Photodynamic Reaction Research Articles

Photonics of Halogenated Zinc(II) and Cadmium(II) Dipyrromethene Complexes

This article compares spectroscopic properties of the series of dipyrromethene dyes, namely their complexes of boron (III), zinc(II) and cadmium(II) with the halogenated ligands of the same structure. Absorption and emission spectra, lifetimes of long-lived emission and quantum yields of luminescence were studied as the functions of molecular structure of dipyrromethene complexes. The role of the position and nature of a substituent in a ligand, polarity of a solvent and temperature of media were also investigated. The studies demonstrate that replacing the central atom boron(III) by zinc(II) decreases the fluorescence quantum yield, indicating the increased role of non-radiative processes in excitation energy deactivations such as intersystem crossings. In addition, according to the heavy atom effect, the efficiency of intersystem crossings in halogen-substituted zinc(II) and cadmium(II) dipyrromethene complexes is higher than in the corresponding boron fluoride dipyrromethenes (BODIPY), which leads to increase in phosphorescence at low temperatures (frozen solutions). The obtained results make it possible to carry out further investigations of potential sensory properties that are required for systematic use of halogenated dipyrromethene complexes for the creation of modern optical oxygen sensors and singlet oxygen photosensitizers for photodynamic therapy or photocatalytic oxidative reactions.

Chemotherapy and Physical Therapeutics Modulate Antigens on Cancer Cells.

Cancer cells possess specific properties, such as multidrug resistance or unlimited proliferation potential, due to the presence of specific proteins on their cell membranes. The release of proliferation-related proteins from the membrane can evoke a loss of adaptive ability in cancer cells and thus enhance the effects of anticancer therapy. The upregulation of cancer-specific membrane antigens results in a better outcome of immunotherapy. Moreover, cytotoxic T-cells may also become more effective when stimulated ex-vivo toward the anticancer response. Therefore, the modulation of membrane proteins may serve as an interesting attempt in anticancer therapy. The presence of membrane antigens relies on various physical factors such as temperature, exposure to radiation, or drugs. Therefore, changing the tumor microenvironment conditions may lead to cancer cells becoming sensitized to subsequent therapy. This paper focuses on the therapeutic approaches modulating membrane antigens and enzymes in anticancer therapy. It aims to analyze the possible methods for modulating the antigens, such as pharmacological treatment, electric field treatment, photodynamic reaction, treatment with magnetic field or X-ray radiation. Besides, an overview of the effects of chemotherapy and immunotherapy on the immunophenotype of cancer cells is presented. Finally, the authors review the clinical trials that involved the modulation of cell immunophenotype in anticancer therapy.

Fluorescence-Reporting-Guided Tumor Acidic Environment-Activated Triple Photodynamic, Chemodynamic, and Chemotherapeutic Reactions for Efficient Hepatocellular Carcinoma Cell Ablation.

Tumor acidic environment-activated combination therapy holds great promise to significantly decrease side effects, circumvent multiple drug resistance, and improve therapeutic outcomes for cancer treatment. Herein, Sorafenib/ZnPc(PS)4@FeIII-TA nanoparticles (SPFT) are designed with acid-environment turned-on fluorescence to report the activation of triple therapy including photodynamic, chemodynamic, and chemotherapy on hepatocellular carcinoma. The SPFT are composed of SP cores formulated via self-assembly of sorafenib and ZnPc(PS)4, with high drug loading efficiency, and FeIII-TA shells containing FeCl3 and tannic acid. Importantly, the nanoparticles suppress reactive oxygen species (ROS) generation of ZnPc(PS)4 due to their formation in nanoparticles, while assisting simultaneous uptake of the uploaded drugs in cancer cells. The tumor acidic environment initiates FeIII-TA decomposition and accelerates a chemodynamic reaction between FeII and H2O2 to generate toxic •OH. Then, the SP core is decomposed to separate ZnPc(PS)4 and sorafenib, which leads to fluorescence turning-on of ZnPc(PS)4, expedited photodynamic reactions, and burst release of sorafenib. Notably, SPFT shows low dark cytotoxicity to normal cells but exerts high potency on hepatocellular carcinoma cells under near-infrared light irradiation, which is much more potent than either sorafenib or ZnPc(PS)4 alone. This research offers a facile nanomedicine design strategy for cancer therapy.

Superoxide anion radical induced phototoxicity of 2,4,5,6-Tetraminopyrimidine sulfate via mitochondrial-mediated apoptosis in human skin keratinocytes at ambient UVR exposure

2,4,5,6-Tetraaminopyrimidine sulfate (TAPS) is worldwide the most commonly used developer in hair dyes. As skin is the major organ, which is directly exposed to these permanent hair dyes, a comprehensive dermal safety assessment is needed. Hereto, we studied the photosensitization potential and mechanism involved in dermal phototoxicity of TAPS exposed to the dark and UVA/UVB/Sunlight by using different in-chemico and mammalian (HaCaT) cells, as test systems. Our experimental outcomes illustrate that TAPS get photodegraded (LC-MS/MS) and specifically generated superoxide anion radical (O2•−) under UVA and UVB via type-I photodynamic reaction. The phototoxic potential of TAPS is measured through MTT, NRU, and LDH assays that depicted a significant cell viability reduction at 25 μg/ml concentration and higher. Different cellular stainings (PI uptake, AO/EB, JC-1, NR uptake) suggested the role of mitochondrial-mediated apoptosis. Further, the transcriptomics study revealed upregulation of Apaf-1, Bax, Cytochrome c, Caspase 3, Caspase 9 and downregulation of Catalase and Bcl-2 by TAPS treated cells that strengthen our findings. Thus, the above findings suggest that chronic application of TAPS may be hazardous for human skin and promote various skin diseases.

Photodynamic inactivation of Staphylococcus aureus in the system of titanium dioxide nanoparticles sensitized by hypocrellin B and its application in food preservation

Staphylococcus aureus (S. aureus) is a foodborne pathogen that endangers human health worldwide. Antimicrobial photodynamic inactivation (aPDI), mediated by titanium dioxide nanoparticles (TiO2NP), was recently used to control the growth of S. aureus, however, UV illumination had to be offered to initiate the photodynamic reaction. To overcome this drawback, a dual-photon system was established here based on TiO2NP and hypocrellin B (HB), a natural pigment with photocatalyst activity. Irradiated at the visible light (9 J/cm2) at the wavelength of 460 nm, the joint use of both photosensitizers (PS) caused a substantial decline of staphylococcal survival, reaching a maximum decrease of 4 ∼ 5 logs. When 10 nM HB and 100 µM TiO2NP were applied, a synergistic photokilling effect was achieved, only in the mixed phase of anatase/rutile, Degussa P25. Regarding the antimicrobial mechanisms, it was found that the membrane integrity of S. aureus was heavily disrupted, surface morphology was altered, intracellular substances like potassium and DNA were leaked, and biofilm formation was significantly circumvented due to the excitation of sensitized PS. In terms of antioxidant responsiveness of S. aureus, qPCR results showed that a series of genes encoding the membrane-associated cell death effectors were deregulated. Among them, LrgA was recognized as a key responsive element, due that the mutant strain harboring a constitutively-expressed LrgA strengthened the bactericidal effect of aPDI. Finally, the dual-photon strategy lowered the microbial contamination in the tested apple with its quality maintained, under the condition of visible light. Taken together, a new dual-photon system based on TiO2NP and HB was constructed and validated in photokilling S. aureus, providing a well-adapted technique to maintain food safety.

Using laser in the treatment of chronic skin diseases

In most cases, the treatment of skin diseases, especially chronic processes, is a difficult task due to the low effectiveness of the traditional methods of treatment, the emergence of drug resistance, the development of frequent allergic and other adverse reactions. In total, the impact of the above factors has led to the need to find new ways and methods in the treatment of dermatological lesions. Against the background of using ultrasound, cryotherapy and magnetotherapy, good efficiency was also noted as a result of exposure to laser beams. For the first time, the laser began to be used to treat skin diseases about 40 years ago. When laser radiation is applied to the skin, the processes of photostimulation, photothermolysis and photodynamic reactions occur in its layers. Photostimulation processes began to be used to activate wound healing, and photodynamic reactions were used to treat acne vulgaris, vitiligo, psoriasis, urticaria, and lichen planus. At the same time, low-intensity laser radiation is used for therapeutic purposes, and high-intensity laser radiation is used in surgical practice, in particular, for the removal of warts, papillomas, and genital warts. The use of laser radiation in the treatment of skin diseases contributes to the activation of tissue respiration processes, a decrease in the activity of free radicals, and the stabilization of lipid complexes of cell membranes. In general, improvement in the condition after laser therapy is noted in 40–80 % of patients.

Green phytoextracts as natural photosensitizers in LED-based photodynamic disinfection of multidrug-resistant bacteria in wastewater effluent

The photodynamic treatment (PDT) process is a promising technology to control emerging pollutants and antimicrobial resistance problems in the water environment. The reactive oxygen species (ROS) produced when natural and nontoxic photosensitizers (PS) are exposed to light are the key functional components of the PDT process that can effectively achieve microbial inactivation with minimal negative impact. This study examined the application of green phytoextracts from two plants, Chamaecyparis obtusa and Moringa oleifera, as natural photosensitizers for the white light-emitting diode (LED) based photodynamic disinfection of multidrug-resistant (MDR) and total coliforms (TC) from secondary effluent in full-scale municipal wastewater treatment plants. Gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy showed that the phytoextracts contained 57 compounds, particularly aromatic and phenolic hydroxyl compounds. The phytoextracts showed an excellent activity as a PS compared to the intrinsic antibacterial effect. Under a light intensity of 17 mW/cm2, the complete inactivation (6.55 Log CFU/mL) was observed at an irradiation time of 100 min for Escherichia coli ART-2 and 80 min for Staphylococcus aureus, meaning that E. coli was resistant. The light intensity was an important factor influencing photodynamic disinfection. For the complete disinfection of TC satisfying the water reclamation regulation, the irradiation time requirement was 20 min under a light intensity of 80 mW/cm2. During the photodynamic reaction, a significant amount of ROS was generated from the phytoextracts as the light irradiation time was increased. The major ROS was singlet oxygen (1O2, Type II) during the initial 40 min of reaction time and hydroxyl radical (•OH, Type I) after 40 min until complete inactivation.

The photodynamic reaction with IR-775 cyanine combined with 2-methoxyestradiol in ovarian (SKOV-3) and human breast adenocarcinoma (MDA MB-231) cell lines

BackgroundPhotodynamic therapy (PDT) is known anticancer approach used mainly for topical skin cancer. However, it could serve as an excellent alternative to traditional anticancer therapies, such as chemotherapy or radiotherapy. AimsThe study aimed to assess the effect of PDT, where the combination of cyanine with 2-methoxyestradiol (2-Me) was used on mammary and ovary adenocarcinoma human cell lines. Materials and methodsThe cyanine IR-775 was used as the photosensitizer. Two human malignant adenocarcinoma cell lines – ovary and mammary adenocarcinoma (MDA MB-231 and SKOV-3) were investigated in photodynamic reaction (PDR), with the enhancement of 2-Me. PDR efficiency was evaluated by the MTT test. Photosensitizer intracellular distribution was assessed by fluorescent microscopy. Additionally, apoptotic and oxidative stress markers were investigated by immunocytochemistry staining. Results and conclusionsIt was observed that PDR enhanced by 2-Me is effective against two common but different types of cancer. The treatment decreased cells’ viability by around 70%. Immunocytochemical staining of SOD2 and caspase-12 indicated apoptosis and oxidative stress induction in tested cell lines. The results suggest that the therapy could be involved in further oncological applications.

Involvement of Type-I and Type-II Photodynamic Reactions in Photosensitization of Fragrance Ingredient 2-acetonaphthone.

2-Acetonaphthone (2-ACN) is a synthetic fragrance material used in various cosmetics as an adulterant. Due to its frequent use, we have conducted an in-depth study to understand the photosensitizing potential of 2-ACN. Results of this study illustrate that 2-ACN showed photodegradation in 4 h under ambient UV radiation (UVR) and sunlight exposure. It generated (1-25 µg mL-1 ) superoxide anion radical (O2 ·- ) and singlet oxygen (1 O2 ) in the presence of UVR/sunlight through in chemico and invitro test systems. 2-ACN (10 µg mL-1 ) showed a 43.9% and 57.4% reduction in cell viability under UVA and sunlight, respectively. Photosensitized 2-ACN generated intracellular reactive oxygen species (ROS) (6-folds in UVA and 8-folds in sunlight), which compromises the endoplasmic reticulum and mitochondrial membrane potential leading to cell death. Acridine orange/ethidium bromide dual staining and annexin-V/PI uptake showed cell death caused via 2-ACN under UVR exposure. The above findings signify the role of ROS via Type-I and Type-II photodynamic pathways in photosensitization of 2-ACN that ultimately promotes photodamage of important cellular organelles leading to cell death. The study advocates that solar radiation should be avoided by the users after the application of cosmetic products containing 2-ACN.

UVR-induced phototoxicity mechanism of methyl N-methylanthranilate in human keratinocyte cell line

Fragrances are used in almost every cosmetic product. International Fragrance Association (IFRA) is the regulatory body that controls the use of fragrances in cosmetic products. Methyl-N-methylanthranilate (DMA) is a naturally derived fragrance, commonly used in cosmetic products such as fine perfumes, skin care products, etc. But there is a lack of detailed study in terms of its phototoxic and photogenotoxicity mechanisms under UVA/sunlight exposure. In this study, we have shown that DMA photodegrades in 4 h under UVA (1.5 mW/cm2) and sunlight. DMA (0.0001%–0.0025%) significantly reduced the cell viability as demonstrated by NRU and MTT assays in a dose-dependent manner under UVA (5.4 J/cm2) and sunlight (1 h) exposure in the HaCaT cell line. It generated excessive intracellular ROS (superoxide anion radical via type-I photodynamic reaction), resulting in lysosomal destabilization and mitochondrial membrane depolarization. Photo-activated DMA caused DNA fragmentation as observed by olive tail moment. DNA double-strand breaks was demonstrated by phosphorylation of H2AX-histone protein and formation of photo-micronuclei in skin keratinocytes. Additionally, photo-activated DMA upregulated the oxidative stress marker gene hemeoxygenase-1 and apoptotic marker genes (cytochrome-C, caspase-3, caspase-9). Activated caspase-cascade pathway established that photo-activated DMA can potentially trigger apoptosis in the human skin cells.

Multifunctional FeS2@SRF@BSA nanoplatform for chemo-combined photothermal enhanced photodynamic/chemodynamic combination therapy.

Combination therapy has been widely studied due to its promising applications in tumor therapy. However, a sophisticated nanoplatform and sequential irradiation with different laser sources for phototherapy complicate the treatment process. Unlike the integration of therapeutic agents, we report a FeS2@SRF@BSA nanoplatform for the combination of chemo-combined photothermal therapy (PTT) enhanced photodynamic therapy (PDT) and chemodynamic therapy (CDT) to achieve an "all-in-one" therapeutic agent. Ultrasmall FeS2 nanoparticles (NPs) with a size of 7 nm exhibited higher Fenton reaction rates due to their large specific surface areas. A photodynamic reaction could be triggered and could generate 1O2 to achieve PDT under 808 nm irradiation. FeS2 NPs also exhibited the desired photothermal properties under the same wavelength of the laser. The Fenton reaction and photodynamic reaction were both significantly improved to accumulate more reactive oxygen species (ROS) with an increase of temperature under laser irradiation. Besides, loading of the chemotherapeutic drug sorafenib (SRF) further improved the efficacy of tumor treatment. To realize long blood circulation, bovine serum albumin (BSA) was used as a carrier to encapsulate FeS2 NPs and SRF, remarkably improving the biocompatibility and tumor enrichment ability of the nanomaterials. Additionally, the tumors on mice treated with FeS2@SRF@BSA almost disappeared under 808 nm irradiation. To sum up, FeS2@SRF@BSA NPs possess good biocompatibility, stability, and sufficient therapeutic efficacy in combination therapy for cancer treatment. Our study pointed out a smart design of the nanoplatform as a multifunctional therapeutic agent for combination cancer therapy in the near future.

Structures, spectral and photodynamic properties of two nitrosylruthenium (II) isomer complexes containing 8-quinolinolate and L-proline ligands

Two [RuCl(Qn)(Pro)NO] (Qn = 8-quinolinol, Pro = L-proline) isomer complexes, in which the O atom of L-proline coordinated trans to NO (Complex a) and the O atom of 8-quinolinol coordinated trans to NO (Complex b), were synthesized. Their structures were identified with X-ray diffraction and compared with optimized geometries by DFT calculations at the B3LYP level. The electronic absorption and IR spectroscopy of the isomers were experimentally measured and theoretically assigned, the front molecular orbitals were analyzed. Moreover, the photodynamic reaction for the isomers was investigated with time resolved FTIR spectroscopy, photo induced NO release of the isomers were observed. The effect of ligands and configuration on photodynamic properties of the isomers was discussed. The structural and dynamic analyses combined with DFT calculations provide insights into the physicochemical properties and reactivity of the isomeric complexes, which makes a foundation for their potential applications.

Фотодинамическая терапия в лечении меланомы хориоидеи. Обзор литературы

Choroidal melanoma is one of the most malignant tumors of the organ of vision, the development of which is associated with the risk of metastasis and the possibility of death, which indicates the relevance of the search and application of effective methods of treatment of this pathology. To date, in the treatment of choroidal melanoma, preference is given to organ-preserving methods aimed at achieving local control over the tumor. One of the promising organ-preserving techniques is photodynamic therapy, which is a treatment method based on the ability of a photosensitizer to absorb light, receive energy and interact with chemical substances, with the further development of toxic photodynamic reactions in target tissues, the occurrence of which is possible with the simultaneous presence of three components: a photosensitizer, light and oxygen. In our country, there is a number of studies devoted to the treatment of choroidal melanoma with PDT, basically presenting experimental research, pilot studies and demonstrating clinical cases. The purpose of this review is to summarize data on photodynamic therapy and the use of this technique in the treatment of choroidal melanoma.

History and Basic Principles of Photodynamic Therapy Use in Ophthalmology

Photodynamic therapy (PDT) is a therapy that uses drugs, called photosensitizers or photosensitizing agents, and a specific type of light. When photosensitizers are exposed to certain wavelengths of light, they produce oxygen that kills nearby cells. PDT is achieved by a photodynamic reaction induced by the excitation of a photosensitizer exposed to light. In the field of ophthalmology, PDT was approved for the first time about ten years ago for cases of age-related macular degeneration (AMD). Neovascular age-related macular degeneration (AMD) is a vision-threatening disease characterized by pathological macular neovascularization. After that, PDT was approved for use in choroidal neovascularization (CNV) cases in pathological myopia.3 This literature review aims to describe the history of PDT use and the basic principles of photodynamic therapy in ophthalmology.

Photo-Driven Delivery of 125I-Labeled Nanomicelles for Nucleus-Targeted Internal Conversion Electron-Based Cancer Therapy.

As a kind of high linear energy transfer (LET) radiation, internal conversion electrons are emitted from some radionuclides, such as 125I, triggering severe DNA damage to tumor cells when transported into the nucleus. Herein, we develop a curcumin-loaded nanomicelle composed of a photosensitizer chlorin e6 (Ce6) and amphiphilic poly(ethylene glycol) (poly(maleic anhydride-alt-1-octadecene)-poly(ethylene glycol) (C18-PMH-PEG)) to deliver 125I into the nucleus under 660 nm laser irradiation, leading to the optimized imaging-guided internal conversion electron therapy of cancer. Ce6-containing nanomicelles (Ce6-C18-PEG) self-assemble with nucleus-targeted curcumin (Cur), obtaining Ce6-C18-PEG/Cur nanoparticles. After labeling Cur with 125I, Ce6-C18-PEG/Cur enables single-photon emission computed tomography and fluorescence imaging of the tumor, serving as a guide for follow-up laser irradiation. Notably, the 660 nm laser-triggered photodynamic reaction of Ce6 optimizes the delivery of Ce6-C18-PEG/125I-Cur at various stages, including tumor accumulation, cellular uptake, and lysosome escape, causing plenty of 125I-Cur to enter the nucleus. By this strategy, Ce6-C18-PEG/125I-Cur showed optimal antitumor efficacy and high biosafety in mice treated with local 660 nm laser irradiation using efficient energy deposition of internally converted electrons over short distances. Therefore, our work provides a novel strategy to optimize 125I delivery for tumor treatment.

A Literature Review on High-Performance Photocatalysts for Sustainable Cancer Therapy

Since cancer is a serious threat to public health worldwide, the development of novel methods and materials for treating cancer rapidly and thoroughly is of great significance. This review summarizes the mechanism and application of photocatalytic materials used to kill cancer cells. The photosensitivity and toxicological properties of several common photcatalysts used in anti-cancer treatment are discussed in detail. The ideal photocatalyst must possess the following characteristics: a highly stable production of active oxygen species and high selectivity to cancer cells without causing any damage to healthy tissues. This work concluded the existing photocatalytic materials used to treat cancer, as well as the current challenges in the application of cancer therapy. We aim to provide a basis for the development of new photocatalytic anti-cancer materials with high stability and selectivity while maintaining high photodynamic reaction performance.

Recent Advances in Photodynamic Imaging and Therapy in Hepatobiliary Malignancies: Clinical and Experimental Aspects.

The therapeutic and diagnostic modalities of light are well known, and derivative photodynamic reactions with photosensitizers (PSs), specific wavelengths of light exposure and the existence of tissue oxygen have been developed since the 20th century. Photodynamic therapy (PDT) is an effective local treatment for cancer-specific laser ablation in malignancies of some organs, including the bile duct. Although curability for extrahepatic cholangiocarcinoma is expected with surgery alone, patients with unresectable or remnant biliary cancer need other effective palliative therapies, including PDT. The effectiveness of PDT for cholangiocarcinoma has been reported experimentally or clinically, but it is not the standard option now due to problems with accompanied photosensitivity, limited access routes of irradiation, tumor hypoxia, etc. Novel derivative treatments such as photoimmunotherapy have not been applied in the field hepatobiliary system. Photodynamic diagnosis (PDD) has been more widely applied in the clinical diagnoses of liver malignancies or liver vascularization. At present, 5-aminolevulinic acid (ALA) and indocyanine green (ICG) dyes are mainly used as PSs in PDD, and ICG has been applied for detecting liver malignancies or vascularization. However, no ideal tools for combining both PDD and PDT for solid tumors, including hepatobiliary malignancies, have been clinically developed. To proceed with experimental and clinical trials, it is necessary to clarify the effective photosensitive drugs that are feasible for photochemical diagnosis and local treatment.

A 2-(benzothiazol-2-yl)-phenolato platinum(II) complex as potential photosensitizer for combating bacterial infections in lung cancer chemotherapy†

Cancer and antibiotic resistance are two global health threats that usually hamper clinical chemotherapeutic efficacy. Particularly for lung cancer, bacterial infections frequently arise thereby complicating the course of cancer treatment. In this sense, three new neutral luminescent cycloplatinated(II) photosensitizers of the type [Pt(dmba)(L)] (dmba=N,N-dimethylbenzylamine-κN,κC; L=2-(benzo[d]oxazol-2-yl)-phenolato-κN,κO1, 2-(benzo[d]thiazol-2-yl)-phenolato-κN,κO2, and 2-(1-methyl-1H-benzo[d]imidazole-2-yl)phenolato-κN,κO3) have been characterized and developed to potentially eliminate both resistant bacteria and lung cancer cells. The phototherapeutic effects of complex 2 have been evaluated using low doses of blue light irradiation. Complex 2 exerted promising photoactivity against pathogenic Gram-positive bacteria strains of clinical interest, displaying a phototoxic index (PI) of 15 for methicillin-resistant Staphylococcus aureus, one of the major microorganisms predominating lung infections. Likewise, the anticancer activity of 2 was also increased upon light irradiation in human lung A549 cancer cells (PI=36). Further invitro experiments with this platinum(II) complex suggest that ROS-generating photodynamic reactions were involved upon light irradiation, thus providing a reasonable mechanism for its dual anticancer and antibacterial activities.

EPR spectroscopy investigation of oxygen radical production by methylene blue and indocyanine green in aqueous solutions under laser irradiation in the context of antibacterial photodynamic therapy.

Antibacterial photodynamic therapy is a promising treatment modality in the anti-infective therapy of numerous oral diseases. It involves photo activation of a reactive substance (dye), thus releasing reactive oxygen species (ROS-radicals) which are highly destructive to the bacterial cell. However, thorough investigation of radical production properties of different dyes is not common in literature. The aim of this study was to investigate and evaluate oxygen radical-producing potential of two commonly used photoactive dyes in the context of antibacterial photodynamic therapy. The radical-producing properties of two commonly used dyes for photodynamic therapy in oral medicine, methylene blue and indocyanine green, irradiated under laser irradiation are investigated using electron paramagnetic resonance (EPR) spectroscopy. The detection of reactive oxygen species is performed with "spin-trapping" technique. The selected photoactive dyes showed promising yields of reactive oxygen species (ROS) in aqueous solutions. The comparative analysis of the results deemed methylene blue as the more productive photoactive agent. By employing the spin-trapping technique, this study indicates EPR-spectroscopy as a promising method of relative quantification of reactive oxygen species released by the photodynamic reaction in aqueous solutions.

Visible Light-Induced Antibacterial Activity of Pigments Extracted from Dregs of Green and Black Teas.

Chlorophyll and its derivatives are potential natural sensitizers frequently applied in antimicrobial photodynamic therapy. Chlorophyll derivatives are formed naturally during tea processing, but they do not contribute to the color of tea infusions and thus are presumably left in the tea dregs. The present study aimed to investigate (i) the chlorophyll remnants in the pigments recovered from dregs of green and black teas and (ii) the antibacterial activity of pigments extracted from the tea dregs upon illumination using a light-emitting diode (LED) as the light source. Pigment analysis using high-performance liquid chromatography (HPLC) revealed the presence of main degradation products of chlorophylls, such as pheophytin and its epimers, pyropheophytin, and pheophorbides. In vitro assays demonstrated significant reductions in the number of viable bacteria in the presence of the pigments after 30 min of incubation with LED light irradiation. The descending order of bacterial susceptibility was Listeria monocytogenes > Staphylococcus aureus > Escherichia coli > Salmonella typhi. At an equivalent irradiation intensity, the blue and red LEDs could stimulate a comparable inactivation effect through photodynamic reactions. These findings demonstrated the valorization potential of tea dregs as a source of chlorophyll derivatives with visible light-induced antibacterial activity.