Rapid and sensitive lateral flow immunoassay for influenza antigen using fluorescently-doped silica nanoparticles

We report on a lateral flow immunoassay (LFIA) for influenza A antigen using fluorescently-doped silica nanoparticles as reporters. The method is taking advantage of the high brightness and photostability of silica nanoparticles (doped with the dye Cy5) and the simplicity and rapidity of LFIA. The nucleoprotein of influenza A virion (one of its most abundant structural proteins) was used as a model to demonstrate a performance of the LFIA. Under optimized conditions and by using a portable strip reader, the fluorescence-based LFIA is capable of detecting a recombinant nucleoprotein as low as 250 ng · mL-1 using a sample volume of 100 μL, within 30 min, and without interference by other proteins. The successful detection of the nucleoprotein in infected allantoic fluid demonstrated the functionality of the method. By comparison with a commercial influenza A test based on gold nanoparticles as reporters, the system provides an 8-fold better sensitivity.