Red Laser Research Articles

Generation of green electricity from sludge using photo-stimulated bacterial consortium as a sustainable technology

Microbial fuel cell (MFC) is a bio-electrical energy generator that uses respiring microbes to transform organic matter present in sludge into electrical energy. The primary goal of this work was to introduce a new approach to the green electricity generation technology. In this context a total of 6 bacterial isolates were recovered from sludge samples collected from El-Sheikh Zayed water purification plant, Egypt, and screened for their electrogenic potential. The most promising isolates were identified according to 16S rRNA sequencing as Escherichia coli and Enterobacter cloacae, promising results were achieved on using them in consortium at optimized values of pH (7.5), temperature (30°C) and substrate (glucose/pyruvate 1%). Low level red laser (λ = 632.8nm, 8mW) was utilized to promote the electrogenic efficiency of the bacterial consortium, maximum growth was attained at 210 sec exposure interval. In an application of adding standard inoculum (107 cfu/mL) of the photo-stimulated bacterial consortium to sludge based MFC a significant increase in the output potential difference values were recorded, the electricity generation was maintained by regular supply of external substrate. These results demonstrate the future development of the dual role of MFCs in renewable energy production and sludge recycling.

Noninvasive Red Laser Intervention before Radiotherapy of Triple-negative Breast Cancer in a Murine Model.

Radiotherapy is a well-established cancer treatment; it is estimated that approximately 52% of oncology patients will require this treatment modality at least once. However, some tumors, such as triple-negative breast cancer (TNBC), may present as radioresistant and thus require high doses of ionizing radiation and a prolonged period of treatment, which may result in more severe side effects. Moreover, such tumors show a high incidence of metastases and decreased survival expectancy of the patient. Thus, new strategies for radiosensitizing TNBC are urgently needed. Red light therapy, photobiomodulation, has been used in clinical practice to mitigate the adverse side effects usually associated with radiotherapy. However, no studies have explored its use as a radiosensitizer of TNBC. Here, we used TNBC-bearing mice as a radioresistant cancer model. Red light treatment was applied in three different protocols before a high dose of radiation (60 Gy split in 4 fractions) was administered. We evaluated tumor growth, mouse clinical signs, total blood cell counts, lung metastasis, survival, and levels of glutathione in the blood. Our data showed that the highest laser dose in combination with radiation arrested tumor progression, likely due to inhibition of GSH synthesis. In addition, red light treatment before each fraction of radiation, regardless of the light dose, improved the health status of the animals, prevented anemia, reduced metastases, and improved survival. Collectively, these results indicate that red light treatment in combination with radiation could prove useful in the treatment of TNBC.

Effects of low-level laser therapy in adults with rheumatoid arthritis: A systematic review and meta-analysis of controlled trials.

Rheumatoid arthritis (RA) is an inflammatory, systemic and chronic disease that mainly affects the joints. It is characterized mainly by pain, edema and joint stiffness, which can lead to significant loss of functional capacity and quality of life. Several physical therapy resources are used in the treatment of AR, such as low-level laser therapy (LLLT) and its analgesic and anti-inflammatory effects. However, the efficacy of LLLT in AR is still controversial. The objective of this study is to evaluate the efficacy of low-level laser therapy in adults with RA. Methods and findings: We searched MEDLINE, EMBASE, CENTRAL, PEDro, LILACS, IBECS, CUMED, SCIELO and ClinicalTrials.gov. Two researchers independently selected studies, extracted data, evaluated the risk of bias and assessed the certainty of evidence using GRADE approach. Disagreements were resolved by a third author. Meta-analyses were performed. Currently available evidence was from 18 RCTs, with a total of 793 participants. We found low-quality evidence suggesting there may be no difference between using infrared laser and sham in terms of pain, morning stiffness, grip strength, functional capacity, inflammation, ROM, disease activity and adverse events. The evidence is very uncertain about the effects of red laser compared to sham in pain, morning stiffness. The evidence is also very uncertain about the effects of laser acupuncture compared to placebo in functional capacity, quality of life, range of motion and inflammation. Conclusions: Thus, infrared laser may not be superior to sham in RA patients. There is insufficient information to support or refute the effectiveness of red laser, laser acupuncture and reflexology for treating patients with RA.

Polyurethane-based nanofibrous mat containing porphyrin with photosensitivity and bactericidal properties can promote cutaneous tissue healing in rats

The regeneration of cutaneous tissue is one of the most challenging issues in human regenerative medicine. To date, several studies have been done to promote cutaneous tissue healing with minimum side effects. The healing potential of polyurethane (PU)/Poly (caprolactone)–poly (ethylene glycol)–poly (caprolactone) (PCEC)/chitosan (CS) (PCS) nanofibrous mat with cationic photosensitizer meso tetrakis (N-methyl pyridinium-4-yl) porphyrin tetratosylate salt (TMP) was examined. The CS tripolyphosphate nanoparticles (CSNPs) were prepared and loaded by TMP to provide an efficient drug release system (TMPNPs) for delivery of TMP to promote wound healing. In in vitro setting, parameters such as bactericidal effects, cytocompatibility, and hemolytic effects were examined. The healing potential of prepared nanofibrous mats was investigated in a rat model of full-thickness cutaneous injury. PCS/TMP/TMPNPs nanofibers can efficiently release porphyrin in the aqueous phase. The addition of TMPNPs and CS to the PU backbone increased the hydrophilicity, degradation, and reduced mechanical properties. The culture of human fetal foreskin fibroblasts (HFFF2) on PCS/TMP/TMPNPs scaffold led to an increased survival rate and morphological adaptation analyzed by MTT and SEM images. Irradiation with a red laser (635 nm, 3 J/cm2) for the 30 s reduced viability of S. aureus and E. Coli bacteria plated on PCS/TMP and PCS/TMP/TMPNPs nanofibrous mats compared to PU/PCEC (PC) and PU/PCEC/CS (PCS) groups, indicating prominent antibacterial effects of PCS/TMP and PCS/TMP/TMPNPs nanofibrous (p < 0.05). Data indicated that PCS/TMP/TMPNPs mat enhanced healing of the full-thickness excisional wound in a rat model by the reduction of inflammatory response and fibrotic changes compared to the PC, and PCS groups (p < 0.05). Immunofluorescence imaging indicated that levels of Desmoglein were increased in rats that received PCS/TMP/TMPNPs compared to the other groups. It is found that a PU-based nanofibrous mat is an appropriate scaffold to accelerate the healing of injured skin.Graphical abstract

The Effects of Photobiomodulation Therapy on the Healing of Eastern Box Turtle (Terrapene carolina) Shells

Photobiomodulation therapy (cold laser or low-level laser therapy) has been evaluated in human and small animal medicine; however, there is a lack of knowledge about the role photobiomodulation therapy could play in reptile rehabilitation and release. This study used a quantifiable unit, Hounsfield units (bone density measurement), in computed tomography (CT) to evaluate if photobiomodulation therapy showed a significant healing difference between groups treated with photobiomodulation and those that were not. This study included 20 eastern box turtles (Terrapene carolina) presented to a rehabilitation center that sustained shell fractures without penetrating the coelom. They all received similar medical treatments, except that the photobiomodulation group received 250 Hz of red light laser for three minutes three times a week for eight weeks. The turtles were evaluated over the course of two months of therapy. Computed tomography scans were performed prior to therapy, at the midpoint of treatment (one month postinjury), and at the end of the study (two months postinjury). The average Hounsfield units of the fractures were evaluated using nonparametric means, the Wilcoxon/Kruskal–Wallis tests (ranked sums), and found that there were no significant differences in shell density between the photobiomodulation and control groups amongst the scans. This study did find that there was a significant difference (p = 0.0455) between the two groups in regard to the width of the fracture between pre- and post-treatment scans. This study found that the photobiomodulation group had a significantly decreased width of the fracture site between pre-treatment and post-treatment measurements, showing that photobiomodulation could be a relatively easy and effective treatment to promote healing of fractured turtle shells.

Effects of photobiomodulation by low-power lasers and LEDs on the viability, migration, and invasion of breast cancer cells.

Among the malignant tumors, breast cancer is the most commonly diagnosed worldwide, being the most prevalent in women. Photobiomodulation has been used for wound healing, swelling and pain reduction, and muscle repair. The application of photobiomodulation in cancer patients has been controversial. Therefore, a better understanding of radiation-induced effects involved in photobiomodulation on cancer cells is needed. Thus, this study aimed to investigate the effects of exposure to low-power lasers and LEDs on cell viability, migration, and invasion in human breast cancer cells. MCF-7 and MDA-MB-231 cells were irradiated with a low-power red laser (23, 46, and 69J/cm2, 0.77 W/cm2) and blue LED (160, 321, and 482J/cm2, 5.35 W/cm2), alone or in combination. Cell viability was assessed using the WST-1 assay, cell migration was evaluated using the wound healing assay, and cell invasion was performed using the Matrigel transwell assay. Viability and migration were not altered in MCF-7 and MDA-MB-231 cultures after exposure to low-power red laser and blue LED. However, there was a decrease in cell invasion from the cultures of the two cell lines evaluated. The results suggest that photobiomodulation induced by low-power red laser and blue LED does not alter cell viability and migration but decreases cell invasion in human breast cancer cells.

Dual-Color Lasers in Interlayer-Free Solution Processed Polymeric Bilayer Devices.

Multiwavelength organic lasers have attracted considerable interest in recent years due to the cost efficiency, wide luminescence coverage, and simple processability of organics. In this work, by simply spin coating immiscible polymeric gain media in sequence, dual-wavelength (blue-green or blue-red) amplified spontaneous emission (ASE) was achieved in bilayer devices. The blue emission, water/alcohol-soluble conjugated polyelectrolyte, poly[(9,9-bis(3'-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)]dibromide (PFN-Br), was used as the bottom layer. The commercially available nonpolar solvent soluble polymer poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) and its blend with poly(3-hexylthiophene) (P3HT) were used as the top active layers offering green and red emission, respectively. This novel compact configuration, without interlayers between the two active layers, offers potential for developing various applications. The carefully selected top and bottom layer polymers not only meet the conditions of immiscibility and different emission wavelength range but also have a common absorption band in UV, which allows simultaneous blue-green or blue-red dual-color ASE behaviors observed in the bilayer devices under the same 390 nm laser excitation. By introducing two-dimension (2D) square distributed feedback (DFB) gratings with different periods (300 nm for blue, 330 nm for green, and 390 nm for red) as cavities, single mode blue-green (Eth = 245 μJ cm-2) and blue-red (Eth = 189 μJ cm-2) lasers were achieved by focusing the excitation laser spot on different 2D DFB gratings area. Furthermore, we found it possible to gain sufficient light confinement for red emission along its diagonal direction (Λ ∼424 nm), whereas the 2D DFB gratings offer feedback for blue emission from the 300 nm period along the rectangle direction. Therefore, both blue and red lasers were eventually achieved in the same PFN-Br/F8BT:P3HT bilayer device on the single 2D DFB gratings with a period of 300 nm in this work.

Underwater power compensated white light source based on synthetic white laser

The semiconductor white laser light source is used as a light source for underwater illumination. The required standard color temperature of white light is obtained at the underwater target surface. We studied the power compensation of a synthetic white laser source and its application to underwater illumination. First, the power ratios of the red (638 nm), green (520 nm), and blue (450 nm) lasers at a color temperature of 6500 K were obtained by using chromaticity theory. Next, the three-color and synthetic white laser parameters were obtained with transmission distance, according to the exponential attenuation characteristics of different light in clear water and seawater medium. The three-color laser power at the output was compensated, and the underwater target illumination surface reached the standard 6500 K color temperature of the white laser, improving the illumination. Finally, an experimental system for underwater white laser illumination based on power compensation was established. The errors between experimental and theoretical results of color temperature and illuminance are no more than 0.43% and 22.15%. This power-compensated synthetic white laser light source has both the advantages of long-range underwater detection and the spectral advantages of LED white light sources. The white laser light source meets specific requirements by compensating for power and optimizing white light characteristics for underwater lighting applications.

Comparison of chlorin-e6 detection efficiency by video systems with excitation wavelengths of 405nm and 635nm

BackgroundFluorescence diagnostics with two different wide field-of-view imaging systems with fluorescence excitation at 405 nm and 635 nm, respectively, were compared. Both systems include fluorescence quantification and experimental geometry normalization algorithms. MethodsA newly developed system with an excitation wavelength of 405 nm was tested on intralipid fluorescent tumor phantoms with chlorin-e6. Both, this new system and a second existing system with an excitation wavelength of 635 nm, were used for fluorescent diagnosis in six patients with basal cell carcinoma and cancer of the oral mucosa. For PDT, a red diode laser with a wavelength of 660 nm was used for all 6 patients. One patient received an additional irradiation using the red LED source of the new system ResultsThe boundaries of the lesions and the fluorescence intensity were successfully determined by both video systems. ConclusionsBoth fluorescence imaging approaches showed comparable contrast between diseased and healthy tissues. For oral mucosal cancer, a system with violet fluorescence excitation, bispectral frame analysis, and time-resolved background suppression showed better contrast between the tumor and normal tissue and effective elimination of autofluorescence. Moreover, both systems provided efficient quantification of fluorescence and gave fluorescence indices that were weakly dependent on the distance between the device and the tissue.

Effects of acupuncture and acupressure of the acupoint compared to the tendon on the blood circulation of human tendon in vivo

PurposeThe purpose of this study was to compare the effects of acupuncture and acupressure of acupoints on tendon blood circulation with those of both types of stimulation of tendon itself.MethodsBefore, during (except for acupressure), and after acupuncture and acupressure of the tendon and acupoint, blood circulation of the Achilles tendon was measured using red laser lights.ResultsThe blood volume of the treated and non-treated tendons increased after acupuncture of the tendon (effect of time p = 0.030), whereas that tended to increase after acupuncture of the acupoint (effect of time p = 0.063). In addition, no significant difference in the increases in blood volume was found among the four conditions, i.e., after acupuncture stimulation of the tendon and acupoint for the treated and non-treated tendons (p = 0.492). The blood volume of the treated tendon significantly increased after acupressure of the tendon (effect of time p < 0.001), but not of the acupoint (effect of time p = 0.260), whereas that of the non-treated tendon did not change after acupressure of both the tendon and acupoint.ConclusionThese results suggested that acupuncture of the tendon and acupoint acted centrally to enhance blood circulation of both the treated and non-treated tendons during the recovery period, whereas acupressure of the tendon locally increased blood circulation of the treated tendon only, but not the non-treated tendon and both the treated and non-treated tendons after acupressure of acupoint.

Red, infrared, and simultaneous laser-wavelengths irradiation effects on 5-Fluorouracil-induced oral mucositis in hamsters.

The association of more than one wavelength for photobiomodulation therapy (PBMT) to treat oral mucositis (OM) is unusual in the literature. Thus, this study aims to compare the simultaneous irradiation effects with their isolated application to treat OM. In order of that, 48 male Syrian hamsters were divided into 4 groups: Chemotherapy (Ch), which received only a OM induction protocol (5-Fluorouracil chemotherapy and superficial oral mucosa scratches); Red laser (RL), which received the OM induction and a PBMT protocol at 660 nm; Infrared laser (IRL), which received the OM induction, and a PBMT protocol at 808 nm; and the RL+IRL group, which received the simultaneous application, of 660 nm and 808 nm wavelengths. Clinical (OM grade classification), histological (light microscopy analysis with H&E and collagen staining), immunohistochemical (TNF-α expression), and biochemical (TNF-α and hydroxyproline concentration) analyzes were performed after 7 and 10 days. Mainly on the 10th day, the RL and IRL groups showed lower OM grades and faster microscopic repair process, with greater expression of collagen fibers and lower TNF-α levels, besides the higher hydroxyproline concentrations, mainly in comparison with the Ch group. In conclusion, in this study, the simultaneous protocol did not present superior results than the isolated irradiations. This article is protected by copyright. All rights reserved.

Advancing Photodynamic Therapy Efficiency on MCF-7 Breast Cancer Cells through Silica Nanoparticles-Safranin Encapsulation: In-Vitro Evaluation

Efficient drug delivery to target tissue is a major challenge in many cancer treatment modalities. Silica nanoparticles (SiNPs) have been identified as an ideal drug carrier due to their unique properties. In Photodynamic therapy (PDT), one of the key challenges in utilizing photosensitizers (PS) lies in effectively delivering the PS to the targeted tissue. Using Silica nanoparticles encapsulation will effectively prevent the leakage of entrapped PS from the particles, protects against reduction by the retinal endothelial system, and reduces PS toxicity. In this study, Silica nanoparticles (SiNPs) were used as carriers for Safranin (SF) as a photosensitizer agent to treat MCF-7 breast cancer cells in vitro. The SiNPs nanoparticles were synthesized, and their size and shape were measured using Transmission Electron Microscopy (TEM). Cytotoxicity was evaluated for different concentrations of encapsulated and naked SF. The optimal concentrations and exposure times required to eliminate the MCF-7 under light (Intensity ~110 mW/cm2, red laser) were determined. The results indicated that encapsulated SF by SiNPs exhibited higher efficacy than naked SF with a +50% concentration efficacy and +78% exposure time efficacy. This confirmed the superior ability of encapsulated SF to eliminate MCF-7 cells compared to naked SF. The use of synthesized silica nanoparticles loaded with SF improved photodynamic therapy by increasing the bioavailability of SF in the target cells. Our results demonstrate that SiNP encapsulation significantly improves the efficacy of SF in eliminating MCF-7 cells compared to bare SF. This study underscores the potential of SiNPs as a drug delivery system for photodynamic therapy and could pave the way for developing more effective cancer treatments.

Power stability of different lasers and its effect on the outcome of phase-stepping shearography experiments

We examined the effect and influence of power stability of different commonly used lasers on the outcome of phase-stepping shearographic experiments. We performed power stability measurements with three different lasers (helium–neon laser, red diode laser and green frequency-doubled neodymium laser). We subsequently performed phase-stepping shearography experiments using these lasers as light sources. We found a correlation with the quality of the shearograms and the power stability of the lasers. This enables us to compare the suitability of various lasers for phase-stepping shearography experiments and to choose the best laser for this application.

Low-power blue LED and red laser effects on plasmid DNA, survival, and photolyase mRNA levels in Escherichia coli cultures

Low-power lasers and light-emitting diodes (LEDs) are used for photobiomodulation therapy, but the photobiological effects on DNA repair mechanisms in bacteria cells are disputed yet. This work aimed to evaluate the induction of DNA damages in plasmids, bacterial survival and proliferation, and photolyase mRNA levels in E. coli cultures exposed to low-power blue LED and red laser, followed by ultraviolet c (UVC) radiation. Aliquots of pUC19 plasmids and E. coli C600 cultures were exposed to low-power blue LED (470 nm) and red laser (658 nm) at different fluences. Other E. coli C600 cultures were exposed to UVC radiation after exposure to low-power blue LED and red laser. After irradiations, plasmids were submitted to agarose gel electrophoresis to evaluate DNA damage, bacterial cultures were spread onto Petri dishes content rich medium and incubated to evaluate bacterial survival and proliferation, and photolyase mRNA levels in bacterial cells were evaluated by reverse transcription-quantitative polymerase chain reaction. The results suggest that exposure to blue and red lights emitted from low-power LEDs and lasers does not cause DNA strand breaks in bacterial plasmids and does not alter the survival and mRNA levels from photolyase gene in E. coli cells, but increases bacterial survival and proliferation in E. coli cultures exposed to UVC radiation depending on LED and laser fluences.

RED LASER PHOTODYNAMIC THERAPY OF MELANOMA B16 IN AN EXPERIMENTAL MODEL IN VIVO

Introduction: In recent decades, the incidence of melanoma among European population has been steadily increasing. In addition, the age of patients with this pathology is declining - today more than half of patients with melanoma are under 65 years. Melanoma is an aggressive metastatic tumor that is difficult to treat. The tumor is resistant to chemotherapy and radiotherapy. However, the mechanism of photodynamic action differs from the mechanism of cell damage by antitumor drugs or ionizing radiation. Therefore, there is a high probability that with the help of photodynamic therapy it will be possible to overcome the resistance of melanoma cells to damage. Materials and methods: The study was performed on melanoma tumors of B16 mice. The due methylene blue (MB) was used as a photosensitizer through the known affinity of this colorant to the melanin pigment of melanoma cells. The experiments used the radiation of two semiconductor lasers (Fotonika Plus, Cherkasy. Ukraine) with a wavelength of 660 nm, which corresponds to the maximum absorption of methylene blue. Results:The possibility of increasing the anti-melanoma photodynamic activity of MB with the help of a modifier - the natural polysaccharide chitosan was studied. B16 melanoma has been shown to be sensitive to PDT with MB and its sensitivity can be increased by using MB with the natural polysaccharide chitosan, which has immunoadjuvant properties. Conclusion: As a result of the presented research, a variant of PDT of B16 melanoma of mice was developed using MB sensitizer and chitosan immunoadjuvant, which includes intratumoral injection of MB together with chitosan, irradiation of tumors with a red laser with a wavelength of 660 nm, as well as the use of chitosan as an immunomodulatory factor.

Nonlinear optical phase shift in blood plasmas for neoplasia diagnosis.

Detecting cancer at an early stage is crucial for timely treatment and better chances of survival. This research focuses on a scanning method for detecting cancer by examining the nonlinear optical characteristics of blood plasma samples. The study used both cancerous and noncancerous plasma samples and presented the results statistically by utilizing an incident laser power-dependent nonlinear optical phase shift variable called ζ in the Z-scan technique. The results showed a clear difference between the cancerous and non-cancerous samples with an accuracy of 92%. Furthermore, the study suggests the potential for measuring the cancer staging from the cancerous plasma. The study also confirmed a significant difference in ζ for plasma samples undergoing chemotherapy. A red laser with high power (above 18mW) was used to avoid the involvement of fluorophores or other chemical reagents in the plasma samples during the measurement.

Tungstates of the Boyovskoye tungsten deposit (Southern Urals)

The relevance of the work is due to the need for a mineralogical study of tungsten deposits in the Ural region, which have been mined since the end of the 19th century. The purpose of the work is the diagnostics and detailed description of tungstates from the Boyovskoye tungsten deposit located on the border of the Chelyabinsk and Sverdlovsk regions in the Southern Urals. Analytical studies were carried out in the Laboratory of Physical and Chemical Research Methods of the Institute of Geology and Geochemistry, UB RAS, Ekaterinburg. The chemical composition of minerals was analyzed in polished sections on a CAMECA SX 100 microanalyzer. Measurement conditions: accelerating voltage 15 kV, current 150 nA, electron beam diameter 2 μm. The pressure in the sample chamber is 2 ⋅ 10–4 Pa. The spectra were obtained on tilted wave spectrometers; the intensity was measured from analytical lines. Standard samples: scheelite, wolframite, galena, rutile and chromite. Raman spectra of minerals were obtained using a LabRam HR Evolution spectrometer (Horiba Scientific). A red laser, 532 nm, was used for analysis. As a result of the work, new data on the chemical composition of hubnerite and scheelite were obtained and their Raman spectra were presented. For the first time for the Boyovskoye tungsten deposit, a reliable diagnosis and description of lead tungstate – stolzite was made. The mineral was found in samples with veined quartz in association with muscovite, fluorite, hubnerite and scheelite. It fills cracks and voids in hubnerite, rarely overgrows scheelite or fills cracks in scheelite. It is a later mineral in relation to hubnerite and scheelite. Its chemical composition contains impurities of manganese, calcium, iron and titanium. The stolzite found by us is a mineral of the oxidation zone and, most likely, was formed due to the weathering of wolframite and galena, which is also present in quartz veins.

EFFECT OF LOW-LEVEL LASER ON CYTOKINE PRODUCTION BY MONOCYTES EXPOSED TO CISPLATIN AND STIMULATED WITH P. GINGIVALIS

Objective This study aimed to evaluate the effect of photobiomodulation (PBM) on monocytes exposed to cisplatin and P. gingivalis (Pg). Study Design Peripheral blood mononuclear cells from 10 healthy donors were exposed to cisplatin, irradiated with red laser (AlGaInP, 660nm, 0.028cm², 20mW, 0.71W/cm², 0.14J, 7s, 5J/cm²) and stimulated with Pg. Cell viability and cytokine expression by total monocytes and monocyte subpopulations were evaluated by flow cytometry. Results The treatments did not affect the viability of monocytes and TGF-β1 expression. In Pg-stimulated cells, cisplatin reduced the expression of IL-6, IL-8, and IL-10 in total and classical monocytes and increased IL-6 and TNF expression in the intermediate monocytes. In cisplatin exposed cells, PBM reduced the expression of IL-6 and IL-8 in total, classical, and intermediate monocytes, and IL-10 and TNF in total monocytes. In cisplatin and Pg-stimulated cells, PBM increased the expression of IL-6 and IL-8 in total and intermediate monocytes. Conclusion The red laser modulates the expression of cytokines by human monocytes treated with cisplatin, which may represent PBM mechanisms of action in the management of oral mucositis. Apoio: FAPEMIG APQ03601-16, FIP/PUC Minas 2020/24894-1S, and CAPES Code 001. This study aimed to evaluate the effect of photobiomodulation (PBM) on monocytes exposed to cisplatin and P. gingivalis (Pg). Peripheral blood mononuclear cells from 10 healthy donors were exposed to cisplatin, irradiated with red laser (AlGaInP, 660nm, 0.028cm², 20mW, 0.71W/cm², 0.14J, 7s, 5J/cm²) and stimulated with Pg. Cell viability and cytokine expression by total monocytes and monocyte subpopulations were evaluated by flow cytometry. The treatments did not affect the viability of monocytes and TGF-β1 expression. In Pg-stimulated cells, cisplatin reduced the expression of IL-6, IL-8, and IL-10 in total and classical monocytes and increased IL-6 and TNF expression in the intermediate monocytes. In cisplatin exposed cells, PBM reduced the expression of IL-6 and IL-8 in total, classical, and intermediate monocytes, and IL-10 and TNF in total monocytes. In cisplatin and Pg-stimulated cells, PBM increased the expression of IL-6 and IL-8 in total and intermediate monocytes. The red laser modulates the expression of cytokines by human monocytes treated with cisplatin, which may represent PBM mechanisms of action in the management of oral mucositis.

Sub-bandgap photon-assisted electron trapping and detrapping in AlGaN/GaN heterostructure field-effect transistors

We have investigated photon-assisted trapping and detrapping of electrons injected from the gate under negative bias in a heterostructure field-effect transistor (HFET). The electron injection rate from the gate was found to be dramatically affected by sub-bandgap laser illumination. The trapped electrons reduced the two-dimensional electron gas (2DEG) density at the AlGaN/GaN heterointerface but could also be emitted from their trap states by sub-bandgap photons, leading to a recovery of 2DEG density. The trapping and detrapping dynamics were found to be strongly dependent on the wavelength and focal position of the laser, as well as the gate bias stress time prior to illumination of the HFET. Applying this phenomenon of trapping and detrapping assisted by sub-bandgap photons, red, green, and purple lasers were used to demonstrate photo-assisted dynamic switching operations by manipulation of trapped carriers at the surface of an AlGaN/GaN HFET. A physical model based on band diagrams, explaining the trapping and detrapping behavior of electrons, has been presented.

Growth and spectroscopic characterization of Pr:Gd2SrAl2O7 crystal – A potential solid red laser material

In this article, a series of (PrxGd1-x)2SrAl2O7 (x = 0.006–0.05) polycrystalline compounds were synthesized by traditional solid-state reaction to find out the optimum Pr ion’s concentration of the best fluorescence performance for single crystal growth. Then, a transparent 0.95 at.% Pr:Gd2SrAl2O7 (Pr:GSAO) single crystal was successfully grown by the Czochralski method. Spectroscopic properties and Judd-Ofelt theory analysis of this crystal were investigated in detail. The Pr:GSAO crystal has a strong and broad absorption band at about 453 nm, with the absorption cross section of 4.53 × 10−20 cm2 and the full width at half maximum (FWHM) of 5.10 nm (π-polarization), which matches well with the emission bands of InGaN laser diodes. There are a large number of emission peaks in the visible region, the strongest emission peak is located at about 662 nm with the cross section of 1.20 × 10-18 cm2 (π). The fluorescence lifetime of the 3P0 energy level of Pr:GSAO crystal is 5.55 μs. These results reveal that the Pr:GSAO crystal is a potential candidate for red lasers.