Critical Evaluation of Air-Liquid Interface Cell Exposure Systems for In Vitro Assessment of Atmospheric Pollutants##
Citation:
Zavala, J. AND M. Higuchi. Critical Evaluation of Air-Liquid Interface Cell Exposure Systems for In Vitro Assessment of Atmospheric Pollutants##. American Assoc. for Aerosol Research (AAAR) Conference, Raleigh, NC, October 16 - 20, 2017.
Impact/Purpose:
Conventional in vitro exposure studies of airborne pollutants involve, for example, the addition of particulate matter (PM) or PM extracts to the cell culture medium, or the bubbling of gases into the culture medium; these methods alter the pollutant’s physical and chemical characteristics. Exposing cells at the air-liquid interface (ALI) mimics a more realistic cell exposure due to the direct pollutant-to-cell interaction. We compared various ALI in vitro exposure systems under identical conditions for their ability to expose cells to particles and gases.
Description:
Conventional in vitro exposure studies of airborne pollutants involve, for example, the addition of particulate matter (PM) or PM extracts to the cell culture medium, or the bubbling of gases into the culture medium; these methods alter the pollutant’s physical and chemical characteristics. Exposing cells at the air-liquid interface (ALI) mimics a more realistic cell exposure due to the direct pollutant-to-cell interaction. We compared various ALI in vitro exposure systems under identical conditions for their ability to expose cells to particles and gases. The systems tested used different mechanisms to deliver aerosols, vapors, and gases to the cells: diffusion, sedimentation, thermophoresis (THP), and electrostatic precipitation (ESP). We used fluorescent polystyrene spheres (50-1000 nm) as a surrogate for particulate matter to assess particle deposition. Deposition was determined by dissolving the spheres in ethyl acetate and measuring the fluorescence. Applying external forces, such as THP or ESP, enhanced deposition for all particle sizes. For example, deposition was 3-fold higher with THP compared to diffusion. Similarly, deposition was 3- to 6.5-fold higher with ESP compared to diffusion, depending on particle size and in vitro system. We also assessed the ability of the systems to deliver gases to cells by using ozone (O3) as a test gas. The reaction of O3 with an indigo dye at the ALI surface showed that diffusion allowed gas-cell interaction. Increasing the flow rate in diffusion systems where air flow was perpendicular to the cells increased gas delivery. Our study showed that in vitro systems with THP or ESP were the most effective at delivering aerosols to the cells, whereas flow rate was a critical parameter for the delivery of vapors and gases. [Abstract does not necessarily reflect the views or policies of the U.S. EPA.]