catch a large number of alkaline phosphatase (ALP) and detection antibody (Ab 2 ), thus very small amounts of the virus can be easily detected. Compared with conventional method, this approach exhibits outstanding sensitivity for ALP detection, 0.2   U/L of ALP can be distinguished with a spectrometer and 2   U/L with the naked eye. And as low as 25   pg/mL of H7N9 can be detected by the naked eye. This approach shows an extensive horizon for bioassays and is available in clinical diagnosis with the advances of simplification, effectiveness, low cost and sensitive readout.