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Endolysosomes perform a wide range of cellular functions, including nutrient sensing, macromolecule digestion and recycling, as well as plasma membrane repair. Because of their high activity in cancerous cells, endolysosomes are attractive targets for the development of novel cancer treatments. Light-activated compounds termed photosensitizers (PS) can catalyze the oxidation of specific biomolecules and intracellular organelles. To selectively damage endosomes and lysosomes, HT-29 colorectal cancer cells were incubated with nanomolar concentrations of meso-tetraphenylporphine disulfonate (TPPS2a), an amphiphilic PS taken up via endocytosis and activated by green light (522 nm, 2.1 J.cm-1). Several cellular responses were characterized by a combination of immunofluorescence and immunoblotting assays. We showed that TPPS2a photosensitization blocked autophagic flux without extensive endolysosomal membrane rupture. Nevertheless, there was a severe functional failure of endolysosomes due to a decrease in CTSD (cathepsin D, 55%) and CTSB (cathepsin B, 52%) maturation. PSAP (prosaposin) processing (into saposins) was also considerably impaired, a fact that could be detrimental to glycosphingolipid homeostasis. Therefore, photosensitization of HT-29 cells previously incubated with a low concentration of TPPS2a promotes endolysosomal dysfunction, an effect that can be used to improve cancer therapies.

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Thiophene-containing photosensitizers are gaining recognition for their role in photodynamic therapy (PDT). However, the inherent reactivity of the thiophene moiety toward singlet oxygen threatens the stability and efficiency of these photosensitizers. This study presents a novel mathematical model capable of predicting the reactivity of thiophene toward singlet oxygen in PDT, using Conceptual Density Functional Theory (CDFT) and genetic programming. The research combines advanced computational methods, including various DFT techniques and symbolic regression, and is validated with experimental data. The findings underscore the capacity of the model to classify photosensitizers based on their photodynamic efficiency and safety, particularly noting that photosensitizers with a constant rate 1000 times lower than that of unmodified thiophene retain their photodynamic performance without substantial singlet oxygen quenching. Additionally, the research offers insights into the impact of electronic effects on thiophene reactivity. Finally, this study significantly advances thiophene-based photosensitizer design, paving the way for therapeutic agents that achieve a desirable balance between efficiency and safety in PDT.

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The bovine tick Rhipicephalus microplus, a primary ectoparasite of veterinary concern, contributes significantly to disease transmission and reduced cattle productivity, resulting in substantial economic losses. The overuse of chemical acaricides has led to the emergence of resistant strains, posing a considerable challenge to veterinary medicine. Consequently, the development of alternative parasite control methods is essential to ensure livestock quality and enhance food safety worldwide. Our study introduces an innovative approach to photodynamic inactivation (PDI) of the bovine tick, harnessing natural daylight for a potential field application. Reproductive parameters (female and egg mass, egg production index, and larval hatch) were evaluated in engorged female ticks under photodynamic action using the hematoporphyrin (HP) and tetra-cationic porphyrins free-base meso-tetra-ruthenated (4-pyridyl) (RuTPyP) and its zinc(II) complex (ZnRuTPyP) as photosensitizers (PS). The results showed that there was no significant difference between the groups treated with tetra­ruthenium porphyrins and the control group. However, HP exhibits a control percentage of 97.9% at a concentration of 2.5 µmol.L-1, aligning with the expected control rates achieved by conventional chemical acaricides. Photophysical and physicochemical parameters such as the number of singlet oxygen produced and lipophilicity were discussed for each PS and related to tick control percentages. Furthermore, the interaction between HP and chitin, an important macromolecule presents in the tick's cuticle, considered as the primary target tick structure during PDI was observed by the absorption and fluorescence emission spectroscopic techniques. Therefore, the results presented here extend the potential for controlling R. microplus through photodynamic inactivation while utilizing sunlight as a source of natural irradiation.

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A polymeric photosensitizer was synthesized through covalent attachment of the natural photosensitizer 6-carboxypterin (Cap) to a poly(allylamine hydrochloride) (PAH) polymer. The optimization of the functionalization steps and purification procedure is described. The overall yield of the functionalization reaction was 67% to generate the modified polymer (PAH-Cap), featuring a Cap substitution degree of approximately 1% and advantageous spectroscopic properties. Photosensitizing properties of PAH-Cap were observed to occur via both photooxidation mechanisms, i.e., type I and type II. This feature was demonstrated using a biologically relevant target molecule, 2'-deoxyguanosine (dG). The spectroscopic, photophysical, and photochemical behaviors in aqueous environments were studied and compared to Cap. To explore possible further relevant biological applications, experiments with PAH-Cap and dG were carried out at physiological pH. PAH-Cap can generate singlet molecular oxygen and initiate an electron transfer process at pH 7 in air-saturated solutions upon UVA irradiation. Moreover, based on its spectroscopic features, visible light can be used to initiate the photooxidation of biological compounds in water, with many interesting advantages compared to free Cap and other related pteridines. These advantages include an enhancement of the photosensitizing effect at physiological pH and the potential of PAH-Cap for its use as a building block in supramolecular assemblies. The functionalization strategy hereby described can be employed for the preparation of robust photoactive polymers with great potential for its application in photodynamic therapy (PDT) and disinfection technologies.

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The combined action of singlet oxygen (1O2) and photoinduced carbon monoxide (CO) released by tricarbonyl metal complexes is a promising synergic treatment against multi-resistant bacterial infections. In this work, we explore the use of a polydentate ligand (bpm = 2,2-bipyrimidine) that offers the opportunity to accommodate two metal centers exhibiting both singlet oxygen generation and carbon monoxide releasing properties in a single molecule. A series of monometallic ([(bpm)M(CO)3Br]; M = Mn, Re) and homo or hetero bimetallic ([Br(CO)3M(bpm)M'(CO)3Br]; M = Mn, Re) compounds were synthesized in moderate to good yields by modulating the metal precursor or the stoichiometry, also the syn:anti isomers ratio for the bimetallic complexes was dependent on the experimental conditions used. DFT modelling shows the anti-isomer is more stable than the syn-isomer by less than 8 kJ mol-1, which is consistent with those experimentally observed in terms of majority product and the effect of experimental conditions over the anti-syn ratio. The HOMO-LUMO gap is lower for the mono and bimetallic rhenium(I) compounds compared to the values for the manganese(I) analogues, while the heterometallic complex shows intermediate values for the anti-isomer. The photophysical characterization shows typical absorption and emission bands with MLCT character. In addition, CO-release and 1O2 generation quantum yields were evaluated for the monometallic Mnbpm and Rebpm homologues and compared with values obtained for the homo- and hetero-bimetallic complexes. Interestingly the replacement of a Mn(CO)3Br moiety in MnbpmMn by a Re(CO)3Br one makes the heterometallic MnbpmRe molecule a molecular oxygen sensitizer and partially retaining its carbon monoxide releasing ability.

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The ability of the ultrasound (US) combined with peroxymonosulfate (PMS), and a carbonaceous material (BC) was evaluated in the degradation of a model pollutant (acetaminophen, ACE). The US/BC/PMS system was compared with other possible systems (US, oxidation by PMS, BC adsorption, BC/PMS, US/PMS, and US/BC. The effect of the ultrasonic frequency (40, 375, and 1135 kHz) on the kinetics and synergy of the ACE removal was evaluated. In the US system, kinetics was favored at 375 kHz due to the increased production of hydroxyl radicals (HO•), but this did not improve in the US/PMS and US/BC systems. However, synergistic and antagonistic effects were observed at the low and high frequencies where the production of radicals is less efficient but there is an activation of PMS through mechanical effects. US/BC/PMS at 40 kHz was the most efficient system obtaining ∼95% ACE removal (40 µM) in the first 10 min of treatment, and high synergy (S = 10.30). This was promoted by disaggregation of the carbonaceous material, increasing the availability of catalytic sites where PMS is activated. The coexistence of free-radical and non-radical pathways was analyzed. Singlet oxygen (1O2) played the dominant role in degradation, while HO• and sulfate radicals (SO4•-), scarcely generated at low frequency, play a minimum role. Performance in hospital wastewater (HWW), urine, and seawater (SW) evidenced the competition of organic matter by BC active sites and reactive species and the removal enhancement when Cl- is present. Besides, toxicity decreased by ∼20% after treatment, being the system effective after three cycles of reuse.

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Natural products and their semi-synthetic derivatives undoubtedly constitute an important source of therapeutic agents. Their importance lies in their own origin and evolution, since they have great chemical diversity, biochemical specificity, and pharmacological properties. Currently, there is a renewed interest in the development of methodologies capable of efficiently modifying the chemical structure of these bioactive platforms. In this work, the photoderivatization of the diterpene solidagenone was performed using a complexity-to-diversity-oriented approach. By exploring [2+2]-photocycloaddition, photoinduced-hydrogen abstraction, and photoxygenation reactions, a set of solidagenone derivatives was obtained, showing different ring fusions, side chain rearrangements, and modifications of the original furan ring's substitution pattern. The derivatives obtained were characterised by NMR methodologies. To evaluate the structural diversity of the labdane-derived compounds, their physicochemical properties, structural similarity, and chemical space were analysed. These results suggest that photochemical reactions are a useful tool for performing ring distortion transformations, generating derivatives of natural compounds with wide diversity, structural complexity, and with potential biological properties.

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Pristine pyrogenic carbonaceous material (BRH) obtained from rice husk and modified with FeCl3 (BRH-FeCl3) were prepared and explored as carbocatalysts for the activation of peroxymonosulfate (PMS) to degrade a model pharmaceutical (acetaminophen, ACE) in water. The BRH-FeCl3/PMS system removed the pharmaceutical faster than the BRH/PMS. This is explained because in BRH-FeCl3, compared to BRH, the modification (iron played a role as a structuring agent mainly) increased the average pore diameter and the presence of functional groups such as -COO-, -Si-O-, or oxygen vacancies, which allowed to remove the pollutant through an adsorption process and significant carbocatalytic degradation. BRH-FeCl3 was reusable during four cycles and had a higher efficiency for activating PMS than another inorganic peroxide (peroxydisulfate, PDS). The effects of BRH-FeCl3 and PMS concentrations were evaluated and optimized through an experimental design, maximizing the ACE degradation. In the optimized system, a non-radical pathway (i.e., the action of singlet oxygen, from the interaction of PMS with defects and/or -COO-/-Si-O- moieties on the BRH-FeCl3) was found. The BRH-FeCl3/PMS system generated only one primary degradation product that was more susceptible to biodegradation and less active against living organisms than ACE. Also, the BRH-FeCl3/PMS system induced partial removals of chemical oxygen demand and dissolved organic carbon. Furthermore, the carbocatalytic system eliminated ACE in a wide pH range and in simulated urine, having a low-moderate electric energy consumption, indicating the feasibility of the carbocatalytic process to treat water polluted with pharmaceuticals.

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Flavin mononucleotide (FMN) is a dye belonging to the flavin family. These dyes produce photosensitized degradation of organic compounds via reaction with the excited states of the dye or with reactive oxygen species photogenerated from the triplet of the dye. This article presents a new polymeric dye (FMN-CS) composed of the photosensitizer FMN covalently bonded to chitosan polysaccharide (CS). FMN-CS obtained has a molecular weight of 230 × 103 g mol-1 and a deacetylation degree of 74.8%. The polymeric dye is an environmentally friendly polymer with spectroscopic and physicochemical properties similar to those of FMN and CS, respectively. Moreover, under sunlight, it is capable of generating 1O2 with a quantum yield of 0.31. FMN-CS, like CS, is insoluble in basic media. This allows easy recovery of the polymeric dye once the photosensitized process has been carried out and makes FMN-CS a suitable photosensitizer for the degradation of pollutants in contaminated waters. To evaluate whether FMN-CS may be used for pollutant degradation, the photosensitized degradation of two trihydroxybenzenes by FMN-CS was studied.

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The emergence of drug-resistant pathogenic microorganisms has become a public health concern, with demand for strategies to suppress their proliferation in healthcare facilities. The present study investigates the physicochemical and antimicrobial properties of carbon dots (CD-MR) derived from the methyl red azo dye. The morphological and structural analyses reveal that such carbon dots present a significant fraction of graphitic nitrogen in their structures, providing a wide emission range. Based on their low cytotoxicity against mammalian cells and tunable photoluminescence, these carbon dots are applied to bioimaging in vitro living cells. The possibility of using CD-MR to generate reactive oxygen species (ROS) is also analyzed, and a high singlet oxygen quantum efficiency is verified. Moreover, the antimicrobial activity of CD-MR is analyzed against pathogenic microorganisms Staphylococcus aureus, Candida albicans, and Cryptococcus neoformans. Kirby-Bauer susceptibility tests show that carbon dots synthesized from methyl red possess antimicrobial activity upon photoexcitation at 532 nm. The growth inhibition of C. neoformans from CD-MR photosensitization is investigated. Our results show that N-doped carbon dots synthesized from methyl red efficiently generate ROS and possess a strong antimicrobial activity against healthcare-relevant pathogens.

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An "off-on" fluorescent nanoprobe for near-infrared multiphoton imaging of singlet oxygen has been developed. The nanoprobe comprises a naphthoxazole fluorescent unit and a singlet-oxygen-sensitive furan derivative attached to the surface of mesoporous silica nanoparticles. In solution, the fluorescence of the nanoprobe increases upon reaction with singlet oxygen both under one- and multiphoton excitation, with fluorescence enhancements up to 180-fold. The nanoprobe can be readily internalized by macrophage cells and is capable of imaging intracellular singlet oxygen under multiphoton excitation.

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Visible light (VL) surely affects human skin in several ways, exerting positive (tissue regeneration, pain relief) and negative (oxidation, inflammation) effects, depending on the radiation dose and wavelength. Nevertheless, VL continues to be largely disregarded in photoprotection strategies, perhaps because the molecular mechanisms occurring during the interaction of VL with endogenous photosensitizers (ePS) and the subsequent biological responses are still poorly understood. Besides, VL encompass photons with different properties and interaction capacities with the ePS, but there are no quantitative comparisons of their effects on humans. Here, we studied the effects of physiologically relevant doses of four wavelengths ranges of VL, i.e. (in nm), 408-violet, 466/478-blue, 522-green, 650-red, in immortalized human skin keratinocytes (HaCaT). The level of cytotoxicity/damage follows the order: violet>blue >green>red. Violet and blue light induced the highest levels of Fpg-sensitive lesions in nuclear DNA, oxidative stress, lysosomal and mitochondrial damage, disruption of the lysosomal-mitochondrial axis of cell homeostasis, blockade of the autophagic flux, as well as lipofuscin accumulation, greatly increasing the toxicity of wideband VL to human skin. We hope this work will stimulate in development of optimized sun protection strategies.

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UV-A radiation affects skin homeostasis by promoting oxidative distress. Endogenous photosensitizers in the dermis and epidermis of human skin absorb UV-A radiation forming excited states (singlet and triplet) and reactive oxygen species (ROS) producing oxidized compounds that trigger biological responses. The activation of NF-kB induces the expression of pro-inflammatory cytokines and can intensify the generation of ROS. However, there is no studies evaluating the cross talks between inflammatory stimulus and UV-A exposure on the levels of redox misbalance and inflammation. In here, we evaluated the effects of UV-A exposure on J774 macrophage cells previously challenged with LPS in terms of oxidative distress, release of pro-inflammatory cytokines, and activation of regulated cell death pathways. Our results showed that LPS potentiates the dose-dependent UV-A-induced oxidative distress and cytokine release, in addition to amplifying the regulated (autophagy and apoptosis) and non-regulated (necrosis) mechanisms of cell death, indicating that a previous inflammatory stimulus potentiates UV-A-induced cell damage. We discuss these results in terms of the current-available skin care strategies.

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The appearance of microbes resistant to antibiotics requires the development of alternative therapies for the treatment of infectious diseases. In this work two polymers, PTPPF16-EDA and PZnTPPF16-EDA, were synthesized by the nucleophilic aromatic substitution of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin and its Zn(II) complex with ethylenediamine, respectively. In these structures, the tetrapyrrolic macrocycles were N,N'-ethylene crosslinked, which gives them greater mobility. The absorption spectra of the polymers showed a bathochromic shift of the Soret band of ~10 nm with respect to the monomers. This effect was also found in the red fluorescence emission peaks. Furthermore, both polymeric materials produced singlet molecular oxygen with high quantum yields. In addition, they were capable of generating superoxide anion radicals. Photodynamic inactivation sensitized by these polymers was tested in Staphylococcus aureus and Escherichia coli bacteria. A decrease in cell viability greater than 7 log (99.9999%) was observed in S. aureus incubated with 0.5 µM photosensitizer upon 30 min of irradiation. Under these conditions, a low inactivation of E. coli (0.5 log) was found. However, when the cells were treated with KI, the elimination of the Gram-negative bacteria was achieved. Therefore, these polymeric structures are interesting antimicrobial photosensitizing materials for the inactivation of pathogens.

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The review focuses on four issues that are critical for the understanding of monofunctional catalases. How hydrogen peroxide (H2O2) reaches the active site and outcompetes water molecules to be able to function at a very high rate is one of the issues examined. Part of the answer is a gate valve system that is instrumental to drive out solvent molecules from the final section of the main channel. A second issue relates to how the enzyme deals with an unproductive reactive compound I (Cpd I) intermediate. Peroxidatic two and one electron donors and the transfer of electrons to the active site from NADPH and other compounds are reviewed. The new ascribed catalase reactions are revised, indicating possible measurement pitfalls. A third issue concerns the heme b to heme d oxidation, why this reaction occurs only in some large-size subunit catalases (LSCs), and the possible role of singlet oxygen in this and other modifications. The formation of a covalent bond between the proximal tyrosine with the vicinal residue is analyzed. The last issue refers to the origin and function of the additional C-terminal domain (TD) of LSCs. The TD has a molecular chaperone activity that is traced to a gene fusion between a Hsp31-type chaperone and a small-size subunit catalase (SSC).

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Using intracellular-controlled photochemistry to track dynamic organelle processes is gaining attention due to its broad applications. However, most of the employed molecular probes usually require toxic photosensitizers and complex bioanalytical protocols. Here, the synthesis and performance of two new subcellular probes (MitoT1 and MitoT2) are described. The probes undergo photooxidation in the damaged tissue of zebrafish, a model system for tissue regeneration studies. Using high-resolution confocal microscopy and fluorescence spectroscopy, we combine the mentioned photoinduced interconversion at the homeostatic membrane viscosity to track singlet oxygen activity selectively. The continuous and real-time biosensing method reported here provides a new approach for simultaneously detecting endogenous singlet oxygen and viscosity status.

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SUMMARY Introduction: Phthalocyanines are porphyrin-based dyes. They have plenty applications in different fields, including biomedical and chemical research. From a chemical point of view, Phthalocyanines are macrocyclictetraaza compounds, which mainly are made up of isoindol groups that confer aromaticity and planarity on Phthalocyanine structure. Unlike other kinds of porphyrin compounds, Phthalocyanine structure is able to chelate a lot of metals, which more often contribute to their huge variety of functions, including ROS generation, fluorescence, absorption spectra, and others. Aim: To evaluate phthalocyanines compounds owing their excellent photochemical and pharmaceutical properties that explain their wide use at the clinical and medical level. Methodology: We have carried out a meticulous search for scientific works related to the subject between April 2020 and April 2021, the most of them were written in English. As a result, we can say that, for studying Phthalocyanines' properties, the work can be separated into two issues: synthesis of the metalized phthalocyanines and photochemical and photobiological properties. Results: Phthalocyanines have plenty properties that are desirable to biomedical and pharmaceutical research. Because of their photochemical and photobiological properties, as well as ROS generation, Phthalocyanines are one of the photosenstitizers most widely used in photodynamic therapy. They also have antibacterial, antiviral and anticancer activities. In this sense, Phthalocyanine synthesis and in vitro studies are a very important scientific issue.

Introducción: las ftalocianinas son tintes porfirínicos. Tienen muchas aplicaciones en diferentes campos, incluida la investigación biomédica y química. Desde el punto de vista químico, las ftalocianinas son compuestos macrocíclicos de tetraaza. Se componen principalmente de grupos isoindol que confieren aromaticidad y planaridad a la estructura de la ftalocianina. Esta última es capaz de quelar muchos metales, que con mayor frecuencia contribuyen a su gran variedad de funciones, incluida la generación de EROS, la fluorescencia, los espectros de absorción y otros. Objetivo: evaluar algunos derivados de ftalocianinas gracias a las excelentes propiedades fotoquímicas y farmacéuticas que explican su amplio uso a nivel clínico y médico. Metodología: hemos realizado una búsqueda minuciosa de trabajos científicos relacionados con el tema entre abril de 2020 y abril de 2021, la mayoría de ellos escritos en inglés. Como resultado, podemos decir que, para estudiar las propiedades de las ftalocianinas, el trabajo se puede dividir en dos temas: síntesis de las ftalocianinas metalizadas y propiedades fotoquímicas y ffotobiológicas. Resultados: las ftalocianinas tienen muchas propiedades que son deseables para la investigación biomédica y farmacéutica. Por sus propiedades fotoquímicas y fotobiológicas, así como por la generación de EROS, las ftalocianinas son uno de los fotosensibilizadores más utilizados en terapia fotodinámica. También tienen actividades antibacterianas, antivirales y anticancerígenas. En este sentido, la síntesis de ftalocianina y los estudios in vitro son un tema científico muy importante.

Introdução: as ftalocianinas são corantes à base de porfirinas. Eles têm muitas aplicações em diferentes campos, incluindo pesquisas biomédicas e químicas. Do ponto de vista químico, as ftalocianinas são compostos macrocíclicos tetraaza, que são constituídos principalmente por grupos isoindol que conferem aromaticidade e planaridade à estrutura das ftalocianinas. Ao contrário de outros tipos de compostos de porfirina, a estrutura da ftalocianina é capaz de quelar uma grande quantidade de metais, que mais frequentemente contribuem para sua enorme variedade de funções, incluindo geração de ROS, fluorescência, espectro de absorção e outros. Objetivo: avaliar alguns derivados de ftalocianinas graças às excelentes propriedades fotoquímicas e farmacêuticas que explicam a sua ampla utilização a nível clínico e médico. Metodologia: efetuamos uma busca minuciosa de trabalhos científicos relacionados ao assunto entre abril de 2020 e abril de 2021, a maioria deles redigidos na língua inglesa. Como resultado, podemos dizer que, para estudar as propriedades das ftalocianinas, o trabalho pode ser dividido em duas questões: síntese das ftalocianinas metalizadas e propriedades fotoquímicas e fotobiológicas. Resultados: as ftalocianinas têm muitas propriedades desejáveis para a pesquisa biomédica e farmacêutica. Pelas suas propriedades fotoquímicas e fotobiológicas, além da geração de ROS, as ftalocianinas são um dos ffotossensibilizantes mais amplamente utilizados na terapia fotodinàmica e processos fototóxicos. Eles também têm atividades antibacteriana, antiviral e anticàncer. Nesse sentido, a síntese de ftalocianina e os estudos in vitro são uma questão científica muito importante.

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Metallic nanostructures can improve the production of singlet oxygen (1O2) of a photosensitizer during photodynamic therapy (PDT) . Engineering a high performance nanoparticle is mandatory for an appropriate use of plasmonic nanostructures in PDT. Metal enhanced singlet oxygen generation requires the use of nanoparticles with high scattering efficiency, capable of inducing a significant electric field enhancement and with plasmon peak overlapping the photosensitizer absorption spectrum. Herein, we report the optimization of nanoshells structure (silica core radius and gold shell thickness) to increase the singlet oxygen production by Methylene Blue photosensitizer. A 3D Full-wave field analysis was used to evaluate the plasmonic spectrum, scattering efficiency and localized field intensity of Au nanoshells as a function of their dimensions. The 40/20 core radius/shell thickness optimized gold nanoshell showed 75% scattering efficiency and field enhancement up to 35 times. Metal-enhanced singlet oxygen generation was observed and quantified for Methylene Blue water solution with gold nanoshell particles. Moreover, the influence of the irradiation time and the metallic nanostructures concentration on metal enhanced singlet oxygen generation were also appraised. The experimental results showed that the use of gold nanoshell improved 320% the 1O2 production in a MB solution. The approach used to select a high performance metallic nanoparticle provides insights on engineering plasmonic structures for metal enhanced singlet oxygen generation for PDT.

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The present work reports the effects of meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS4) aggregation on its excited states absorption spectra, triplet states quenching by molecular oxygen and singlet oxygen production. Experimental techniques such as optical absorption, Z-scan with a white light continuum source and the Laser Flash Photolysis were used to fulfil the study. J-aggregates possess reverse saturable absorption in the 505-660 nm spectral range with a peak centered close to 540 nm. These facts together with their fast relaxation time suggest that they can be employed as material for ultrafast optical limiting and switching. Even though aggregation reduces the porphyrin excited-state lifetimes and quantum yields, it does not reduce the probability of the contact between the quencher and the excited aggregate. Aggregation does not change the contribution of energy transfer mechanisms to triplet state quenching by molecular oxygen. The production of singlet oxygen, the intense absorption in the phototherapeutic window and the high efficiency of conversion of light energy into heat, allow consider J-aggregates as a theranostic agent for photomedicine. It is proposed to use J-aggregates for diagnostics by photoacoustic images and in combination with a near-infrared photodynamic/photothermal dual mode therapy, thus improving synergistically the therapeutic response.

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We have synthesized anthracene and metal@anthracene core-shell nanoparticles to combine radiation (RT) and photodynamic (PDT) therapies. Synthesis of anthracene nanoparticles in the presence of colloidal silver or gold reduced the nanoparticles hydrodynamic radius, caused core-shell nanostructures to grow, and led to plasmon-enhanced fluorescence. Singlet oxygen (1O2) generation was investigated by electron spin resonance (ESR) and fluorescence spectroscopies. In the presence of a porphyrin, anthracene nanoparticles and the core-shell nanoparticles acted as energy mediators and increased 1O2 generation under exposure to light, as evidenced by the ESR results. Fluorescence suppression experiments showed that the core-shell nanoparticles captured 1O2 at rates higher than anthracene nanoparticles, suggesting that overall production of 1O2 (1O2 captured by spin-trap + 1O2 captured by surface anthracene molecules) was higher for the core-shell nanoparticles. Moreover, the Ag@anthracene nanoparticles stood out as a new and more sensitive fluorescent probe for 1O2. During irradiation with X-rays, both anthracene and Ag@anthracene nanoparticles trapped 1O2; subsequently, they afforded sustained release of the trapped 1O2 for up 12 days after irradiation. This could be an interesting strategy to extend the radiation therapy treatment after the irradiation sessions. Furthermore, the presence of the metallic nanoparticle in the core of the core-shell nanostructure increased interaction with X-rays, raising the radiation dose around the nanoparticle. Therefore, metal@anthracene nanostructures may allow combination of cancer treatments by different approaches depending on the adopted nanoparticle configuration.

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