Photochemical & Photobiological Sciences最新文献

Sunscreens are mainly characterized by their sun-protection factor (SPF), which is measured according to the in vivo gold standard ISO 24444. Although the SPF concept is simple, SPF values are difficult to measure, due to the rather high variability caused by the complex interaction of light and skin. For half a century, there have been attempts to correlate the costly and ethically controversial in vivo procedure with a non-invasive (in vitro) method. After decades of development, alternative non-invasive SPF methods are expected to become available as ISO standards in early 2025. In particular, sunscreen manufacturers who use zinc oxide (ZnO) in higher concentrations (conc.) (10-25%) in their formulations, are concerned that these new in vitro methods would not confirm the SPF-values on their labels that have been determined in vivo, according to ISO 24444. This brief review reveals that sunscreen formulations with high conc. of ZnO often yield SPF_{in vitro} values that are lower than the SPF_{in vivo} values. This can be explained by the fact that in vitro methods have been developed for conventional emulsions products with organic UV filters, but not for highly concentrated ZnO-alone sunscreens. Fortunately, there seems to be a fix for this problem. There is a difference in density between ordinary emulsions with organic filters (density of the residual oil phase ~ 1.0 g/ml) and highly concentrated ZnO-alone formulations (~ 1.3-1.7 g/ml). As the application of current standards is weight-based, this makes the film on the PMMA plate much thinner, which is likely to lead to lower SPF_{in vitro} values. Preliminary experiments show that using the same volume on the PMMA plates instead of the same weight as organic UV filters gives a much better correlation between in vitro and in vivo SPF results. A recent evaluation of three samples of highly concentrated ZnO sunscreens by the Dutch NVWA seems to confirm these findings. Further experimental evidence is required to fully understand this phenomenon and to adapt the in vitro method for higher conc. ZnO formulations accordingly.

Perovskite quantum dots (pQDs) have gathered a lot of attention because of their outstanding optoelectronic properties. Photoswitchable pQDs have the potential for application in single particle optical memories and bio-imaging. Hybrids of photochromic diarylethenes (DAE) and pQDs show a luminescence photoswitching property, however, the cycle stability in such systems is low because of photoinduced electron transfer (PET) from pQDs to DAE. In this study, various hybrids of DAEs and pQDs with different spacer lengths between the pQD donors and DAE acceptors were synthesized and their stability towards multiple cycles of luminescence photoswitching was evaluated. It was found that the electron transfer pathway can be blocked and very stable switchable hybrids can be produced when the distance between the donors and acceptors was long enough. Furthermore, the effect of softness of the basic ligands and the synthesis method of the pQDs on the cycle stability of the hybrids were investigated. The findings of this study suggest that the photoswitching stability can be improved in hybrid systems by proper molecular design of the photochromic molecule.

The ultrafast processes caused by photoexcitation of (n-Bu₄N)₂[Pt(NO₃)₆] complex in acetonitrile were studied by means of transient absorption (TA) pump-probe spectroscopy and verified by quantum chemical calculations. The primary photochemical process was found to be an inner-sphere electron transfer followed by an escape of an ^•NO₃ radical to the bulk solution. The reaction occurs via the dissociative triplet excited LMCT state of the initial complex. Based on the experimental data and quantum chemical calculations, the mechanism of ultrafast photophysical and photochemical processes is proposed.

Two azo dyes 2-hydroxy-5-(4-nitrophenylazo)benzaldehyde and 2-hydroxy-5-(4-chlorophenylazo)benzaldehyde dissolved in carbon tetrachloride, hexane, acetone and acetonitrile were irradiated with 365 nm UV light, and processes, occurring in them, were studied by NMR and UV-vis spectroscopy. It was established that reversible trans/cis photoisomerization of the molecules occurs in the non-polar solvents and is not observed in the polar solvents. 2D NOESY NMR spectroscopy was used to identify isomers of the azo compounds. Based on the chemical shifts of the signals, it was established that these compounds are in the trans-form before UV irradiation. Spectra of the azo dyes before and after UV irradiation allowed assignment of the chemical shifts of the cis-isomers. In polar solvents these compounds undergo a hypochromic effect under heating or irradiation with UV light. Both compounds exhibit solvatochromism. The shifts in NMR signals caused by photoisomerization of the molecules were compared with the shifts in the NMR signals of other azo compounds such as Disperse Orange 3, Disperse Red 1 and azobenzene.

Individuals suffering from asthenospermia, an infertility disorder, have reduced sperm motility. This study's goal was to identify the impacts of diverse photobiomodulation procedures on the motility of sperm in vitro in patients with asthenospermia, either in isolation or in combination with Apigenin. At 633 nm and 808 nm, the lasers are used with multiple dose values (0.6, 1.2, and 2.4) J/cm² and altering Apigenin concentrations (5, 10, 25, and 50 μM). All of the photobiomodulation procedures were assessed. Assessing factors were the DNA fragmentation index, sperm viability, as well as progressive sperm motility. The progressive sperm motility results for 633 nm and 808 nm show a significant increase over 633 nm + 808 nm after 60 min after irradiation. Sperm motility increased more quickly under the 808 nm procedure than under the other procedures (p < 0.02). The observation of progressive sperm motility indicated that a 10 μM concentration of Apigenin created higher results than other concentrations (p < 0.01). Apigenin with 808 nm at 1.2 J/cm² resulted in better sperm motility (p < 0.01) and decreased DNA fragmentation index. There was a notable increase (p < 0.05) in the DNA fragmentation index with the 633 nm + 808 nm procedure. At a 10 μM concentration of Apigenin, the DNA fragmentation index was lower than at a 50 μM concentration (p < 0.02). Neither Apigenin nor photobiomodulation significantly decreased sperm viability. The study suggests that asthenozoospermia patients may benefit from apigenin utilized alongside photobiomodulation, while further investigation is required.

The disruption of lipid droplet function is associated with the pathogenesis of various diseases. Clarifying the response behavior of lipid droplets to the microenvironment at the cellular level is of great significance. Plant lipids not only exist in phospholipids in cell membranes, but also in aromatic essential oils. Monitoring the level of lipid droplets in plant cells using fluorescent probes provides a simple method for screening lipid-rich varieties. We synthesized a polarity-viscosity responsive coumarin fluorescent probe, Cou-CN, which achieved sensitive detection of polarity and viscosity in dilute solution environments by constructing this simple probe with ICT and TICT properties and verifying it using Gaussian computational simulation. Cou-CN exhibited good lipid droplet illumination effects in HepG2 cells with a correlation coefficient of 0.92 compared to the commercial lipid droplet dye BODIPY. Additionally, co-staining the probe with the lipophilic commercial dye Nile Red in tobacco root stem seedling cells resulted in a high correlation coefficient of 0.9.

Excessive exposure to sunlight can contribute for skin photo-damage, such as sunburn, dryness, wrinkles, hyperpigmentation, immunosuppressive events and skin sensitization reactions. The use of aftersun products is an effective strategy to reduce the visible signs and symptoms of acute photodamage in the skin. Aiming to unveil the active ingredients able to offset acute sun damage, this work focuses on the characterization of the aftersun products market. A total of 84 after-sun formulations from 41 international brands currently marketed in Portugal were analyzed concerning the composition described on the product label, identifying natural and synthetic/semi-synthetic ingredients with the ability to mitigate solar-induced effects. The majority of aftersun formulations contained ingredients derived from terrestrial and marine sources (> 80%). An in-depth examination of these compounds is also offered, revealing the top of the most used natural and synthetic/semi-synthetic ingredients present in aftersun products, as well as their mechanism of action. A critical appraisal of the scientific data was made aiming to highlight the scientific evidence of ingredients able to mitigate skin photodamage. Amino acids and peptides, and A. barbadensis extract were tested for their in vivo efficacy. Nevertheless, all the ingredients were analyzed with in vitro studies as preliminary screening before in vivo, ex vivo and/or clinical studies. In summary, this study provides an overview of the use of active ingredients in commercial aftersun products to understand better the benefits associated with their use in cosmetic formulations and identify opportunities for innovation.

Cefadroxil is a widely used antibiotic with a low elimination efficiency in wastewater treatments plants, so it represents a contaminants of emerging concern that should be removed. The photosensitization process that involves natural pigments and visible sunlight can be offered as an environmentally friendly alternative to be considered for Cefadroxil degradation. In this investigation, we carried out a mechanistic and kinetic approach to Cefadroxil photodegradation sensitized by Riboflavin and Humic Acid, in individual and combined processes. Our experiments indicate that Cefadroxil is able to interact with the excited states of Riboflavin as well as with the photogenerated reactive oxygen species, with an important contribution of singlet oxygen. The antibiotic was less sensitive to the photodegradation in the presence of Humic Acids and in the mixture of Riboflavin and Humic Acids. Self-sensitization processes and internal filter effects are proposed as possible explanations for the observed phenomenon. The reaction between Cefadroxil and singlet oxygen showed a dependence with the pH of the medium, the photodegradation kinetic constants are greater at alkaline pH compared to neutral pH. The reaction is favored when the anionic species of the antibiotic is present. Microbiological tests on S. aureus indicated that the antibiotic reduce its antimicrobial activity as a consequence of the photooxidative process mediated by singlet oxygen. We believe that the results are relevant since, the sensitized photodegradation process could lead to the oxidation of Cefadroxil and to the progressive loss of its antimicrobial function, this fact could contribute to the decrease in the generation of bacterial multi-resistance to antibiotics in the environment.