Search

Ultraviolet-A persistent luminescence (UVA PersL) materials have attracted considerable attention due to their extensive potential in applications such as photodynamic therapy, photocatalysis, and sterilization. Herein, we report a novel UVA PersL phosphor Y 3 Ga 3 MgSiO 12 :Bi3+ (YGMSO:Bi3+) with continuous photocatalytic capabilities. The PersL duration of the YGMSO:0.005Bi3+ sample can exceed 8 h after excitation with 254 nm UV light, and the UVA PersL emission peak is located at 324 nm. Specifically, we investigated the distribution and depth of traps using thermoluminescence curves and further demonstrated that oxygen vacancy is the main defect type responsible for producing PersL by X-ray photoelectron spectroscopy. On this basis, the PersL mechanism of YGMSO:Bi3+ is established. Furthermore, considering that the UVA PersL spectrum of YGMSO:Bi3+ aligns with the absorption band of TiO 2 , we synthesized YGMSO:Bi3+/TiO 2 composite for methylene blue degradation experiments. The experimental results indicate that the material can serve as a continuous excitation source for TiO 2 , facilitating its application in continuous photocatalysis. Overall, the developed UVA PersL material YGMSO:Bi3+ offers valuable insights for the design of UVA light sources for photocatalytic applications. [Display omitted] • A novel UVA PersL phosphor Y 3 Ga 3 MgSiO 12 :Bi3+ (YGMSO:Bi3+) PersL time can last for more than 8 h after 254 nm UV light excitation. • Oxygen vacancies serve as the primary defect type, store electrons, and function as the trap center. • The phosphor can serve as a continuous excitation source of TiO 2 and be applied to continuous photocatalysis. [ABSTRACT FROM AUTHOR]

Abstract The bactericidal activity of ferulic acid (FA) against various microorganisms was remarkably enhanced by ultraviolet-A (UV-A) irradiation (wavelength, 365 nm). However, the bactericidal mechanism in the photo-combination system has not been evaluated. In the present study, this combined treatment was characterized by investigating associated changes in cellular functions of Escherichia coli , including assessments of respiratory activity, lipid peroxidation, membrane permeability, and damage to DNA and the cell surface. FA adsorbed onto and was incorporated into bacterial membranes, and the affinity resulted in decreased respiratory activity and enhanced lipid peroxidation in the cytoplasmic membrane with low-fluence (1.0 J/cm2) UV-A irradiation. Flow cytometry analysis revealed that additional exposure (8 J/cm2) combined with FA (1 mg/mL) induced increased cell permeability, yielding a 4.8-log decrease in the viable cell count. Morphologically, the treated cells exhibited a bacterial membrane dysfunction, producing many vesicles on the cell surface. However, despite this effect on the cell surface, plasmid DNA transformed into FA-treated E. coli maintained supercoiled integrity with negligible DNA oxidation. Our data strongly suggested that FA functions inside and outside the bacterial membrane; UV-A exposure in the presence of FA then causes increased oxidative modification and subsequent disruption of the bacterial membrane, without causing detectable genotoxicity. Graphical Abstract Unlabelled Image Highlights • Bactericidal action of combined ferulic acid and ultraviolet-A was investigated. • Respiratory activity was decreased by uptake of ferulic acid into bacterial membrane. • Short UV-A exposure for the combination facilitated lipid peroxidation. • The combination enhanced permeability and cell damage during UV-A irradiation. • No genotoxicity, DNA oxidation, or DNA strand breaks were seen for the combination. [ABSTRACT FROM AUTHOR]

Abstract Ultraviolet-A and melanin are implicated in melanoma, but whether melanin in vivo screens or acts as a UVA photosensitiser is debated. Here, we investigate the effect of UVA-irradiation on non-pigmented, lightly and darkly pigmented melanocytes and melanoma cells using electron spin resonance (ESR) spectroscopy. Using the spin trap 5,5 Dimethyl-1-pyrroline N -oxide (DMPO), carbon adducts were detected in all cells. However, higher levels of carbon adducts were detected in lightly pigmented cells than in non-pigmented or darkly pigmented cells. Nevertheless, when melanin levels were artificially increased in lightly pigmented cells by incubation with L -Tyrosine, the levels of carbon adducts decreased significantly. Carbon adducts were also detected in UVA-irradiated melanin-free cell nuclei, DNA-melanin systems, and the nucleoside 2′-deoxyguanosine combined with melanin, whereas they were only weakly detected in irradiated synthetic melanin and not at all in irradiated 2′-deoxyguanosine. The similarity of these carbon adducts suggests they may be derived from nucleic acid– guanine – radicals. These observations suggest that melanin is not consistently a UVA screen against free-radical formation in pigmented cells, but may also act as a photosensitizer for the formation of nucleic acid radicals in addition to superoxide. The findings are important for our understanding of the mechanism of damage caused by the UVA component of sunlight in non-melanoma and melanoma cells, and hence the causes of skin cancer. Graphical abstract fx1 Highlights • Carbon radicals are detected in UVA-irradiated cells. • More carbon radicals detected in lightly melanin-pigmented cells than cells without melanin. • Increase in melanin in lightly pigmented cells decreases radical levels. • Carbon radicals detected in cell nuclei, DNA-melanin and 2′-deoxyguanosine-melanin. • Carbon radicals likely to be nucleic acid - guanine – radicals. [ABSTRACT FROM AUTHOR]

Abstract Antimicrobial chemotherapy based on ultraviolet-A (UVA) irradiation of polyphenol solution has been proposed as an adjunctive treatment for dental caries. However, the safety of this treatment has not been thoroughly evaluated. Therefore, the aim of the present study was to assess the influence of this treatment on the oral mucosa in hamsters and wounded skin in rats. An oral mucosal irritation test was performed in hamsters. The cheek pouch was everted and treated with UVA irradiation (wavelength: 365 nm) of pure water, 1 mg/mL of caffeic acid, or 1 mg/mL of grape seed extract using a light-emitting diode at an irradiance of 275 mW/cm2. Each treatment was performed for 2 or 5 min and repeated three times. Macroscopic and histological evaluations were performed 24 h after the last treatment. We also examined the effects of the treatment on the healing process of skin wounds in rats. Full-thickness skin wounds created on the back of the rats were treated for 2 min as described above, but only once. The wound area was then assessed daily for 9 days. The results demonstrated that the treatment induced oral mucosal irritation depending on the irradiation time; however, it did not influence the wound healing process. The oral mucosal irritation potential of three treatment sessions performed for 2 and 5 min was minimal and mild to moderate, respectively, according to histological analysis. These findings suggest that the duration of treatment based on UVA irradiation of polyphenols in the oral cavity should be as short as possible, considering the clinical efficacy of the antimicrobial effects and the irritation potential. Graphical Abstract Unlabelled Image Highlights • Adverse effect of treatment with ultraviolet-A irradiation of polyphenols was tested. • Treatment (2 min × 3 times) caused minimal irritation to the oral mucosa in hamsters. • Treatment (2 min × once) did not affect the healing process of skin wounds in rats. • UVA irradiation of caffeic acid for 2 min could effectively kill Streptococcus mutans. • This technique may be used in the oral cavity with minimal acute adverse effects. [ABSTRACT FROM AUTHOR]

Ultraviolet-A radiation (UV-A: 315–400 nm) is a component of solar radiation that exerts a wide range of physiological responses in plants. Currently, field attenuation experiments are the most reliable source of information on the effects of UV-A. Common plant responses to UV-A include both inhibitory and stimulatory effects on biomass accumulation and morphology. UV-A effects on biomass accumulation can differ from those on root: shoot ratio, and distinct responses are described for different leaf tissues. Inhibitory and enhancing effects of UV-A on photosynthesis are also analysed, as well as activation of photoprotective responses, including UV-absorbing pigments. UV-A-induced leaf flavonoids are highly compound-specific and species-dependent. Many of the effects on growth and development exerted by UV-A are distinct to those triggered by UV-B and vary considerably in terms of the direction the response takes. Such differences may reflect diverse UV-perception mechanisms with multiple photoreceptors operating in the UV-A range and/or variations in the experimental approaches used. This review highlights a role that various photoreceptors (UVR8, phototropins, phytochromes and cryptochromes) may play in plant responses to UV-A when dose, wavelength and other conditions are taken into account. [ABSTRACT FROM AUTHOR]

Highlights: [•] KatA activity is present in the matrix of P. aeruginosa biofilms. [•] Extracellular KatA is essential in the defense of P. aeruginosa biofilms against UVA. [•] KatA is not involved in the resistance to photocatalysis of P. aeruginosa biofilms. [Copyright &y& Elsevier]

Highlights: [•] Gemini-quaternary ammonium salt and UV-A light were combined to disinfect bacteria. [•] The combined disinfection decreased the viability of bacteria rapidly. [•] The decrease in viability depended on doses of the biocide and the UV-A fluence. [•] The combination caused overproduction of reactive oxygen species in cells. [•] The combination facilitated lipid peroxidation and DNA oxidation. [Copyright &y& Elsevier]

Abstract: Ultraviolet (UV) radiation can cause oxidative stress in insects. To gain insight into the roles of different antioxidant enzymes of Helicoverpa armigera adults in response to oxidative stress caused by UV-A at a molecular level, three antioxidant enzyme genes [encoding copper zinc superoxide dismutase (Cu/ZnSOD), catalase (CAT) and glutathione peroxidase (GPX)] were cloned. The deduced amino acid sequences of these genes are similar to that of other insects. In addition, the expression profiles of genes from a classic antioxidant defense system, comprising Cu/ZnSOD, manganese superoxide dismutase (MnSOD), CAT, thioredoxin peroxidase, GPX and glutathione-S-transferase, were also determined. The results indicated that all antioxidant enzyme genes (except MnSOD in females) were significantly upregulated at certain time points (from 30 to 90min) in both male and female adults of H. armigera following UV-A radiation. We also found that longer periods of radiation exposure did not yield higher levels of mRNA expression. Furthermore, changes of determined physiological parameters (glutathione, Cu/ZnSOD and MnSOD activity) were basically consistent with the gene expression profiles. We therefore infer that the different antioxidant enzymes of H. armigera act in a coordinated manner at the transcriptional level against oxidative stress caused by UV-A radiation. [Copyright &y& Elsevier]

Abstract: We have designed experimental conditions allowing the replacement of 50% of cholesterol of human keratinocytes (SVK14 line) with sitosterol or stigmasterol without affecting cellular viability. We have investigated the influence of incorporating phytosterol on the ultraviolet-A-induced formation of lipid-peroxidation products (thiobarbituric reactive substances (TBARS)) in these cells. Our results show that ultraviolet-A-induced lipid peroxidation depends on the nature of the phytosterol. Sitosterol induces a significant decrease (−30%) of TBARS relative to the control whereas stigmasterol markedly increases lipid peroxidation (+70%). We have also studied the effect of plant sterols on prostaglandin release by using the Ca2+ ionophore A23187 as an in vitro model of the inflammation induced by UVA radiation. We show that in the presence of 50% of phytosterol (particularly stigmasterol), the release of prostaglandin (6-ketoPG1α, PGE2) is increased compared to untreated cells. This pro-inflammatory effect of phytosterols is correlated with a loss of the regulation of the intracellular Ca2+ concentration. [Copyright &y& Elsevier]

Abstract: We examined the structure–phototoxicity relationship for fluoroquinolone antimicrobial agents (quinolones) using female albino Balb/c mice. First of all, to obtain an optimum dosage level for induction of phototoxicity, the prototype phototoxicant sparfloxacin was intravenously administered once at 10mg/kg, 30mg/kg or 100mg/kg to female mice, followed immediately by ultraviolet-A (UVA) irradiation for 4h (21.6J/cm2). The auricular thickness was measured at pre-dose (0h), 4, 24, 48, 72 and 96h post-dose, and then the histopathological examination of the auricle was performed. As results, the auricular thickness increased from 30mg/kg, in conjunction with edema, cellular infiltration, epidermal necrosis and focal loss of the auricle. On the basis of these information, ciprofloxacin, enoxacin, fleroxacin, gatifloxacin, lomefloxacin, norfloxacin and ofloxacin were given intravenously to mice at a fixed dose of 100mg/kg to compare their potential phototoxicities. Certain quinolones caused the auricular lesions in the following rank order (from lowest to highest): vehicle control (non-phototoxicity)=gatifloxacin=ofloxacin<ciprofloxacin=norfloxacin<enoxacin=fleroxacin<lomefloxacin=sparfloxacin. From the viewpoint of the structure–phototoxicity relationship, quinolones possessing the C-8 substituent with a fluorine or hydrogen and 1,8-naphthyridine derivative evoked phototoxicity in the mouse auricle. These results demonstrate that phototoxicity induced by quinolones would be related to the property of the eighth position. [Copyright &y& Elsevier]

The results reported herein indicate that the ultraviolet-A (UVA) radiation-induced effects in Escherichia coli depend on its growth phase. Stationary-phase cells recover faster from a sub-lethal UVA exposure and have a higher resistance to lethal effect of the radiation than exponential growing cells. Although pre-incubation in spent medium supernatant increased the resistance of log-phase cells to lethal UVA effects, this pre-treatment considerably prolonged the duration of the radioinduced sub-lethal growth delay. The aim of the present study was to investigate the effect exerted by the E. coli conditioned media and evaluate the influence of nutritional stress, hydrogen peroxide and acetate. Pre-incubated in conditioned medium, cells in exponential growth phase were irradiated and the induced effects were compared with those found when catalase, high culture densities and acetate were employed. Unexpectedly, the duration of the growth delay in cells submitted to these treatments was shortened in comparison with control cells incubated in conditioned medium with no modifications. Lengthening of the growth delay was mimicked when exponentially growing cells were incubated in fresh medium supplied with 5 μM H2O2. The effects of spent medium on wild type and rpoS mutant strains were similar, indicating that this response is independent of RpoS controlled functions. We assumed that an oxidative component of the spent medium, probably H2O2, could be involved in the observed phenomenon. This effect is specific of E. coli and independent of rpoS. [Copyright &y& Elsevier]

Ultraviolet-A (UV-A) radiation induced changes in photosystem II (PS II) of senescing leaves of wheat seedlings were investigated. UV-A radiation did not show any significant effect on the level of photosynthetic pigments. However, the decline in Fv/Fm and oxygen evolution rate indicated the damaging effect of the radiation on primary photochemistry of PS II. Modification at the QB-binding site was inferred from the observed downshift of peak temperature of thermoluminescence (TL) B-bands. The UV-A induced changes in PS II of chloroplasts from senescing leaves were found to be synergistically accelerated by high growth temperature. [Copyright &y& Elsevier]

Titanium dioxide (TiO2) has been reported to produce OH radical under ultraviolet-A (UVA) irradiation and to induce cytotoxicity. Various crystal forms and sizes of TiO2 with UVA irradiation from OH radical generation was analysed spin trapping-X band (electron-spin resonance (ESR) spectroscopy. The amount of OH radical was determined with ESR signal intensity of the adducts in which OH radical was trapped with the spin-trapping reagent dimethyl pyrroline-N-oxide (DMPO). The formation of OH radicals varied in both crystal size and form of TiO2. Irradiation of the anatase form of TiO2 produced large numbers of OH radical in TiO2 and UVA in a dose-dependent manner, but rutil form (90 nm in size) showed less OH radical generation. The crystal size had large influence on OH radical generation, but the optimum size for the OH radical generation was different between both forms. The UVA absorption spectrum of TiO2 differed in regard to crystal size and form of TiO2, but no relation was observed between UVA absorbency and OH radical formation. The cytotoxicity of TiO2–UVA irradiation was determined against Chinese hamster ovary (CHO) cells and a significant relationship was obtained between the cytotoxicity and the OH generation. Measurement of the amount of OH radical production by UVA irradiation with ESR is needed to clarify the effect of crystal form or sizes of TiO2 on OH radical production and cytotoxicity. [ABSTRACT FROM AUTHOR]

Nitritation is currently known as a bottleneck for mainstream nitrite shunt or partial nitritation/anammox (PN/A). Here we propose a new approach to selectively eliminate nitrite oxidizing bacteria (NOB) for mainstream nitritation by low-dose ultraviolet-A (UVA) irradiation. The results showed that mainstream nitritation was rapidly achieved within 10 days with UVA irradiation at the dose of 0.87 μE L−1 s−1, and nitrite accumulation ratio (NO 2 −-N/(NO 2 −-N + NO 3 −-N) ×100%) stabilized over 80%. Microbial community analysis revealed that two typical NOB populations (Nitrospira and Ca. Nitrotoga) detected in the control reactor were suppressed efficiently in UVA irradiation reactor, whereas the Nitrosomonas genus of ammonium oxidizing bacteria (AOB) remained at similar level. Intracellular reactive oxygen species (ROS) analysis indicated that NOB-dominant sludge tends to generate more intracellular ROS compared with AOB-dominant sludge in the presence of UVA, leading to the inactivation and elimination of NOB. Additionally, amounts of microalgae found in UVA irradiation reactor could help to suppress NOB by generating ROS during photosynthesis. Briefly, the UVA irradiation approach proposed in this study was shown to be promising in NOB suppression for reliable mainstream nitritation. Image 1 • Low-dose UVA irradiation can selectively eliminate NOB, while no effect on AOB growth. • NOB suppression is due to the biocidal effects of intracellular ROS induced by UVA. • UVA irradiation can serve as a promising approach for mainstream nitritation. [ABSTRACT FROM AUTHOR]