Jiaoling Huang, Zhixun Xie,* Liji Xie, Zhiqin Xie, Sisi Luo, Xianwen Deng, Li Huang,Tingting Zeng, Yanfang Zhang, Sheng Wang and Minxiu Zhang

Abstract  Immunochromatography test strips that use metal particles constructed from Au, Fe3O4, and Au/Fe3O4 nanoparticles were developed for the rapid detection of avian influenza virus subtype H7 (AIV H7). The principle of this immunochromatography test strip was based on a sandwich immunoreaction in which AIV H7 antigens bind specifically to their corresponding antibodies on a nitrocellulose membrane. An antibody–metal (Au, Fe3O4 or Au/Fe3O4) nanoparticle conjugate was used as a label and coated onto a glass fiber membrane, which was used as a conjugate pad. To create a test and a control zone, an anti-H7 polyclonal antibody and an anti-IgG antibody were immobilized onto the nitrocellulose membrane, respectively. Positive samples displayed brown/red lines in the test and control zones of the nitrocellulose membrane, whereas negative samples resulted in a brown/red line only in the control zone. The limit of detection (LOD) of the Au/Fe3O4 nanoparticle-based immunochromatography test strips was found to be 103.5 EID50 (EID50: 50% Egg Infective Dose), which could be visually detected by the naked eye within 15 min. In addition, 200 clinical samples were tested using the Au/Fe3O4 nanoparticle-based immunochromatography test strip to estimate its performance, and seven were positive for AIV H7. In summary, the Au/Fe3O4 nanoparticle-based immunochromatography test strip offers a simple and cost-effective tool for the rapid detection of AIV H7.