Photochemistry and Photobiology最新文献

Circadian clocks facilitate organisms' adaptation to the day-night environmental cycle. Some of the component genes of the clocks ("clock genes") respond directly to changes in ambient light, supposedly allowing the clocks to synchronize to and/or oscillate robustly in the environmental cycle. In the dicotyledonous model plant Arabidopsis thaliana, the clock genes CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), LATE ELONGATED HYPOCOTYL (LHY) and PSEUDO-RESPONSE REGULATOR 9 (PRR9) show transient expression in response to the morning light. Here we studied light responses of CCA1a/CCA1b and PRR2, homologous genes to CCA1/LHY and PRR9, respectively, in the moss Physcomitrium patens. We found that light of different wavelengths induced PRR2 while they repressed CCA1a/CCA1b. A disruption strain lacking all phytochrome genes lost PRR2 induction, but still maintained CCA1a/CCA1b repression. The remaining light repression of CCA1a/CCA1b was impaired by the photosynthesis inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Probably therefore, a phytochrome signaling induces PRR2, whereas a photosynthesis-mediated signaling represses CCA1a/CCA1b. Conservation and divergence in the clock gene responses between P. patens and A. thaliana are discussed.

Pyranoflavylium cations are synthetic analogues of pyranoanthocyanins, the much more color-stable compounds that are formed spontaneously from grape anthocyanins during the maturation of red wines. In the present work, our studies of the photophysical properties of pyranoanthocyanin analogues are extended to include nine pyranoflavylium cations substituted with one or two bromo and/or iodo heavy atoms. The room temperature fluorescence, 77 K fluorescence and phosphorescence, triplet formation in solution, and sensitized singlet oxygen formation, with excited state acidity suppressed by the addition of trifluoroacetic acid, are compared to those of similar pyranoflavylium cations that do not contain a heavy atom. Heavy atom effects on the photophysics of the S₁ state of pyranoflavylium cations are found to be relatively small, which is attributed to the nodal properties of the orbitals involved, which prevent effective mixing of the spin-orbit coupling on the heavy atoms into the excited singlet state, S₁, of the pyranoflavylium chromophore. Heavy atom effects on the phosphorescence of these heavy atom-substituted pyranoflavylium cations at 77 K are somewhat larger, consistent with a spin-orbit coupling-induced increase in the radiative rate constant for phosphorescence, as are the triplet-sensitized singlet oxygen formation quantum yields in fluid solution.

Phototoxicity of skin due to the application of skincare products or fragrances is increasing from day to day, since a lot of natural extracts, with low or no toxicity in the dark, are being used in the skin exposed to solar radiation. In particular, the use of 4-hydroxy-3-methoxy benzaldehyde, known as vanillin, in the pharmaceutical, food, and cosmetic industries has increased in the last years. This compound is generally considered as safe for humans, and it has been used in a wide range of applications. Significant beneficial properties, such as antioxidant, anticancer, antimicrobial, among others, have been described for vanillin, along with low toxicity. However, although vanillin is used as an ingredient in cosmetic formulations that are applied to the skin, there are few studies on the photochemistry of vanillin degradation. The degradation of vanillin in aqueous solutions exposed to UV-A radiation (365 nm), both by direct absorption and by means of a photosensitized mechanism, was evaluated in different experimental conditions. On the bases of the experimental results, direct photodegradation of vanillin seems unlikely; however, photosensitized degradation of vanillin was observed in the presence of pterin, and vanillin dimers (6,6-dihydroxy-5,5- dimethoxy-[1,1-biphenyl]-3,3-dicarboxaldehyde) were detected as products. The mechanistic analysis indicates that the long-lived pterin triplet excited state is responsible of vanillin degradation, while the contribution of reactive oxygen species, such as superoxide anion, hydrogen peroxide, or singlet oxygen, is negligible. The thermodynamic feasibility of the potential reactions involved in the degradation mechanism was evaluated with the Rehm-Weller equation. Considering both the thermodynamic and kinetic evidence, we proposed a mechanism for the photosensitized degradation of vanillin.

Fungal infections related to biofilm formation on medical devices, such as endotracheal tubes (ETTs), pose significant health risks, especially during intubation procedures where fungi like Candida spp. can migrate into the lower respiratory tract. This study explores the use of Photodynamic Therapy (PDT) to prevent fungal cell migration from ETT surfaces to lungs, focusing on the role of curcumin as a photosensitizer. ETTs were coated with varying concentrations of curcumin, and biofilm formation was measured after applying PDT with a 50 J/cm² irradiation dose. The study found that ETTs functionalized with a one-third concentration of CUR reduced biofilm formation by 1.78 Log, significantly lowering microbial load and potentially decreasing hospital-acquired infections. Confocal fluorescence microscopy confirmed that PDT damaged the biofilm's extracellular matrix and caused detachment of dead fungal cells. Moreover, the fluorescence analysis reveals the photodegradation behavior of the photosensitizer within the tube, providing critical insights into its stability and durability, which are essential for evaluating the long-term applicability of these tubes in clinical settings. These results suggest PDT as a promising strategy to reduce fungal infections in high-risk patients, offering potential for future clinical application in preventing device-associated infections.

Modulating the photophysical properties of photosensitizers is an effective approach to enhance singlet oxygen generation for photodynamic therapy. Porphyrins are the most widely used photosensitizers due to their biocompatible nature. Aggregation-induced emission (AIE) characteristics of photosensitizers are one of the advantageous features that will enhance fluorescence, intersystem crossing, and efficient triplet state generation. Herein, we demonstrate two glycosylated porphyrin photosensitizers, ZnGEPOH (with two ethynyl groups) and ZnGPOH (without two ethynyl groups), which exhibit AIE. Detailed studies revealed that ZnGEPOH exhibited a two-fold increase in singlet oxygen production than ZnGPOH due to AIE. The photo-cytotoxicity of ZnGPOH and ZnGEPOH were evaluated using cancer cell lines A549 and AGS. ZnGEPOH shows superior photo-cytotoxicity with cell viability of 21% and 19% for A549 and AGS, respectively, at 250 μg/mL concentration in 48 h. Moreover, ZnGEPOH exhibits minimal photo-cytotoxicity towards the control cell line HEK 293.

The ocular safety of 222-nm far-ultraviolet-C (UV-C) irradiation, widely recognized for its germicidal properties, was evaluated in a clinical setting to assess its long-term health effects on the human eye. This prospective observational study involved a 36-month follow-up of physicians working in an ophthalmic examination room equipped with 222-nm UV-C lamps. Initially, a 12-month observation showed no signs of acute or chronic ocular damage. To further substantiate these findings, the study period was extended to 36 months, during which four participants underwent regular ocular examinations, including assessments of visual acuity, refractive error, and corneal endothelial cell density. The irradiation dose was meticulously controlled to remain within the previous threshold limit of 22 mJ/cm² over an 8-h period, as advised by the ACGIH prior to 2022. Results indicated no significant changes in these parameters, suggesting no clinically significant ocular hazards associated with prolonged exposure to 222-nm UV-C irradiation under real-world conditions. Additionally, no delayed side effects, such as pterygium, keratopathies, or cataracts, were observed. Our study supports the safe use of 222-nm UV-C for microbial disinfection in occupied environments and provides a robust foundation for updated safety guidelines.

Green and Red LEDs increase insulin production, but their comparative effects on pancreatic and beta cell development are unclear. Zebrafish embryos were divided into three groups: Control (n = 60), Green (G) (n = 60), and Red (R) (n = 60), then irradiated for three days (14 hours/day) with 0.5 W/cm² G (λpeak = 520 nm, 180 mA) and R (λpeak = 660 nm, 210 mA). At the end of 72 h, pancreatic and beta cells, circadian rhythm, and oxidative stress gene were analyzed using RT-PCR. Malondialdehyde, nitric oxide, superoxide dismutase, and glutathione levels were also evaluated. In the Red group, pancreatic area increased by ~97.13% compared to the Control group and by approximately ~62.16% compared to the G group (both p < 0.0001), and no significant difference in beta cell area (p = 0.964). G group insulin expression increased 2.31-fold compared to R group (p < 0.0001). Red LED treatment increased MDA levels (p < 0.001), oxidative stress (fth1b, nqo1) (p < 0.0001), and per1b during the photophase (p < 0.0001) compared to G group. R LED treatment increases oxidative stress and disrupts circadian rhythm, leading to reduced insulin secretion. The positive effects of G LED treatment have potential for metabolic syndrome, diabetes, and pancreatic diseases.

Ultraviolet radiations (UVR) produce harmful entities and reactive oxygen species (ROS) in skin cells, leading to skin photoaging. Caviar extract (CE) showed outstanding effects in delaying skin aging, but the underlying mechanism remains largely unknown. In this study, we prepared CE with acid protease and examined the anti-skin photoaging effects. The results showed that CE performed no cytotoxicity to HaCaT cells. For antioxidant properties, the EC50 values of DPPH and ABTS radical scavenging activity for CE were 1.27 and 5.20 mg/mL, respectively. It significantly reduced NF-κB, MMP-3 and MMP-9 protein expression levels, and increased IκB and TIMP-1 expression level in UVA-irradiated HaCaT cells. In the skin aging mice model, CE reduced the degree of UV-induced skin photoaging. Histological study confirmed that CE can ameliorate the adverse effects of UV exposure on the skin. Moreover, we found that CE could enhance the activities of Superoxide dismutase (SOD), and increased the contents of hydroxyproline (HYP) in photoaged mice skin. And CE elevated the protein expression level of COL17A1, KRT10, and KRT14 in mice skin. Taken together, our results bright systemic and new insights of CE into preventing UV-induced skin photoaging.

The Mimosa pudica leaf has motor organs allowing movements driven by cell osmotic changes in the parenchyma cells in response to various stimuli. Short white light pulses induce rapid and large seismonastic-like movements (denoted "photostimulation") of the primary pulvini in various leaves within 120 s after the onset of light. An early event recorded is a wavelength-related modification of the plasma membrane difference: potential depolarization under white, blue, green, and red wavelengths, and hyperpolarization under far red wavelengths (and also in darkness). The photoreactivity of the pulvini is controlled by a circadian rhythm and modulated by the applied diurnal photoperiod cycle (photophase ranging from 6 to 18 h). The reactivity varied among plants and even between leaves on the same plant. The level of reactivity is related to the photon fluence rate in the range from 10 to 140 μmol m^-2 s^-1 under white light and to the experimental temperature in the range 15°C-35°C. An "accommodation" to light supply is evidenced by a modulation of the reactivity in relation to the schedule of light application under low fluence rates and the introduction of short darkness intervals during the first 30-s light pulse. The blue light-induced photostimulation is under phytochrome control.

The green-light driven photocatalytic N-deethylation reaction of Rhodamine B (RhB) on a TiO₂ film was investigated by UV-vis absorption and fluorescence emission spectroscopies, in addition to HPLC and HR-MS, to ascertain the nature of the reaction products. The evolution of the photocatalytic reaction was chemometrically analyzed using Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) of the spectroscopic data to obtain the kinetic and spectral decomposition of the RhB derivatives involved in the reaction. This was then compared with the results obtained by standard HPLC analysis. The MCR-ALS analysis yielded satisfactory spectral and kinetic profiles for RhB and the fully deethylated product, Rhodamine 110. However, the spectral profiles for the N-triethyl (3EtRh) and the mixture of the two isomeric N-diethyl (2EtRh) derivatives exhibited some spectral distortions due to significant spectral overlap between these compounds. In contrast to the HPLC analysis, the MCR-ALS could not resolve the N-ethylrhodamine (EtRh) derivative. The deethylation reactions occurred via independent zero-order steps at the surface of TiO₂, indicating that the RhB degradation reaction is governed by the adsorption-desorption equilibrium of the dye and derivatives on the photocatalyst surface, thereby enhancing the diffusion of compounds on the surface.