Rudolf Vasold

Light-Induced Decomposition of Indocyanine Green

PURPOSE To investigate the light-induced decomposition of indocyanine green (ICG) and to test the cytotoxicity of light-induced ICG decomposition products. METHODS ICG in solution was irradiated with laser light, solar light, or surgical endolight. The light-induced decomposition of ICG was analyzed by high-performance liquid chromatography (HPLC) and mass spectrometry. Porcine retinal pigment epithelial (RPE) cells were incubated with the light-induced decomposition products of ICG, and cell viability was measured by trypan blue exclusion assay. RESULTS Independent of the light source used, singlet oxygen (photodynamic type 2 reaction) is generated by ICG leading to dioxetanes by [2+2]-cycloaddition of singlet oxygen. These dioxetanes thermally decompose into several carbonyl compounds. The decomposition products were identified by mass spectrometry. The decomposition of ICG was inhibited by adding sodium azide, a quencher of singlet oxygen. Incubation with ICG decomposition products significantly reduced the viability of RPE cells in contrast to control cells. CONCLUSIONS ICG is decomposed by light within a self-sensitized photo oxidation. The decomposition products reduce the viability of RPE cells in vitro. The toxic effects of decomposed ICG should be further investigated under in vivo conditions.

Tattoo pigments are cleaved by laser light-the chemical analysis in vitro provide evidence for hazardous compounds.

Abstract In the western world, more than 80 million people decorate their skin with tattoos. Tattoo colorants are injected into the skin, like medical drugs. Most tattoo colorants are industrial pigments, and chemical industries have never produced them for human use but only to stain consumer goods. Up to 10% of tattooed people request removal of their tattoos because of an improved self-image or social stigmatization. In contrast to tattooing, physicians usually perform the tattoo removal. For that purpose laser light at very high intensities irradiates the skin to destroy the tattoo pigments. Based on a recent analysis of tattoo pigments, two widely used azo compounds were irradiated in suspension with laser and subsequently analyzed by using quantitative high-performance liquid chromatography and mass spectrometry. The high laser intensities cleaved the azo compounds, leading to an increase of decomposition products such as 2-methyl-5-nitroaniline, 2-5-dichloraniline and 4-nitro-toluene, which are toxic or even carcinogenic compounds. Moreover, the results of the chemical analysis show that the tattoo colorants already contain such compounds before laser irradiation. Because of a high number of patients undergoing laser treatment of tattoos and based on the results of our findings in vitro, it is an important goal to perform a risk assessment in humans regarding laser-induced decomposition products.

Modern tattoos cause high concentrations of hazardous pigments in skin

Background:  Modern tattoo colourants frequently consist of azo pigments that not only contain multiple impurities but also are originally produced for car paint and the dyeing of consumer goods.

Tattooing of skin results in transportation and light-induced decomposition of tattoo pigments – a first quantification in vivo using a mouse model

Abstract:  Millions of people are tattooed with inks that contain azo pigments. The pigments contained in tattoo inks are manufactured for other uses with no established history of safe use in humans and are injected into the skin at high densities (2.5 mg/cm2). Tattoo pigments disseminate after tattooing throughout the human body and although some may photodecompose at the injection site by solar or laser light exposure, the extent of transport or photodecomposition under in vivo conditions remains currently unknown. We investigated the transport and photodecomposition of the widely used tattoo Pigment Red 22 (PR 22) following tattooing into SKH‐1 mice. The pigment was extracted quantitatively at different times after tattooing. One day after tattooing, the pigment concentration was 186 μg/cm2 skin. After 42 days, the amount of PR 22 in the skin has decreased by about 32% of the initial value. Exposure of the tattooed skin, 42 days after tattooing, to laser light reduced the amount of PR 22 by about 51% as compared to skin not exposed to laser light. A part of this reduction is as a result of photodecomposition of PR 22 as shown by the detection of corresponding hazardous aromatic amines. Irradiation with solar radiation simulator for 32 days caused a pigment reduction of about 60% and we again assume pigment decomposition in the skin. This study is the first quantitative estimate of the amount of tattoo pigments transported from the skin into the body or decomposed by solar or laser radiation.

Tattoo inks contain polycyclic aromatic hydrocarbons that additionally generate deleterious singlet oxygen

Please cite this paper as: Tattoo inks contain polycyclic aromatic hydrocarbons that additionally generate deleterious singlet oxygen. Experimental Dermatology 2010; 19: e275–e281.

Photochemical cleavage of a tattoo pigment by UVB radiation or natural sunlight.

Background: Millions of people have at least one tattoo. Complex and light absorbing molecules are implanted in the skin. When tattooed skin receives UV radiation or natural sunlight, photochemical cleavage of the pigments may occur. As a first step, we dissolved pigments in a suitable solvent and analyzed them after light irradiation.

Health risks of tattoo colors

The number of tattooed individuals has increased significantly, especially among youth. In the United States ∼24% of the population is tattooed [1], whereas in Europe it is ∼10% [2]. Cosmetic tattoos (permanent make up) to mimic eye, lip or eyebrow-liner, have also become increasingly popular [3]. Tattoos or permanent make-up are simply performed by injection of colorants into the skin using solid needles. Injury of the skin and the application of unregulated colorants cause health problems in humans [4]. A survey is being performed by the Department of Dermatology of the University of Regensburg in order to elucidate the frequency of medical problems with tattoos [5], in particular after laser treatment [6].

Azo Pigments and a Basal Cell Carcinoma at the Thumb

Basal cell carcinoma is the most common malignant neoplasm of the skin, whereas the localization at the nail unit is very rare. We report the case of a 58-year-old patient with a periungual basal cell carcinoma at the thumb. The specific feature of the reported case is the frequent exposure to fishing baits that the patient had stained with an unknown colorant. The use of chromatography, mass spectrometry and infrared spectroscopy revealed the colorant as the azo pigment Solvent Red 8. Solvent Red 8 is a widespread synthetic azo pigment that is applied to stain consumer products. Compounds such as Solvent Red 8 can be cleaved to carcinogenic amines under, for example, light exposure, in particular after incorporation into the human body. As a result of the frequent skin contact to this azo pigment, this hazard compound might have induced the basal cell carcinoma in our patient.

Black tattoo inks are a source of problematic substances such as dibutyl phthalate.

Background. Tattooing has recently become increasingly popular. Using tiny needles, tattooists place the tattoo ink in the dermis along with numerous unknown ingredients. Most tattoos consist of black inks, which are predominantly composed of soot products (carbon black with polycyclic aromatic hydrocarbons).

Time dependence of singlet oxygen luminescence provides an indication of oxygen concentration during oxygen consumption

Singlet oxygen plays a major role in photodynamic inactivation of tumor cells or bacteria. Its efficacy depends critically on the oxygen concentration [O(2)], which can decrease in case oxygen is consumed caused by oxidative reactions. When detecting singlet oxygen directly by its luminescence at 1270 nm, the course of the luminescence signal is critically affected by [O(2)]. Thus, it should be feasible to monitor oxygen consumption during photo-oxidative processes. Singlet oxygen was generated by exciting a photosensitizer (TMPyP) in aqueous solution (H(2)O or D(2)O) of albumin. Chromatography shows that most of the TMPyP molecules are unbound, and therefore singlet oxygen molecules can diffuse in the solution. A sensor device for oxygen concentration revealed a rapid decrease of [O(2)] (oxygen depletion) in the solution during irradiation. The extent of oxygen depletion in aqueous albumin solution depends on the radiant exposure and the solvent. When detecting the luminescence signal of singlet oxygen, the shape of the luminescence signal significantly changed with irradiation time. Thus, local oxygen consumption could be monitored during photodynamic action by evaluating the course of singlet oxygen luminescence.