Photochemical & Photobiological Sciences

Artificial tanning devices expose users to ultraviolet radiation and are associated with an increased risk of skin cancer. To protect users, Swiss legislation, among other requirements based on the SN EN 60335-2-27, limits the total erythema effective irradiance of artificial tanning devices to [Formula: see text]. Additionally, only UV-Type 3 devices may be used in unsupervised settings. From 2022 to 2024, Swiss cantonal authorities conducted a nationwide measurement campaign to assess compliance with the limits. For this, a portable measurement system, based on a stray-light-suppressing array spectroradiometer was developed and evaluated against precision double-monochromator measurements. The developed system achieved comparable accuracy while enabling rapid in-situ conformity assessments. Overall, 1'521 individual measurements were performed on 436 artificial tanning devices across Switzerland. While [Formula: see text] of the measured devices complied with the legal limit for the total erythema effective irradiance, only [Formula: see text] met the criteria of UV-Type 3 devices. After corrective actions on previously non-compliant devices, follow-up measurements showed that [Formula: see text] of all tested devices were compliant. The results demonstrate the suitability of the developed measurement system and reveal substantial compliance deficiencies, highlighting the need for continued inspection of artificial tanning devices.

Abstract Bone repair depends on a regulated macrophage-driven inflammatory response. Non-activated macrophages (M0) differentiate into pro-inflammatory (M1) or anti-inflammatory (M2) phenotypes in response to microenvironmental signals. This study evaluated, in vitro, the effects of photobiomodulation (PBM) on bone marrow-derived macrophage polarisation. Monocytes were isolated, differentiated into macrophages (M0), and induced to acquire M1- or M2-associated characteristics. Cells were irradiated using a PBM protocol for bone regeneration (equivalent dose of 2.1 E). Cells were analysed according to morphology, expression of M1 ( iNOS , Tnf-α ) or M2 markers ( Arg1 , Cd206 ), protein expression (iNOS and ARG1), and nitric oxide (NO) and reactive oxygen species (ROS) production. Data were analysed using 1-way analysis of variance or Student’s t -test ( p ≤ 0.05). PBM promoted selective and transient modulation of inflammatory and metabolic markers in M0, M1, and M2 macrophages. Compared to non-PBM-treated cells, M1 PBM cells had reduced NO levels, increased early ROS levels, and decreased gene and protein expression. In M2 PBM cells, transient changes in NO and ROS production were detected, with reduced Cd206 expression and similar Arg1 expression, although increased ARG1 protein expression was detected compared to non-irradiated controls. In M0 PBM cells, NO levels remained unchanged, while early ROS levels increased, accompanied by reduced iNos and Arg-1 , and increased Cd206 expression. Under the selected parameters, PBM modulated macrophage inflammatory behaviour, but was insufficient to induce classical macrophage polarisation towards a specific phenotype. These findings suggest that modulation of macrophage-mediated inflammatory responses may contribute to the effects of this PBM protocol during bone repair. Graphical abstract Illustrations were generated using the Illustrae AI-assisted illustration platform.

OBJECTIVE: Optical detection of singlet oxygen in cells affects the investigated cells and potentially, photosensitization skews the observed results, since the generated singlet oxygen undergoes chemical reactions with cellular quenchers. For this reason, the illumination intensity has to be kept low during a measurement to avoid killing and destruction of the investigated cells. The scope of this paper is to show, that scanning detection can meet both, sufficient sensitivity and low illumination dose, for adherent cells in 6-well plates. MATERIAL AND METHODS: The individual illumination dose for cells under investigation is reduced by distributing it among a large number of adherent growing cells. Adherent cell lines were investigated with regard to singlet oxygen production by means of simultaneous fiber-coupled irradiation at 635 nm and singlet oxygen phosphorescence detection. Singlet oxygen kinetics could be measured in two different cell types incubated with different photosensitizers, by scanning a major part of the area of a confluent layer of cells in a well. RESULT: In each case, singlet oxygen signals kinetics could be observed and analyzed. Incubation with increasing amounts of photosensitizer did correlate to the determined signal amplitude and photosensitizer triplet decay times. CONCLUSION: Focused excitation and observation in combination with scanning across the whole well results in successful determination of singlet oxygen kinetics from incubated adherent cells without detaching them. Further development is required to reduce artifacts, likely originating from scattered excitation light.

Cutaneous carcinomas and melanoma are important skin malignancies for which photodynamic therapy (PDT) has shown therapeutic potential. Although the biological effects of PDT have been extensively investigated, particularly in carcinomas, the phenotype and behavior of tumor cells that survive treatment remain poorly understood, despite their potential role in tumor persistence and recurrence. Characterizing the proliferative behavior of PDT-surviving tumor cells may therefore provide insights into the cellular consequences of treatment and their potential implications for tumor regrowth. In this study, we investigated the proliferative capacity of cutaneous squamous cell carcinoma and melanoma cells following porphyrin-mediated PDT using a combined in vitro clonogenic assay and in vivo tumor model of treated cells. Temporal recovery was assessed using viability and clonogenic assays at two lethal doses of PDT (LD₅₀ and LD₃₀). The results demonstrated that the temporal impact of PDT on proliferative capacity was dose-dependent, persisting for up to 72 h in the LD₅₀ group. Tumors derived from LD₅₀-treated cells showed reduced volume, delayed onset, and slower growth, corroborated by decreased proliferating cell nuclear antigen (PCNA) expression. These findings support PDT as a strategy for melanoma and define a critical "damage window," during which adjuvant therapies may improve efficacy and limit recurrence.