Photochemistry and Photobiology最新文献

Inorganic semiconductors such as TiO₂ absorb ultraviolet light to promote reactions. However, sunlight consists mainly of visible light, and so the development of photocatalysts that can use visible light is being actively researched. Density functional theory (DFT) calculations previously showed that the introduction of formyl, carboxyl, and carboxyethyl groups into picene can absorb visible light and generate hydrogen via the decomposition of water. In this study, these substituted picene derivatives were employed as photocatalysts, and their water photolysis activities were evaluated under visible light irradiation. All three picene derivatives were active photocatalysts, with hydrogen production activities decreasing in the order of: picene-13-carbaldehyde (CHO-picene) > picene-13-carboxylic acid (COOH-picene) ≈ Ethyl picene-13-carboxylate (COOEt-picene) > picene. Subsequently, the effects of the three functional groups on the hydrogen production activity in the water photolysis reaction were investigated in further detail. The effects of the functional groups were found to be in accordance with the Hammett equation, wherein a greater electron-withdrawing property led to a higher hydrogen production activity.

Reducing airborne disease transmission is a public health goal. Far-UVC light, defined as 200-235 nm, is a promising technology to inactivate viruses within occupied spaces. This work examines state of the art far-UVC emitting LEDs, with a center emission wavelength of 233 nm, for virus inactivation efficacy and for DNA damage to skin models. The LEDs were used to expose an aerosolized surrogate of SARS-CoV2, the human coronavirus OC43, and survival results estimated a susceptibility constant of k_233-aerosol = 4.0 ± 0.2 cm²/mJ, which corresponds to a D₉₀ of 0.58 mJ/cm². HCoV-OC43 was also exposed after drying on a plastic or glass surface, and inactivation results estimated susceptibility values of k_{1_233-plastic} = 6.7 ± 3.8 cm²/mJ and k_{1_233-glass} = 7.2 ± 3.0 cm²/mJ which were not significantly different. For safety evaluation, human skin biopsies exposed to 100 mJ/cm² from the 233 nm LEDs indicated only 8% of the epidermal cells were positive for DNA damage, whereas the same dose from a 254 nm lamp showed damage in 45% of epidermal cells. A radiant exposure of 100 mJ/cm² from the 233 nm LEDs did not produce DNA double strand breaks within the skin biopsies. These tests for the safety and efficacy of a 233 nm far-UVC LED system provide support for the continued development of far-UVC LED sources.

Photobiomodulation (PBM) has demonstrated potential in promoting peripheral nerve regeneration. However, there is a limited and inconclusive study on the application of light-emitting diode (LED) for nerve injury repair. In this study, we designed an 807-nm LED device with high luminous uniformity to investigate the effects of LED-based PBM on peripheral nerve injury repair. RSC96 cells were utilized as the target cells and optimal light parameters were selected based on ATP concentration, CCK-8 assays, PCR, and immunofluorescent staining. One-way analysis of variance and Student's t-test was used for statistical tests. LED irradiation at 10 mW/cm² for 30 min effectively enhanced Schwann cell proliferation, neurotrophic factor secretion, and MBP synthesis. To translate the cellular light parameters for animal studies, the transmittance through freshly obtained rat skin and biceps femoris muscle was assessed, and the transmittance was approximately 30%. After directly daily irradiating the sciatic nerve injury area in rats for 21 days at 33 mW/cm² for 30 min, we used gait analysis, immunofluorescence staining, muscle wet weight ratio, Masson staining, and transmission electron microscopy to evaluate nerve recovery. LED irradiation significantly improved sciatic nerve index, increased MBP staining intensity, and enhanced myelin sheath thickness, nerve diameter, and axon diameter. These results indicated the feasibility of LED-based PBM as a treatment method for peripheral nerve injuries.

Photocatalytic CO₂ fixation into solar fuels offers a promising route for renewable energy storage by converting CO₂ into chemical bonds. Among various products, formic acid is considered the most reliable candidate for industrial applications due to its high efficiency and sustainable feasibility. Various catalysts, including metals, chalcogenides, transition metals, and carbon-based materials, have been explored for this purpose. Polymeric organic frameworks are a class of crystalline polymers with tunable structures, making them potential candidates for metal-free photocatalysts. However, their low crystallinity often limits light-harvesting efficiency and photocatalytic activity, posing a challenge for industrial applications. The primary obstacles in this field are low activity and poor selectivity of photocatalysts. In this study, we propose a soft-template induction strategy to construct a metal-free heterojunction polymeric framework based on 5,15-di-(4-aminophenyl)-10,20-diphenyl porphyrin (BP) and perylene tetra-anhydride (PT), referred to as PTBP. This polymer exhibits high crystallinity and strong solar light absorption. The PTBP framework demonstrates better performance in solar-powered molecular artificial photosynthesis, achieving significant improvements over PT. Specifically, PTBP exhibits high 1,4-NADH/NADPH regeneration efficiencies (52.51%/58.41%) compared to PT (9.11%/10.1%), a substantial NADH consumption (119.25 μmol) in exclusive solar fuel production from CO₂ within 1 h, and excellent yield (50.37%) in the photocatalytic conversion of dopamine into an indole-derivative, surpassing PT (13.93%). The current finding highlights the benchmark photocatalytic potential of the PTBP polymeric framework's capacity for photocatalysis for CO₂ fixation and conversion of dopamine into indole derivatives.

In this study, a highly sensitive, cost-effective, and environmentally friendly fluorescent sensing platform is presented for the rapid detection of pyrene (PYR), a polycyclic aromatic hydrocarbon (PAH), by leveraging the optical properties of the plant pigment chlorophyll (Chl). The detection mechanism relies on monitoring changes in Chl's photoluminescence (PL) intensity, fluorescence lifetime, and Fourier-transform infrared spectra. An impressive detection limit of 0.25 picomolar was achieved, surpassing the sensitivity reported in many previous studies. Fluorescence resonance energy transfer (FRET) was identified as the primary mechanism underlying the observed sensing response. The platform's effectiveness was further validated using soil and water sediment samples collected from oil exploration sites, demonstrating reliable quantification of PYR. This research underscores the potential of Chl-based fluorescence as a sustainable and efficient tool for a wide range of sensing applications, particularly in environmental monitoring.

Antibacterial photodynamic therapy (aPDT) is a promising approach for inactivation of antibiotic-resistant bacteria; however, its effectiveness is compromised, particularly when bacteria hide within biofilm and if infection spreads deeper in tissue. To overcome this limitation, photosensitizers having absorption in the near-infrared region (NIR) (650-800 nm), where light penetrates deeper in tissue, need to be developed. We report aPDT efficacy of Cycloimide Purpurin-18 betaine hydrazide conjugate (CIPp-18-BH), a cationic chlorophyll derivative, against Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO). CIPp-18-BH was synthesized by conjugating CIPp-18 to betaine hydrazide (BH) using a carbodiimide coupling reaction. CIPp-18-BH, as compared to CIPp-18, exhibited lower lipophilicity; thereby, it did not aggregate in aqueous conditions and generated a substantial amount of singlet oxygen upon photo-excitation with red light. CIPp-18-BH exhibited no fluorescence in water and substantial fluorescence in less polar solvents. CIPp-18-BH bound to planktonic bacteria did not show fluorescence; whereas remarkable fluorescence was seen in biofilms, indicating it lies on the surface of bacteria and accumulates within the apolar micro-environment of biofilms. PDT of planktonic MRSA and PAO with 40 μM CIPp-18-BH led to ~7 log and ~2.5 log reduction in cell viability, respectively. Confocal microscopy showed that PDT led to substantial bacterial inactivation within MRSA and PAO biofilms, resulting in inhibition of biofilm growth by ~50% and ~20%, respectively. Results demonstrate that CIPp-18-BH is a promising photosensitizer for photodynamic inactivation of planktonic and biofilm-borne bacteria.

Nonmelanoma skin cancers are rising in incidence and are largely driven by solar ultraviolet B radiation (UVB) exposure. A growing body of evidence suggests that m⁶A RNA methylation plays a critical role in regulating the DNA damage response to UVB. Here, we identify a novel function for the m⁶A demethylase FTO in modulating the UVB damage response and skin carcinogenesis. We show that FTO loss enhances the repair of cyclobutane pyrimidine dimers (CPD), the major DNA lesions induced by UV radiation, in a METTL14-dependent manner, at least in part by promoting protein translation of the global genome repair (GGR) factor DDB2 through increased m⁶A methylation of DDB2 mRNA. These effects were recapitulated using two small-molecule FTO inhibitors, CS1 and FB23-2. Furthermore, loss of FTO reduced tumor growth in mice and FTO expression was upregulated in cutaneous squamous cell carcinoma (cSCC) compared with normal skin. Together, these findings uncover a critical role for FTO in regulating post-transcriptional gene expression in the UVB damage response and suggest that FTO may be a therapeutic target in skin cancer.

The increasing contamination of aquatic systems by synthetic dyes such as methylene blue (MB) underscores the urgent need for sustainable and cost-effective wastewater treatment technologies. In this study, a novel biocomposite photocatalyst composed of chitosan and thermally treated ZSM-5 zeolite, denoted as ZSM-5 (800)/CS, was synthesized and systematically evaluated for its environmental remediation potential. The ZSM-5 (800)/CS composite exhibited superior photocatalytic activity, achieving 63% MB degradation within 210 min-significantly higher than pure chitosan, which achieved only 21% removal under identical conditions. The reduced optical bandgap (2.24 eV) of the biocomposite enhanced visible-light absorption, thereby improving its photocatalytic performance. Moreover, under aerobic conditions, ZSM-5 (800)/CS demonstrated excellent catalytic efficiency for the selective oxidation of organic sulfides to sulfoxides, achieving up to 96% yield and selectivity. These results highlight the dual functionality of the biocomposite for both wastewater detoxification and valuable chemical transformation. The study emphasizes the potential of integrating biopolymeric and zeolitic frameworks to develop sustainable photocatalysts that contribute to cleaner water resources and greener environmental technologies.

6-Thioguanine (6-TGua) is one of the thiopurines used as a cytostatic drug. When internalized by cells, 6-TGua is metabolized through the purine salvage pathway and readily incorporated into DNA. Patients treated with these thiopurines are more prone to develop squamous cell carcinoma of the skin. The absorbance spectrum of 6-TGua, in contrast to guanine (Gua) or any other canonical base, has a maximum absorbance at 342 nm. Therefore, 6-TGua undergoes photoexcitation upon exposure to UVA radiation, with maximum absorption at 340 nm. In this study, the used approach unequivocally demonstrates the generation and quenching of ¹O₂ by 6-TGua via the direct spectroscopic detection of ¹O₂ monomol light emission at 1270 nm. Chemiluminescence-based methods were employed for the determination of the ¹O₂ generation quantum yield (Φ¹O₂) and the total ¹O₂ quenching rate constant (k_t). For the ¹O₂ quantum yield, we found values of 0.22 ± 0.03 for 6-TGua and 0.12 ± 0.03 for 2'-deoxy-6-thioguanosine (6-TdGuo). These compounds presented k_t values of 1.5 × 10⁷ L mol^-1 s^-1 and 1.1 × 10⁷ L mol^-1 s^-1, respectively. Through the comparison of these values with the ones obtained for 2'-deoxyguanosine (dGuo) and its oxidation product 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), we aim to provide new insights into the 6-TGua-containing DNA (DNA-6-TGua) reactivity towards ¹O₂ in a biological context.