Supplementary Material for: Tattoo pigment biokinetics in vivo in a 28-day porcine model: elements undergo fast distribution to lymph nodes and reach steady state after 7 days

Pigments of tattoo inks may over time migrate to other parts of the body. Inks kinetics are still poorly understood and little studied. The aim of this first study was to investigate the kinetics of tattoo inks pigment in tattooed porcine skin, which is closer to human skin than mouse skin studied in the past. Three animals were tattooed on the inner thigh and one animal served as untreated control. Skin biopsies were taken on days 7, 14, and 28 after tattooing. Animals were sacrificed on day 28 and homogenate samples of the liver, spleen, kidney, and brain, as well the local lymph nodes were prepared. All samples were analyzed for ink components using inductively coupled plasma-mass spectrometry (ICP-MS). The ink itself was characterized by dynamic light scattering (DLS) and matrix assisted laser desorption-Ionization (MALDI) mass analysis. Titanium (212 g/kg), copper (6 mg/kg), aluminum (1 mg/kg), zirconium (1 mg/kg) and chromium (3 mg/kg) were found in the ink. Significant deposits of ink elements were detected in the tattooed skin when compared to non-tattooed skin from the same animal (mean±standard deviation: titanium 24081 mg/kg, copper 95  39 mg/kg, aluminum 11563 mg/kg, zirconium 2312 mg/kg, and chromium 1.00.2 mg/kg; p < 0.05). Lymph node concentrations of titanium, copper, aluminum, zirconium, and chromium were 422 mg/kg, 6925 mg/kg, 4918 mg/kg, 0.30.2 mg/kg, 0.50.2 mg/kg, respectively. Deposits in skin were unchanged from day 7-28 indicating no redistribution or elimination. No significant deposits of ink elements were found in the liver, spleen, kidney, and brain. In conclusion, our findings confirmed distribution of elements from tattoos to regional lymph nodes, but neither to excretory organs, e.g. liver and kidney, nor to spleen and brain. Thus systemic internal organ exposure was not found.