Photochemistry and Photobiology最新文献

Inspired by natural photosynthesis, the study article offers a novel solution to the problem of creating cost-effective and efficient photocatalysts for CO₂ fixation. The subject of study is a sulfur-doped graphitic carbon nitride (SGCN) photocatalyst that is metal-free and has drawn a lot of interest because of its possible uses in energy storage, biomaterials, and photocatalysis. The work presents PVDF-HFP@SGCN film, a novel photocatalyst that is created by grafting poly (vinylidene fluoride-co-hexafluoropropylene) polymer brushes onto SGCN under the influence of visible light. The remarkable properties of film photocatalysts, including their capacity to effectively harvest solar light, their compatibility with the optical bandgap, and their well-structured π-electron channels, which enable efficient charge movement, are leveraged in this method. As a result, the recently developed film photocatalyst shows exceptional effectiveness in fixing CO₂, resulting in the generation of formic acid as a solar chemical with green energy. This result emphasizes how crucial the study is to developing renewable energy sources and lowering carbon emissions. Ultimately, the work makes a substantial contribution to the development of photocatalytic materials and emphasizes the possibility of PVDF-HFP@SGCN as a very efficient and adaptable catalyst for solar-driven chemical reactions, especially those involving the fixation of CO₂ and the generation of renewable energy.

Bacterial persistence is characterized by a subpopulation of metabolically dormant cells that exhibit transient tolerance to antibiotics, contributing to chronic and recurrent infections, particularly in Staphylococcus aureus, a pathogen responsible for severe infections. This phenomenon is evidenced by a biphasic killing curve, where an initial rapid decline is followed by a slowed death phase. Photodynamic inactivation (PDI) represents a promising strategy for microbial eradication through the generation of reactive oxygen species (ROS). This study investigated persistence formation in two S. aureus strains and evaluated the effects of PDI using curcumin. Time-kill assays with oxacillin revealed biphasic killing curves, indicative of persistence. Heritability testing confirmed that persistence was not passed on to progeny, supporting its phenotypic nature. PDI was performed using curcumin and blue light (450 nm), resulting in a dose-dependent reduction in bacterial viability. However, populations that survived PDI exhibited tolerance-like behavior, with unchanged MIC values, suggesting that ROS generated during PDI may induce a transient dormant state. Notably, post-PDI time-kill assays conducted after metabolic recovery showed a higher rate of bacterial death, indicating enhanced antibiotic susceptibility. In contrast, methicillin-resistant strains (MRSA) showed limited persistence induction, likely due to enhanced oxidative stress defenses. These are important to the understanding of bacterial physiological states when designing therapeutic strategies. The timing of antibiotic administration relative to PDI treatment plays a crucial role in treatment efficacy, which may be either enhanced or compromised depending on bacterial adaptation and recovery dynamics.

Melanin pigments find a diverse field of practical application including art. One of the authors has developed a method of printing images with genetically modified Escherichia coli cells that produce melanin onto paper using the screen-printing process. The method prints the cell culture and then incubates the paper over 3 days, allowing the cells to deposit the melanin as they reproduce. However, using melanin comes with challenges related to color fading of "melanin-on-paper." The aim of this study was to evaluate how melanin-on-paper was photobleached. First, we characterized E. coli (EC)-melanins by spectrophotometric and chemical degradation methods, which indicated that EC-melanins consisted of 98% eumelanin and 2% pheomelanin with high purity (ca. 80%). Second, we evaluated photomodification of melanin-on-paper during 19 months of exposure to ambient light, showing that the exposure caused photobleaching of the melanin color intensity to a half with cross-linking of 5,6-dihydroxyindole-2-carboxylic acid units of eumelanin structure and photodegradation of 5,6-dihydroxyindole units. These results indicate that melanin-on-paper undergoes gradual bleaching during months of exposure to sunlight with robust changes in melanin structure. To mitigate deterioration of melanin-on-paper by sunlight, one option would be to frame it under UV protective acrylic.

The study investigated the impact of different treatments on recovery from calcaneal tendinopathy in rats, focusing on the gastrocnemius muscle. Tendinopathy is caused by repetitive overload, leading to structural collagen damage and chronic muscle inflammation. Three therapeutic approaches were compared: photobiomodulation (PBM), advanced platelet-rich fibrin (A-PRF) injection, and a combination of the two. Seventy-five rats were separated into five groups: control (CON), injury (LES), PRF (A-PRF), photobiomodulation (PBM) and combined therapy (A-PRF + PBM). Tendinopathy was induced by compression of the calcaneal tendon. The treatment was applied at specific intervals, and the animals were assessed for muscle strength and subjected to histological and morphometric analysis of the muscle. LES showed the lowest muscle strength. The treated groups (PBM, A-PRF and A-PRF + PBM) had an increase in strength between days 7 and 21, but there were no signs of muscle damage or significant recovery in the muscle fibers. The combined therapy group showed greater production of type III collagen in the connective tissue, indicating a more significant repair effect. In contrast, the neuromuscular junctions in the groups treated with PRF were smaller, suggesting possible structural alterations. The combination of therapies showed superior results to treatment alone, promoting greater tissue repair in the gastrocnemius muscle, especially due to the increase in type III collagen.

The development of biocompatible organic photosensitizers remains an important challenge for advancing image-guided photodynamic therapy. Specifically, photosensitizers that combine strong photodynamic activity, fluorescence emission for bioimaging, decrease or stop the proliferation of cancer cells, and allow synthetic accessibility are in high demand. Herein, we report the synthesis and characterization of a new class of alloxazine-based photosensitizers (ANOMe, A8OMe and A7OMe). They are engineered through sugar conjugation and structurally modified at the C7 and C8 positions with electron-donating methoxy groups to tune their photochemistry and photobiology. These photosensitizers exhibit efficient population of long-lived triplet states, near unity singlet oxygen quantum yields, and fluorescence, as revealed by steady-state spectroscopy, time-correlated single-photon counting, and nanosecond transient absorption spectroscopy. Computational studies (DFT and TD-DFT) are combined with experimental data to disclose their electronic relaxation mechanisms. In vitro cellular assays demonstrate that these photosensitizers enter the cytoplasm, generate cytotoxic reactive oxygen species upon light activation, exhibit substantial fluorescence, and can significantly slow down the proliferation of cancer cells in the absence of light. Collectively, the experimental and computational results demonstrate the utility of rationally designed alloxazine derivatives as multifunctional agents for image-guided photodynamic therapy.

Ultraviolet C (UV-C) not only has a bactericidal effect, but is also cytotoxic; however, UV-C at a wavelength of 222 nm with a high absorption coefficient for proteins is considered safe. We have previously reported the safety of 222-nm UV-C irradiation in humans and rabbits. This study evaluated the bactericidal effect of 222-nm UV-C irradiation on exposed surgical fields. Sixteen-week-old female rabbits were used, and the exposed area on their backs was sprayed with a bacterial solution from swabs collected from their soles. Three groups were formed based on UV-C irradiation: 500 mJ/cm² of 222-nm UV-C, 200 mJ/cm² of 254-nm UV-C, which is commonly used in germicidal lamps, and non-UV-C irradiation. The bacterial colonies were counted after irradiation. Both UV-C groups showed a significant reduction in bacterial colonies compared to the nonirradiated group, with no significant difference between the two UV-C groups. Microbiota analysis identified species that could cause surgical site infections. The results of the study suggest that 500 mJ/cm² of 222-nm UV-C irradiation effectively reduces bacterial load, with a bactericidal effect comparable to 254-nm UV-C; hence, 222-nm UV-C irradiation is a promising and safe tool for minimizing the risk of surgical site infections.

Despite advancements made in treatment options, cancer continues to be one of the leading causes of death worldwide. Photodynamic therapy (PDT) has gained attention as a minimally invasive and highly selective treatment option for cancer. However, challenges due to the hydrophobicity of photosensitizers and their poor tumor selectivity have limited their use in cancer therapy. Recent developments in nanotechnology, particularly the use of gold nanoparticles (AuNPs), help overcome these challenges. AuNPs provide a stable and biocompatible platform to deliver photosensitizers, improving their solubility, stability, and ability to target tumors while reducing side effects. Functionalized AuNPs take advantage of mechanisms like the enhanced permeability and retention (EPR) effect and active targeting, improving reactive oxygen species (ROS) production and overall therapeutic efficacy. This review explores innovations in AuNP-based PDT systems, including ligand-functionalized nanoparticles, bioresponsive coatings, and theranostic approaches that combine imaging with therapy. By delving into important aspects of synthesis, characterization, and functionalization, we show how AuNPs improve the delivery and performance of photosensitizers. For instance, systems functionalized with prostate-specific membrane antigen (PSMA) have shown increased therapeutic precision and efficacy in vivo. These advancements are paving the way for more targeted and safer cancer treatments, establishing AuNP-based PDT as a promising approach for developing highly effective oncological therapies with greater precision and fewer side effects.

Photodynamic therapy (PDT) effectively kills cancer cells and initiates immune responses that promote anticancer effects locally and systemically. Primarily developed for local and regional cancers, the potential of PDT for systemic antitumor effects [in situ photo-vaccination (ISPV)] remains underexplored. This study investigates: (1) the comparative effectiveness of paclitaxel (PTX) prodrug [Pc-(L-PTX)₂] for PDT and site-specific PTX effects versus its pseudo-prodrug [Pc-(NCL-PTX)₂] for PDT combined with checkpoint inhibitors; (2) mechanisms driving systemic antitumor effects; and (3) the prophylactic impact on preventing cancer recurrence. A bilateral tumor model was established in BALB/c mice through subcutaneous injection of CT26 cells. Mice received the PTX prodrug (0.5 μmole kg^-1, i.v.), and tumors were treated with a 690-nm laser (75 mW cm^-2 for 30 min, drug-light interval 0.5 h, light does 135 J cm^-1), followed by anti-CTLA-4 (100 μg dose^-1, i.p.) on days 1, 4, and 7. Notable enhancement in both local and systemic antitumor effectiveness was observed with [Pc-(L-PTX)₂] compared to [Pc-(NCL-PTX)₂] with checkpoint inhibitor. Immune cell depletion and immunohistochemistry confirmed neutrophils and CD8+ T cells are effectors for systemic antitumor effects. Treatment-induced immune memory resisted newly rechallenged CT26, showcasing prophylactic benefits. ISPV with a PTX prodrug and anti-CTLA-4 is a promising approach for treating metastatic cancers and preventing recurrence.

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.

Vascular-targeted photodynamic therapy (V-PDT) offers a precise therapeutic approach for treating diseases associated with abnormal vasculature. The therapeutic efficacy of type II V-PDT mainly relies on the vascular response to singlet oxygen (¹O₂), which could convert prothrombin into thrombin and then result in vasocontraction and subsequent tissue ischemia. In this study, the photosensitizer pyropheophorbide-a (Pyro) was conjugated with the fluorescent molecule 5-carboxy-X-rhodamine (Rox) through a thrombin-cleavable peptide, forming a thrombin-activated molecular beacon Pyro-thrombin-cleavable peptide-Rox (PPR). Furthermore, a novel multimodal imaging system was developed for simultaneously imaging near-infrared (NIR) ¹O₂ luminescence at around 1270 nm and Rox fluorescence, which could be used to directly and indirectly assess the ¹O₂ generation during V-PDT for an in vivo model, respectively. It was found that the vasoconstrictions are positively correlated with both ¹O₂ luminescence intensity and Rox fluorescence intensity, respectively. For this, the PPR could serve as a therapeutic PS and as an indirect indicator for ¹O₂ generation during V-PDT, which has the advantage of higher sensitivity compared to the direct measurement of ¹O₂ luminescence.