An interdigitated array microelectrodes (IDAMs) based impedance biosensor in combination with immunomagnetic separation was developed for rapid detection of avian influenza virus (AIV) subtype H5. Streptavidin-coated magnetic nanobeads were immobilized onto the biotin-labeled anti-H5 monoclonal antibodies to capture AIV H5 (e.g., H5N1) from sample solutions by the specific immunoreaction and form antibodies coated nanobeads-AIV complexes. Then these complexes were separated and concentrated by a magnetic field and the impedance magnitude was measured by IDAMs in a frequency range from 20 Hz to 1 MHz. The sensitivity and specificity of this biosensor were investigated. The biosensor could detect as few as 2-1 HA unit/50 μl of inactivated AIV H5N1. A linear relationship between the change of impedance magnitude and the logarithmic value of AIV H5N1 concentration was found in the range of 2-1 to 24 HA unit/50 μl. Non-target viruses, such as AIV subtype H1 and Newcastle disease virus, could not induce detectable signals. Equivalent circuit analysis showed that the medium resistance was responsible for the impedance change caused by the presence of AIV H5N1. The whole detection process from sampling to impedance measurement was able to be completed within 1.5 h.
Rapid detection of anti-H5 avian influenza virus antibody by fluorescence polarization immunoassay using a portable fluorescence polarization analyzer
