Untersuchungen zum Wirkmechanismus von nanostrukturiertem Carbon Black mit unterschiedlicher Oberflächenbeschaffenheit

The production of nanostructured carbon black increased significantly over the past years. With an annual production volume of 10 megatons (2005) carbon black is one of the 50 most widely used industrial chemicals worldwide. Various types allow for a broad range of applications to optimize product properties. Based on numerous toxicological investigations the World Health Organization categorizes carbon black as a potentially carcinogenic substance. Polycyclic aromatic hydrocarbons (PAHs) formed during the production process and adsorbed on the surface area are suspected of causing an additive effect to the organism. Therefore, four industrial carbon black modifications with different surface properties were evaluated in this thesis: One modification (Printex®90) with 99% carbon and two supplemented with PAHs (benzo[a]pyrene, nitroanthracene) adsorbed to the surface. Additionally acetylene black was used which contains various PAHs. Printex®90 has the largest specific surface area while the other three carbon black modifications have a smaller but comparable specific surface area. Carbon black is supposed to reach the body primarily via inhalation. For that reason, a cell line (A549) originating from the respiratory tract was used in this study. Different assays were used to investigate the mechanism of action of the respective carbon blacks and a possible synergetic effect by adsorbed PAHs. Using the pulmonary epithelial cell line A549 an ATP-dependent cytotoxicity assay and nuclear staining for the assessment of genotoxicity were performed. Furthermore a plasmid assay was established for the detection of oxidative damage and tested with carbon black. Printex®90 was the only soot exerting a cytotoxic effect after 48 hours as judged by the ATP-Assay. Nuclear staining experiments (DAPI) revealed that all carbon black modifications caused a slight increase in abnormal cell divisions. Due to the high number of abnormal cell divisions in untreated control cultures, this cell line is unsuitable to study genotoxic effects in nuclear staining experiments. Using the plasmid assay significant abiotic oxidative DNA damage was observed with all carbon black modifications. Merely carbon black with nitroanthracene caused no significant DNA damage at the low dose (0.1 g/ml). The results of the present bachelor thesis suggest that the biological effects of carbon black on cytotoxicity and DNA damage, are mainly due to the specific surface area and to a lesser extend to the particle-bound PAHs