Figure 5.

The cytotoxicity of MWCNTs is equivalent to that of the carbon black used in tattoos. a) Validity of cytotoxicity evaluation in a colonization test. The colonization capacity of V79 cells (Chinese hamster lung fibroblast line JCRB0603) decreased in a concentration‐dependent manner in the presence of the positive control ZDBC, and the 50% inhibitory concentration for colony count (reference value range: 1–4 µg mL⁻¹) is between 1.56 and 3.12 µg mL⁻¹. The cytotoxicity of the test substance is therefore found to be evaluated properly. b) Photomicrographs from the colonization test by the direct contact method. The V79 cell colony count with the culture broth alone is compared with the colony counts with an MWCNT solution as well as two carbon black solutions for tattoos (TCB‐1 solution and TCB‐2 solution, respectively). The concentrations of the solutions are 12.5, 50, 200, 400, 800, and 1600 µg mL⁻¹, respectively. c) Colony formation of the MWCNT, TCB‐1, and TCB‐2 solutions by concentration. MWCNTs inhibited colony formation concentration‐dependently, as did both TCB‐1 and TCB‐2. A significantly larger colony number is observed in the MWCNT group than in the TCB‐1 group at 200 mg/mL or more. In comparisons of MWCNTs and TCB‐2, the colony number of MWCNTs is significantly larger at 400 mg mL⁻¹ or more. Error bars indicate the standard deviation (n = 6). *p < 0.001. **p = 0.016. Adapted with permission.^{[ 97 ]} Copyright 2011, Elsevier.