Genotoxicity of nano/microparticles in in vitro micronuclei, in vivo comet and mutation assay systems

Background: Recently, manufactured nano/microparticles such as fullerenes (C-60), carbon black (CB) and ceramic fiber are being widely used because of their desirable properties in industrial, medical and cosmetic fields. However, there are few data on these particles in mammalian mutagenesis and carcinogenesis. To examine genotoxic effects by C-60, CB and kaolin, an in vitro micronuclei (MN) test was conducted with human lung cancer cell line, A549 cells. In addition, DNA damage and mutations were analyzed by in vivo assay systems using male C57BL/6J or gpt delta transgenic mice which were intratracheally instilled with single or multiple doses of 0.2 mg per animal of particles. Results: In in vitro genotoxic analysis, increased MN frequencies were observed in A549 cells treated with C-60, CB and kaolin in a dose-dependent manner. These three nano/microparticles also induced DNA damage in the lungs of C57BL/6J mice measured by comet assay. Moreover, single or multiple instillations of C-60 and kaolin, increased either or both of gpt and Spi-mutant frequencies in the lungs of gpt delta transgenic mice. Mutation spectra analysis showed transversions were predominant, and more than 60% of the base substitutions occurred at G:C base pairs in the gpt genes. The G:C to C:G transversion was commonly increased by these particle instillations. Conclusion: Manufactured nano/microparticles, CB, C-60 and kaolin, were shown to be genotoxic in in vitro and in vivo assay systems.