Penetration Of Laser Light Research Articles

Two-photon NIR-responsive carbon dots incorporated into NMOFs for targeted photodynamic therapy

In recent years, Photodynamic therapy (PDT) has shown great potential in clinics to treat cancer. Due to the limited depth range of UV or visible laser light penetration, the eradication of solid tumors using traditional photosensitizer is difficult. Here, we report the development of a new NIR active photosensitizer covalently conjugated to nanoscale metal-organic frameworks (NMOFs) for the eradication of deep-seated tumors. This photosensitizer can generate reactive oxygen species (ROS) in the presence of near-infrared light irradiation (980 nm) for PDT. Therefore, we use a strategy to develop two-photon absorbing carbon dots with a fluorescence quantum yield of 13%. The NMOFs are fabricated in the presence of folic acid, which enables them to target cancer cells that overexpress the folate receptor. NMOFs are used as a nanocarrier for CDs and are employed to achieve targeted PDT. This study is the first to observe that carbon dots embedded in NMOF composite could generate singlet oxygen (1O2) under the 980 nm laser light irradiation and also specifically target cancer cells. At a concentration of 100 μg/ml, the nanocomposite demonstrated a 73% rate of cell inhibition. The primary results reported here will show great potential in the future to develop multifunctional carbon dots for targeted two-photon PDT in the presence of higher wavelength light irradiation.

Comparison of Wavelength-Dependent Penetration Depth of 532 nm and 660 nm Lasers in Different Tissue Types.

Introduction: The depth of laser light penetration into tissue is a critical factor in determining the effectiveness of photodynamic therapy (PDT). However, the optimal laser light penetration depth necessary for achieving maximum therapeutic outcomes in PDT remains unclear. This study aimed to assess the effectiveness of laser light penetration depth at two specific wavelengths, 532 nm and 660 mm. Methods: Chicken and beef of different thicknesses (1, 3, 5, 10, and 20 mm±0.2 mm) were used as in vitro tissue models. The samples were subjected to irradiation by a low-level laser diode of 532 and 660 nm in continuous mode for 10 minutes. with power densities of 167 and 142 J/cm2, respectively. Laser light transmission through the tissue was measured using a power meter. Results: For beef samples, the 660 nm wavelength achieved a maximum transmission intensity of 30.7% at 1 cm thickness, while the 532 nm laser had a transmission intensity of 6.5%. Similarly, in chicken breast samples, the maximum transmission occurred at 1 cm thickness with 68.1% for the 660 nm wavelength and 18.2% for the 532 nm laser. Conclusion: Results consistently demonstrated a significant correlation (P<0.05) between tissue thickness and laser light penetration. Thicker tissues exhibited faster declines in light transmission intensity compared to thinner tissues within 10 minutes. These findings highlight the importance of further research to enhance light delivery in thicker tissues and improve the efficacy of PDT in various medical conditions.

A Computational Method for the Visualization of Nitrated Hsp90 Distribution in 3D Culture Models

Protein tyrosine (Y) nitration is an oxidative post‐translational modification that occurs in pathological conditions but is absent in normal tissue. We previously showed that nitrated proteins support tumor cell survival and migration, and recently identified the chaperone Heat Shock Protein 90 (Hsp90) as the first protein that, when nitrated, acquires a novel tumorigenic activity in glioblastoma multiforme (GBM). While Hsp90 is expressed in all cells, we showed that nitration of Hsp90 on Y33 and/or Y56 induces a pathological gain‐of‐function. Nitration on Y33 (Hsp90NY33) decreases mitochondrial metabolism by inhibiting complex IV activity, while nitration on Y56 (Hsp90NY56) activates the P2X7 receptor (P2X7R), which is linked to increased glycolysis in tumors. Together, these metabolic changes are characteristics of the Warburg effect, a metabolic phenotype common amongst tumors, suggesting that nitrated Hsp90 may play a role as a metabolic switch driving tumor progression. Here, we developed a computational approach to visualize the subcellular and spatial distribution of differentially nitrated Hsp90 in 3D cell culture models of GBM (tumoroids) using confocal Z‐Stack images. Our automated, high‐throughput method takes Z‐stack outputs and generates a 3D heatmap of a differentially localized protein of interest, normalized to a housekeeping fluorescence signal. These normalized heatmaps can be generated from any fluorescence image and serve as an unbiased visualization tool to use in conjunction with fluorescence microscopy images. GBM tumoroids were fluorescently labelled for Hsp90NY33or Hsp90NY56using specific and selective in‐house monoclonal antibodies, and for mitochondrial complex IV and P2X7R. DAPI was used as nuclear stain and tumoroids were imaged using confocal laser scanning microscopy. We observed a ~50% loss in fluorescence signal across the depth of tumoroid Z‐stacks, a common problem related to tissue penetration of laser light that leads to an underrepresented fluorescent signal at the core and bottom of imaged tumoroids. To overcome this problem, Python was used to analyze each focal plane within a confocal Z‐stack, normalizing the signal corresponding to the protein of interest by the mean DNA content (DAPI signal) at each focal plane. This normalized signal was used to generate a 3D heatmap of the protein of interest within the tumoroids. Method‐generated heatmaps confirmed the intracellular localization of Hsp90NY33in mitochondria and cytosol, and a distinct localization in the tumoroid periphery. In contrast, Hsp90NY56 was also localized in the nucleus, and was homogeneously distributed throughout the tumoroid. P2X7R showed a clear cell membrane localization, with increased expression in the tumoroid periphery. This suggests that Hsp90NY33may reduce aerobic respiration in the periphery of the tumoroid, allowing oxygen diffusion into the core, while Hsp90NY56 supports glycolysis throughout the tumoroid. Our results provide a novel fluorescence image analysis tool with potential to be expanded for several other 2D and 3D imaging modalities.

The Role of Melanoma Cell-Derived Exosomes (MTEX) and Photodynamic Therapy (PDT) within a Tumor Microenvironment

Photodynamic Therapy (PDT), an unconventional cancer therapy with optimistic desirable effects, utilizes the delivery of a photosensitizer (PS) that is activated by light at a particular wavelength and inducing oxidative cytotoxic damage of a tumor and its surrounding vasculature. Deeper seated tumors such as internally metastasized melanomas are more difficult to treat with PDT as the penetration of laser light to those sites is less. Limitations in targeting melanomas can also be attributed to melanin pigments that hinder laser light from reaching targeted sites. Exosomes serve as naturally occurring nanoparticles that can be re-assembled with PSs, improving targeted cellular absorption of photosensitizing agents during PDT. Additionally, studies indicate that exosomes released from PDT-treated tumor cells play a critical role in mediating anti-tumor immune responses. This review collates the role of Melanoma Cell-Derived Exosomes (MTEX) in immune response mediation and metastasis. Tumor Cell-Derived Exosomes (TEX) post PDT treatment are also reviewed, as well as the effects of exosomes as carriers of photosensitizers and delivery systems for PDT. The understanding and research on the role of melanoma exosomes induced by Photodynamic Therapy and their tumor microenvironment will assist in future research in treatment prospects and implications.

The Study on penetration variation of nickel ion in wastewater by laser light technology

The rapid development of industry in the world has brought serious negative effects, so pollution control and prevention is an important issue for the future environment. The discharge and treatment of metal ions in water environment are becoming more and more serious. Common heavy metal analysis methods need the support of large-scale instruments. In the study, the differently control of wavelength, temperature and concentration. Explore theoretical analysis solutions based on laser absorption and scattering, Design of metal ion analysis of laser light penetration. The influence of medium change of metal ions on the light dispersion path is measured by direct light. Preliminary results found that the 532nm wavelength laser light has a deviation in the determination of metal ions. Laser wave was analysed by water diffusion chromatography. In order to facilitate the change from large equipment to portable metal ion detection technology.

Optimization of laser technology for removing tatuage pigment

Purpose: To study the effectiveness of tattoo pigment removal with laser light depending on the wavelength and depth of penetration into tissues in order to optimize a technique of laser selective photocavitation. Material and methods. 127 male white mongrel rats, aged 8 weeks, were intradermally injected with pigment particles into their backs looking like 2 rows of spots 0.5 cm in diameter. In 6 weeks, 367 skin samples with tattoo pigment were taken. Each sample was a patch of epidermis with pigment crystals surrounded by connective tissue capsules not less than 2.5 mm of thickness. Before the experiment, the epidermal stratum corneum – 10–15 mkm in depth and about 1 mm in diameter- was removed with spray-coagulation (apparatus EHVCH-50-MEDSI). The rest of skin flap surface remained intact. Thus, each skin sample had two areas on the surface – one with removed stratum corneum (experimental) and the other one intact (control). To register changes in the luminous flux, the authors placed an emitter (IPL xenon lamp 7.65.130), tissue sample and photomultiplier (PMT-62) on one and the same axis. To cut off light waves, the authors used a set of light filters – 315, 364, 400, 440, 490, 540, 590, 670, 750, 870, 980 nm. Results. Destruction of skin surface layers was not statistically significant under wavelengths up to 450 nm and after 1000 nm. The epidermal stratum corneum prevents laser light penetration with wavelengths 450–694 nm by 27%, in average, and with wavelengths 700–1000 nm by 33%, in average. Conclusion. Epidermal stratum corneum destruction statistically significantly increases light density in deep tissue layers and increases the depth of penetration of laser light into biological tissues.

Introducing New Conjugated Quantum Dots for Photothermal Therapy in Biological Applications

It is well-known that near-infrared (NIR) light sources are appropriate to ablate benign tumor irreversibly using heat treatment even in deep tissues. The laser light penetration into the skin in these wavelengths is deep (3–5 mm). Applying new stable materials for emitting NIR wavelengths in tumor positions can help cancer treatment. In this paper, synthesis of the conjugated core-multishell Ag/SiO2/Ag and Au/SiO2/Au quantum dots (QDs) with indocyanine green (ICG) is done and their theoretical and experimental absorptions and emissions in the NIR region are investigated. Thus, heat generation (high-resolution medical imaging capabilities) and emission enhancement are explained and described based on the FRET model for the proposed core-multishell QDs and it is shown that Ag/SiO2/Ag with ICG presents 4 times higher emission rate versus ICG alone in NIR region. Also, because of the plasmon hybridization and also resonance light penetration enhancement, the temperature in tissues increases that is useful for photothermal therapy and NIR high-resolution medical imaging for deep tissues. As an alternative application, these nanoparticles with amazing features are used as a heat source in cancer treatment for shallow and deep tissues. Finally, it is shown that Ag/SiO2/Ag QDs are the best solution for this purpose.

Confocal Laser Scanning Microscopy of Morphology and Apoptosis in Organogenesis-Stage Mouse Embryos.

After fluorochromes are incorporated into cells, tissues, and organisms, confocal microscopy can be used to observe three-dimensional structures. LysoTracker Red (LT) is a paraformaldehyde-fixable probe that concentrates into acidic compartments of cells and indicates regions of high lysosomal activity and phagocytosis, both of which correlate to apoptotic activity. Thus, LT is a good indicator of apoptosis visualized by confocal microscopy. Results of LT staining of apoptotic cell death correlate well with other whole mount apoptosis vital dyes such as Nile blue sulfate and neutral red, with the added benefit of being fixable in situ. Nile blue sulfate can also be used as a non-vital, nonspecific dye to visualize general morphology. Stains such as acridine orange can be used for surface staining of fixed embryos to yield confocal images that are similar to scanning electron micrographs. Mouse embryos were stained with LT, fixed with paraformaldehyde/glutaraldehyde, dehydrated with methanol (MEOH), and cleared with benzyl alcohol/benzyl benzoate (BABB). Following this treatment, the tissues were nearly transparent. Embryos are mounted on depression slides, and serial sections are imaged by confocal microscopy, followed by 3-D reconstruction. Embryos or tissues as thick as 500microns (μm) can be visualized after clearing with BABB. LysoTracker staining reveals apoptotic regions in organogenesis-stage mouse embryos. Morphological observation of tissue was facilitated by combining autofluorescence with Nile blue sulfate staining of fixed embryos or opaque surface staining with acridine orangestaining. The use of BABB for clearing LT vital-stained and fixed embryos matches the refractive index of the tissue to the suspending medium, allowing increased penetration of laser light in a confocal microscope. Nile blue sulfate used as a non-vital dye provides a nonspecific staining of fixed embryos that can then be cleared with methyl salicylate for confocal observation. Sample preparation and staining procedures described here, with optimization of confocal laser scanning microscopy, allow for the detection and visualization of morphological structure and apoptosis in embryos up to 500μm thick, and stained specimens can be fixed and mounted on depression slides.

Raman spectroscopy as a depth sensor in cubic phase n-GaN

In this work, we investigate the elementary excitations of epitaxial n-doped GaN grown in its meta-stable cubic phase on GaAs substrate. The Raman spectra were obtained in backscattering geometry with the incoming and outgoing light polarizations parallel. We covered the whole spectrum of wavelengths of an argon laser (457–514.5 nm) in a wide range of Raman energy shift, with a minimum temperature of 10 K. We focused our attention on the nature of the Raman structures, in particular, the ones which Stokes shifts are between 550 and 4000 cm−1 whose natures were identified. The control of laser light penetration in the GaN samples together with electronic Raman cross-sections calculations lead us to assign the structures as plasmon-LO phonon coupled modes and density of states of phonons resulting from structural disorder.

Achilles Tendon Penetration for Continuous 810 nm and Superpulsed 904 nm Lasers Before and After Ice Application: An In Situ Study on Healthy Young Adults.

There is a lack of knowledge about the influence tissue temperature may have on laser light penetration and tendon structure. The purpose of this study was to investigate whether penetration of laser energy in human Achilles tendons differed before and after ice pack application. The Achilles tendons (n = 54) from 27 healthy young adults were irradiated with two class 3B lasers (810 nm 200 mW continuous mode laser and a 904 nm 60 mW superpulsed mode laser). The optical energy penetrating the Achilles area was measured before and after 20 min of ice application. Measurements were obtained after 30, 60, and 120 sec irradiation with the 904 nm laser and after 30 and 60 sec irradiation with the 810 nm laser. Achilles tendon thickness was measured with ultrasonography. Optical energy penetration increased significantly (p < 0.01) after ice application for both lasers and at all time points from 0.34% to 0.39% of energy before ice application to 0.43-0.52% of energy after ice application for the 904 nm laser and from 0.24% to 0.25% of energy before ice application to 0.30-0.31% of energy after ice application for the 810 nm laser. The energy loss per centimeter of irradiated tissue was significantly higher (p < 0.05) at all time points after ice application. Ultrasonography imaging of skin-to-skin and transversal tendon thickness was significantly reduced after ice application at p = 0.05 and p = 0.03, respectively. Achilles tendon thickness in the longitudinal plane remained unchanged (p = 0.49). The penetration of laser light increased significantly through healthy Achilles tendons subjected to 20 min of cooling. These findings occurred in the presence of a significant reduction in skin temperature and Achilles tendon thickness.

Dark Signals in the Choroidal Vasculature on Optical Coherence Tomography Angiography: An Artefact or Not?

Optical coherence tomography angiography (OCTA) based on mathematical processing of sequentially acquired structural OCT images has been applied widely in both retinal and choroidal research and may have advantages over traditional angiography. Images obtained by OCTA are rendered under the assumption that the only moving entity in the retina is blood flow. Optical phenomena and image processing algorithms may create imaging artefacts. Therefore, OCTA images require careful interpretation. This review discusses the dark signals seen in the choroidal vasculature on OCTA using multiple factor analysis. For accurate and comprehensive interpretation of the choroidal vasculature, we recommend simultaneous consideration of the laser light penetration depth and masking effect of retinal pigment epithelium, the orientation of vessels in relation to the scanning lasers and blood flow, the range of regional detectable velocity of blood flow, atrophic tissues in the periphery, and absorption of superior vessels on the scanning laser.

SU-E-T-381: Radio-Dynamic Therapy (RDT) for the Treatment of Late-Stage Cancers

Purpose: Photo-dynamic therapy (PDT) is an effective treatment modality because of the preferential absorption of photosensitizing agent in tumor cells than in surrounding normal tissues. A limitation of PDT for cancer therapy is the finite penetration of laser light to activate the targeting agent in deep-seated tumors. Radio-dynamic therapy (RDT) is designed to overcome this problem by the combination of high-energy (up to 45MV) photon beams and photo/radio-sensitizers. This work investigates the feasibility of PDT for late-stage cancer patients who are no longer respond to conventional therapies available. Methods: The high-energy photon beams are generated using a LA45 RaceTrack Microtron (Top Grade Medical, Beijing, China). The targeting agent investigated is 5- aminolevulinic acid (5-ALA). Both in vitro cell lines and in vivo animal models have been used to investigate the mechanisms of RDT and its therapeutic effects and normal tissue toxicities. Oral 5-ALA (30-60 mg/kg) was administered 4-6 hours before the radiation treatment and the total radiation dose varied between 0.1-4.0Gy in 1-4 fractions. Clinical trials are initiated in China for late-stage cancer patients targeting both primary tumors utilizing localized therapies such as 3DCRT/IMRT and metastases using TBI. Results: There is clear correlation between the cell death and the 5-ALA concentration/radiation dose. The therapeutic effect of RDT is demonstrated using an animal model where the volume of parotid tumors for the RT only group continued to grow after 3Gy irradiation while the RDT group showed a complete response with the same radiation dose. The preliminary clinical results showed encouraging clinical outcome. Conclusion: RDT is a novel treatment technique that may be developed into an effective cancer treatment modality. Further studies on the mechanisms of RDT and its potential clinical applications are warranted.

Penetration of Laser Light at 808 and 980 nm in Bovine Tissue Samples

The purpose of this study was to compare the penetration of 808 and 980 nm laser light through bovine tissue samples 18-95 mm thick. Low-level laser therapy (LLLT) is frequently used to treat musculoskeletal pathologies. Some of the therapeutic targets are several centimeters deep. Laser light at 808 and 980 nm (1 W/cm(2)) was projected through bovine tissue samples ranging in thickness from 18 to 95 mm. Power density measurements were taken for each wavelength at the various depths. For 808 nm, 1 mW/cm(2) was achieved at 3.4 cm, but for 980 nm, 1 mW/cm(2) was achieved at only 2.2 cm depth of tissue. It was determined that 808 nm of light penetrates as much as 54% deeper than 980 nm light in bovine tissue.

Intracellular surface-enhanced Raman scattering (SERS) with thermally stable gold nanoflowers grown from Pt and Pd seeds

SERS provides great sensitivity at low concentrations of analytes. SERS combined with near infrared (NIR)-resonant gold nanomaterials are important candidates for theranostic agents due to their combined extinction properties and sensing abilities stemming from the deep penetration of laser light in the NIR region. Here, highly branched gold nanoflowers (GNFs) grown from Pd and Pt seeds are prepared and their SERS properties are studied. The growth was performed at 80 °C without stirring, and this high temperature growth method is assumed to provide great shape stability of sharp tips in GNFs. We found that seed size must be large enough (>30 nm in diameter) to induce the growth of those SERS-active and thermally stable GNFs. We also found that the addition of silver nitrate (AgNO3) is important to induce sharp tip growth and shape stability. Incubation with Hela cells indicates that GNFs are taken up and reside in the cytoplasm. SERS was observed in those cells incubated with 1,10-phenanthroline (Phen)-loaded GNFs.

The Propagation of Laser Light in Skin by Monte Carlo- Diffusion Method: A Fast and Accurate Method to Simulate Photon Migration in Biological Tissues

INTRODUCTION : Due to the importance of laser light penetration and propagation in biological tissues, many researchers have proposed several numerical methods such as Monte Carlo, finite element and green function methods. Among them, the Monte Carlo method is an accurate method which can be applied for different tissues. However, because of its statistical nature, Monte Carlo simulation requires a large number of photon pockets to be traced, so it is computationally expensive and time- consuming. Although other numerical methods based on the diffusion method are fast, they have two important limitations: first, they are not valid near the bounder of sample and source, and second, their accuracy is less than Monte Carlo method. METHODS: In this study, we combine the accuracy of Monte Carlo method and speed of the diffusion method. This hybrid method is faster than Monte Carlo Method and its accuracy is higher than the diffusion method. RESULTS: We first evaluate this hybrid model and the reflectance of a biological phantom is calculated by Monte Carlo method and this hybrid model. Then the propagation of laser light in the skin tissue has been studied. CONCLUSION : In this study, a combined method based on the Monte Carlo method and the diffuse equation is introduced. This hybrid method is five times faster than Monte Carlo Method, and its accuracy is higher than the diffusion method. The propagation of laser light in skin has also been studied by this hybrid method and its accuracy shows that it can be applied for laser penetration in biological tissues. It seems that this method is good for photo dynamic therapy (PDT) and optical imaging

Matrix assisted pulsed laser evaporation: the surface cluster problem

The unexpected presence of agglomerates in polymer films deposited by the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique is discussed. Many experimental and theoretical works suggest that the simple model of individual molecule evaporation must be abandoned. Solute concentration, boiling temperature and vapor pressure of solvents, laser pulse number, and laser light penetration depth are important parameters to be considered to explain the morphology of the MAPLE deposited films. Nanorods films, which can be efficiently deposited on rough surfaces using the MAPLE technique, present more or less large surface droplets, also. Here, the reduced melting temperature of nanostructured materials can explain agglomeration even at low laser fluences.

Penetration of laser light through red blood cell ghosts

Hemoglobin is the main absorber of visible light in blood and blood-perfused tissues. However, hemoglobin is released from a red blood cell (RBC) during hemolysis. Hemolysis may be caused by a large number of medical conditions, including photodynamic therapy (PDT) and this subsequently can affect passage of light through the treated biological structures. The purpose of the present study was to determine the penetration of a laser beam through a suspension of hemoglobin-free human red blood cells (RBCs) – ghosts. Although hemoglobin has been efficiently removed from the samples used in our experiments, our measurements show that the samples still effectively attenuate the radiant power of penetrating laser light. We established penetration depths of 12.6 mm and 15.4 mm for two different laser light wavelengths, 532 nm and 630 nm, respectively. The penetration depth of laser light was about one order of magnitude higher for hemoglobin-free RBC ghosts as compared to intact RBCs [8,10,12]. These results can be important in case of phototherapy or biostimulation, since all photons that penetrate in a biological object may interact with it and evoke biological response.

A pragmatic model for selective laser melting with evaporation

Selective laser melting (SLM) is a Rapid Manufacturing technique in which parts of complex shape are produced by selectively melting layers of powder. A thorough understanding of the process is crucial for a good control of the properties of the produced parts. In this paper we present a pragmatic engineering model to study aspects of the SLM process using an enthalpy formulation and accounting for shrinkage and laser light penetration. We investigate the importance of evaporation for a set of process parameters relevant to production and find that evaporation is a phenomenon that cannot be neglected at realistic power inputs. However, phenomena such as Marangoni convection and wetting due to surface tension effects need to be considered in the future.

Determination of the effects of blood depth in the dermis on skin colour in a novel skin phantom using digital imaging

A phantom of human port wine stain (PWS) skin, previously described by the authors, that takes into account its light propagation and scattering properties, was used to model varying depths of blood within PWS skin. Digital images of these phantoms were then acquired under controlled conditions, and the colour information was abstracted with a digital image processing suite. These colour data were analysed quantitatively for each depth of blood, and the relationship between depth of blood and colour was defined. A linear relationship was observed between depth of blood within the phantom and hue, hue being an intuitive measure of how colour is perceived by the human eye. As PWS clearance by laser treatment is dependant, to a large degree, on vessel depth within the skin, the ability to abstract colour data from PWS or, in fact, any vascular lesion within the skin, may help predict the degree of clearance before treatment is actually instigated. In the future, the comparison of phantom colour data with data from actual digital images of affected PWS skin, combined with a knowledge of laser light penetration depths, may provide a useful adjunct to clinical judgement in the prediction of PWS treatment outcomes.

Hot-Electron Temperature and Laser-Light Absorption in Fast Ignition

Experimental data [F. N. Beg, Phys. Plasmas 4, 447 (1997)10.1063/1.872103] indicate that for intense short-pulse laser-solid interactions at intensities up to 5 x 10(18) W cm(-2) the hot-electron temperature proportional, variant(Ilambda(2)) (1/3). A fully relativistic analytic model based on energy and momentum conservation laws for the laser interaction with an overdense plasma is presented here. A general formula for the hot-electron temperature is found that closely agrees with the experimental scaling over the relevant intensity range. This scaling is much lower than ponderomotive scaling. Examination of the electron forward displacement compared to the collisionless skin depth shows that electrons experience only a fraction of a laser-light period before being accelerated forward beyond the laser light's penetration region. Inclusion of backscattered light in a modified model indicates that light absorption approaches 80%-90% for intensity >10(19) W cm(-2).