Light-emitting Diode Irradiation Research Articles

Safety Profile of Slit-Lamp-Delivered Retinal Laser Photobiomodulation.

PurposePhotobiomodulation (PBM) refers to therapeutic irradiation of tissue with low-energy, 630- to 1000-nm wavelength light. An increasing body of evidence supports a beneficial effect of PBM in retinal disorders. To date, most studies have utilized light-emitting diode irradiation sources. Slit-lamp-mounted retinal lasers produce a coherent beam that can be delivered with precisely defined dosages and predetermined target area; however, the use of retinal lasers raises safety concerns that warrant investigation prior to clinical application. In this study, we determined safe dosages of laser-delivered PBM to the retina.MethodsA custom-designed, slit-lamp-delivered, 670-nm, red/near-infrared laser was used to administer a range of irradiances to healthy pigmented and non-pigmented rat retinas. The effects of PBM on various functional and structural parameters of the retina were evaluated utilizing a combination of electroretinography, Spectral Domain Optical Coherence (SD-OCT), fluorescein angiography, histology and immunohistochemistry.ResultsIn non-pigmented rats, no adverse events were identified at any irradiances up to 500 mW/cm2. In pigmented rats, no adverse events were identified at irradiances of 25 or 100 mW/cm2; however, approximately one-third of rats that received 500 mW/cm2 displayed very localized photoreceptor damage in the peripapillary region, typically adjacent to the optic nerve head.ConclusionsA safety threshold exists for laser-delivered PBM in pigmented retinas and was identified as 500 mW/cm2 irradiance; therefore, caution should be exercised in the dosage of laser-delivered PBM administered to pigmented retinas.Translational RelevanceThis study provides important data necessary for clinical translation of laser-delivered PBM for retinal diseases.

Bicarbazole‐based oxalates as photoinitiating systems for photopolymerization under UV–Vis LEDs

AbstractPhotoinitiators are critical to initiate chain reactions in photopolymerization. For such applications, the absorption of photoinitiator must be compatible with the emission of light sources and enables the fast manufacturing of three‐dimensional network or structures. Light‐emitting diode (LED) is a new kind of energy‐saving and environmental protection light source, exhibiting a substantial response in the near UV and visible range to replace the traditional mercury lamp and other light sources in photopolymerization. Here, we introduce methyl oxalate into bicarbazole chromophore (BiCz). By variation of the single or double substituents in the BiCz, we demonstrate that the absorption spectra can be adjusted and redshift to visible range and show good absorption in the near UV and visible range (365–475 nm). We explore their photochemistry based on experimental results and theoretical calculations and the mechanism of photoreactions have been verified. The super photostability by themselves and good hydrogen abstraction ability from amine co‐initiator make them as excellent near UV and visible light active photoinitiators. Critically, the photoinitiation of the free‐radical polymerization of acrylate monomers with low content (0.1% concentration) upon LED irradiation at 365–475 nm, exhibits excellent application potential in light curing and other fields.

Photochemical Synthesis of Silver Nanodecahedrons under Blue LED Irradiation and Their SERS Activity

Silver nanodecahedrons were successfully synthesized by a photochemical method under irradiation of blue light-emitting diodes (LEDs). The formation of silver nanodecahedrons at different LED irradiation times (0–72 h) was thoroughly investigated by employing different characterization methods such as ultraviolet–visible spectroscopy (UV–Vis), transmission electron microscopy (TEM), and Raman spectroscopy. The results showed that silver nanodecahedrons (AgNDs) were formed from silver nanoseeds after 6 h of LED irradiation. The surface-enhanced Raman scattering (SERS) effects of the synthesized AgNDs were also studied in comparison with those of spherical silver nanoparticles in the detection of 4-mercapto benzoic acid. Silver nanodecahedrons with a size of 48 nm formed after 48 h of LED irradiation displayed stronger SERS properties than spherical nanoparticles because of electromagnetic enhancement. The formation mechanism of silver nanodecahedrons is also reported in our study. The results showed that multihedral silver nanoseeds favored the formation of silver nanodecahedrons.

Light Emitting Diode Phototherapy for Skin Aging.

Skin aging is associated with changes that include atrophy, pigmentation, decreased ability for wound healing, and rhytides. Recently, there has been growing research interest and consumer demand for minimally invasive cosmetic procedures involving light and energy-based devices, particularly for facial skin rejuvenation. Light emitting diode (LED) phototherapy is a promising treatment modality for photorejuvenation as it is safe, noninvasive, accessible, and can be easily combined with other treatment options. LED irradiation alters intrinsic cellular activity via absorption by chromophores located in the skin and may result in desirable photorejuvenation effects. In this review, we discuss the physiologic process of cutaneous aging, how visible light phototherapy with LEDs may be used to treat aging skin, and the importance of photoprotection. J Drugs Dermatol. 2020;19(4):359-364. doi:10.36849/JDD.2020.4711.

Cerium(IV) Carboxylate Photocatalyst for Catalytic Radical Formation from Carboxylic Acids: Decarboxylative Oxygenation of Aliphatic Carboxylic Acids and Lactonization of Aromatic Carboxylic Acids.

We found that in situ generated cerium(IV) carboxylate generated by mixing the precursor Ce(OtBu)4 with the corresponding carboxylic acids served as efficient photocatalysts for the direct formation of carboxyl radicals from carboxylic acids under blue light-emitting diodes (blue LEDs) irradiation and air, resulting in catalytic decarboxylative oxygenation of aliphatic carboxylic acids to give C-O bond-forming products such as aldehydes and ketones. Control experiments revealed that hexanuclear Ce(IV) carboxylate clusters initially formed in the reaction mixture and the ligand-to-metal charge transfer nature of the Ce(IV) carboxylate clusters was responsible for the high catalytic performance to transform the carboxylate ligands to the carboxyl radical. In addition, the Ce(IV) carboxylate cluster catalyzed direct lactonization of 2-isopropylbenzoic acid to produce the corresponding peroxy lactone and γ-lactone via intramolecular 1,5-hydrogen atom transfer (1,5-HAT).

Exploring the Photodynamic Properties of Two Antiproliferative Benzodiazopyrrole Derivatives.

The identification of molecules whose biological activity can be properly modulated by light is a promising therapeutic approach aimed to improve drug selectivity and efficacy on the molecular target and to limit the side effects compared to traditional drugs. Recently, two photo-switchable diastereomeric benzodiazopyrrole derivatives 1RR and 1RS have been reported as microtubules targeting agents (MTAs) on human colorectal carcinoma p53 null cell line (HCT 116 p53-/-). Their IC50 was enhanced upon Light Emitting Diode (LED) irradiation at 435 nm and was related to their cis form. Here we have investigated the photo-responsive behavior of the acid derivatives of 1RR and 1RS, namely, d1RR and d1RS, in phosphate buffer solutions at different pH. The comparison of the UV spectra, acquired before and after LED irradiation, indicated that the trans→cis conversion of d1RR and d1RS is affected by the degree of ionization. The apparent rate constants were calculated from the kinetic data by means of fast UV spectroscopy and the conformers of the putative ionic species present in solution (pH range: 5.7–8.0) were modelled. Taken together, our experimental and theoretical results suggest that the photo-conversions of trans d1RR/d1RS into the corresponding cis forms and the thermal decay of cis d1RR/d1RS are dependent on the presence of diazonium form of d1RR/d1RS. Finally, a photo-reaction was detected only for d1RR after prolonged LED irradiation in acidic medium, and the resulting product was characterized by means of Liquid Chromatography coupled to High resolution Mass Spectrometry (LC-HRMS) and Nuclear Magnetic Resonance (NMR) spectroscopy.

Metal-free photocatalysts for the oxidation of non-activated alcohols and the oxygenation of tertiary amines performed in air or oxygen.

This protocol describes the use of 9-fluorenone as a cheap and non-toxic photocatalyst for the oxidation of non-activated alcohols performed under the irradiation of a blue light-emitting diode. It also describes the use of the similarly cheap and non-toxic photocatalyst rose bengal for the selective α-oxygenation of tertiary amines to produce the corresponding amides in a selective way using the same light source. We have provided detailed instructions on how to assemble the light-emitting diode equipment and set up the photocatalytic reaction, where an oxygen atmosphere is created with an O2-filled balloon. Further details are provided using four example reactions that illustrate how this system works: alcohol oxidation to prepare terephthlalaldehyde and androstanedione, and amine oxidation to make 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one and (4-((4-chlorophenyl)(phenyl)methyl)piperazin-1-yl)m-tolyl)methanone. The times needed to perform these photocatalytic reactions are 18, 76, 22 and 54 h, respectively. We believe that this protocol represents a robust methodology for the late-stage modification of amines and the selective oxidation of steroids.

Synthesis of 2-Arylpyridines and 2-Arylbipyridines via Photoredox-Induced Meerwein Arylation with in Situ Diazotization of Anilines.

We report herein a sustainable method for the preparation of 2-arylpyridines through C-H arylation of pyridines using in situ formed diazonium salts (from commercially available aromatic amines) in the presence of a photoredox catalyst under blue light-emitting diode (LED) irradiation. The reaction is tolerant to a wide range of functional groups (e.g., halogen, nitrile, formyl, acetyl, ester). Applications to the C-H bond arylation of bipyridine ligands is also presented.

Integrated Analysis of Transcriptomic and Metabolomic Data Reveals the Mechanism by Which LED Light Irradiation Extends the Postharvest Quality of Pak-choi (Brassica campestris L. ssp. chinensis (L.) Makino var. communis Tsen et Lee).

Low-intensity (10 μmol m−2 s−1) white LED (light-emitting diode) light effectively delayed senescence and maintained the quality of postharvest pakchoi during storage at 20 °C. To investigate the mechanism of LED treatment in maintaining the quality of pakchoi, metabolite profiles reported previously were complemented by transcriptomic profiling to provide greater information. A total of 7761 differentially expressed genes (DEGs) were identified in response to the LED irradiation of pak-choi during postharvest storage. Several pathways were markedly induced by LED irradiation, with photosynthesis being the most notable. More specifically, porphyrin and chlorophyll metabolism and glucosinolate biosynthesis were significantly induced by LED irradiation, which is consistent with metabolomics reported previously. Additionally, chlorophyllide a, chlorophyll, as well as total glucosinolate content was positively induced by LED irradiation. Overall, LED irradiation delayed the senescence of postharvest pak-choi mainly by activating photosynthesis, inducting glucosinolate biosynthesis, and inhibiting the down-regulation of porphyrin and chlorophyll metabolism pathways. The present study provides new insights into the effect and the underlying mechanism of LED irradiation on delaying the senescence of pak-choi. LED irradiation represents a useful approach for extending the shelf life of pak-choi.

Illuminating a Practical Solution to Clothing Protection from Mustard Gas

Lee et al. reported the first metal-organic framework (MOF)-fiber composite for the catalytic detoxification of a mustard gas simulant. The development of such wearable catalytic materials is an important step toward developing protection equipment that can simultaneously detoxify several chemical warfare agents (CWAs) under ambient conditions.

Effect of Fe doping on the photocatalytic activity of TiO2 hollow fibers under LED light irradiation

Fe-doped TiO2 hollow fibers (Fe-THF) were prepared using a template replication method with kapok as the template. The Fe concentration was varied by adjusting the amount of iron (III) nitrate from 0 to 5 mol%. The effect of Fe doping on morphology, crystal structure, bandgap energy, and photocatalytic activity was investigated and discussed. Based on the characterization results, it was found that all samples possessed a hollow structure with anatase as the main crystalline phase. The rutile phase began to be observed with high-level doping. Bandgap energy decreased significantly from 3.02 to 2.12 eV as the Fe concentration increased, owing to the formation of intermediate energy level. The photocatalytic activity was probed using the degradation of methylene blue under light-emitting diode (LED) irradiation. We found that the photocatalytic activity of Fe-THF was inferior to undoped THF and decreased with increasing Fe concentration. This result indicated that Fe dopant could act as the recombination centers in the lattice system, thus inhibiting the photocatalytic activity of THF.

Pyridine-Diketopyrrolopyrrole-Based Novel Metal-Free Visible-Light Organophotoredox Catalyst for Atom-Transfer Radical Polymerization.

In the field of electronics, organocatalysts are in high demand for use in the synthesis of clean polymers using solar radiation rather than potentially contaminating metals. Combining theoretical design, simulation, and experiments, this work presents a novel, pyridine-diketopyrrolopyrrole (P-DPP)-based metal-free visible-light organophotoredox catalyst (P-DPP). It is effective in the photocontrolled organocatalytic atom-transfer radical polymerization (O-ATRP) of methyl methacrylate (MMA) and styrene. The use of this catalyst and white light-emitting diode (LED) irradiation produces polymers with a cross-linked feature. In O-ATRP, the P-DPP catalyst has an oxidative quenching catalytic mechanism with an excited-state reductive potential of -1.8 V, fluorescence lifetime of 7.5 ns, and radical-cation oxidative potential of 0.45 V. Through molecular simulation, we found that the adjacent pyridine group is key to reducing the alkyl halide initiator and generating radicals, while the diketopyrrolopyrrole core stabilizes the triplet state of the catalyst through intramolecular charge transfer. The findings related to this novel photoredox catalyst will aid in the search for much more effective organophotoredox catalysts for use in controlled radical polymerization. They will also be of value in the fields of polymer chemistry and physics and in various applications.

Plasmonic hot electron transfer-induced multicolor MoO3-x-based chromogenic system for visual and colorimetric determination of silver(I).

A plasmonic hot electron transfer-induced multicolor chromogenic system is described for label-free visual colorimetric determination of silver(I). The chromogenic system consists of plasmonic MoO3-x nanosheets with oxygen vacancies and Ag(I). Under white light-emitting diode (LED) excitation, energetic hot hole-electron pairs are formed on the surface of the blue MoO3-x nanosheets. The resulting hot electrons are transferred to Ag(I) upon which it becomes reduced. This results in the generation of yellow silver nanoparticles. Simultaneously, the hot holes lead to the oxidation of the MoO3-x nanosheets to yield colorless MoO3 nanosheets. Similarly, energetic hot hole-electron pairs can also be generated on the surface of AgNPs under white LED irradiation, which contributes to the reduction of Ag(I) and the oxidation of MoO3-x. Overall, a colorful transition from blue to green and finally to yellow can be observed. This multicolor chromogenic system was applied to the colorimetric determination of Ag(I) in the 33-200μM concentration range and a 0.66μM limit of detection, at analytical wavelengths of 430 and 760nm. The method also is amenable to semi-quantitative visual determination of Ag(I). Graphical abstractSchematic representation of plasmonic hot electron transfer-induced multicolor MoO3-x-based chromogenic system for visual and colorimetric determination of silver(I).

Photodynamic inactivation of oral bacteria with silver nanoclusters/rose bengal nanocomposite.

Antimicrobial photodynamic therapy (a-PDT) is a promising anti-infective technique for generation of singlet oxygen (1O2) to target dental disease. However, conventional organic photosensitizers have problems for clinical use in terms of cytotoxicity, quenching of a-PDT activity by self-dimerization, and the lack of long-term antibacterial effect. We herein propose silver nanoclusters/rose bengal nanocomposite (AgNCs/RB) as a novel photosensitizer with two primary antibacterial effects: (1) 1O2 generation by irradiated RB and (2) Ag+ ion release from AgNCs. AgNCs/RB irradiated with white light-emitting diode (LED) for a short irradiation time of 1 min significantly decreased the bacterial turbidity of Streptococcus mutans, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans (P < 0.05). In SEM, TEM and LIVE/DEAD staining images, photoexcited AgNCs/RB reduced S. mutans colonization, destroyed the cell membrane, and increased the number of dead cells. The antibacterial efficiency of photoexcited AgNCs/RB was greater than that of AgNCs or RB alone (P < 0.05), suggesting a synergistic effect of 1O2 and Ag+ ions from photoexcited AgNCs/RB. By contrast, photoexcited AgNCs/RB did not affect WST-8 and LDH activities and morphology of NIH3T3 mammalian cells, indicating low cytotoxicity. Interestingly, the antibacterial activity of AgNCs/RB on S. mutans was maintained even after the cessation of LED irradiation, indicating a long-term antibacterial effect due to released Ag+ ions. The present AgNCs/RB photosensitizers provide effective synergistic antibacterial effects for dental a-PDT via 1O2 and Ag+ ions coupled with low cytotoxicity.

Titanate nanotube confined merger of organic photocatalysis and TEMPO catalysis for highly selective aerobic oxidation of sulfides

Here, it is discovered that titanate (H2Ti3O7) nanotubes can confine the merger of erythrosin B (ErB) photocatalysis and TEMPO catalysis for highly selective aerobic oxidation of sulfides under irradiation of green light-emitting diodes (LEDs).

Study on the Effect of Light Emitting Diode Irradiation on Improving Skin Condition

Study on the Effect of Light Emitting Diode Irradiation on Improving Skin Condition

Low-Intensity Photobiomodulation Decreases Neuropathic Pain in Paw Ischemia-Reperfusion and Spared Nervus Ischiadicus Injury Experimental Models.

There is a wide range of animal models available today for studying chronic pain associated with a variety of etiologies and an extensive list of clinical manifestations of peripheral neuropathies. Photobiomodulation is a new tool for the treatment of pain in a convenient, noninvasive way. The aim of this work is to elucidate the effects of infrared light-emitting diodes (LEDs) on behavioral responses to nociceptive stimuli in chronic pain models. Forty-eight Swiss male mice weighing 25 to 35 g were used. Two chronic pain models, ischemia-reperfusion (IR) and spared spinal nerve injury, were performed and then treated with infrared LED irradiation (390 mW, 890 nm, 17.3 mW/cm2 , 20.8 J/cm2 , for 20 minutes). The behavioral tests used were a mechanical hypersensitivity test von Frey test) and a cold allodynia test (acetone test). The results showed that, in the IR model, the infrared LED had a significant effect on mechanical stimulation and cold allodynia on every day of treatment. In the spared nerve injury model, an analgesic effect was observed on every treatment day (when started on the 3rd and 7th days after the surgery). In both models, the effect was abolished when the treatment was interrupted. These findings suggest that photobiomodulation therapy may be a useful adjunct treatment for chronic pain.

Effect of Light-Emitting Diodes and Ultraviolet Irradiation on the Soluble Sugar, Organic Acid, and Carotenoid Content of Postharvest Sweet Oranges (Citrus sinensis (L.) Osbeck).

Mature ‘Hamlin’ sweet oranges (Citrus sinensis (L.) Osbeck) were irradiated using light-emitting diodes (LEDs) and ultraviolet (UV) light for six days after harvest. Based on evaluation of the basic ripening parameters of fruits, the contents of soluble sugars, organic acids, and carotenoids were analyzed (in pulps) on the sixth day by high-performance liquid chromatography (HPLC). The results showed that LED and UV irradiation not only accelerated orange ripening but also caused significant changes in the soluble sugar, organic acid, and carotenoid content. Compared with fruit subjected to dark shade (DS) treatment, the total soluble sugar, fructose, and glucose contents increased significantly in UV-treated (UVA, UVB, and UVC) fruits, while the sucrose content increased remarkably in white light, UVB, and UVC-treated fruits (p < 0.05). UV treatment was associated with inducing the largest effect on the total soluble sugar content. Except for UVB, other types of light notably induced an accumulation of the total organic acid content, none but blue light and red light markedly induced citric acid accumulation (p < 0.05). Interestingly, only the red light and dark shade treatments had markedly positive effects in terms of inducing carotenoid accumulation, including the total carotenoid, isolutein, zeaxanthin, lutein, neoxanthin, all-trans-violaxanthin, phytofluene, cis-ζ-carotene, and β-carotene concentrations. Other light treatments had significantly negative effects on carotenoid accumulation (p < 0.05). Therefore, soluble sugar, organic acid, and carotenoid accumulation in sweet oranges vary depending on the levels of UV and LED irradiation. Appropriate light irradiation is a potentially effective way to maintain or improve postharvest fruit quality.

Effect of surface characteristics on the bactericidal efficacy of UVC LEDs

UVC LED lamps have gained interest as a possible technology to replace the use of low– pressure mercury UV lamps due to the Minamata convention which is an international treaty enacted to eliminate the use of mercury. In this study, we investigated the influence of surface properties on inactivation efficacy of foodborne pathogens (E. coli O157:H7, S. Typhimurium, and L. monocytogenes) on various food contact surfaces, including glass, PVC, Stainless steel (SUS), Teflon, and silicon by using UVC light-emitting-diode (LED) irradiation. An optimized treatment chamber was constructed and UVC LED irradiation was applied to spot-inoculated surfaces. Also, in order to achieve enhanced pathogen inactivation, combined intervention of 60 °C mild heat and UVC LED irradiation was applied. Different levels of inactivation of foodborne pathogens were observed among surfaces; bactericidal effect decreased in this order: glass, PVC, SUS, Teflon, and silicon (0.5–1 log reduction differences), and this order was closely associated with surface hydrophobicity and roughness. Because of varying hydrophobicity among different surfaces, different bacterial stacking arrangements were developed, and causing undesirable shading effects negating collimated UVC LED irradiation of pathogens located beneath the top layer. Combination treatment of 60 °C mild heat and UVC LED achieved an additive or synergistic inactivation effect (up to 1 log reduction) on E. coli O157:H7, S. Typhimurium, and L. monocytogenes. The combined treatment can compensate for lower penetration and other limitations of UV irradiation, so that effective control of bacteria on food processing surfaces can occur.

Photosensitized oxidative addition to gold(I) enables alkynylative cyclization of o-alkylnylphenols with iodoalkynes.

The well-established oxidative addition-reductive elimination pathway is the most followed one in transition metal-catalysed cross-coupling reactions. While readily occurring with a series of transition metals, gold(I) complexes have shown some reluctance to undergo oxidative addition unless special sets of ligands on gold(I), reagents or reaction conditions are used. Here we show that under visible-light irradiation, an iridium photocatalyst triggers-via triplet sensitization-the oxidative addition of an alkynyl iodide onto a vinylgold(I) intermediate to deliver C(sp)2-C(sp) coupling products after reductive elimination. Mechanistic and modelling studies support that an energy-transfer event takes place, rather than a redox pathway. This particular mode of activation in gold homogenous catalysis was applied in several dual catalytic processes. Alkynylbenzofuran derivatives were obtained from o-alkynylphenols and iodoalkynes in the presence of catalytic gold(I) and iridium(III) complexes under blue light-emitting diode irradiation.