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Oral mucosal irritation potential of antimicrobial chemotherapy involving hydrogen peroxide photolysis with high-power laser irradiation for the treatment of periodontitis
摘要： In the present study, we assessed the oral mucosal irritation potential of antimicrobial chemotherapy involving hydrogen peroxide (H2O2) photolysis with a 405-nm laser device at an output power of ≥100 mW in hamsters. Twenty-four cheek pouches from 12 male Syrian hamsters received 7-min treatment with pure water (PW), 3% H2O2, laser irradiation of PW at 100 mW, laser irradiation of 3% H2O2 at 100 mW, laser irradiation of PW at 200 mW, or laser irradiation of 3% H2O2 at 200 mW (n = 4 each). The diameter of the irradiation area was set at 3 mm; accordingly, the calculated irradiances (optical power densities) of the 100- and 200-mW laser lights were approximately 1400 and 2800 mW/cm2, respectively. In addition, 12 cheek pouches from six animals received laser irradiation of 3% H2O2 at 100 mW for 1, 3, or 5 min (n = 4 each). Each treatment was repeated three times at 1-h intervals. Macroscopic and histological changes were evaluated 24 h after the last treatment. In addition, in vitro bactericidal activity of the treatment against periodontal pathogens was evaluated. We found that 405-nm laser irradiation of 3% H2O2 caused moderate to severe oral mucosal irritation when performed at powers of 100 and 200 mW for ≥3 min, while the same treatment performed at 100 mW for 1 min resulted in mild irritation. Moreover, 1-min H2O2 photolysis at 100 mW caused a >4-log decrease in viable bacterial counts. These findings suggest that 1-min H2O2 photolysis, which can effectively kill periodontal pathogens, may be acceptable when a 405-nm laser device is used at 100 mW. However, use of the laser at a lower power would be preferable for the prevention of unnecessary oral mucosal irritation.
关键词： hydroxyl radicals,photolysis,periodontitis,oral mucosal irritation,laser irradiation,antimicrobial chemotherapy,hydrogen peroxide
更新于2025-09-16 10:30:52
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In Vivo Experimental Study on the Enhancement of Optical Clearing Effect by Laser Irradiation in Conjunction with a Chemical Penetration Enhancer
摘要： The penetration of optical clearing agents (OCAs) is restricted by the natural barrier function of the stratum corneum (SC) of the skin, which can be breached by physical and chemical methods to enhance the transcutaneous delivery of OCAs. To breach the barrier function of SC, we carried out the in vivo experimental study to enhance the optical clearing effect of PEG-400 by laser irradiation in conjunction with a chemical penetration enhancer thiazone. We compared the re?ectance spectra of skin without laser irradiation or thiazone. Mono-treatment of thiazone could not signi?cantly enhance the optical clearing ef?cacy of the skin. After 60 min, the re?ectance spectrum decreased by only approximately 10%. With the combined treatment, the re?ectance spectrum decreased by approximately 30% after 10 min. Subsequently, the effect of laser dose on the enhancement of optical clearing ef?cacy was studied. The optimal irradiation dose was determined. The re?ectance of skins irradiated by a laser dose at 0.7 J/cm2 decreased by approximately 10% and were 20% lower than those at 0.5 and 0.9 J/cm2. The laser at 0.5 J/cm2 could not damage the SC completely, whereas the laser at 0.9 J/cm2 in?uenced the epidermis and dermis; thus, the re?ectance of skin samples irradiated by 0.9 J/cm2 did not decrease.
关键词： laser irradiation,tissue optical clearing technique,in vivo skin,optical clearing,thiazone,combined penetration enhancement
更新于2025-09-16 10:30:52
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Gold Nanoparticle-Mediated Generation of Reactive Oxygen Species During Plasmonic Photothermal Therapy: A Comparative Study for Different Particles Size, Shape, and Surface Conjugation
摘要： Gold nanoparticles (AuNPs)-mediated photothermal therapy represents an alternative to the effective ablation of cancer cells. However, the photothermal response of AuNPs must be tailored to improve the therapeutic efficacy of plasmonic photothermal therapy (PPT) and mitigate its side effects. This study presents an alternative to ease the tuning of photothermal efficiency and target selectivity. We use laser-treated spherical and anisotropic AuNPs with different sizes and biocompatible folic acid (FA)-conjugated AuNPs (FA-AuNPs) in the well-known human epithelial cervical cancer (HeLa) cell line. We show that large AuNPs produce a more significant photothermal heating effect than small ones. The thermal response of spherical AuNPs of 9 nm was found to reach a maximum increase of 3.0 ± 1 °C, whereas, with spherical AuNPs of 14 nm, the temperature increased by over 4.4 ± 1 °C. Anisotropic AuNPs of 15 nm reached a maximum of 4.0 ± 1 °C, whereas anisotropic AuNPs of 20 nm reached a significant increase of 5.3 ± 1 °C in the cell culture medium (MEM). Notably, anisotropic AuNPs of 20 nm successfully demonstrates the potential for use as a photothermal agent by showing reduced viability down to 60% at a concentration of 100 μM. Besides, we reveal that high concentrations of reactive oxygen species (ROS) are formed within the irradiated cells. It is likely to give rise in combination with stress by photothermal heating, resulting in significant cell death through acute necrosis by compromising the plasma membrane integrity. Cell death and ROS overproduction during PPT were characterized and quantified using transmission electron microscopy (TEM) and confocal fluorescence microscopy with different fluorescent markers. In addition, we show that FA-AuNPs induce cell death through apoptosis by internal damage, whereas diminishing ROS formation during PPT treatment. Our findings suggest the ability of plasmon-mediated ROS to sensitize cancer cells and make them vulnerable to photothermal damage, as well as the protective role of FA-AuNPs from excessive ROS formation, whereas reducing the risk of undesired side effects due to necrotic death pathway. It allows an improvement in the efficacy of AuNP-based photothermal therapy and a reduction in the number of exposures to high temperatures required to induce thermal stress.
关键词： Reactive oxygen species,Laser irradiation,Gold nanoparticles,Folic acid,Photothermal effect
更新于2025-09-16 10:30:52
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Laser Irradiation of Mung Bean ( <i>Vigna radiata</i> L.) at Two Wavelengths for Enhanced Seedling Development
摘要： Two laser sources operating at wavelengths of 632.8 nm (He-Ne) and 488 nm (Ar+) are used in examining the effects of coherent, low-power, continuous wave exposure on the development of Vigna radiata L. Presowing laser irradiation of seeds leads to an improvement of mung bean seedling characteristics, with increased values of hypocotyl length (an increase of up to 22.5%), root length (an increase of up to 28.8%), and seedling mass (a maximum increase of 29.2%). Measured parameters between seedlings from laser-irradiated seeds and from control samples are statistically different at a level of significance equal to 0.05. For both laser wavelengths, an optimal exposure time of 2 minutes is determined for enhanced growth of mung bean seedlings.
关键词： Ar+ laser,He-Ne laser,laser irradiation,mung bean,seedling development
更新于2025-09-12 10:27:22
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Laser-induced optically modified Se <sub/>58</sub> Ge <sub/>27</sub> Pb <sub/>15</sub> and Se <sub/>58</sub> Ge <sub/>24</sub> Pb <sub/>18</sub> thin films
摘要： Amorphous samples of Se58Ge27Pb15 and Se58Ge24Pb18 glasses were prepared using the melt quenching method. Thin films of samples were deposited using the vacuum evaporation method. These films were illuminated with Nd: YAG 532 nm green laser radiation. The samples were structurally characterised using X-ray Diffraction (XRD) and Energy-dispersive X-ray analysis. XRD indicated an increase in the crystallinity of samples on laser irradiation. The samples were optically tested through absorption, reflection and transmission spectra recorded on UV-vis spectrophotometer. The obtained values of energy band gap, refractive index, extinction coefficient and Urbach energy of the films were compared both before and after laser exposure. Furthermore, it was found that sample thickness also changes on laser irradiation. The band gap of the samples was found to decrease laser irradiation in Se58Ge27Pb15thin films, while for Se58Ge24Pb18 thin film samples, an unexpected increase in band gap was observed at a laser irradiation time of 8 min. The variable behaviour of band gap has been explained on the basis of Mott and Davis model and heteropolar bond formation.
关键词： thin films,laser irradiation,Chalcogenide glasses,optical properties
更新于2025-09-12 10:27:22
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Laser irradiation-induced structural, microstructural and optical properties change in Bi-doped As <sub/>40</sub> Se <sub/>60</sub> thin films
摘要： The laser irradiation of thermally evaporated As40Se55Bi5 and As40Se45Bi15 thin films was found to be accompanied by structural changes which in turn changed the optical constant. The thin films under investigation were characterized by the X-ray diffraction method to study the structural change and the surface morphology was checked by field emission scanning electron microscope. The composition of the films was verified from the energy dispersive X-ray analysis. The changes in optical properties due to the influence of laser irradiation were calculated from the transmission spectrum recorded by UV–Visible spectrometer in the wavelength region 400–1200 nm. The decrease in optical band gap (photodarkening) is explained on the basis of density of state model proposed by Mott–Davis. The Raman analysis showed the Raman shift and symmetric stretching vibration of As–Se.
关键词： thin films,optical properties,optical band gap,Chalcogenides,laser irradiation
更新于2025-09-12 10:27:22
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Laser Induced Plasmonic Heating with Au Decorated TiO2 Nanoparticles
摘要： In this study, we explore the feasibility of laser as source of photons for plasmonic heating of metal nanoparticles. Au decorated TiO2 nanoparticles with different Au wt.% loading were prepared using deposition-precipitation method and their physical and optical properties were characterized by X-Ray diffraction (XRD), Diffuse reflectance spectra (DRS) and Raman spectroscopy. The enhancement of the optical properties of Au plasmonic nanoparticles arises from localized surface plasmon resonance (LSPR) effect achieved under 532 nm laser irradiation. Additionally, the photothermal performance of Au/TiO2 nanofluid was tested compared with other nanofluids under visible laser irradiation. The results revealed that the temperature of Au/TiO2 nanofluid was significantly higher compared to that of bare TiO2 and pure milli-Q water, attributing to the plasmonic excitation of Au nanoparticles under laser irradiation.
关键词： Plasmonic nanoparticles,photothermal,laser irradiation
更新于2025-09-12 10:27:22
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Generation of microcones on reaction-bonded silicon carbide by nanosecond pulsed laser irradiation
摘要： Silicon carbide (SiC) is heavily used in the industry due to its resistance to chemical wear and excellent mechanical properties such as high hardness and high stiffness. However, these properties make it difficult to produce micro and nanostructures on the surface of SiC by conventional methods. In this study, high-density microcones that protrude ~ 10 μm above the initial surface have been fabricated by nanosecond pulsed Nd:YAG laser irradiation (λ = 532 nm) on reaction-bonded SiC. Geometrically aligned cones were also fabricated by modifying the laser scanning path, and effect of different parameters such as pulse frequency, laser fluence was studied. It was observed that the surface morphology of microcones was affected by the pulse width and beam overlap. X-ray spectroscopy and Raman spectroscopy showed that the microcones were mainly composed of silicon. Formation of these cone structures made the surface highly superhydrophilic with a contact angle of ~ 0°.
关键词： Laser irradiation,Microcone,Surface texturing,Reaction-bonded silicon carbide,Superhydrophilic surface
更新于2025-09-12 10:27:22
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Diffusion of Oxygen and Nitrogen into Titanium under Laser Irradiation in Air
摘要： This paper examines the dynamic interactions between pure titanium and ambient air under transient laser processing conditions. The microstructures and composition distributions of the reaction products on and within the titanium samples are reported, which lead to the estimation of high-temperature diffusion coefficients for nitrogen and oxygen into the titanium substrate. In-situ synchrotron X-ray diffraction testing is conducted to reveal the high temperature reaction steps between titanium and air. The formation mechanisms of both titanium nitrides and titanium oxides are discussed.
关键词： titanium oxidation,titanium nitridation,synchrotron X-ray diffraction.,in-situ phase transformation,laser irradiation
更新于2025-09-12 10:27:22
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Enhancement of solar cell efficiency via luminescent downshifting by an optimized coverglass
摘要： A novel approach to enhance the solar cell efficiency via employing a luminescent downshifting mechanism is presented in this work. Gold metal ions were diffused into a commercially available sodalime silicate glass using a versatile field-assisted solid-state ion diffusion technique under different experimental conditions. Some of these samples were irradiated with ns-laser to segregate the diffused ions into dimers and trimers to enhance their luminescence characteristics. The consequent structural modifications in the glass matrix were examined using Fourier transform infrared spectroscopy. Optical absorption and luminescence measurements were performed to check the presence of resonant plasmonic absorption of nanoclusters and suitability of the samples as luminescent downshifters, respectively. At UV excitation wavelengths (260 and 340 nm), the doped samples downshifted the solar spectrum compared to their undoped counterparts. Furthermore, ns-laser irradiation of the doped samples significantly enhanced the luminescence intensity in comparison to the unirradiated samples. Real-time performance of these samples was tested by measuring the output power of a Si solar cell covered with the treated coverglass when illuminated with a solar simulator. Finally, the Vicker's micro-indentation was applied to conclude that ionic diffusion increased the glass hardness as well.
关键词： Vicker's hardness,Ionic diffusion,Power conversion efficiency,Solar cell coverglass,Luminescent downshifting,Ns-laser irradiation
更新于2025-09-12 10:27:22