Development of an electrostatic air sampler as an alternative method for aerosol in vitro exposure studies

There is growing interest in studying the toxicity and health risk of exposure to multi-pollutant mixtures found in ambient air, and the U.S. Environmental Protection Agency (EPA) is moving towards setting standards for these types of mixtures. Additionally, the Health Effects Institute's strategic plan aims to develop and apply next-generation multi-pollutant approaches to understanding the health effects of air pollutants. There's increasing concern that conventional in vitro exposure methods are not adequate to meet EPA's strategic plan to demonstrate a direct link between air pollution and health effects. To meet the demand for new in vitro technology that better represents direct air-to-cell inhalation exposures, a new system that exposes cells at the air-liquid interface was developed. This new system, named the Gillings Sampler, is a modified two-stage electrostatic precipitator that provides a viable environment for cultured cells. The performance of the sampler was evaluated under controlled laboratory conditions. Fluorescent polystyrene latex spheres were used to determine deposition efficiencies (38-45%), while microscopy and imaging techniques verified particle deposition. Negative control cell exposures indicated the sampler can be operated for up to 4 hours without inducing any significant toxic effects on the cells. A novel positive aerosol control exposure method was also developed to test this system. This new positive control test confirmed that reproducible biological results can be obtained when exposing cultured cells with the Gillings Sampler. Further testing exposing cells to various test atmospheres included diesel exhaust, kerosene soot, secondary organic aerosols, and ozone. Results showed various cell types (human and mouse) can be used with the Gillings Sampler and estimated doses less than 1 mug/cm2 can elicit acute biological effects on cultured cells. These tests demonstrated the advantages of the sampler and also highlighted limitations to be addressed in the future. The Gillings Sampler is intended to be used as an alternative research tool for aerosol in vitro exposure studies and while further testing and optimization is still required to produce a "commercially ready" system, it serves as a stepping-stone in the development of cost-effective in vitro technology that can be made accessible to researchers in the near future.