New technologies for in vitro aerosol exposures at air liquid interfaces

Air pollution is a serious public health concern with local and global implications. Sometimes the effects of air pollution are distinct, and the causative pollutants can be easily identified and subsequently reduced. In many large cities, however, the cause-and-effect relationship is more problematic due to the type of ambient exposure. These atmospheres consist of gases and particulate matter (PM) that have undergone dynamic changes in their composition through oxidation chemistry that likely affects their overall toxicity. Thus, current research efforts focused on understanding the public health implications of exposure to these mixtures will need in vitro exposure technologies with the sensitivity and throughput at ambient concentrations to keep pace with compositional changes. In this tutorial you will learn about various in vitro exposure technologies developed by researchers at UNC-Chapel Hill and the U.S. Environmental Protection Agency to address these specific needs. The tutorial will provide detailed explanations of various technologies being used by UNC and EPA researchers and will also feature results from the first ever exposure system comparison study of many of in vitro exposure technologies.

Conventional in vitro dosing methods and systems are not adequate to expose cultured cells in a manner that mimics a more realistic cell exposure at ambient levels or in a complex mixture (gases, vapors, and aerosols). Exposing cells at the air-liquid interface (ALI) has been used to better represent direct pollutant-to-cell interaction and can be reasonably regarded as an effective in vitro surrogate for inhalation. To achieve an ALI condition, cultured cells are grown on porous membrane inserts (i.e., MilliCell, Transwell, etc.). The novel instrument designed at UNC uses electrostatic charging to efficiently and uniformly deposit the particles directly onto cells at ALI conditions. The electrostatic charging has been shown to not to induce adverse effects on cultured cells under specific operational conditions. While working under biological constraints, the process of collecting and depositing particles onto the cells for toxicological measurements remains highly effective. EPA has developed a suite of Cell Culture Exposure Systems (CCES) that permits the use of multi-well plates within the systems, thus minimizing handling and transferring of membrane inserts. Thermophoresis has been incorporated into one of the CCES to enhance particle deposition efficiency during exposure. These in vitro technologies can be used, in conjunction with chemical characterization instruments, to identify the specific composition of an ambient mixture to determine what is most relevant to overall toxicity. The identification and toxicity profiling of ambient pollutant mixtures is essential to support public health and assist in development of Adverse Outcome Pathways (AOPs). [Abstract does not reflect policies of the EPA.]