Visible Blue Light Research Articles

Unveiling concentration effects on the structural and optoelectronic characteristics of Zn1-x Cd x S (x = 0, 0.25, 0.50, 0.75, 1) cubic semiconductors: a theoretical study.

The structural and optoelectronic characteristics of Zn1−xCdxS (x = 0, 0.25, 0.50, 0.75, 1) semiconductors are reported using density functional theory within GGA, EV-GGA, and mBJ functionals. These semiconductors are observed in cubic symmetry at all Cd-concentrations and the lattice constant increases linearly with Cd-concentration while the bulk modulus shows a reverse behavior. These materials are direct bandgap semiconductors at all Cd-concentrations and their bandgap energy decreases from 3.67 eV to 2.59 eV. The isotropic optical properties of these direct bandgap semiconductors vary with Cd concentration as well, with absorption coefficients decreasing and absorbed near-UV light converting to visible blue light. Optical properties like refractive index, dielectric constant, conductivity, extinction coefficient, and reflectance are also displayed and discussed. These results provide useful theoretical understanding for the application of CdZnS semiconductors in photonic, photovoltaic, and optoelectronic devices.

Synthesis of N-aryl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-amines and their photodynamic properties in the human skin melanoma cell line G361

A small series of N-aryl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-amines was synthesized from easily accessible 1-phenyl-1H-pyrazol-3-ol via 7-iodo-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridine and 7-iodo-4-methyl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridine intermediates and their subsequent use in palladium catalyzed Buchwald-Hartwig cross-coupling reaction with various anilines. Majority of the compounds were not significantly cytotoxic to melanoma G361 cells in the dark up to 10 µM concentration, but their activity could be increased by irradiation with visible blue light (414 nm). The most active compound 10 possessed EC50 values of 3.5, 1.6 and 0.9 µM in cells irradiated with 1, 5 and 10 J/cm2, respectively. The treatment caused generation of reactive oxygen species in cells and extensive DNA damage, documented by the comet assay and by detection of phosphorylated histone H2A.X, followed by apoptotic cell death. Our results suggest that N-aryl-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-amines could serve as a potential source of photosensitizing compounds with anticancer activities.

Anticancer Agent with Inexplicable Potency in Extreme Hypoxia: Characterizing a Light-Triggered Ruthenium Ubertoxin.

Tumor hypoxia renders treatments ineffective that are directly (e.g., radiotherapy and photodynamic therapy) or indirectly (e.g., chemotherapy) dependent on tumor oxygenation. This study introduces a ruthenium compound as a light-responsive anticancer agent that is water-soluble, has minimal dark cytotoxicity, is active at concentrations as low as 170 pM in ∼18.5% O2 normoxia and near 10 nM in 1% O2 hypoxia, and exhibits phototherapeutic indices as large as >500,000 in normoxia and >5,800 in 1% O2 hypoxia using broadband visible and monochromatic blue light treatments. These are the largest values reported to date for any compound class. We highlight the response in four different cell lines to improve rigor and reproducibility in the identification of promising clinical candidates.

Preparation and coloring mechanism of MAl2O4/CoAl2O4/quartz sand (M = Ca or Ba) composite pigments

The doping of divalent metal ions is considered as a feasible strategy for reducing the consumption of expensive cobalt source and regulating the color performance of CoAl2O4 pigments. However, it may be controversial for formation of solid solution in the system of MAl2O4/CoAl2O4 (M = Ca or Ba) due to the bigger differences in ionic radius and coordination number between Ba2+ (or Ca2+) and Co2+, and thus the coloring mechanism of CoAl2O4 pigments is vague after incorporation of Ba2+ (or Ca2+). In this study, MAl2O4/CoAl2O4/quartz sand (M = Ca or Ba) composite pigments are fabricated using the quartz sand waste discarded from mineral processing as substrate. The effect of the added amount of Ba2+ (or Ca2+) on the color properties of composite pigments are investigated, and the optimum b∗ values of CaAl2O4/CoAl2O4/quartz sand and BaAl2O4/CoAl2O4/quartz sand reach −47.92 and −48.06, respectively. Furthermore, it reveals that the obtained pigments are composed of quartz, hexagonal CaAl2O4 or BaAl2O4, and cubic spinel CoAl2O4, and thus CaAl2O4 or BaAl2O4 cannot form solid solution with CoAl2O4 by replacing Co2+ with Ba2+ or Ca2+ owing to the significant differences in ionic radius and coordination number between Ba2+ (or Ca2+) and Co2+. The improvement in the color performance of CoAl2O4 pigments may be related to the intrinsic oxygen vacancy defect of CaAl2O4 or BaAl2O4, which promote CoAl2O4 to reflect more blue visible light at 430 nm.

Visible blue light inhibits infection and replication of SARS-CoV-2 at doses that are well-tolerated by human respiratory tissue

The delivery of safe, visible wavelengths of light can be an effective, pathogen-agnostic, countermeasure that would expand the current portfolio of SARS-CoV-2 intervention strategies beyond the conventional approaches of vaccine, antibody, and antiviral therapeutics. Employing custom biological light units, that incorporate optically engineered light-emitting diode (LED) arrays, we harnessed monochromatic wavelengths of light for uniform delivery across biological surfaces. We demonstrated that primary 3D human tracheal/bronchial-derived epithelial tissues tolerated high doses of a narrow spectral band of visible light centered at a peak wavelength of 425 nm. We extended these studies to Vero E6 cells to understand how light may influence the viability of a mammalian cell line conventionally used for assaying SARS-CoV-2. The exposure of single-cell monolayers of Vero E6 cells to similar doses of 425 nm blue light resulted in viabilities that were dependent on dose and cell density. Doses of 425 nm blue light that are well-tolerated by Vero E6 cells also inhibited infection and replication of cell-associated SARS-CoV-2 by > 99% 24 h post-infection after a single five-minute light exposure. Moreover, the 425 nm blue light inactivated cell-free betacoronaviruses including SARS-CoV-1, MERS-CoV, and SARS-CoV-2 up to 99.99% in a dose-dependent manner. Importantly, clinically applicable doses of 425 nm blue light dramatically inhibited SARS-CoV-2 infection and replication in primary human 3D tracheal/bronchial tissue. Safe doses of visible light should be considered part of the strategic portfolio for the development of SARS-CoV-2 therapeutic countermeasures to mitigate coronavirus disease 2019 (COVID-19).

313 Photoprotective effects of liposomal DNA repair enzymes are independent of its effect on the microbiome

Solar ultraviolet radiation (UVR) is a mutagenic agent causing damage to the DNA and resulting in photoageing and carcinogenesis. Polymorphic light eruption (PLE) is a frequent skin disorder characterized by the appearance of itchy polymorphic skin lesions (photodermatosis) which is triggered by natural sunlight. In our previous study, PLE patients treated with liposomal DNA repair enzymes diminished induction of PLE symptoms, however the underlying mechanisms remained unraveled. We now investigated whether the therapeutic potential of topical DNA repair enzymes is due to its effect on the skin resident microbes, which are also impacted by UV exposure. To test this hypothesis, we investigated the effect of DNA repair enzymes (photolyase from Anacystis nidulans and Micrococcus luteus extract with endonuclease activity) on the survival of commensal skin microbes subjected to UVB radiation. Briefly, strains of microbes (Staphylococcus aureus or S. epidermidis) were cultured and exposed to varying doses of UVB. DNA repair enzymes incorporated in liposomes or vehicle (liposomes alone) were added to the culture medium/plate either before or after UVB exposure, followed by photoactivating visible (blue) light exposure or not in the case of photolyase administration. The colony forming units of the cultures was quantified throughout the protocol. The results showed no significant difference in the survival of either the pathogenic or the commensal bacterial strain treated with liposomal DNA repair enzymes following exposure to UVB radiation. Taken together, this data suggests that photoprotective effect of DNA repair enzymes is independent of its direct activity on the skin microbiome.

Structural and photoluminescence properties of Eu3+-activated BaTiO3 phosphors

Herein, we have reported the facile synthesis of phase pure and crystalline Eu doped BaTiO3 phosphors via solid-state method. The concentration of the Eu3+ ions in BaTiO3 is varied from 1 to 5 mol%. The structural, morphological and optical properties are characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Visible and photoluminescence (PL) technique, respectively. The structural parameters are further determined by using Rietveld refinement. The excitation spectra revealed that synthesized samples can be excited by near UV (396 nm) and visible blue light (465 nm) and the highest emission intensity is observed at 617 nm under 465 nm excitation, corresponding to the 5D0–7F2 transition of Eu3+ ions. The photoluminescent properties are studied via applying Dexter and Blasse's theory and CIE coordinates are calculated. The decay curves exhibited bi-exponential behavior for all the samples and lifetimes values varied from 0.409 to 0.320 msec, for 1 to 5 mol% Eu doped BaTiO3 phosphors. The obtained results indicate that synthesized samples have potential applications in optoelectronic and display devices.

Fluorescent Hybrid Porous Polymers as Sustainable Heterogeneous Photocatalysts for Cross-Dehydrogenative Coupling Reactions.

A series of hybrid porous polymers (HPPs) based on polyhedral oligomeric silsesquioxane (POSS) were synthesized, characterized, and successfully used as metal-free heterogeneous photocatalysts for cross-dehydrogenative coupling reactions (CDC), for which the aza-Henry coupling of tetrahydroisoquinolines and nitroalkanes was studied as the model reaction. The reactions run smoothly at room temperature under visible (blue) light irradiation using gaseous oxygen as an oxidant under atmospheric pressure. These novel metal-free heterogeneous photocatalysts can be readily recovered and reused without a significant loss of reactivity. Mechanistic investigations revealed the intermediacy of 1O2, obtained from 3O2 sensitization (energy transfer) by the photoexcited catalyst.

Dimension- and position-controlled growth of GaN microstructure arrays on graphene films for flexible device applications

This paper describes the fabrication process and characteristics of dimension- and position-controlled gallium nitride (GaN) microstructure arrays grown on graphene films and their quantum structures for use in flexible light-emitting device applications. The characteristics of dimension- and position-controlled growth, which is crucial to fabricate high-performance electronic and optoelectronic devices, were investigated using scanning and transmission electron microscopes and power-dependent photoluminescence spectroscopy measurements. Among the GaN microstructures, GaN microrods exhibited excellent photoluminescence characteristics including room-temperature stimulated emission, which is especially useful for optoelectronic device applications. As one of the device applications of the position-controlled GaN microrod arrays, we fabricated light-emitting diodes (LEDs) by heteroepitaxially growing InxGa1−xN/GaN multiple quantum wells (MQWs) and a p-type GaN layer on the surfaces of GaN microrods and by depositing Ti/Au and Ni/Au metal layers to prepare n-type and p-type ohmic contacts, respectively. Furthermore, the GaN microrod LED arrays were transferred onto Cu foil by using the chemical lift-off method. Even after being transferred onto the flexible Cu foil substrate, the microrod LEDs exhibited strong emission of visible blue light. The proposed method to enable the dimension- and position-controlled growth of GaN microstructures on graphene films can likely be used to fabricate other high-quality flexible inorganic semiconductor devices such as micro-LED displays with an ultrahigh resolution.

Assisted removal of metal housings from overdentures with a 445-nm diode laser: A dental technique

A straightforward, laser-assisted method of extracting the metal housings from an overdenture by using the visible (blue) light of a high-power dental diode laser is presented. This approach produced localized softening of the acrylic resin, allowing the metal housing to be dislodged without damage. This technique minimizes damage to the metal housings during removal, is rapid and conservative, and may help reduce patient costs.

Cataract Development by Exposure to Ultraviolet and Blue Visible Light in Porcine Lenses.

Background and Objectives: Cataract is still the leading cause of blindness. Its development is well researched for UV radiation. Modern light sources like LEDs and displays tend to emit blue light. The effect of blue light on the retina is called blue light hazard and is studied extensively. However, its impact on the lens is not investigated so far. Aim: Investigation of the impact of the blue visible light in porcine lens compared to UVA and UVB radiation. Materials and Methods: In this ex-vivo experiment, porcine lenses are irradiated with a dosage of 6 kJ/cm2 at wavelengths of 311 nm (UVB), 370 nm (UVA), and 460 nm (blue light). Lens transmission measurements before and after irradiation give insight into the impact of the radiation. Furthermore, dark field images are taken from every lens before and after irradiation. Cataract development is illustrated by histogram linearization as well as faults coloring of recorded dark field images. By segmenting the lens in the background’s original image, the lens condition before and after irradiation could be compared. Results: All lenses irradiated with a 6 kJ/cm2 reveal cataract development for radiation with 311 nm, 370 nm, and 460 nm. Both evaluations reveal that the 460 nm irradiation causes the most cataract. Conclusion: All investigated irradiation sources cause cataracts in porcine lenses—even blue visible light.

Sulfonate Hydrogel-siRNA Conjugate Facilitates Osteogenic Differentiation of Mesenchymal Stem Cells by Controlled Gene Silencing and Activation of BMP Signaling.

Hydrogels have been widely used in bone tissue engineering due to their tunable characteristics that allow facile modifications with various biochemical properties to support cell growth and guide proper cell functions. Herein, we report a design of hydrogel-siRNA conjugate that facilitates osteogenesis via gene silencing and activation of bone morphogenetic protein (BMP) signaling. A sulfonate hydrogel is prepared by modifying chitosan with sulfoacetic acid to mimic a natural sulfated polysaccharide and to provide a hydrogel surface that enables BMP binding. Then, siRNA targeting noggin, an endogenous extracellular antagonist of BMP signaling, is covalently conjugated to the sulfonate hydrogel by visible blue light crosslinking. The sulfonate hydrogel-siRNA conjugate is efficient to bind BMPs and also successfully prolongs the release of siRNA for sustained noggin suppression, thereby resulting in significantly increased osteogenic differentiation. Lastly, demineralized bone matrix (DBM) is incorporated into the sulfonate hydrogel-siRNA conjugate, wherein the DBM incorporation induces noggin expression via a negative feedback mechanism that regulates BMP signaling in DBM. However, simultaneous delivery of siRNA downregulates noggin thus facilitating endogenous BMP activity and enhancing the osteogenic efficacy of DBM. These findings support a promising hydrogel RNA silencing platform for bone tissue engineering applications.

Optimization of multiscale digital speckle patterns for multiscale deformation measurement using stereo-digital image correlation.

Simultaneous monitoring of multiple fields of view (FOVs) by multiscale stereo-digital image correlation (stereo-DIC) can quantify the deformation of a material when localized phenomena occur within a larger FOV or moving object. In multiscale deformation measurement via stereo-DIC, optimization of the digital speckle patterns (DSPs) is essential to achieve high accuracy and efficiency. This work optimizes and fabricates multispectral DSPs used for multiple scales. First, an optimization of the DSP for two FOVs is achieved using both spatial modulation and specified spectra. A spatially modulated DSP is compared with two spectral DSPs achieved by visible and ultraviolet-excited blue light. Then, a spatially modulated visible DSP fabricated by an ultraviolet printer overlaid with an ultraviolet-excited blue DSP fabricated by a photosensitive seal is designed for multiscale stereo-DIC measurements of three FOVs. Experiments were performed to illustrate the functionality and utility of this multiscale DSP. Such experimental analyses can supply adequate full-field data to validate localized or kinetic mechanical behavior.

Crystal Structure Induced Enhanced Afterglow Luminescence from Rare‐Earth Ion Doped Strontium Silicate Phosphors

AbstractAn orange‐red (∼610 nm) emitting Sr3SiO5:Eu2+,Zn2+,Dy3+ long afterglow phosphor was synthesized using high temperature (1100 °C–1500 °C) based solid‐state reaction method under controlled reducing atmosphere. X‐ray diffraction (XRD) study confirms the tetragonal lattice structure having space group P4/ncc. Scherrer's size plot and Williamson‐Hall methods have been applied to study the particle size distribution and inherent strain, respectively, using crystallographic data obtained from XRD patterns. Electron microscopy images showed the surface morphology with an average crystallite size of 0.412 μm. Furthermore, detailed luminescence study was performed to observe photoluminescence (PL) and afterglow characteristics. An optimal PL emission peak was registered at ∼610 nm when the phosphor was excited by visible blue (∼465 nm) light, which is due to the transitions from 4f65d1 to 4f7 energy levels of Eu2+ ions. The enhanced afterglow property of >20 minutes has been achieved for dark‐adapted human eyes, which could be utilized for designing strategic markings and signage boards that could glow in dark.

Synthesis of Xanthones, Thioxanthones and Acridones by a Metal-Free Photocatalytic Oxidation Using Visible Light and Molecular Oxygen.

9H-Xanthenes, 9H-thioxanthenes and 9,10-dihydroacridines can be easily oxidized to the corresponding xanthones, thioxanthones and acridones, respectively, by a simple photo-oxidation procedure carried out using molecular oxygen as oxidant under the irradiation of visible blue light and in the presence of riboflavin tetraacetate as a metal-free photocatalyst. The obtained yields are high or quantitative.

Inactivation Effect of Violet and Blue Light on ESKAPE Pathogens and Closely Related Non-pathogenic Bacterial Species - A Promising Tool Against Antibiotic-Sensitive and Antibiotic-Resistant Microorganisms.

Due to the globally observed increase in antibiotic resistance of bacterial pathogens and the simultaneous decline in new antibiotic developments, the need for alternative inactivation approaches is growing. This is especially true for the treatment of infections with the problematic ESKAPE pathogens, which include Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species, and often exhibit multiple antibiotic resistances. Irradiation with visible light from the violet and blue spectral range is an inactivation approach that does not require any additional supplements. Multiple bacterial and fungal species were demonstrated to be sensitive to this disinfection technique. In the present study, pathogenic ESKAPE organisms and non-pathogenic relatives are irradiated with visible blue and violet light with wavelengths of 450 and 405 nm, respectively. The irradiation experiments are performed at 37°C to test a potential application for medical treatment. For all investigated microorganisms and both wavelengths, a decrease in colony forming units is observed with increasing irradiation dose, although there are differences between the examined bacterial species. A pronounced difference can be observed between Acinetobacter, which prove to be particularly light sensitive, and enterococci, which need higher irradiation doses for inactivation. Differences between pathogenic and non-pathogenic bacteria of one genus are comparatively small, with the tendency of non-pathogenic representatives being less susceptible. Visible light irradiation is therefore a promising approach to inactivate ESKAPE pathogens with future fields of application in prevention and therapy.

Catalyst-free visible-light induced synthesis of nitrogen- and oxygen-containing heterocycles from 1,3-diketones

The synthesis of nitrogen- and oxygen-containing heterocycles has found many applications in the preparation of biomedical intermediates, yet actual synthetic procedures display limitations such as high-loading catalysts, harsh reaction conditions and tedious preparation of heterogeneous catalysts. Alternatively, photocatalysis allows to access functional products with minimum synthetic procedures and waste generation. Here, we present an efficient, simple, green protocol for the synthesis of N- and O-containing six-membered-ring compounds under mild conditions under visible blue light. Various aldehydes and 1,3-diketones can be reacted to afford eight series of corresponding 1,4-dihydropyridines and 4H-benzo[b]pyrans. This protocol has some merits such as the use of abundant and sustainable aqueous ethanol as solvent, short reaction time (within 60 min), no need of catalyst and broad functional group tolerance to afford 81 different series of target molecules in 75–96% yield under mild conditions.

Technical Note: Scintillation markers for real-time visual source tracking during skin high dose rate brachytherapy.

Treatment misadministration during high dose rate (HDR) brachytherapy is mainly caused due to gross errors in incorrect manual entry of catheter length and manual connection of hardware. The probability of these errors increases with increasing complexity of a surface applicator. A simple, real-time visual verification method was developed using a scintillator to enhance quality assurance (QA) measures for HDR surface brachytherapy and thus reduce manual errors and improve patient safety. Scintillation markers were fabricated from cerium-doped lutetium yttrium orthosilicate (LYSO) embedded in a polymer compound to form 5-mm diameter markers. To verify catheter-transfer tube connections, markers were attached to each channel of a Freiburg flap and irradiated with an 192 Ir source. To determine if the source reached the edge of a target, markers were placed along the periphery. The HDR source was visually tracked by following the illumination from the markers. The response of the markers was also verified in the presence of thermoplastic material overlaid on the Freiburg applicator. Scintillation markers emitted intense blue visible light upon irradiation when the HDR source was beneath the marker, verifying the source's presence in the correct catheter. The signal was clearly visible even when the marker was placed on top of the thermoplastic material covering the Freiburg Flap. Crosstalk from adjacent catheters was <50% of the maximum light intensity. Scintillation markers and paint were developed to successfully meet the challenge of visually tracking of HDR source during brachytherapy by surface applicators. This direct visualization of source allows real-time catheter verification during treatment, and correct superficial target coverage, thus preventing a medical event. It can easily be integrated into pre-existing QA program.

Synthesis and photodynamic properties of pyrazole-indole hybrids in the human skin melanoma cell line G361

Three conjugated pyrazole-indole hybrids, 5, 7 and 10, were synthesized from easily accessible 3-(hexyloxy)-1-phenyl-1H-pyrazole-4-carbaldehyde 1 and 5-iodo-3,3-dimethyl-2-phenyl-3H-indole 4 employing olefination reactions (Wittig, Ramirez), Vilsmeier-Haack formylation and palladium-catalysed cross coupling reactions (ligand-free Heck, Sonogashira). The compounds displayed no cytotoxicity in the melanoma cell line G361 unless irradiated with visible blue light (414 nm), and the potency of the compounds increased with light intensity. Lead compound 7 displayed EC50 values of 3.08, 0.26 and 0.05 μM in cells irradiated with 1, 10 and 50 J/cm2, respectively. The following experiments revealed increased levels of reactive oxygen species in treated cells and a decrease in JC-1 polymer aggregation within the mitochondria, suggesting mitochondrial membrane depolarization. In addition, extensive DNA fragmentation was detected using the comet assay and by detection of phosphorylated histone H2A.X, the level of which increased with both increased compound concentration and irradiation energy. In control experiments, cells kept either in the dark or without compound 7 did not show any DNA damage. Overall, the results demonstrated that fluorescent pyrazole-indole hybrids may serve as an interesting source of photosensitizing compounds with anticancer activity.

A High‐Performing Metal‐Free Photoactivatable Nitric Oxide Donor with a Green Fluorescent Reporter

AbstractAbstract: We report herein a novel nitric oxide (NO) donor activatable by visible blue light with an in‐built green fluorescence reporter. This NO photodonor, based on the amino‐nitro‐benzofurazan chromogenic skeleton, releases NO in solution with a quantum yield ΦNO=0.15 which increases up to 0.80 in Pluronic® micelles, the largest values ever reported for nonmetal‐containing NO donors activatable by visible light. Besides, the large contrast between the fluorescence emission of the chromogenic moiety after and before the NO release (&gt;10) permits the easy and in real‐time quantification of the amount of NO released, without the addition of external fluorescent probes. This NO photodonor can also be effectively entrapped in a Pluronic‐based thermoresponsive hydrogel with excellent preservation of its photochemical and photophysical behaviour. These properties, together with the facile synthetic procedure, make the present compound an intriguing candidate for fundamental and potential applicative research studies where spatiotemporally regulated NO delivery is required.