Dual-peak long period fiber grating coated with graphene oxide for label-free and specific assays of H5N1 virus.

Avian influenza is an acute infectious disease caused by the avian influenza virus (AIV), which has caused enormous economic losses and posed considerable threats to public health. This study aimed to demonstrate an immunosensor based on dispersion turning point long-period fiber grating (DTP-LPFG) integrated with graphene oxide (GO) for the specific detection of a type of AIV H5N1 virus. LPFG was designed to work at DTP, whose dual-peak spacing was very high sensitive to a refractive index. Anti-H5N1 monoclonal antibodies were covalently bonded with the GO film on the fiber surface, thus constructing an immunosensor for the label-free and specific detection of the H5N1 virus. The proposed method was capable of the reliable detection of H5N1 virus with the limit of detection as low as ~1.05 ng/ml within the large range of 1 ng/mL to 25 µg/mL. More importantly, immunoassays of the whole H5N1 virus in clinical samples further confirmed that the GO-integrated DTP-LPFG immunosensor showed very high specificity to the H5N1 virus and demonstrated great potential for clinical use.