Figure 10.
The cytotoxicity of MWCNTs is not higher than that of carbon black. TCB-1, Tattoo carbon black-1; TCB-2, Tattoo carbon black-2 (see Figure 8). (a) Appropriateness of cytotoxicity assessment in colonization test. The colonization capacity of V79 cells (Chinese hamster lung fibroblast cell line JCRB0603) decreased as the concentration of the positive control ZDBC increased. The concentration for 50% colony count reduction (IC50, reference value range: 1–4 μg/mL) was found to be between 1 and 2 μg/mL, confirming that the cytotoxic action of the test substance was properly assessed. (b) Macroscopic photographs showing colonization test results. Colony counts of V79 cells cultured using a culture broth alone and those cultured in the presence of MWCNT solution, TCB-1 solution, and TCB-2 solution were compared. The concentrations in the solutions were 12.5, 50, 200, 400, 800, and 1600 μg/mL, respectively. (c) Colony counts versus carbon concentrations in MWCNT, TCB-1, and TCB-2 solutions. MWCNTs inhibited the colonization in a concentration-dependent fashion, and TCB-1 and TCB-2 likewise inhibited the colonization in a concentration-dependent fashion. When comparing colony counts, MWCNTs produced significantly higher colony counts than TCB-1 at concentrations of 200 μg/mL or more, and than TCB-2 at concentrations of 400 μg/mL or more. Error bars indicate standard deviations (n = 6); *, p < 0.001; **, p = 0.016. Reprinted with permission from ref (97). Copyright 2011 Elsevier.