Inhalation exposure to airborne particles, such as nickel, increases the risk for several respiratory tract diseases. Even though the effects of nickel have been extensively studied, the data for some nickel particle types is currently inconclusive. Certain nickel compounds are established human carcinogens, but for example the carcinogenicity of nickel metal particles has not been confirmed. There are also uncertainties concerning the actual mode of action of nickel. Furthermore, it is unclear, how the physico-chemical particle characteristics affect the carcinogenic potential of nickel. This lack of comprehension is considered to be largely due to the uncertainties in the current toxicological exposure methods both in vivo and in vitro.
The need for more advanced exposure systems for airborne particles is broadly recognized. Taking into account the distinct characteristics of the human respiratory tract and the ways in which airborne particles move and interact with the pulmonary tissue is essential for better health risk characterizations and assessments of nanoparticles. The vastly expanding nanotechnology industry has amplified this need, as it is likely, that a growing group of workers become exposed to nanoparticles via inhalation for example during the production or conditioning phases of different nanomaterials.
When the specific cellular-level mechanisms are investigated, the use of in vitro methods is often desirable. Therefore, we have developed a novel in vitro exposure system for toxicological studies of metal-containing nanoparticles. The system comprises human lung cells grown on air liquid interface (ALI), the generation of nanoparticles and their deposition, enhanced by electrostatic force, on the cells. The ALI system resembles more closely the realistic conditions in the human respiratory tract when compared to the more traditional submerged in vitro cell culture exposures.
Based on our results, we can conclude that studying the relationships between nickel particle characteristics and their toxicological properties is problematic with submerged cell cultures. The ALI exposure system proves, however, promising as a more advanced and realistic exposure approach. We could show an efficient deposition of silver nanoparticles on human alveolar epithelial type II cells (A549) and we did not detect any increased cytotoxicity or DNA damage after clean air exposures. This preliminary study with silver nanoparticles as a test material suggests, that the ALI system can be used for studying the toxicity of airborne metal particles. It remains as our future challenge to use the ALI system for investigating the toxicological mechanisms of nickel, as well as other metal-containing, nanoparticles.
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University , 2015. , 16 p.