A PCR-free point-of-care capacitive immunoassay for influenza A virus

This article describes a highly sensitive and specific capacitive immunosensor for rapid, low cost and simple-to-use detection of virus particles from clinical swab samples. An inhomogeneous AC electric field is applied on sensor electrodes. This induces positive dielectrophoresis that attracts virus particles to the sensor electrodes. As a result, rapid and sensitive detection of influenza A virus is accomplished without the need for nucleotide isolation and amplification. The same AC signal is used to detect the binding of virus particle to the sensor surface immobilized with the antibody probe. The assay is highly suitable for point-of-care use. When testing clinical swab samples, the response of samples at various dilutions is analyzed, and an optimal dilution is found and used for subsequent blind tests of clinical swab samples. Analytical experiments on standard influenza virus sample demonstrate a limit of detection of 0.25 pgai...mL(-1). Other figures of merit include (a) an assay time of 30 seconds; (b) a diagnostic sensitivity of 90%; and (c) a specificity of 70%. Blind tests are conducted for a panel of twenty nasal swab samples, and the results are in good agreement with those by using the commercial reverse transcription polymerase chain reaction.