Development and evaluation of a paramagnetic nanoparticle based immunochromatographic strip for specific detection of 2009 H1N1 influenza virus.

Influenza A/H1N1 virus spreads worldwide and has been a threat to human health and the poultry industry. Although H1N1 lateral-flow immunoassay strips are available for the detection of 2009/A/H1N1 antigens, the specificity and sensitivity of these strips are limited. Because of the monodispersity, the strong magnetic signal and the stable brown color of superparamagnetic nanoparticles, which were employed in this study as label instead of commonly used colloidal gold particles. Two different monoclonal anti-HA (hemagglutinin) and anti-HA-tag mAbs were paired for conjugating with paramagnetic beads and immobilizing on the surface of nitrocellulose (NC) membrane as capture antibody respectively. After optimizing the experimental condition, we generated a superparamagnetic bead-based immunochromatographic strip. The strip could detect HA antigen from H1N1 influenza A virus sample sensitively, its detection limit was 100 pg/mL. It had low cross reactivity with H3N2 influenza A virus and did not detect influenza B virus. It had no false positive detection in all of the tested control samples. With the help of magnetic assay reader (MAR), the magnetic intensity on test lines could be recorded and quantified proportionally with the amount of antigens captured. Those properties were indeed superior to the colloidal gold-based strips. More importantly, the strip was affordable and easy to use. Conceivably, superparamagnetic bead-based immunochromatographic strip should be a valuable point-of-care test for the rapid and specific detection of influenza A virus.