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Critical Evaluation of Air-Liquid Interface Cell Exposure Systems for in Vitro Assessment of Atmospheric Pollutants
Citation:
Higuchi, M., A. Ledbetter, D. Morgan, S. McCullough, R. Devlin, AND J. Zavala. Critical Evaluation of Air-Liquid Interface Cell Exposure Systems for in Vitro Assessment of Atmospheric Pollutants. Society of Toxicology Meeting, New Orleans, LA, March 13 - 17, 2016.
Impact/Purpose:
This abstract will be presented at the Society of Toxicology Meeting, March 13-17, 2016, New Orleans, LA
Description:
We compared various in vitro exposure systems for their ability to expose cells to particles and gases. The systems tested use different mechanisms to deliver multi-pollutants to the cells: diffusion, sedimentation, thermophoresis (THP) and electrostatic precipitation (ESP). Various factors, such as flow rate, can adversely affect performance and reliability. 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. Particles <100-nm rely on diffusion for deposition, whereas particles >1-µm rely on sedimentation. Applying external forces, such as THP or ESP, enhances deposition for all particle sizes. For example, with a 50-nm particle, deposition is 3-fold higher with THP compared to diffusion. To assess the ability of the systems to deliver gases to cells, ozone (O3) was used as a test agent. The reaction of O3 with an indigo dye on well surfaces showed that diffusion allowed gas-cell interaction. Increasing the flow rate in diffusion systems, when air flow is perpendicular to the cells, increases gas delivery to wells. To demonstrate this effect biologically, we used EPA’s cell culture exposure system (CCES) to expose primary human bronchial epithelial cells to 0.3 parts per million (ppm) acrolein for 2 h at different flow rates. Measuring heme oxygenase-1 (HO-1) 1 h post-exposure resulted in elevated fold changes over control of 1.64, 1.82, and 4.39 at 3, 5, and 25 mL/min/well, respectively. These results show that flow rate is a critical factor that influences the biological effects. Our study shows that diffusion systems are favorable for exposures of gases, whereas systems with THP or ESP are suitable for particles. Characterization of in vitro exposure systems is needed prior to their use in order to understand their advantages and limitations. [Abstract does not necessarily reflect the views or policies of the U.S. EPA.]