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Understanding Air-Liquid Interface Cell Exposure Systems: A Comprehensive Assessment of Various Systems Under Identical Conditions
Citation:
Zavala-Mendez, J. AND M. Higuchi. Understanding Air-Liquid Interface Cell Exposure Systems: A Comprehensive Assessment of Various Systems Under Identical Conditions. Society of Toxicology Annual Meeting, San Antonio, TX, March 11 - 15, 2018.
Impact/Purpose:
Exposure of cells to atmospheric pollutants at the air-liquid interface (ALI) is a more realistic approach than exposures of attached cells submerged in liquid medium. However, there is still limited understanding of the ideal ALI system design features that permit reproducible assessments.
Description:
Exposure of cells to atmospheric pollutants at the air-liquid interface (ALI) is a more realistic approach than exposures of attached cells submerged in liquid medium. However, there is still limited understanding of the ideal ALI system design features that permit reproducible assessments. 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 of a 50-nm particle was 1.6- to 4.8-fold higher with a THP compared to diffusion systems. Similarly, deposition for both 50-nm and 1000-nm particles were 3.4- to 10.5-fold higher with ESP compared to diffusion, depending on in vitro system with ESP. Results indicated that THP is an effective external force on nano-sized particles with decrease effectiveness as particle size increases, whereas ESP maintains a stable performance regardless of particle size. 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. Results show a 13-fold difference in gas delivery performance between the best and poorest performing system. Additionally, 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.]