(302c) Evaluation of Biological Effects Using a Nano-Ceria Based Diesel Fuel Additive with in vitro Air-Liquid Interface Cell Exposure Systems of Different Flow Patterns

Diesel exhaust is a large contributor of particulate matter in air pollution, which can lead to pulmonary conditions such as chronic obstructive pulmonary disorder and even lung cancer. To reduce emissions, the introduction of metal oxide fuel additives into the engine provides additional oxidation points for soot particles and greenhouse gases. These additives have been shown to increase the number of nanoparticles in the exhaust which when inhaled can deposit in the lower lungs with an extended residence time, allowing more time for particle-cell interactions. Aerosols can be tested for toxicity in vitro at the air-liquid interface (ALI), where the cells are grown on a porous membrane, allowing one side to be exposed after equilibration with air, while the other side receives nutrients from liquid media. The biological effects of diesel exhaust have not been extensively studied in vitro at the ALI, nor with metal oxide additives.

The objective of this work is to determine the potential cytotoxicity and oxidative activity changes in lung cells cultured at the ALI after exposure to exhaust generated by a commercial, nano-cerium oxide based diesel fuel additive as directed with low-sulfur fuel. Two ALI cell exposure systems with two different flow patterns were utilized. Exhaust was generated by a partly loaded, single cylinder, four-stroke, air cooled, direct inject diesel power generator. The particle concentration was maintained at approximately 10⁶ particles/cm³ as measured by a Scanning Mobility Particle Sizer. Deposition was measured gravimetrically on glass-fiber filters and blank cell culture inserts, qualitatively using Transmission Electron Microscopy, and online during exposure using quartz crystal microbalance measurements. These can be correlated to the biological effects of cytotoxicity and the oxidative activity, including reactive oxidative species generation and oxidative protection.

Acellular experiments suggest a correlation between the deposition and the type of fuel used for the newly designed Portable In Vitro Exposure Cassette. Using diesel exhaust, approximately one half of the filter mass is collected on the insert; whereas for additive fuel, approximately one sixth of the filter mass is collected. Preliminary cellular results suggest a decrease in cytotoxicity and no statistically significant effect on reactive oxygen species generation with the use of the nano-cerium oxide additive.