Showing papers in "Photochemical and Photobiological Sciences in 2018"

Formation of UV-induced DNA damage contributing to skin cancer development

Abstract: UV-induced DNA damage plays a key role in the initiation phase of skin cancer. When left unrepaired or when damaged cells are not eliminated by apoptosis, DNA lesions express their mutagneic properties, leading to the activation of proto–oncogene or the inactivation of tumor suppression genes. The chemical nature and the amount of DNA damage strongly depend on the wavelength of the incident photons. The most energetic part of the solar spectrum at the Earth's surface (UVB, 280–320 nm) leads to the formation of cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6–4) pyrimidone photoproducts (64PPs). Less energetic but 20–times more intense UVA (320–400 nm) also induces the formation of CPDs together with a wide variety of oxidatively generated lesions such as single strand breaks and oxidized bases. Among those, 8–oxo–7,8–dihydroguanine (8–oxoGua) is the most frequent since it can be produced by several mechanisms. Data available on the respective yield of DNA photoproducts in cells and skin show that exposure to sunlight mostly induces pyrimidine dimers, which explains the mutational signature found in skin tumors, with lower amounts of 8–oxoGua and strand breaks. The present review aims at describing the basic photochemistry of DNA and discussing the quantitative formation of the different UV–induced DNA lesions reported in the literature. Additional information on mutagenesis, repair and photoprotection is briefly provided.

Environmental effects of ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2017

Abstract: This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595-828), of recent findings of current and projected interactive environmental effects of ultraviolet (UV) radiation, stratospheric ozone, and climate change. These effects include those on human health, air quality, terrestrial and aquatic ecosystems, biogeochemical cycles, and materials used in construction and other services. The present update evaluates further evidence of the consequences of human activity on climate change that are altering the exposure of organisms and ecosystems to UV radiation. This in turn reveals the interactive effects of many climate change factors with UV radiation that have implications for the atmosphere, feedbacks, contaminant fate and transport, organismal responses, and many outdoor materials including plastics, wood, and fabrics. The universal ratification of the Montreal Protocol, signed by 197 countries, has led to the regulation and phase-out of chemicals that deplete the stratospheric ozone layer. Although this treaty has had unprecedented success in protecting the ozone layer, and hence all life on Earth from damaging UV radiation, it is also making a substantial contribution to reducing climate warming because many of the chemicals under this treaty are greenhouse gases.

Photobiomodulation: lasers vs. light emitting diodes?

Abstract: Photobiomodulation (PBM) is a treatment method based on research findings showing that irradiation with certain wavelengths of red or near-infrared light has been shown to produce a range of physiological effects in cells, tissues, animals and humans. Scientific research into PBM was initially started in the late 1960s by utilizing the newly invented (1960) lasers, and the therapy rapidly became known as “low-level laser therapy”. It was mainly used for wound healing and reduction of pain and inflammation. Despite other light sources being available during the first 40 years of PBM research, lasers remained by far the most commonly employed device, and in fact, some authors insisted that lasers were essential to the therapeutic benefit. Collimated, coherent, highly monochromatic beams with the possibility of high power densities were considered preferable. However in recent years, non-coherent light sources such as light-emitting diodes (LEDs) and broad-band lamps have become common. Advantages of LEDs include no laser safety considerations, ease of home use, ability to irradiate a large area of tissue at once, possibility of wearable devices, and much lower cost per mW. LED photobiomodulation is here to stay.

Recent strategies to improve boron dipyrromethene (BODIPY) for photodynamic cancer therapy: an updated review

Abstract: BODIPYs are photosensitizers activatable by light to generate highly reactive singlet oxygen (1O2) from molecular oxygen, leading to tissue damage in the photoirradiated region. Despite their extraordinary photophysical characteristics, they are not featured in clinical photodynamic therapy. This review discusses the recent advances in the design and/or modifications of BODIPYs since 2013, to improve their potential in photodynamic cancer therapy and related areas.

Solar UV damage to cellular DNA: from mechanisms to biological effects.

Abstract: Solar ultraviolet (UV) radiation generates bulky photodimers at di-pyrimidine sites that pose stress to cells and organisms by hindering DNA replication and transcription. In addition, solar UV also induces various types of oxidative DNA lesions and single strand DNA breaks. Relieving toxicity and maintenance of genomic integrity are of clinical importance in relation to erythema/edema and diseases such as cancer, neurodegeneration and premature ageing, respectively. Following solar UV radiation, a network of DNA damage response mechanisms triggers a signal transduction cascade to regulate various genome-protection pathways including DNA damage repair, cell cycle control, apoptosis, transcription and chromatin remodeling. The effects of UVC and UVB radiation on cellular DNA are predominantly accounted for by the formation of photodimers at di-pyrimidine sites. These photodimers are mutagenic: UVC, UVB and also UVA radiation induce a broadly similar pattern of transition mutations at di-pyrimidine sites. The mutagenic potency of solar UV is counteracted by efficient repair of photodimers involving global genome nucleotide excision repair (GG-NER) and transcription-coupled nucleotide excision repair (TC-NER); the latter is a specialized repair pathway to remove transcription-blocking photodimers and restore UV-inhibited transcription. On the molecular level these processes are facilitated and regulated by various post-translational modifications of NER factors and the chromatin substrate. Inherited defects in NER are manifested in different diseases including xeroderma pigmentosum (XP), Cockayne syndrome (CS), UV sensitive syndrome (UVsS) and the photosensitive form of trichothiodystrophy (TTD). XP patients are prone to sunlight-induced skin cancer. UVB irradiated XP and CS knockout mouse models unveiled that only TC-NER counteracts erythema/edema, whereas both GG-NER and TC-NER protect against UVB-induced cancer. Additionally, UVA radiation induces mutations characterized by oxidation-linked signature at non-di-pyrimidine sites. The biological relevance of oxidation damage is demonstrated by the cancer susceptibility of UVB-irradiated mice deficient in repair of oxidation damage, i.e., 8-oxoguanine.

Fullerenes as photosensitizers in photodynamic therapy: pros and cons.

Abstract: One class of carbon nanomaterials is the closed cages known as fullerenes. The first member to be discovered in 1985 was C60, called “buckminsterfullerene” as its cage structure resembled a geodesic dome. Due to their extended π-conjugation they absorb visible light, possess a high triplet yield and can generate reactive oxygen species upon illumination, suggesting a possible role of fullerenes in photodynamic therapy (PDT). Pristine C60 is highly hydrophobic and prone to aggregation, necessitating functionalization to provide aqueous solubility and biocompatibility. The most common functional groups attached are anionic (carboxylic or sulfonic acids) or cationic (various quaternary ammonium groups). Depending on the functionalization, these fullerenes can be designed to be taken up into cancer cells, or to bind to microbial cells (Gram-positive, Gram-negative bacteria, fungi). Fullerenes can be excited with a wide range of wavelengths, UVA, blue, green or white light. We have reported a series of functionalized fullerenes (C60, C70, C82) with attached polycationic chains and additional light-harvesting antennae that can be used in vitro and in animal models of localized infections. Advantages of fullerenes as photosensitizers are: (a) versatile functionalization; (b) light-harvesting antennae; (c) ability to undergo Type 1, 2, and 3 photochemistry; (d) electron transfer can lead to oxygen-independent photokilling; (e) antimicrobial activity can be potentiated by inorganic salts; (f) can self-assemble into supramolecular fullerosomes; (g) components of theranostic nanoparticles; (h) high resistance to photobleaching. Disadvantages include: (a) highly hydrophobic and prone to aggregation; (b) overall short wavelength absorption; (c) relatively high molecular weight; (d) paradoxically can be anti-oxidants; (e) lack of fluorescence emission for imaging.

The good, the bad, and the ugly – controlling singlet oxygen through design of photosensitizers and delivery systems for photodynamic therapy

Abstract: Singlet oxygen, although integral to photodynamic therapy, is notoriously uncontrollable, suffers from poor selectivity and has fast decomposition rates in biological media. Across the scientific community, there is a conscious effort to refine singlet oxygen interactions and initiate selective and controlled release to produce a consistent and reproducible therapeutic effect in target tissue. This perspective aims to provide an insight into the contemporary design principles behind photosensitizers and drug delivery systems that depend on a singlet oxygen response or controlled release. The discussion will be accompanied by in vitro and in vivo examples, in an attempt to highlight advancements in the field and future prospects for the more widespread application of photodynamic therapy.

Wastewater chemical contaminants: remediation by advanced oxidation processes

Abstract: Approximately 70% of the terrestrial area is covered with water, but only a small water fraction is compatible with terrestrial life forms. Due to the increment in human consumption, the need for water resources is increasing, and it is estimated that more than 40% of the population worldwide will face water stress/scarcity within the next few decades. Water recycling and reuse may offer the opportunity to expand water resources. For that, the wastewater treatment paradigm should be changed and adequately treated wastewater should be seen as a valuable resource instead of a waste product. It is easily understandable that the exact composition and constituent concentration of wastewater vary according to its different sources (industrial, agricultural, urban usage of water). Consequently, a variety of known and emerging pollutants like heavy metals, antibiotics, pesticides, phthalates, polyaromatic hydrocarbons, halogenated compounds and endocrine disruptors have been found in natural water reservoirs, due to the limited effectiveness of conventional wastewater treatment. The conventional approach consists of a combination of physical, chemical and biological processes, aiming at the removal of large sediments such as heavier solids, scum and grease and of organic content in order to avoid the growth of microorganisms and eutrophication of the receiving water bodies. However, this approach is not sufficient to reduce the chemical pollutants and much less the emerging chemical pollutants. In this review, after some considerations concerning chemical pollutants and the problematic efficiency of their removal by conventional methods, an update is presented on the successes and challenges of novel approaches for wastewater remediation based on advanced oxidation processes. An insight into wastewater remediation involving the photodynamic approach mediated by tetrapyrrolic derivatives will be underlined.

Using X-rays in photodynamic therapy: an overview

Abstract: Photodynamic therapy is a therapeutic option to treat cancer and other diseases. PDT is used every day in dermatology, and recent developments in the treatment of glioblastoma, mesothelioma or prostate have demonstrated the efficacy of this modality. In order to improve the efficacy of PDT, different strategies are under development, such as the use of targeted PS or nanoparticles to improve selectivity and the design of light devices to better monitor the light dose. Due to the low penetration of light into tissue, another way to improve the efficacy of PDT to treat deep tumors is the use of upconversion NPs or bi-photon absorption compounds. These compounds can be excited in the red part of the spectrum. A relatively new approach, which we will call PDTX, is the use of X-rays instead of UV-visible light for deeper penetration into tissue. The principle of this technique will be described, and the state-of-art literature concerning this modality will be discussed. First, we will focus on various photosensitizers that have been used in combination with X-ray irradiation. To improve the efficacy of this modality, nanoparticles have been designed that allow the conversion of high-energy ionizing radiation into UV-visible light; these are potential candidates for the PDTX approach. They will be discussed at the end of this review.

Photosensitiser-gold nanoparticle conjugates for photodynamic therapy of cancer

Abstract: Gold nanoparticles (AuNPs) have been extensively studied within biomedicine due to their biocompatibility and low toxicity. In particular, AuNPs have been widely used to deliver photosensitiser agents for photodynamic therapy (PDT) of cancer. Here we review the state-of-the-art for the functionalisation of the gold nanoparticle surface with both photosensitisers and targeting ligands for the active targeting of cancer cell surface receptors. From the initial use of the AuNPs as a simple carrier of the photosensitiser for PDT, the field has significantly advanced to include: the use of PEGylated modification to provide aqueous compatibility and stealth properties for in vivo use; gold metal-surface enhanced singlet oxygen generation; functionalisation of the AuNP surface with biological ligands to specifically target over-expressed receptors on the surface of cancer cells and; the creation of nanorods and nanostars to enable combined PDT and photothermal therapies. These versatile AuNPs have significantly enhanced the efficacy of traditional photosensitisers for both in vitro and in vivo cancer therapy. From this review it is apparent that AuNPs have an important future in the treatment of cancer.

Ultraviolet radiation-induced immunosuppression and its relevance for skin carcinogenesis

Abstract: The realisation that UV radiation (UVR) exposure could induce a suppressed immune environment for the initiation of carcinogenesis in the skin was first described more than 40 years ago. Van der Leun and his colleagues contributed to this area in the 1980s and 90s by experiments in mice involving UV wavelength and dose-dependency in the formation of such tumours, in addition to illustrating both the local and systemic effect of the UVR on the immune system. Since these early days, many aspects of the complex pathways of UV-induced immunosuppression have been studied and are outlined in this review. Although most experimental work has involved mice, it is clear that UVR also causes reduced immune responses in humans. Evidence showing the importance of the immune system in determining the risk of human skin cancers is explained, and details of how UVR exposure can down-regulate immunity in the formation and progression of such tumours reviewed. With increasing knowledge of these links and the mechanisms of UVR-induced immunosuppression, novel approaches to enhance immunity to skin tumour antigens in humans are becoming apparent which, hopefully, will reduce the burden of UVR-induced skin cancers in the future.

Smart nanoporous metal-organic frameworks by embedding photochromic molecules - state of the art and future perspectives.

Abstract: Smart, molecularly structured materials with remote-controllable properties and functionalities attract particular attention and may enable advanced applications. In this respect, the embedment of stimuli-responsive molecules, such as azobenzenes, spiropyrans or diarylethenes, in metal-organic frameworks (MOFs) is a very fascinating approach, resulting in easily accessible photoswitchable, nanoporous hybrid materials. It is an attractive alternative to the incorporation of the smart moieties in the MOF scaffold, which usually demands complex synthetic efforts. Here, the opportunities, properties and perspectives of the embedment of photochromic molecules in MOF pores are reviewed. In addition to presenting a straightforward route to prepare smart materials with, e.g., photoswitchable adsorption properties that can be used for remote-controllable membrane separation, the photoswitch@MOF compounds also represent unique model systems to investigate the dye as well as the MOF properties and their interactions with each other. For instance, the MOF pores possess a polarity similar to a solvent, so that the optical properties of the resulting materials may be influenced by a careful choice of the respective host material.

A novel Schiff base derivative of pyridoxal for the optical sensing of Zn2+ and cysteine.

Abstract: An easy to prepare novel vitamin B6 cofactor derivative 3-hydroxy-N′-((3 hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl)methylene)-2-naphthohydrazide (NPY) was synthesized by a one pot condensation reaction of pyridoxal with 3-hydroxy-2-naphthoic hydrazide and applied for the optical detection of Zn2+ and cysteine in the aqueous DMSO medium. The addition of Zn2+ ions leads to a selective blue-shift in the fluorescence emission spectrum of NPY from 530 nm to 475 nm, which allowed ratiometric detection of Zn2+ ions down to 8.73 × 10−7 M without any interference from other tested metal ions. This system was also successfully applied to detect intracellular Zn2+ ions in live HeLa cells. Further, when the in situ generated NPY·Zn2+ complex was interacted with various amino acids, the addition of cysteine resulted in an instantaneous colour change from light yellow to colourless and the absorbance at 435 nm of the complex was quenched selectively. Also, the fluorescence of the NPY·Zn2+ complex was quenched, which allowed the detection of cysteine down to 6.63 × 10−7 M.

Combination of PDT photosensitizers with NO photodononors

Abstract: Combination of photodynamic therapy (PDT) with other treatment modalities is emerging as one of the most suitable strategies to increase the effectiveness of therapeutic action on cancer and bacterial diseases and to minimize side effects. This approach aims at exploiting the additive/synergistic effects arising from multiple therapeutic species acting on different mechanistic pathways. The coupling of PDT with photocontrolled release of nitric oxide (NO) through the appropriate assembly of PDT photosensitizers (PSs) and NO photodonors (NOPDs) may open up intriguing avenues towards new and still underexplored multimodal therapies not based on “conventional” drugs but entirely controlled by light stimuli. In this contribution, we present an overview of the most recent advances in this field, illustrating several strategies to assemble PSs and NOPDs allowing them to operate independently without reciprocal interferences and describing the potential applications with particular emphasis on their impact in anticancer and antibacterial research.

Some activities of PorphyChem illustrated by the applications of porphyrinoids in PDT, PIT and PDI

Abstract: Photodynamic therapy is an innovative approach to treat diverse cancers and diseases that involves the use of photosensitizing agents along with light of an appropriate wavelength to generate cytotoxic reactive oxygen species. Among the collection of potential dye candidates, porphyrinoids (i.e. porphyrins, chlorins, and phthalocyanines) are probably the most promising photosensitizers for PDT applications. This review shows the great potential of these derivatives for their industrial development in the field of health through different applications in photodynamic therapy (PDT), photoimmunotherapy (PIT), ophthalmology, dermatology and photodynamic inactivation (PDI). The purpose of this survey is also to show the new trends and evolutions in these fields.

Stability and degradation of indocyanine green in plasma, aqueous solution and whole blood

Abstract: Fluorescence-based imaging has evolved into an important technology during recent years. Specifically indocyanine green (ICG) has invaded most fields of diagnostic and interventional medicine. Considering the numerous advantages of the substance like the rapid degradation and rare adverse reactions, ICG is currently the most commonly used fluorescing agent. High-performance liquid chromatography (HPLC) was used for measuring absorbance and fluorescence of ICG and its potential degradation compounds. Stability and degradation were evaluated under light exposure or in darkness at various temperatures. Under these conditions, degradation of ICG was evaluated over a period of 11 days. Additional, stability measurements of ICG were performed in EDTA whole blood samples at 37 °C incubation temperature while monitoring. Furthermore, we used mass spectrometric (MS) and nuclear magnetic resonance (NMR) analyses for the identification of supposed ICG degradation compound. Potential quenching effect of ICG was examined in aqueous and plasma solutions at concentrations ranging from 0.01–100 μg ml−1. When diluted in water and stored at 4 °C in the dark, ICG is stable for three days with only 20% of fluorescence intensity lost in this time-span. ICG incubated at 37 °C in whole blood under light exposure is stable for 5 h. In our study we observed the degradation of ICG into two degradation compounds with a mass of m/z 785.32 and m/z 1501.57, respectively. Based on our observations we suggest that ICG should be used within one or two days after preparation, if the ICG solution is stored at 4 °C.

A multifunctional selective "turn-on" fluorescent chemosensor for detection of Group IIIA ions Al3+, Ga3+ and In3.

Abstract: A versatile chemosensor 1 (E)-2-(((8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)methylene)amino)-1H-benzo[de]isoquinoline-1,3(2H)-dione, based on naphthalimide and julolidine moieties, was developed for highly distinguishable and selective recognition of Group IIIA metal ions (Al3+, Ga3+ and In3+). Sensor 1 exhibited significant ‘off–on’ fluorescence responses at 488 nm in the presence of Al3+ and at 570 nm in the presence of Ga3+ and In3+. The same emission of Ga3+ and In3+ could be distinguished through different color changes (from colorless to yellow for Ga3+ and no color change for In3+). Binding constants of 1 for Ga3+ and In3+ are the highest reported to date for an organic chemosensor. A 2 : 1 binding mode between 1 with Al3+, Ga3+ and In3+ is proposed based on electrospray ionization mass spectrometry, Job plot analysis, and theoretical calculations.

New di-anchoring A-π-D-π-A configured organic chromophores for DSSC application: sensitization and co-sensitization studies.

Abstract: Correction for ‘New di-anchoring A–π-D–π-A configured organic chromophores for DSSC application: sensitization and co-sensitization studies’ by Praveen Naik et al., Photochem. Photobiol. Sci., 2018, DOI: 10.1039/c7pp00351j.

Carbazole-based compounds as photoinitiators for free radical and cationic polymerization upon near visible light illumination.

Abstract: Six new carbazole based compounds (Ca1-Ca6) are synthesized and proposed as high performance photoinitiators with iodonium salt (iod) and/or an amine (EDB) for both the free radical polymerization (FRP) of acrylates and the cationic polymerization (CP) of epoxides upon near UV and visible light exposure using light emitting diodes (LEDs) @385 nm and @405 nm. Excellent polymerization initiating abilities are found and high final reactive function conversions are acquired. A full picture of the involved photochemical mechanisms is given.

New insight into an efficient visible light-driven photocatalytic organic transformation over CdS/TiO2 photocatalysts

Abstract: Selective transformation of organics by visible-light-driven photocatalysis has been considered as a green and efficient strategy for the synthesis of fine chemicals. Herein, we fabricated mesoporous structured TiO2 with CdS nanoparticles successfully by a photodeposition method. The photocatalytic selective oxidation of benzyl alcohols and reduction of 4-nitroaniline were demonstrated over the as-prepared samples under visible-light irradiation. The CdS-decorated TiO2 with the photodeposition time of 90 min exhibited highest activity, which was higher than that of the commercial CdS, bare TiO2, CdS/P25, and CdS/SiO2. Further experimental results indicated that the higher performance was attributed to the moderate deposition of CdS forming a closely connected heterojunction with TiO2, which promoted the separation of photogenerated electrons and holes. Based on the results of active species detection, possible mechanisms for photocatalytic selective oxidation of benzyl alcohol and reduction of 4-nitroaniline were proposed. Our study may provide guidance for selective transformation of organics via construction of heterojunction photocatalysts.

Mesoporous silica nanoparticles in recent photodynamic therapy applications

Abstract: In this review, the use of mesoporous silica nanoparticles for photodynamic therapy (PDT) applications is described for the year 2017. Since the pioneering work in 2009, nanosystems involving mesoporous silica nanoparticles have gained in complexity with a sophisticated core–shell system able to perform multi-imaging and multi-therapies, not only for cancer diseases but also for anti-microbial therapy, atherosclerosis, or Alzheimer disease. Near-infrared, excitation light based on up-converting systems, X-rays or persistent luminescent systems are described for deeper tissue treatments.

A versatile method for the determination of photochemical quantum yields via online UV-Vis spectroscopy

Abstract: We have developed a simple method for determining the quantum yields of photo-induced reactions. Our setup features a fibre coupled UV-Vis spectrometer, LED irradiation sources, and a calibrated spectrophotometer for precise measurements of the LED photon flux. The initial slope in time-resolved absorbance profiles provides the quantum yield. We show the feasibility of our methodology for the kinetic analysis of photochemical reactions and quantum yield determination. The typical chemical actinometers, ferrioxalate and ortho-nitrobenzaldehyde, as well as riboflavin, a spiro-compound, phosphorus- and germanium-based photoinitiators for radical polymerizations and the frequently utilized photo-switch azobenzene serve as paradigms. The excellent agreement of our results with published data demonstrates the high potential of the proposed method as a convenient alternative to the time-consuming chemical actinometry.

Effects of gold nanoparticles on the photophysical and photosynthetic parameters of leaves and chloroplasts.

Abstract: Effects of gold nanoparticles (average diameter: 10–14 nm) on leaves and chloroplasts have been studied. Gold nanoparticles (AuNPs) quenched significantly chlorophyll fluorescence when introduced both in intact leaves and isolated chloroplasts. Additionally, the fluorescence spectra corrected for light re-absorption processes showed a net decrease in the fluorescence ratio calculated as the quotient between the maximum fluorescence at 680 and 735 nm. This fact gave evidence for a reduction in the fluorescence emission of the PSII relative to that of the PSI. Strikingly, the photosynthetic parameters derived from the analysis of the slow phase of Kautsky's kinetics, the rate of oxygen evolution and the rate of photo-reduction of 2,6-dichlorophenolindophenol were increased in the presence of AuNPs indicating an apparent greater photosynthetic capacity. The observed results were consistent with an electron transfer process from the excited PSII, which was thermodynamically possible, and which competed with both the electron transport process that initiated photosynthesis and the deactivation of the excited PSII by fluorescence emission. Additionally, it is here explained, in terms of a completely rational kinetic scheme and their corresponding algebraic expressions, why the photosynthetic parameters and the variable and non-variable fluorescence of chlorophyll are modified in a photosynthetic tissue containing gold nanoparticles.

A naked-eye fluorescent sensor for copper(ii) ions based on a naphthalene conjugate Bodipy dye.

Abstract: A novel naphthalene-Bodipy dye (N-Bodipy) was designed, prepared and characterized. N-Bodipy showed a selective and sensitive recognition toward Cu(II) ions as a fluorescent antenna group in acetonitrile/water over other metal cations. The complexation between Cu(II) ions and N-Bodipy gave a specific color change as well as caused fluorescence quenching under long-wavelength light (365 nm). The remarkable quenching effect in fluorescence intensity centered at 538 nm was only observed in the presence of copper(II) ions. Moreover, the orange color of N-Bodipy solution turned pale-yellow depending on the complexation effect in daylight. The complex stoichiometry was determined using a Job's plot and it was found to be 2 : 1 (ligand/metal). The binding constant was calculated with the Benesi–Hildebrand equation to be 1.39 × 1010 M−1 and the detection limit was 1.28 μM (LOD = 3α/slope, α is the standard deviation) for Cu(II). The data proved that the binding between N-Bodipy and Cu(II) is chemically reversible.

Visible-light-activated photoCORMs: rational design of CO-releasing organic molecules absorbing in the tissue-transparent window

Abstract: To date, most known molecules that release carbon monoxide by the action of light are based on carbonyl complexes of metals. However, they suffer from several disadvantages, so the focus of this perspective is on photoactivatable metal-free CO precursors. The development and design of these systems from the starting point of deep-UV-absorbing hydrophobic molecules and leading to hydrophilic biocompatible visible-light-absorbing CO-releasing molecules (photoCORMs) is described with mechanistic details for several structural motifs. The possibilities of this development are not exhausted and here we discuss the design of new biologically interesting candidates.

Controlling methylene blue aggregation: a more efficient alternative to treat Candida albicans infections using photodynamic therapy.

Abstract: Methylene Blue (MB) has been widely used in antimicrobial Photodynamic Therapy (aPDT), however, the mechanisms of action (Type I or Type II) are defined by its state of aggregation. In this sense, the identification of the relationships between aggregation, the mechanisms of action and the effectiveness against microorganisms, as well as the establishment of the means and the formulations that may favor the most effective mechanisms, are essential. Thus, the objective of this study was to assess the in vitro aPDT efficacies against Candida albicans, by using MB in vehicles which may influence the aggregation and present an oral formulation (OF) containing MB, to be used in clinical aPDT procedures. The efficacy of MB at 20 mg L−1 was tested in a range of vehicles (water, physiological solution – NaCl 0.9%, phosphate saline buffer – PBS, sodium dodecyl sulfate 0.25% – SDS and urea 1 mol L−1) in a C. albicans planktonic culture, when using 4.68 J cm−2 of 640 ± 12 nm LED for the irradiations, as well as 5 minutes of pre-irradiation time, together with measuring the UFC mL−1. Based upon these analyses, an OF containing MB in the most effective vehicle was tested in the biofilms, as a proposal for clinical applications. When comparing some of the vehicles, sodium dodecyl sulfate was the only one that enhanced an MB aPDT efficacy in a planktonic C. albicans culture. This OF was tested in the biofilms and 50 mg L−1 MB was necessary, in order to achieve some reduction in the cell viabilities after the various treatments. The light dosimetries still need further adaptations, in order for this formulation to be used in clinical applications. The present research has indicated that the development of this formulation for the control of MB aggregations may result in more effective clinical protocols.

Photodynamic effect of zinc porphyrin on the promastigote and amastigote forms of Leishmania braziliensis.

Abstract: Leishmaniasis is a neglected disease present in more than 88 countries. The currently adopted chemotherapy faces challenges related to side effects and the development of resistance. Photodynamic therapy (PDT) is emerging as a therapeutic modality for cutaneous leishmaniasis. Zn(II) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (ZnTE-2-PyP4+, ZnP) is a cationic, water-soluble, zinc porphyrin-based photosensitizer whose photodynamic effect on Leishmania braziliensis was analyzed by evaluating the number of visibly undamaged and motile cells, cell membrane integrity, mitochondrial membrane potential, and ultrastructural damage. Treatment of parasites with ZnP and light induced damage in up to 90% of L. braziliensis promastigote cells. Propidium iodide labeling suggested the loss of plasma membrane integrity. In samples treated with ZnP and light, a hyperpolarization of the mitochondrial membrane potential was also observed. Ultrastructural evaluation of promastigotes after photodynamic treatment indicated a loss of cytoplasmic material and the presence of vacuoles. Scanning electron microscopy showed wrinkling of the plasma membrane and a reduced cell volume. Additionally, the number of amastigotes per macrophage was reduced by about 40% after photodynamic application. The treatment showed no considerable toxicity against mammalian cells. Therefore, the results indicated that PDT associated with ZnTE-2-PyP4+ represents a promising alternative to cutaneous leishmaniasis treatment.

The modeling of the absorption lineshape for embedded molecules through a polarizable QM/MM approach

Abstract: We present a computational strategy to simulate the absorption lineshape of a molecule embedded in a complex environment by using a polarizable QM/MM approach. This strategy is presented in two alternative formulations, one based on a molecular dynamics simulation of the structural fluctuations of the system and the other using normal modes and harmonic frequencies calculated on optimized geometries. The comparison for the case of a chromophore within a strongly inhomogeneous and structured environment, namely the intercalation pocket of DNA, shows that the MD-based approach is able to reproduce the experimental spectral bandshape. In contrast, the static approach overestimates the vibronic coupling, resulting in a much broader band.

Ternary semiconductor ZnxAg1-xS nanocomposites for efficient photocatalytic degradation of organophosphorus pesticides †

Abstract: The construction of ternary semiconductor nanostructures has attracted much attention in photocatalysis by virtue of their tunable elemental composition and band structure Here, ternary semiconductor ZnxAg1−xS (0 ≤ x ≤ 1) composites were successfully prepared by a simple and low-cost hydrothermal method without using any surfactant Combined analyses using XRD, N2 sorption, SEM, TEM and UV-vis DRS revealed that the ternary composite semiconductor materials exhibited well-developed crystalline frameworks, large surface areas of 15–70 m2 g−1, sizes of 10–30 nm, and outstanding UV light absorption properties Data from XRD and TEM indicate that photocatalysis might contribute to the formation of the strong interfacial interaction between ZnS and Ag2S nanoparticles The photocatalytic activities were investigated via the degradation of organophosphorus pesticides, including malathion (MLT), monocrotophos (MCP) and chlorpyrifos (CPS), using the ZnxAg1−xS composites under UV light irradiation The toxicity of MLT, MCP, and CPS was reduced by photocatalysis and photolysis; however, photocatalysis had a greater impact Superior photocatalytic performance was exhibited by the Zn05Ag05S catalyst owing to its large surface area and the presence of Ag0 with improved charge transfer in comparison with that of bare ZnS and Ag2S Assays of stability and reusability indicated that the Zn05Ag05S composite retained more than 85% of its activity after five cycles of use On the basis of the results, a possible photocatalytic mechanism of the prepared samples was proposed This study indicates a potential application of the ternary semiconductor materials in the efficient UV light-driven photocatalytic degradation of other pollutants that may cause environmental pollution

Are current guidelines for sun protection optimal for health? Exploring the evidence

Abstract: Exposure of the skin to ultraviolet (UV) radiation is the main risk factor for skin cancer, and a major source of vitamin D, in many regions of the world. Sun protection messages to minimize skin cancer risks but avoid vitamin D deficiency are challenging, partly because levels of UV radiation vary by location, season, time of day, and atmospheric conditions. The UV Index provides information on levels of UV radiation and is a cornerstone of sun protection guidelines. Current guidelines from the World Health Organization are that sun protection is required only when the UV Index is 3 or greater. This advice is pragmatic rather than evidence based. The UV Index is a continuous scale; more comprehensive sun protection is required as the UV Index increases. In addition, a wide range of UVA doses is possible with a UVI of 3, from which there may be health consequences, while full sun protection when the UVI is "moderate" (between 3 and 5) may limit vitamin D production. Finally, the duration of time spent in the sun is an essential component of a public health message, in addition to the intensity of ambient UV radiation as measured by the UV Index. Together these provide the dose of UV radiation that is relevant to both skin cancer genesis and vitamin D production. Further education is required to increase the understanding of the UV Index; messages framed using the UV Index need to incorporate the importance of duration of exposure and increasing sun protection with increasing dose of UV radiation.