Wolfgang Bäumler

Background/Objectives: Actinic keratosis (AK) occurs on sun-damaged skin and is considered a precursor to squamous cell carcinoma (SCC). Photodynamic therapy (PDT), using 5-aminolevulinic acid (ALA) and red light, is a common treatment for AK. However, its clinical efficacy for invasive tumors such as SCC is limited by the poor penetration and distribution of the photosensitizer. Cold atmospheric plasma (CAP), a partially ionized gas, increases skin permeability and exhibits anti-cancer properties through the generation of reactive oxygen species (ROS). In a previous study, CAP showed promising synergistic effects when combined with ALA-PDT for the treatment of SCC cells in vitro. The present study investigated the effects of combining CAP with ALA-PDT on cutaneous AK and SCC induced by ultraviolet B (UV-B) irradiation in SKH1 hairless mice. Methods: We compared various application sequences (CAP-ALA–red light, ALA–red light–CAP, and ALA-CAP–red light) against conventional ALA-PDT using visual, histological, and molecular assessments of the affected skin. Results: The results demonstrated that combined treatments strongly inhibited the growth of UV-B-induced skin lesions. TUNEL staining revealed increased apoptosis following both single and combined therapies, while Ki-67 staining indicated reduced keratinocyte proliferation and diminished DNA damage in treated areas. mRNA expression analysis showed the upregulation of apoptosis-related genes (p16^INK4a, p21^CIP1) alongside enhanced anti-tumor immune responses (IL-6, IL-8) in the affected tissue samples. Notably, the combined treatment enhances the therapeutic effect, whereas the sequence of application does not seem to be relevant for therapeutic efficacy in vivo. Conclusions: Overall, these results suggest that CAP may enhance the anti-tumor effect of conventional ALA-PDT, supporting previous findings on SCC cells.

Tattooing has been part of the human culture for thousands of years, yet only in the past decades has it entered the mainstream of the society. With the rise in popularity, tattoos also gained attention among researchers, with the aim to better understand the health risks posed by their application. ‘A medical‐toxicological view of tattooing’—a work published in The Lancet almost a decade ago, resulted from the international collaboration of various experts in the field. Since then, much understanding has been achieved regarding adverse effects, treatment of complications, as well as their regulation for improving public health. Yet major knowledge gaps remain. This review article results from the Second International Conference on Tattoo Safety hosted by the German Federal Institute for Risk Assessment (BfR) and provides a glimpse from the medical‐toxicological perspective, regulatory strategies and advances in the analysis of tattoo inks.

Background: The colonization of skin with pathogenic, partially antibiotic‐resistant bacteria is frequently a severe problem in dermatological therapies. For instance, skin colonization with Staphylococcus aureus is even a disease‐promoting factor in atopic dermatitis. The photodynamic inactivation (PDI) of bacteria could be a new antibacterial procedure. Upon irradiation with visible light, a special photosensitizer exclusively generates singlet oxygen. This reactive oxygen species kills bacteria via oxidation independent of species or strain and their antibiotic resistance profile causing no bacterial resistance on its part.Objective: To investigate the antibacterial potential of a photosensitizer, formulated in a new hydrogel, on human skin ex vivo.Methods: The photochemical stability of the photosensitizer and its ability to generate singlet oxygen in the hydrogel was studied. Antimicrobial efficacy of this hydrogel was tested step by step, firstly on inanimate surfaces and then on human skin ex vivo against S. aureus and Pseudomonas aeruginosa using standard colony counting. NBTC staining and TUNEL assays were performed on skin biopsies to investigate potential necrosis and apoptosis effects in skin cells possibly caused by PDI.Results: None of the hydrogel components affected the photochemical stability and the life time of singlet oxygen. On inanimate surfaces as well as on the human skin, the number of viable bacteria was reduced by up to 4.8 log₁₀ being more effective than most other antibacterial topical agents. Histology and assays showed that PDI against bacteria on the skin surface caused no harmful effects on the underlying skin cells.Conclusion: Photodynamic inactivation hydrogel proved to be effective for decolonization of human skin including the potential to act against superficial skin infections. Being a water‐based formulation, the hydrogel should be also suitable for the mucosa. The results of the present ex vivo study form a good basis for conducting clinical studies in vivo.

Background: Tattooing, whose popularity is growing worldwide, is an invasive body art that involves the injection of chemical mixtures, the tattoo ink, into the upper layer of the dermis. Although these inks may contain environmental toxins, including known human carcinogens, their long-term health effects are poorly studied. To conduct the urgently required epidemiological studies on tattoos and their long-term health effects, a validated method for assessing the complex tattoo exposure is needed. Objective: We aimed to develop and validate the Epidemiological Tattoo Assessment Tool (EpiTAT), a questionnaire to self-assess tattoo ink exposure in tattooed populations suitable for application in large epidemiological cohort studies. Methods: One of 3 preliminary versions of the EpiTAT using one of the alternative tattoo measurement units hand surface, credit card, or body schemes was randomly filled in by tattooed volunteers in Lyon, France. To identify the most suitable unit of tattoo self-assessment, a validation study was conducted with the selected respondents (N=97) to compare the self-assessments of tattoo surface, color, and coverage with validation measurements made by trained study personnel. Intraclass correlation, the Kendall rank correlation, and 2-tailed t tests were used to statistically compare tattoo size, color area, and tattoo coverage separately for each questionnaire version. Participants’ opinions on the alternative measurement units were also considered in the overall evaluation. For quality control of the validation measures, digital surface analysis of 62 photographs of selected tattoos was performed using Fiji/ImageJ. Results: In general, the results revealed overestimation of self-assessed measures compared with validation measures (eg, mean tattooed body surface 1768, SD 1547, cm2 vs 930, SD 1047, cm2, respectively, for hand surface; P<.001) and validation measures compared with digital image analysis (mean individual tattoo surface 147, SD 303.9, cm2 vs 101, SD 154.7, cm2, respectively; P=.05). Although the measurement unit credit card yielded the most accurate measures for all variables of interest, it had a much lower completion rate (78/129, 60.5%) than hand surface (89/104, 85.6%) and body schemes (90/106, 84.9%). Hand surface measured total tattoo size more accurately than body schemes (absolute agreement intraclass correlation coefficient: 0.71 vs 0.64, respectively). Conclusions: The final version of the EpiTAT contains 21 items and uses hand surface as a visual unit of measurement. Likert scales are used to assess color and coverage as a proportion of the total tattoo area. The overestimation of tattoo size by self-reporting merits further research to identify potential influential factors or predictive patterns that could be considered when calculating exposure.

Recent reports provide evidence that contaminated healthcare environments represent major sources for the acquisition and transmission of pathogens. Antimicrobial coatings (AMC) may permanently and autonomously reduce the contamination of such environmental surfaces complementing standard hygiene procedures. This review provides an overview of the current status of AMC and the demands to enable a rational application of AMC in health care settings. Firstly, a suitable laboratory test norm is required that adequately quantifies the efficacy of AMC. In particular, the frequently used wet testing (e.g. ISO 22196) must be replaced by testing under realistic, dry surface conditions. Secondly, field studies should be mandatory to provide evidence for antimicrobial efficacy under real-life conditions. The antimicrobial efficacy should be correlated to the rate of nosocomial transmission at least. Thirdly, the respective AMC technology should not add additional bacterial resistance development induced by the biocidal agents and co- or cross-resistance with antibiotic substances. Lastly, the biocidal substances used in AMC should be safe for humans and the environment. These measures should help to achieve a broader acceptance for AMC in healthcare settings and beyond. Technologies like the photodynamic approach already fulfil most of these AMC requirements.

Background: Laser pulses with nanosecond duration (NSL) have been the golden standard to destroy the pigment particles in skin. It is still controversially discussed whether picosecond pulses (PSL) are superior for tattoo removal.Objectives: To compare the efficacy and the adverse reactions of nanosecond and picosecond laser pulses in a comparative study.Methods: The prospective study included 23 subjects with 30 black or coloured tattoos, which were split into two halves treated with either a new PSL (532, 1064 nm) or standard NSL (694 nm). The lasers were applied at regular time intervals of 4 weeks for up to eight treatments. Tattoo clearance (primary endpoint), pain and adverse reactions (secondary endpoints) were appraised by physicians, blinded observers, and by subjects. The extent and duration of adverse reactions were additionally assessed by using a questionnaire and photo‐documentation after each treatment session.Results: The tattoo clearance appeared to be more effective for PSL compared to NSL but without statistical significance (P > 0.05). Pretreated tattoos responded better to laser treatments than previously untreated tattoos. Subjects felt significantly less pain with PSL than with NSL (P < 0.001). Transient adverse reactions were statistically less pronounced lasting shorter for PSL as for NSL, especially blistering, pruritus, and burning sensation. Hypopigmentation appeared after NSL treatments only, whereas hyperpigmentation was caused by both lasers. No scarring was detected with either laser.Conclusions: Both laser systems enable acceptable clearance of most tattoos in the present study. PSL cause less collateral skin damage as compared to NSL.

Photodynamic inactivation (PDI) of pathogenic bacteria is a promising technology in different applications. Thereby, a photosensitizer (PS) absorbs visible light and transfers the energy to oxygen yielding reactive oxygen species (ROS). The produced ROS are then capable of killing microorganisms via oxidative damage of cellular constituents. Among other PS, some flavins are capable of producing ROS and cationic flavins are already successfully applied in PDI. When PDI is used for example on tap water, PS like flavins will encounter various ions and other small organic molecules which might hamper the efficacy of PDI. Thus, the impact of carbonate and phosphate ions on PDI using two different cationic flavins (FLASH-02a, FLASH-06a) was investigated using Staphylococcus aureus and Pseudomonas aeruginosa as model organisms. Both were inactivated in vitro at a low light exposure of 0.72 J cm^-2. Upon irradiation, FLASH-02a reacts to single substances in the presence of carbonate or phosphate, whereas the photochemical reaction for FLASH-06a was more unspecific. DPBF-assays indicated that carbonate and phosphate ions decreased the generation of singlet oxygen of both flavins. Both microorganisms could be easily inactivated by at least one PS with up to 6 log₁₀ steps of cell counts in low ion concentrations. Using the constant radiation exposure of 0.72 J cm^-2, the inactivation efficacy decreased somewhat at medium ion concentrations but reached almost zero for high ion concentrations. Depending on the application of PDI, the presence of carbonate and phosphate ions is unavoidable. Only upon light irradiation such ions may attack the PS molecule and reduce the efficacy of PDI. Our results indicate concentrations for carbonate and phosphate, in which PDI can still lead to efficient reduction of bacterial cells when using flavin based PS.