No abstract

Numerous threats from biological aerosol exposures, such as those from H1N1 influenza, SARS, bird flu, and bioterrorism activities necessitate the development of a real-time bioaerosol sensing system, which however is a long-standing challenge in the field. Here, we developed a real-time monitoring system for airborne influenza H3N2 viruses by integrating electronically addressable silicon nanowire (SiNW) sensor devices, microfluidics and bioaerosol-to-hydrosol air sampling techniques. When airborne influenza H3N2 virus samples were collected and delivered to antibody-modified SiNW devices, discrete nanowire conductance changes were observed within seconds. In contrast, the conductance levels remained relatively unchanged when indoor air or clean air samples were delivered. A 10-fold increase in virus concentration was found to give rise to about 20-30% increase in the sensor response. The selectivity of the sensing device was successfully demonstrated using H1N1 viruses and house dust allergens. From the simulated aerosol release to the detection, we observed a time scale of 1-2 min. Quantitative polymerase chain reaction (qPCR) tests revealed that higher virus concentrations in the air samples generally corresponded to higher conductance levels in the SiNW devices. In addition, the display of detection data on remote platforms such as cell phone and computer was also successfully demonstrated with a wireless module. The work here is expected to lead to innovative methods for biological aerosol monitoring, and further improvements in each of the integrated elements could extend the system to real world applications.

In this study, an automated bioaerosol collection and output system was developed using a new electrostatic sampling method. The electrostatic sampler was designed using a half-ball shape steel electrode (radius is 45 mm) with three aerosol inlets (radius is 3.5 mm) on the top and a copper plate electrode (6 and 16 mm in diameter) suited inside a circular plastic support. Above the plate electrode, a plastic cylindrical reservoir (14 mm in diameter and 1 mm in height) was built with liquid inlet and outlet made of copper (2 mm in diameter). These outlets are connected to a peristaltic pump for liquid delivery. Next to the reservoir, there are two aerosol outlets (radius is 2.5 mm) connected to a vacuum pump. The physical collection efficiencies of the system were investigated when collecting indoor particles using an optical particle counter under different experimental conditions. The system was also tested when sampling indoor and outdoor bacterial aerosols. Experimental data showed that the system could collect 70%-90% of indoor particles of 0.3-2 µm at a low sampling flow rate of 1.2 L/min when a 20 kV voltage and a particle charger (1.5 V) were applied. Increasing sampling flow rate was observed to lead to the decrease of the collection efficiency. When a particle charger was applied, use of larger plate electrode (16 mm in diameter) was shown to significantly improve the collection efficiency close to two times than that of 6 mm. When operated for sampling environmental bacterial aerosols, the system obtained a similar magnitude of bacterial aerosol concentration levels compared to a mixed cellulose ester (MCE) filter. The integration of the automated electrostatic sampler (AES) sampler developed here with a biosensor device could offer a promising platform for the automated bioaerosol sensing.