Fig 1.
Schematics of the experimental setup (not to scale).
(a) Experiments are conducted in a bio-safety cabinet to keep all aerosolized virus contained. The setup includes a Collison nebulizer to aerosolize using compressed air and viral solutions provided by a syringe pump. Tubing directs the airborne viruses into the sampling unit (b): (1) our ESP sampler or (2) gelatin filters for comparison. A downstream vacuum pump maintains a constant flow and under pressure inside the ESP sampler. (b) Details of the sampling units: (1) Our ESP sampler includes a three-electrode corona discharge electrostatic precipitator to capture the aerosol particle directly into an integrated liquid collector with a miniaturized volume of 150 μL; (2) gelatin filters are used for comparative measurement of the total amount of virus effectively entering the ESP sampler after nebulization. The filters are housed in a specific cassette placed at the aerosol inlet.
Fig 2.
Measurements of the total amount of viruses detected with qPCR versus the total amount of viruses entering the ESP sampler.
Linear regressions were performed using the least-square method on data groups obtained using EP1 and EP2. The qPCR LoD reported to the sampling volume is plotted with a horizontal dashed red arrow and enables calculating the theoretical system LoDs, indicated with black arrows. The collection efficiencies for EP1 and EP2 are significantly different with a probability P = 0.0158 < 0.05 and are indicated with the corresponding standard error. *For EP3, only a single measurement was successfully obtained. The corresponding collection efficiency can be estimated using Eq 1.
Table 1.
Summary of the data extrapolated from our measurements.