An automated system for exposure of cultured cells and other materials to ozone

Ozone, a highly reactive oxidant gas, is a major constituent of urban air pollution. Studies of the toxic effects of ozone on cultured cells and other materials are most appropriately conducted under conditions of humidity, temperature, and ozone concentration similar to those in which those materials are naturally exposed. An automated system designed for exposure of cultured cells and other materials to environmentally relevant levels of ozone under nearly physiological conditions is described. Although based on time-proven manually controlled systems, this system is automated using computer programming and hardware that allow unattended operations for extended time periods while maintaining tight control over ozone levels, humidity, and temperature. Experiments were conducted to ensure that the distribution of ozone within the exposure chambers was homogeneous. In addition, experiments were performed to ensure that changes in media volume within the tissue culture plates were minimal, in order to prevent either desiccation of the cultured cells or dilution of the cell culture media. A rocker system is described that allows the tissue culture plates within each exposure vessel to be rocked from end to end to promote mixing of both the gas phase and the liquid phase on each side of the cell culture insert membrane. Since automation of the system allows unattended operation of the system for extended periods, safety systems are described that prevent exposure of investigators to elevated levels of ozone under a variety of system failure conditions.