Measurement of Airborne Influenza Viruses using an Electrostatic Particle Concentrator and Paper Sensors

Abstract

Air-borne influenza viruses are responsible for serious respiratory diseases and one of biggest threats to human health because they cause high morbidity and mortality. Therefore, it is critical to evaluate the accurate concentration and pathogenicity of the bio-particles via advanced sampling and detection methods. We previously developed a personal electrostatic particle concentrator (EPC) for sampling of submicron airborne virus (MS2 and T3 phage) particles, and the collected viral concentrations were more than 10 times higher than that in the commercial impinger, BioSampler. The EPC was evaluated in this study for influenza virus aerosols which have different structural properties than the MS2 and T3 phage particles. Influenza virus aerosol was collected in 1x phosphate buffered saline solution with constant applied voltage (-5kV) and sampling flow rate (1.2 L/min). The portable Vertical flow assay (VFA) based electrochemical paper immunosensor was used for the detection of the influenza virus particles in bio-aerosols. The collection efficiency of intact influenza viruses were measured using different types of (nucleoprotein antibodies, hemagglutinin monoclonal and polyclonal antibodies) antibodies on the paper based VFA sensors with variation in collection time (10 to 60 min). The VFA based immunosensor measured 647 PFU/mL in 16 min including 10 min sampling. The concentration of virus particles increased with increase in sampling time on using nucleoprotein antibodies for detection. However, the concentration of virus particles decreased with increase in sampling time on using hemagglutinin antibodies which might be due to damage of HA protein of the virus due to sampling stress and applied voltage. The nucleoprotein based VFA sensor measured 647 PFU/mL in 16 min including 10 min sampling time and the results were independently confirmed using conventional ELISA and qPCR. Sample pad in VFA sensor acted as a filter membrane that allows the small particles (>0.45 µm) to pass through it and retains the large particles (dust particles etc.) This combination provided a reliable working system suitable for sampling and detection of bio-aerosol with high sensitivity and selectivity. This work is expected to lead to innovative, novel, inexpensive and feasible methods for biological aerosol monitoring.