Visible Blue Light Research Articles

Effect of 450 nm Visible Blue Light from Light-Emitting Diode on Escherichia coli O157:H7 in Agar Gels: Optimizing the Lighting Array and Quantitative Microbial Exposure Assessment

Visible blue light emitting diodes (LED) have been studied to inactivate Escherichia coli (E. coli) O157:H7 in agar gels. The LED array was optimized to attain uniform light illumination, and the light intensity distribution was visualized through optical simulation. The uniformity of LED light intensity was assessed, and the evenly spaced array showed the best uniformity with a Petri factor of 0.99. Microbial populations in agar gels prepared with and without a dye were analyzed after light irradiation. Each segment of the gels with different heights was taken to measure microbial reduction, and the results indicated that optical properties, such as opaqueness, played an important role in microbial reduction. The agar gel without and with a dye showed a maximum reduction of <3.4 and <2.1 log CFU/g, respectively. An exposure assessment for E. coli O157:H7 was conducted based on the assumption for the agar gel product after LED illumination. The probability results indicated that a risk (>5 log CFU/g) existed mainly in the bottom layer of the sample, despite the average contamination being <5 log CFU/g. This study provides a suitable approach for designing the LED photoinactivation process and subsequent exposure assessment to avoid risk.

55.1: Perovskite as Color Conversion Materials for Micro‐LED Display

Metal halide perovskite materials have attracted great attention owing to their fascinating optoelectronic characteristics and low cost fabrication via facile solution processing. One of the potential applications of these materials is to employ them as color‐conversion layers (CCLs) for visible blue light to achieve micro‐LED full‐color displays. However, obtaining thick perovskite films and fine patterns to realize complete color conversion and vivid display performance is still very challenging. Here, we elaborately addressed above issues and successfully demonstrated efficient blue‐to‐green photoconversion based on perovskite materials and applied in full color micro‐LED displays.

A singlet state oxygen generation model based on the Monte Carlo method of visible antibacterial blue light inactivation.

Visible antibacterial blue light (VABL) has received much attention recently as a nondestructive inactivation approach. However, due to the sparse distribution of bacteria, the light energy evaluation method used in existing studies is inaccurate. Thus, the sensitivity of microorganisms to VABL in different experiments cannot be compared. In this paper, a Monte Carlo-based photon transport model with the optimized scattering phase function was constructed. The model calculated the spatial light energy distribution and the temporal distribution of cumulative singlet state oxygen (CSO) under various cell and medium parameters. The simulation results show that when the cells are sparsely distributed, <30% of light energy from the light source is absorbed by microbes and participates in photochemical reactions. The CSO produced increases with cell density and cell size. Little light energy is available, and thus, the concentration of CSO produced is insufficient to inactivate microbes at deeper depths. As the light intensity and inactivation time increased, the production of singlet state oxygen tended to level off. The model proposed here can quantify the generation of singlet state oxygen and provide a more accurate light energy guide for the VABL inactivation process.

Digital Screen Time and the Risk of Female Breast Cancer: A Retrospective Matched Case-Control Study.

As the use of electronic devices such as mobile phones, tablets, and computers continues to rise globally, concerns have been raised about their potential impact on human health. Exposure to high energy visible (HEV) blue light, emitted from digital screens, particularly the so-called artificial light at night (ALAN), has been associated with adverse health effects, ranging from disruption of circadian rhythms to cancer. Breast cancer incidence rates are also increasing worldwide. This study aimed at finding a correlation between breast cancer and exposure to blue light from mobile phone. In this retrospective matched case-control study, we aimed to investigate whether exposure to blue light from mobile phone screens is associated with an increased risk of female breast cancer. We interviewed 301 breast cancer patients (cases) and 294 controls using a standard questionnaire and performed multivariate analysis, chi-square, and Fisher's exact tests for data analysis. Although heavy users in the case group of our study had a statistically significant higher mean 10-year cumulative exposure to digital screens compared to the control group (7089±14985 vs 4052±12515 hours, respectively, P=0.038), our study did not find a strong relationship between exposure to HEV and development of breast cancer. Our findings suggest that heavy exposure to HEV blue light emitted from mobile phone screens at night might constitute a risk factor for promoting the development of breast cancer, but further large-scale cohort studies are warranted.

Identification of Burned Areas Based on Texture Features of Different Windows

It is vital to choose appropriate pixel spacing as the window size determines the distribution of texture features in a gray-level co-occurrence matrix (GLCM). The window size ranged from 9×9 to 15×15 to keep the richness of texture image information. In this study, the importance evaluation method based on the Gini index was used to determine the appropriate window for the identification of burned areas, and burned areas were identified with the random forest classification method based on texture features. The results showed that 15×15 was the most appropriate texture window size for the identification of burned areas, and the best texture features for the identification of burned areas were the contrast of the visible blue light band and the texture mean of the near-infrared band; burned areas could be fully identified with the random forest classification method based on texture features, with an overall classification accuracy of 83.87%, but there would be interference pixels in reservoirs, pits, ponds, marshes and irrigated dry fields.

Rapid Microwave-Assisted Synthesis of N/TiO2/rGO Nanoparticles for the Photocatalytic Degradation of Pharmaceuticals.

Nanocomposites comprising nitrogen-doped TiO2 and reduced graphene oxide (N/TiO2/rGO), with different rGO loading qualities, were prepared by a cost-effective microwave-assisted synthesis method. The synthesized materials were broadly characterized by Raman spectroscopy, X-ray diffraction (XRD), infrared spectroscopy (FTIR), photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), electron microscopy (SEM-EDS), and nitrogen adsorption/desorption isotherms. Anatase was the only crystalline phase observed for all synthesized materials. The rGO loading did not affect the morphological properties, but it positively influenced the photocatalytic activity of the nanocomposite materials, especially at low rGO loading. Photocatalysts were evaluated via the degradation of specific organic micropollutant (OMP) pharmaceuticals: ciprofloxacin (CIP), diclofenac (DCF), and salicylic acid (SA), under different radiation sources: ultraviolet A (UVA), solar light simulator (SLS), blue visible light (BVL) and cold visible light (CVL). CIP and SA were removed effectively via the synergy of adsorption and photocatalysis, while DCF degradation was achieved solely by photocatalysis. After implementing scavenger agents, photocatalytic degradation processes mainly depended on the specific pollutant type, while irradiation sources barely defined the photocatalytic mechanism. On the other hand, changes in irradiation intensity significantly influenced the photolysis process, while photocatalysis was slightly affected, indicating that irradiation spectra are more relevant than intensity.

Immobilization and Application of Fatty Acid Photodecarboxylase in Deep Eutectic Solvents.

Since its discovery in 2017, the fatty acid decarboxylase (FAP) photoenzyme has been the focus of extensive research, given its ability to convert fatty acids into alka(e)nes using merely visible blue light. Unfortunately, there are still some drawbacks that limit the applicability of this biocatalyst, such as poor solubility of the substrates in aqueous media, poor photostability, and the impossibility of reusing the catalyst for several cycles. In this work, we demonstrate the use of FAP in non-conventional media as a free enzyme and an immobilized preparation. Namely, its applicability in deep eutectic solvents (DESs) and a proof-of-concept immobilization using a commercial His-tag selective carrier, a thorough study of reaction and immobilization conditions in each case, as well as reusability studies are shown. We observed an almost complete selectivity of the enzyme towards C18 decarboxylation over C16 when used in a DES, with a product analytical yield up to 81 % when using whole cells. Furthermore, when applying the immobilized enzyme in DES, we obtained yields >10-fold higher than the ones obtained in aqueous media.

Stimulated Raman generation of aqueous singlet oxygen without photosensitizers.

Singlet oxygen is traditionally produced via photosensitizer molecules such as methylene blue, which function as catalysts. Here we investigate stimulated Raman generation of singlet oxygen from dissolved oxygen in both water (H2O) and heavy water (D2O) using nanosecond-pulsed visible blue laser light in the 400-440nm spectral region without singlet oxygen photosensitizers. We report an oxygen-dependent Stokes peak in the red spectrum (600-670nm) that is identical when produced in H2O and D2O. These red Stokes photons are not detected when an oxygen quencher is present. Temporal photodepletion of the uric acid absorbance peak at 294nm is consistent with singlet oxygen generation. We postulate that a two-photon stimulated Raman process produces singlet oxygen from O2 dissolved within the solvents. We note that the energy difference between input and output photons of 0.97eV is precisely the energy needed to excite O2 to its singlet state.

Spatiotemporally resolved daily relative humidity predictions across Germany during 2000-2021: a Random Forest approach

BACKGROUND AND AIM The lack of high-resolution relative humidity (RH) datasets and the limited ability of available weather stations to fully capture the spatiotemporal RH variability might lead to errors in exposure assessment for epidemiological studies and biased health effects estimates. We aimed to predict German-wide 1×1 km daily mean RH during 2000-2021 by using a machine learning approach. METHODS We used data from multiple sources, including RH observations, modelled precipitation and wind speed as well as remote sensing elevation, vegetation and the visible red, green and blue light bands. Our main predictor for estimating RH was modelled daily mean air temperature that we previously estimated in 1×1 km across Germany through a multi-stage regression-based approach incorporating two linear mixed models. Additionally, we included date in our RH model, capturing the day-to-day variation of the response-explanatory variables relationship. All the aforementioned predictors were included in a Random Forest (RF) model, which was separately developed for each year. RESULTS Ten-fold cross validation showed that the RF model achieved high accuracy (R²=0.81) and low errors (Root Mean Square Error (RMSE)=5.26%). We also compared our output with an independent dataset from a dense monitoring network in Augsburg metropolitan area (R²=0.81, RMSE=5.42%). Our models displayed high RH overall (21y-average RH=78.8%) and high spatial variability within a year across the country, exceeding 12.1% on average. RH distribution followed spatial patterns including urbanization, mountains, rivers and coastlines. For instance, the Alps and the North Sea coast were areas with elevated RH, while extended urban cores or individual cities were less humid than the surrounding rural settings. CONCLUSIONS Our findings indicate the proposed RF model as suitable for countrywide RH modeling at high spatiotemporal resolution, providing a reliable dataset for subsequent epidemiological analyses and other research purposes. KEYWORDS: relative humidity, spatiotemporal modeling, random forest, exposure assessment

Visible‐Light‐Induced Reversible Self‐Assembly of Gold Nanorattles Using Anionic ortho‐Fluoroazobenzene

AbstractControlled assembly of plasmonic particles is vital for catalyst and sensor applications. Because light is considered a promising external stimulus, various methods for assembling plasmonic particles using photoswitching molecules are investigated. However, the light used to photoisomerize such molecules is often limited to the UV region. In this study, anionic ortho‐fluoroazobenzene is synthesized to reversibly control the self‐assembly of plasmonic nanoparticles under only green and blue visible light. This azobenzene alters the dispersibility of cubic gold nanorattles protected by a cationic surfactant via visible‐light irradiation, causing a visible change in the solution color. It is possible that the cationic surfactant and anionic azobenzene interact to neutralize the surface charge of the gold nanorattles. Because the interaction is changed by the photoisomerization of azobenzene, the aggregation and redispersion of the gold nanorattles are repeatable. Through this method, the dispersibility of nonspherical plasmonic particles can be controlled using only visible‐light irradiation.

The microbicidal potential of visible blue light in clinical medicine and public health.

Visible blue light of wavelengths in the 400–470 nm range has been observed to have microbicidal properties. A widely accepted hypothesis for the mechanism of microbial inactivation by visible blue light is that the light causes photoexcitation of either endogenous (present within the microbe) or, exogenous (present in the biological medium surrounding the microbe) photosensitizers such as porphyrins and flavins, which leads to the release of reactive oxygen species that subsequently manifests microbicidal activity. Some of the factors that have been observed to be associated with enhanced microbicidal action include increased duration of exposure, and either pre- or co-treatment with quinine hydrochloride. In case of bacteria, repetitive exposure to the blue light shows no significant evidence of resistance development. Additionally, visible blue light has exhibited the ability to inactivate fungal and viral pathogens and, multidrug-resistant bacteria as well as bacterial biofilms. Visible blue light has demonstrated efficacy in eliminating foodborne pathogens found on food surfaces and exposed surfaces in the food processing environment as well as in the decontamination of surfaces in the clinical environment to minimize the spread of nosocomial infections. We conclude from reviewing existing literature on the application of the blue light in clinical medicine and public health settings that this microbicidal light is emerging as a safer alternative to conventional ultraviolet light-based technologies in multiple settings. However, further comprehensive studies and thorough understanding of the mechanism of microbicidal action of this light in different scenarios is warranted to determine its place in human health and disease.

An Efficient Method for the Intermodal Four-Wave Mixing Process.

We demonstrate a partially degenerated intermodal four-wave mixing (FWM) process realized in a few-mode nonlinear optical fiber, leading to the effective generation of visible red and blue light from 532 nm sub-nanosecond pulses. We present a self-seeded FWM configuration with a signal beam obtained in the additional section of the same type of fiber that ensures perfect matching between the seed and the Stokes beams. Over 40% of the wavelength conversion efficiency in the FWM process was obtained using a fiber length shorter than 1 m.

Photoinduced effects of monochromatic visible light with different wavelengths on realgar

AbstractRealgar is a well‐known light‐sensitive material. Under illumination, realgar is oxidized into arsenolite and uzonite, and uzonite generates pararealgar. To further study the effect of light with different wavelengths on realgar, herein, the light‐induced reaction of realgar under irradiation of four monochromatic visible lights, red light (628.0–648.0 nm), amber light (585.4–604.6 nm), green light (506.0–544.0 nm), and blue light (428.9–447.1 nm), have been studied by confocal Raman, X‐ray diffraction, and ultraviolet–visible absorption spectroscopy. The results of Raman spectra show that the photoinduced effect of different monochromatic lights on realgar is different. Realgar is stable under red light but is sensitive to other visible lights like amber, green, and blue light. The light‐induced reaction of realgar is the fastest under the green light. The effect of the blue light on realgar is complicated. Pararealgar, as the light‐induced product of realgar, transforms into uzonite under the blue light, which is discussed based on the bandgap of pararealgar calculated using the density functional theory method.

Investigation of wound healing potential of photo-active curcumin-ZnO-nanoconjugates in excisional wound model

Wound healing, being a dynamic process consisting of hemostasis, inflammation, proliferation, and remodeling, involves the complicated interplay of various growth mediators and the cells associated repair system. Current wound healing therapies usually fail to completely regain skin integrity and functionality. Traditionally, curcumin is considered a potent natural wound healing agent as it possesses antibacterial, antioxidant, and anti-inflammatory properties. It is also known that zinc oxide (ZnO) nanoparticles (NPs) have photocatalytic properties, including the generation of reactive oxygen species. ZnO nanoaprticles are also Food and Drug Administration (FDA) approved as safe substances. While ZnO oxide requires illumination with ultraviolet light to become photocatalytically active, dye-sensitized ZnO can be activated by illumination with visible light. In the present study, we explored the wound healing potential of ZnO nanoparticles sensitized with curcumin (Cu+ZnO Nps) and illuminated with visible (blue) light generated by an array of high power LEDs. We studied the antibacterial effect of our conjugates by percentage reduction in bacterial growth and biofilm formation. The wound healing potential was analyzed by percentage wound contraction, biochemical parameters, and histopathological analysis of the wounded site. Additionally, angiogenesis and wound associated cytokines was evaluated by immunohistochemistry of CD31 and gene expression analysis of IL-1β, TNF-α, and MMP-9 after 16 days of post-wound treatment, respectively. Our study suggests that the therapeutic effect of Cu+ZnO NPs with LED illumination increases its wound healing potential by producing an antibacterial and anti-inflammatory effect. Moreover, the treatment strategy of using a nano formulation in combination with LED illumination further increases its efficacy. It was concluded that the anti-inflammatory and bactericidal effects of the LED illuminated Cu+ZnO Np showed accelerated wound healing with increased wound contraction, collagen deposition, angiogenesis, and re-epithelialization.

Visible light modulator by sputter-deposited lithium niobate

Thin-film lithium niobate (LN) modulators have significant potential for ultra-high-speed optical communications. Although a significant cost reduction of the modulator is needed to satisfy the growing demands of huge data communications, all the existing studies of thin-film LN modulators were fabricated using the adhesion process of bulk LN to a substrate, and it severely constrains the use case of LN modulators. In order to overcome this critical issue, we have deposited thin-film LN (006) directly on a Al2O3 sapphire (001) substrate and fabricated LN modulators by using the wafer process. Furthermore, previous studies have been largely limited to the use of infrared light (typical wavelengths λ = 1550 nm), which also constrains half-wave voltage and interaction electrode length (Vπ · L) required for modulation. Small Vπ · L is essentially important not only for small die size with lower cost but also for small voltage operation by using a complementary metal oxide semiconductor. Here, we demonstrate the modulation of red (λ = 637 nm), green (λ = 520 nm), and blue (λ = 473 nm) visible light using sputter-deposited thin-film LN; the product of the half-wave voltage and interaction electrode length (Vπ · L) was 1.9, 1.4, and 1.2 V cm, respectively: it decreased with the decreasing wavelength. Thus, LN modulators can be adopted for emerging applications of visible light communications, and wafer-level fabrication using sputter-deposited thin-film LN provides opportunities for future mass production with a much lower fabrication cost.

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.

Blue light irradiation inhibits the growth of colon cancer and activation of cancer‑associated fibroblasts.

Irradiation with a specific wavelength of light using light-emitting diodes (LEDs) has various effects on cells and organisms. Recently, the antitumor effects of visible blue light on tumor cells were reported; however, the mechanism and effects on the tumor microenvironment remain unclear. Human colon cancer cells (HCT-116) were injected into the rectal wall of nude mice. Tumors were irradiated with a 465-nm LED light at 30 mW/cm2 for 30 min. Tumor volumes and the expression levels of opsin 3 (Opn3), autophagy-related factors, cancer-associated fibroblast (CAF) markers, and programmed cell death 1-ligand (PD-L1) were measured. Additionally, human intestinal fibroblasts were cultured in HCT116-conditioned medium (CM) to prepare CAFs. CAFs were divided into an LED group and a control group, and the effect of the LED light on CAF activation in colon cancer cells was examined. Irradiation with blue LED light suppressed tumor growth; Opn3 expression was localized to the cell membrane in the LED group. Irradiated tumors exhibited increased autophagy-related gene expression. Furthermore, in the LED group, TGF-β and α-SMA expression levels in the fibroblasts were decreased. Regarding CAFs, α-SMA and IL-6 expression levels were decreased in the LED group. HCT-116 cells cultured in CAF-CM with LED irradiation showed no enhanced migration or invasion. In the HCT-116 cells cultured in CM of CAFs irradiated with LED, the relative increase in PD-L1 expression was lower than that noted in the CAF-CM without LED irradiation. Blue LED light may have a direct antitumor effect on colon cancer and also an inhibitory effect on CAFs.

Visible light-driven copper(ii) catalyzed aerobic oxidative cleavage of carbon–carbon bonds: a combined experimental and theoretical study

By switching on visible blue light, aerobic oxidation of various substrates, such as α-substituted, β-substituted and α-halo styrenes, was first realized with a copper(ii) catalyst.

The Effects of Irradiation Time on Gelatin Methacrylate Hydrogels Used for Bone Tissue Engineering

Gelatin methacrylate (GelMA) hydrogels are a promising material for use in a variety of tissue engineering applications. Herein, we focused on identifying the optimal irradiation time necessary to photopolymerize GelMA hydrogels with visible blue light in a manner that did not adversely impact the biophysical properties of these cell-containing gels. We assessed the toxic effects of different irradiation times (3, 5, 10, 20 and 40 seconds) on BMMSCs encapsulated in a GelMA hydrogel using lithium phenyl-2,4,6 trimethylbenzoylphosphinate (LAP) as a photoinitiator. Both CCK-8 assays and Live-Dead staining were used to measure BMMSCs viability. We observed increasing compression strength as a function of increased irradiation time, although this corresponded to a reduction in swelling ratio and pore sizes. We ultimately found that when using LAP as a photoinitiator, the optimal irradiation time was 5–10 seconds, which was suitable for bone tissue engineering application. Ultimately we determined that a 5 second irradiation time was optimal for studies of encapsulated stem cells.

Surface disinfection with white-violet illumination device

&lt;abstract&gt; &lt;p&gt;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&lt;sup&gt;2&lt;/sup&gt; 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.&lt;/p&gt; &lt;/abstract&gt;