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Next-generation photodynamic therapy (PDT) is envisaged to be based on light-activated photosensitizers with small sizes and high performance, eradicating microbial and deadly cancer cells without harming healthy cells. Here, nitrogen-doped graphene quantum dots (N-GQDs) are hydrothermally synthesized and composited with TiO2 nanoparticles (NPs). The resulting N-GQDs/TiO2 nanocomposite is then examined as a PDT photosensitizer with an average size of 21 nm. Reactive oxygen species (ROS) production by photo-excited N-GQDs, TiO2, NPs and N-GQDs/TiO2 nanocomposite is investigated using anthracene and methylene blue as chemical probes for the identification of singlet oxygen and hydroxyl radical. The ROS-production ability of the nanocomposite is found to be considerably higher than that of N-GQDs and TiO2 NPs, achieving reduction rates of 94% and 93% in the absorption intensity of anthracene and methylene blue under UVA irradiation for 75 and 60 min, respectively. The higher ROS production is attributed to the efficient energy transfer from N-GQDs to TiO2 NPs due to the fluorescence resonance energy transfer effect as well as a reduction in the recombination of photogenerated electron–hole pairs. Furthermore, afterglow emission intensity of the nanocomposite irradiated by UVA light slightly changes after 360 s. Alternatively, no decrease is observed in the absorption intensity of the chemical probes in the presence of N-GQDs/TiO2 nanocomposite under no irradiation, indicating its lack of dark toxicity. Therefore, the proposed biocompatible TiO2-based nanocomposite with long-lived afterglow, intense photoluminescence, and high ROS production ability can be employed as a photosensitizer for cancer treatment using PDT. [ABSTRACT FROM AUTHOR]

Some ancient Chinese paper artifacts dyed with amur cork tree bark extracts are currently preserved to different extents in museums and libraries worldwide. As traditional natural plant dyes, the long-term performance of the amur cork tree bark extract-dyed handmade paper has been questioned under a preserved environment. The photodegradation process of the extract-dyed papers was examined under accelerating artificial UVA irradiation conditions according to China national standard-paper and board- accelerated aging (exposure to light). Changes during aging were analyzed by optical observation and scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR), pH, and tensile strength and folding endurance tests. The results showed that the main components from extracted dyes played an important role in affecting the photodegradation properties of dyed paper. The changes in surface color, pH, morphology and mechanical properties after the artificial UVA accelerated degradation tests revealed that a suitable concentration of the extract dyes for maintaining the long-term irradiation stability of the paper is important. [ABSTRACT FROM AUTHOR]

The Dead Sea basin is the lowest terrestrial site on the globe. A meteorological station monitoring the global, UVB and UVA irradiation, and the dry bulb temperature was established in 1995 in conjunction with a study of bio-climatological properties of the region with regard to photoclimatherapy treatment of dermatological diseases. The availability of such irradiation and dry bulb temperature databases has been utilized to perform a study to determine if any trends regarding either irradiation or dry bulb temperature exists at this unique site. The global irradiation database included the time interval 1995–2021, whereas the corresponding time interval for the UVB and UVA irradiation databases was 1995–2018. There was no indication of any trends, based upon a p value analysis with regard to the global and UVB and UVA irradiation with the exception of global irradiation during September (− 120.7 Wh/m2/decade; ~ 2%/decade) and UVA irradiation during March (+ 11.1 Wh/m2/decade; ~ 4%/decade) and September (− 9.1 Wh/m2/decade; ~ 0.6%/decade). The dry bulb temperature database consisted of the time interval 1995–2021 and trends were observed during the months of August, September, and October. The dry bulb temperature data were analyzed as a function of time (Israel Standard Time) interval; viz., diurnal from 06:00 to 18:00, nocturnal from 18:00 to 06:00, and daily from 00:00 to 24:00. The trends observed during these three months varied between 0.38 and 0.70 °C/decade. [ABSTRACT FROM AUTHOR]

Repair of ribosomal DNA (rDNA) is a very important nuclear process due to the most active transcription of ribosomal genes. Proper repair of rDNA is required for physiological biogenesis of ribosomes. Here, we analyzed the epigenetics of the DNA damage response in a nucleolar compartment, thus in the ribosomal genes studied in nonirradiated and UVA-irradiated mouse embryonic fibroblasts (MEFs). We found that the promoter of ribosomal genes is not abundant on H4K20me2, but it is densely occupied by H4K20me3. Ribosomal genes, regulated via UBF1/2 proteins, were characterized by an interaction between UBF1/2 and H4K20me2/me3. This interaction was strengthened by UVA irradiation that additionally causes a focal accumulation of H4K20me3 in the nucleolus. No interaction has been found between UBF1/2 and H3K9me3. Interestingly, UVA irradiation decreases the levels of H3K9me3 and H4K20me3 at 28S rDNA. Altogether, the UVA light affects the epigenetic status of ribosomal genes at 28S rDNA and strengthens an interaction between UBF1/2 proteins and H4K20me2/me3. [ABSTRACT FROM AUTHOR]

Exposure of tryptophan (Trp) in aqueous solutions to UVA radiation resulted in decrease of Trp (C1) but generated an unknown fluorescent component (C2) with fluorescence emission maxima extending into wavelength range characteristic of humic substance (HS)-like material. The intensity of the two components (C1 and C2) could be operationally fit to linear functions of the illumination time t (0~40 h). However, C1 and C2 decreased and increased nonlinearly respectively in a mixture (Trp mixed with a reference sample of natural organic matter, i.e., NOM) which was exposed to the same UVA illumination, and the change of both C1 and C2 was faster than that in the absence of NOM. Moreover, the UV-Vis absorption maximum (ex = 278 nm) of Trp was faster removed for the mixture (after 5 h) than for Trp solutions without NOM (after 20 h). These observations suggested NOM-facilitated photobleaching of Trp and photoproduction of a new FDOM component under UVA illumination. Meanwhile, the fluorescence of the NOM in the absence of Trp was well represented by two HS-like components which decayed monotonically upon exposure to UVA light, while the photoinduced decay became nonmonotonic in the presence of Trp, and one component even increased with illumination during certain time window, indicating Trp-facilitated production of HS-like fluorescence signatures from NOM. The findings show that UVA-induced optical signature changes of tryptophan and HS-like materials are coupled and highlight the potential impact of absorption of solar UVA light by natural dissolved organic matter (DOM) on using the optical signatures to trace sources and sinks of DOM. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated the efficacy of PUVA (psoralen plus ultraviolet A irradiation) therapy against sclerotic skin lesions in scleroderma, although the mechanisms underlying the improvement of the skin sclerosis by this therapy remain unknown. We investigated the effects of ultraviolet A (UVA) irradiation following the treatment with 8-methoxypsoralen on types I and III collagen synthesis and the gene expression of collagenase in cultured normal and scleroderma fibroblasts. The treatment reduced types I and III collagen synthesis and consequently, the types I and III collagen mRNA levels, in a UVA dose-dependent manner in both the normal and SSc fibroblasts, whereas the mRNA levels of collagenase remained almost unaltered. These results suggest that reduction of collagen synthesis by the fibroblasts may be one of the mechanisms underlying the efficacy of PUVA therapy against the sclerotic skin lesions in scleroderma. [ABSTRACT FROM AUTHOR]

We report the effect of UVA irradiation on collagen metabolism of fibroblasts, including both synthesis of the collagen degrading enzyme collagenase and de novo synthesis of type I collagen as the major structural component of the dermis. For this purpose confluent fibroblast monolayers were irradiated under standardized conditions (5, 15, 35, 60 J/cm using UVASUN 3000, Mutzhas, Munich, FRG, and UV source Sellas sunlight type 2.001, Sellas, Gevelsberg, FRG). Subsequently, total RNA was isolated and subjected to dot blot and northern blot analysis using oligolabelled cDNA clones for human type I collagen, collagenase and Β-actin. Collagen type I and Β-actin mRNA levels remained unaltered following irradiation, suggesting that the synthetic pathway of collagen metabolism at the pretranslational level is not affected by short-term UVA irradiation. However, collagenase mRNA was found to be dose-dependently induced in fibroblasts after irradiation, thus probably contributing to the actinic damage to the dermis. These in vitro data were confirmed in vivo using in situ hybridization on frozen sections of biopsy material obtained from UVA irradiated patients. [ABSTRACT FROM AUTHOR]