Visible Violet Research Articles

Light-Activated Agonist-Potentiator of GABAA Receptors for Reversible Neuroinhibition in Wildtype Mice.

Gamma aminobutyric acid type A receptors (GABAARs) play a key role in the mammalian central nervous system (CNS) as drivers of neuroinhibitory circuits, which are commonly targeted for therapeutic purposes with potentiator drugs. However, due to their widespread expression and strong inhibitory action, systemic pharmaceutical potentiation of GABAARs inevitably causes adverse effects regardless of the drug selectivity. Therefore, therapeutic guidelines must often limit or exclude clinically available GABAAR potentiators, despite their high efficacy, good biodistribution, and favorable molecular properties. One solution to this problem is to use drugs with light-dependent activity (photopharmacology) in combination with on-demand, localized illumination. However, a suitable light-activated potentiator of GABAARs has been elusive so far for use in wildtype mammals. We have met this need by developing azocarnil, a diffusible GABAergic agonist-potentiator based on the anxiolytic drug abecarnil that is inactive in the dark and activated by visible violet light. Azocarnil can be rapidly deactivated with green light and by thermal relaxation in the dark. We demonstrate that it selectively inhibits neuronal currents in hippocampal neurons in vitro and in the dorsal horns of the spinal cord of mice, decreasing the mechanical sensitivity as a function of illumination without displaying systemic adverse effects. Azocarnil expands the in vivo photopharmacological toolkit with a novel chemical scaffold and achieves a milestone toward future phototherapeutic applications to safely treat muscle spasms, pain, anxiety, sleep disorders, and epilepsy.

A benzoxazole-based turn-on fluorosensor for rapid and sensitive detection of sarin surrogate, diethylchlorophosphate

A benzoxazole-based fluorosensor (IMP) has been synthesized and employed for the selective and sensitive detection of sarin surrogate, diethylchlorophosphate (DCP) in solution, and gas phase, respectively. Remarkable turn-on fluorescence is observed due to the introduction of DCP in the solution of IMP because of inhibition of the intramolecular charge transfer process and disruption of the excited state intramolecular proton transfer (ESIPT) mechanism. The synthesized IMP-based fluorescence sensor exhibits excellent selectivity, high sensitivity, and a wide linear range of 15–60 μM with a detection limit of 44 nM. Low-intense to highly intensified visible violet color could be seen by the naked eye under a portable 365 nm UV lamp due to the addition of DCP in the solution of IMP. IMP-stained paper strips-based test kit experiment has been demonstrated to detect traces of DCP in stockpiles of related analytes. A dip-stick experiment for the detection of DCP vapor has also been demonstrated. The effectiveness of IMP in detecting DCP established that it might be used as a signal tool for real sample analysis.

Bactericidal Effect of 405-nm LED Light against <i>Aggregatibacter Actinomycetemcomitans</i> Is Due Primarily to Disruption of Respiratory Chain Terminal Members Cytochrome <i>bd</i> Oxidase and Quinol Peroxidase

Irradiation with 405-nm visible violet LED light without additional photosensitizers decreased the viability of the aggressive periodontopathic bacterium Aggregatibacter actinomycetemcomitans. The number of CFU/mL decreased linearly on a logarithm chart versus irradiation time, with a 1-log reduction time of 1.32 min. The antimicrobial photodynamic effect of 405-nm LED light involved inhibition of the activity of membrane-bound cytochrome bd, a terminal quinone: oxygen oxidoreductase, and quinol peroxidase, a terminal quinone:H2O2 oxidoreductase. The 405-nm LED irradiation reduced minus oxidized difference spectrum showed that the 640-nm peak (α-peak of heme d) completely disappeared, and the height of the 556-nm (α-peak of hemes b and c) and Soret band (425 nm; γ-peak of hemes b, c, and d) was reduced to approximately half of the peak heights of non-irradiated controls. Survival of bacteria-injected silkworm larvae was also examined. Fifth-instar silkworm larvae were almost completely killed by approximately 40 h after bacterial injection, but almost all silkworm larvae irradiated with 405-nm LED light (20 mW/cm2 for 5 min, energy density: 6 J/cm2) survived, similar to controls not injected with bacteria, indicating that 405-nm LED light killed the injected bacteria. The bactericidal effect of 405-nm blue-light on A. actinomycetemcomitans is primarily due to disruption of cytochrome bd oxidase and quinol peroxidase of the respiratory chain.

Influence of Visible Violet, Blue and Red Light on the Development of Cataract in Porcine Lenses.

Background and Objectives: Cataract is a disease that is globally prevalent in today’s population and occurs mostly in the elderly. It is an opacity of the lens that worsens vision and can lead to blindness. One well-known risk factor of cataract is ultraviolet (UV) radiation. However, increasing exposure to modern artificial light sources like light emitting diodes (LEDs) and displays might have an impact on cataract formation due to possible high (and hidden) blue radiation. An ex-vivo study indicates that intense blue radiation causes cataract in porcine lenses. The goal of this work is the investigation whether violet or red light also lead to cataract formation in porcine lenses and to compare the impact of the different wavelengths. Materials and Methods: LEDs with wavelengths of 407 nm (violet), 463 nm (blue) and 635 nm (red) are used to irradiate ex–vivo porcine lenses with a dose of 6 kJ/cm2. Before and after irradiation the lens transmissions are measured and dark field images are taken to determine cataract formation. The same procedure is performed for unirradiated controls. Results: The results of the transmission measurements are in accordance with the results of the dark field images and state that 635 nm (red) is inducing no or only weak cataract. In comparison to the dark field images the transmission measurements exhibit stronger cataract formation for 407 nm than for 463 nm irradiation while the dark field images show similar cataract formation for both wavelengths. Conclusions: Visible light of short wavelengths cause cataract formation in porcine eyes, and it cannot be excluded that these wavelengths, which are emitted by modern LED illuminants, also pose a danger to human eyes.

Influence of NaOH concentration on the decolorization of crystal violet dyed cotton fabric

Synthetic dye removal is a topic of increasing interest as textile recycling has become more popular in industries. While methods involving dye removal from wastewater effluent have been widely studied and reported on, research on decolorization of fabric itself remains quite unknown. In regard to the lack of research, this study presents cotton fabric samples dyed with crystal violet (CV) that were treated with varying concentrations of sodium hydroxide (NaOH). Fabric decolorization was studied using several characterization methods. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy data showed that the cellulose structure remained unchanged after CV and NaOH treatment. Characteristic CV peaks in the FTIR and Raman spectra were apparent only in the control sample, while the spectra of NaOH-treated samples were very similar to that of the cotton fabric. X-ray diffractometry (XRD) data also confirmed that the crystallite size of cellulose was not affected by CV and NaOH treatment. A visible violet hue remained in all NaOH-treated samples, though CV intensity was inversely proportional to NaOH concentration. The L*a*b* values were utilized to complement characterization results. As the concentration of NaOH was increased, the CIELAB parameters aligned more with those of the plain untreated fabric.

Surface disinfection with white-violet illumination device

<abstract> <p>The spread of infections, as in the coronavirus pandemic, leads to the desire to perform disinfection measures even in the presence of humans. UVC radiation is known for its strong antimicrobial effect, but it is also harmful to humans. Visible light, on the other hand, does not affect humans and laboratory experiments have already demonstrated that intense visible violet and blue light has a reducing effect on bacteria and viruses. This raises the question of whether the development of pathogen-reducing illumination is feasible for everyday applications. For this purpose, a lighting device with white and violet LEDs is set up to illuminate a work surface with 2,400 lux of white light and additionally with up to 2.5 mW/cm<sup>2</sup> of violet light (405 nm). Staphylococci are evenly distributed on the work surface and the decrease in staphylococci concentration is observed over a period of 46 hours. In fact, the staphylococci concentration decreases, but with the white illumination, a 90% reduction occurs only after 34 hours; with the additional violet illumination the necessary irradiation time is shortened to approx. 3.5 hours. Increasing the violet component probably increases the disinfection effect, but the color impression moves further away from white and the low disinfection durations of UVC radiation can nevertheless not be achieved, even with very high violet emissions.</p> </abstract>

Photography in the ultraviolet and visible violet spectra: unravelling methods and applications in palaeontology

Photography in the ultraviolet and visible violet spectra: unravelling methods and applications in palaeontology

High Intensity Violet Light (405 nm) Inactivates Coronaviruses in Phosphate Buffered Saline (PBS) and on Surfaces

It has been proven that visible light with a wavelength of about 405 nm exhibits an antimicrobial effect on bacteria and fungi if the irradiation doses are high enough. Hence, the question arises as to whether this violet light would also be suitable to inactivate SARS-CoV-2 coronaviruses. Therefore, a high-intensity light source was developed and applied to irradiate bovine coronaviruses (BCoV), which are employed as SARS-CoV-2 surrogates for safety reasons. Irradiation is performed in virus solutions diluted with phosphate buffered saline and on steel surfaces. Significant virus reduction by several log levels was observed both in the liquid and on the surface within half an hour with average log reduction doses of 57.5 and 96 J/cm2, respectively. Therefore, it can be concluded that 405 nm irradiation has an antiviral effect on coronaviruses, but special attention should be paid to the presence of photosensitizers in the virus environment in future experiments. Technically, visible violet radiation is therefore suitable for coronavirus reduction, but the required radiation doses are difficult to achieve rapidly.

Photoinactivation of the Coronavirus Surrogate phi6 by Visible Light.

To stop the coronavirus spread, new inactivation approaches are being sought that can also be applied in the presence of humans or even on humans. Here, we investigate the effect of visible violet light with a wavelength of 405nm on the coronavirus surrogate phi6 in two aqueous solutions that are free of photosensitizers. A dose of 1300Jcm-2 of 405nm irradiation reduces the phi6 plaque-forming unit concentration by three log-levels. The next step should be similar visible light photoinactivation investigations on coronaviruses, which cannot be performed in our lab.

Violet-light suppression of thermogenesis by opsin 5 hypothalamic neurons.

The opsin family of G-protein coupled receptors are employed as light detectors in animals. Opsin 5 (neuropsin, OPN5) is a highly conserved, violet light (380 nm λmax) sensitive opsin1,2. In mice, OPN5 is a known photoreceptor in retina3 and skin4 but is also expressed in the hypothalamic preoptic area (POA)5. Here we describe a light-sensing pathway in which Opn5 expressing POA neurons regulate brown adipose tissue (BAT) thermogenesis. We show Opn5 expression in glutamatergic warm-sensing POA neurons that receive synaptic input from multiple thermoregulatory nuclei. We further show that Opn5 POA neurons project to BAT and decrease its activity under chemogenetic stimulation. Opn5 null mice show overactive BAT, elevated body temperature, and exaggerated thermogenesis when cold challenged. Moreover, violet photostimulation during cold exposure acutely suppresses BAT temperature in wild-type, but not in Opn5 null mice. Direct measurements of intracellular cAMP ex vivo reveal that Opn5 POA neurons increase cAMP when stimulated with violet light. This analysis thus identifies a violet light sensitive deep brain photoreceptor that normally suppresses BAT thermogenesis.

Enhancement of Contact Lens Disinfection by Combining Disinfectant with Visible Light Irradiation.

Multiple use contact lenses have to be disinfected overnight to reduce the risk of infections. However, several studies demonstrated that not only microorganisms are affected by the disinfectants, but also ocular epithelial cells, which come into contact via residuals at reinsertion of the lens. Visible light has been demonstrated to achieve an inactivation effect on several bacterial and fungal species. Combinations with other disinfection methods often showed better results compared to separately applied methods. We therefore investigated contact lens disinfection solutions combined with 405 nm irradiation, with the intention to reduce the disinfectant concentration of ReNu Multiplus, OptiFree Express or AOSept while maintaining adequate disinfection results due to combination benefits. Pseudomonads, staphylococci and E. coli were studied with disk diffusion assay, colony forming unit (cfu) determination and growth delay. A log reduction of 4.49 was achieved for P. fluorescens in 2 h for 40% ReNu Multiplus combined with an irradiation intensity of 20 mW/cm2 at 405 nm. For AOSept the combination effect was so strong that 5% of AOSept in combination with light exhibited the same result as 100% AOSept alone. Combination of disinfectants with visible violet light is therefore considered a promising approach, as a reduction of potentially toxic ingredients can be achieved.

Long‐Standing Optically Excited Magnetic States in ZnO Nanoparticles

The spectral dependence of the light‐induced magnetic states generated in zinc oxide nanoparticles by illumination during an electron paramagnetic resonance (EPR) experiment is studied for three incident light wavelengths (451, 405, and 370 nm). The minimal wavelength excitation is found to be in the visible violet region, very close to 405 nm for all of the light‐induced EPR lines. This points to a close relationship between their originating centers, despite the difference in their dynamics previously revealed by saturation recovery measurements. The study of the light‐induced signals decay with time (after illumination removal) and with temperature (under constant illumination) confirms the existence of two groups of lines characterized by different dynamics. The quite unusual persistence of these magnetic states after excitation removal opens promising possibilities for encoding information within semiconducting nanoparticles.

Hummingbird vision.

Hummingbirds are widely recognized by their hovering flight. In this Quick guide, Altshuler and Wylie describe the visual specializations that allow for the hummingbird's flight abilities.

Realisation and assessment of a low-cost LED device for contact lens disinfection by visible violet light.

This study presents a device for efficient, low-cost and eye-friendly overnight disinfection of contact lenses by visible violet light as an alternative to disinfection with biocide-containing solutions. Bacterial solutions with one Pseudomonas and one Staphylococcus strain each were irradiated for up to 8 h in commercial transparent contact lens cases by the presented light-emitting diode (LED) device. Samples were taken at different intervals and distributed on agar plates. The surviving bacteria were determined by counting of colony-forming units and compared to the specific requirements of the stand-alone test for contact lens disinfection of the hygiene standard ISO 14729. The concentration of both microorganisms was reduced by three orders of magnitude after less than 4 h of irradiation. The LED current and intensity have not yet been at maximum and could be further increased if necessary for other microorganisms. The presented device fulfils the requirement of the stand-alone test of the contact lens hygienic standard ISO 14729 for the tested Pseudomonas and Staphylococcus strains. According to literature data, the inactivation of Serratia marcescens, Candida albicans and Fusarium solani seems also possible, but may require increased LED current and intensity.

Use of Flame Color and Chemiluminescence for Early Detection of Lean Blowout in Gas Turbine Combustors at Different Levels of Fuel–Air Premixing

ABSTRACTLean combustion is adopted in the practical gas turbine combustors as it offers a solution to reduce the emission of NOx. But lean blowout (LBO) is considered as the main threat in taking the ultra-lean premixed combustion. LBO can also occur in aircraft engines during rapid decrease in speed or power. Although gas turbine flames can be of both premixed and partially premixed in nature, early detection of LBO of partially premixed flames has received relatively less attention compared to premixed flames. In this paper, attention has been focused on the early detection of LBO in combustors with different levels of premixing. Apart from that, a detail investigation on the electromagnetic emission of the flame is performed in order to have the insight of the dominating chemiluminescence. The primary chemiluminescence species, OH*, CH*,and C2*, are considered in this study. The flame dynamics is captured using spectral signal obtained from a spectrometer. Also, the spectrums of different colors, emitted by the flame at different conditions, are studied using both spectrometer and color Charge Coupled Device (CCD) camera. At lean condition of the premixed flame, three narrowband emissions in the visible (VIS) range, namely, blue, violet, and indigo colors, are observed. Three primary parameters, , , and , are introduced based on the color ratios when numerator of the ratio is the intensity of red band. Near LBO, each of these parameters becomes significantly low. The observation range for this analysis is considered from stoichiometric condition to the extreme lean region, where LBO occurs. At the end, the behavior of the red, green, and blue color ratios toward the LBO using both camera and spectrometer is compared. The similarity between the results of camera and spectrometer indicates that flame imaging through commercial color CCD camera can provide a low cost, simple tool for LBO detection.

Antimicrobial activity of a continuous visible light disinfection system.

We evaluated the ability of high-intensity visible violet light with a peak output of 405 nm to kill epidemiologically important pathogens. The high irradiant light significantly reduced both vegetative bacteria and spores at some time points over a 72-hour exposure period.

New Legionella Control Options by UV and Violet LEDs for Hospitals and Care Facilities

Legionella infections caused by contaminated water are a widespread problem worldwide. Discharge lamps like mercury vapor lamps are widely known for the disinfection properties of their radiation, but they suffer technical disadvantages, like high voltages and toxic content, and are, therefore, not suitable for some infection control applications. New highintensity ultraviolet (UV) and violet LEDs offer new approaches for Legionella control, because these bacteria are significantly light sensitive compared to other pathogens. One of the most important infection pathways is the inhalation of Legionellacontaining aerosols during showering. This problem could be reduced by a single strong UV LED within the shower head, which irradiates the passing water for some milliseconds. This practice can be especially beneficial in hospitals and care facilities. UV light offers only a limited penetration depth, however, even in pure water. To disinfect larger water volumes, e.g., in water dispensers, visible violet LEDs are more appropriate. Unfortunately, up to now, neither approach has been given much attention by potential users.

Morphologic, Photocatalytic and Antibacterial Properties of ZnO-TiO<sub>2</sub> Sol-Gel System

Prepared and heat-treated sol-gel ZnO-TiO2 coatings onto microscope glass slides were characterised by atomic force microscopy (AFM), scanning electron microscopy (SEM), as well as absorption spectra of light has been obtained. Thermally treated xerogels were characterised by X-ray diffraction (XRD). As well as their photocatalytic activity using methyl orange (MO) and observing the colour changes over the time in visible light (VIS) and ultra violet (UV) light has been determined. The influence of ZnO concentration on morphology, photocatalytic activity and antibacterial properties of coatings was analysed. The growth of S. epidermidis on the surface of the samples was inhibited due to photocatalytic properties of coatings.

Improvement of red-emitting afterglow properties via tuning electronic structure in perovskite-type (Ca1-xNax) [Ti1-xNbx] O3: Pr3+ compounds

The red persistent luminescence of CaTiO3:Pr3+ needs further improvement in longer excitation wavelength to fulfill the application demand. By Na+-Nb5+ substituting for Ca2+-Ti4+, a series of Pr3+-doped perovskite-type (Ca1-xNax) [Ti1-xNbx]O3:0.001Pr3+ compounds, with a structural transition at about x = 0.7–0.8, have been successfully synthesized by a solid state reaction. The excitation band first red-shift and then blue-shift gradually with x. The afterglow duration has been prolonged from 30 s for CaTiO3:Pr3+ to about 60 s for the composition x = 0.1. Wavelength-dependent trap filling analysis show that the charging wavelengths can be red-shifted from UV irradiation (<358 nm) for CaTiO3:Pr3+ to visible violet light for compositions with x = 0.1. On the basis of spectral data, we construct the host referred binding energy (HRBE) and vacuum referred binding energy (VRBE) schemes of trivalent lanthanide-doped (Ca1-xNax) [Ti1-xNbx] O3 compounds, and further explain these afterglow behaviors. This work is helpful for exploring novel persistent luminescent materials.

A new MediaChrom (fluorosolvatochromic and acidochromic) based on bipolar donor-acceptor conjoined carbazolo-phenazine

MediaChromes are molecular systems characterized by a rigid aromatic backbone bearing electron-donating (D) and accepting (A) groups conjugated in the so-called push-pull D–π–A fashion. Electronic excitation of such systems results in increase of the dipole moment in the excited state due to intramolecular charge transfer (ICT), leading to remarkable excited-state properties. We have investigated fluorosolvatochromic and halochromic (acidochromic) behavior of carbazolo-phenazine (CP), a new bipolar molecular system characterized by conjoined donor carbazole and acceptor phenazine heterocycles. CP is shown to exhibit exceptional fluoromediachromic behavior due to ICT in the excited state; the difference in the dipole moments of ground- and singlet-excited states of CP is ca. 3.6 D units. ICT occurs also in the ground state upon protonation, which manifests in brilliant naked-eye visible violet coloration, namely, acidochromism.