Scheme 1.

Schematic illustration of strategies to select the H5N1-specific VHHs and to apply the detection functions. The H5N1-specific VHH genes were selected from an immunized dromedary. Nanobodies identified different epitopes were used to couple with biotin or HRP for detecting. Biotinylated Nanobody was directionally captured by streptavidin in microtiter plate. The attachment of H5N1 virus was followed by the attachment of biotinylated Nanobody onto streptavidin. Another Nanobody conjugated with HRP was used as a detector. The measurements were taken at absorbance of 450 nm.