Penetration Depth Of Laser Light Research Articles

Methodological notes on physical parameters of low-level laser irradiation. Part 1. Penetration depth of laser light

Methodological notes on physical parameters of low-level laser irradiation. Part 1. Penetration depth of laser light

Mitochondrial targeted melanin@mSiO2 yolk-shell nanostructures for NIR-Ⅱ-driven photo-thermal-dynamic/immunotherapy

The challenge of photothermal therapy (PTT) clinical transformation is the limited penetration depth of laser light and the general concern of using synthetic photothermal nanomaterials. Hence, it is of great significance to develop combined cancer therapies based on NIR-II photothermal agents from natural materials. Herein, natural melanin nanoparticles from cuttlefish ink coated with large pore mesoporous SiO2 were developed to load azodiisobutylimidazoline hydrochloride (AIPH@MS). After modification with (3-carboxypropyl) triphenylphosphonium bromide (CTPP), AIPH@MS-CTPP nanoparticles showed enhanced retention in the tumor site and were further delivered to thermally susceptible mitochondria. Under 1064 nm laser irradiation, hyperthermia produced by melanin not only directly leads to cell death but also promotes AIPH release to generate oxygen-independent alkyl free radicals, which could further attack tumor cells. The collaboration of the photothermal effect of melanin and thermodynamic therapy of AIPH could induce a local antitumor immune response and effectively reprogram tumor-associated macrophages from the M2 to M1 phenotype. In combination with anti-PD-1 immune checkpoint blockade, the paralyzed immune system was awakened to inhibit and eliminate secondary metastatic tumors. The NIR-II-driven treatment in this paper can achieve energy conversion processes from NIR-II light to thermal energy and then to chemical energy to perform photothermal-dynamic therapy and immunotherapy. This will overcome the high side effects and insufficient antitumor immune response of PTT and provide a strategy for effective and mild antitumor therapy with clinically approved laser power and safe nanotechnology.

Role of Immunosuppressive Microenvironment in Acquiring Immunotolerance Post-Photothermal Therapy.

BackgroundNanoparticle-mediated photothermal therapy (PTT) has been well studied as a treatment for cancer. However, the therapeutic outcome of PTT is often hindered by the penetration depth of laser light. In the tumor margin beyond the laser penetration limit, tumor recurrence often occurs, bypassing the immune response of the host. Accumulating evidence suggests the prominent role of tumor microenvironment (TME) and its interactions with the immune components contribute to an immunosuppressive milieu during the post-therapy period. Here, we explored the immunosuppressive cascade generated after PTT, which is responsible for tumor recurrence, and identified the potential targets to achieve an effective PTT period.MethodsHere, we investigated the immunosuppressive cascade generated after PTT in a CT26 tumor bearing mouse. The liposomal system loaded with the indocyanine green (ICG) was utilized for the generation of PTT with high efficiency. Immunological factors such as cytokines and protein expressions post-therapy were investigated through enzyme-linked immunosorbent assay, flow cytometry and western blot analysis.ResultsOur results suggested that PTT with ICG-loaded liposomes (Lipo-ICG) was effective for the first 5 days after treatment, resulting in tumor suppression. However, an immunosuppressive and pro-inflammatory environment developed thereafter, causing the recruitment and upregulation of the immune evasion factors of heat shock protein 70, programmed death ligand 1, indoleamine-dioxygenase, interleukin-6, transforming growth factor-β, regulatory T-cells, and myeloid-derived suppressor cells, to develop immunotolerance.ConclusionCollectively, these findings have determined potential therapeutic targets to modulate the TME during PTT and achieve tumor ablation without remission.

WE-FG-BRA-12: Research Work of the Radio-Dynamic Treatment Mechanism

Purpose: The finite penetration depth of Laser light has limited clinical applications for PDT. This present work investigates the activation of photosensitizers using Cerenkov light emission from 45MV photon beams produced in an LA45 cancer therapy accelerator. We have named this new treatment technique Radio-Dynamic Therapy (RDT). Methods: Monte Carlo simulations were made on various Cerenkov emission energies and their spectroscopy in excited target areas in order to estimate their photosensitizer inner activation efficiency. The Cerenkov light excitation efficiency used in RDT has been theoretically compared with the exotic excitation efficiency of external Laser light used in PDT. In addition, laboratory tests showed the differences of the excitation efficiencies between a patented catalyst coenzyme added as a substrate, and then without the coenzyme. A specific probe of DMA (Singlet Oxygen fluorescent probe-9, 10-dimethylanthracene) was also used to detect singlet oxygen. Finally, we also compared our results with similar previous experimental work reported in the scientific literature. Results: Our Monte Carlo results showed that the Cerenkov light intensity induced with 45MV beams from an LA45 is 8 – 10 times the Cerenkov light intensity induced with 6MV beams from conventional accelerators. Furthermore, the patented catalyst coenzyme enhanced the excitation efficiency of photosensitizers by 3–6 times under different conditions. In clinical situations, the new RDT technique also showed favorable outcomes for early and late stages of specific cancers and it is also good at metastatic cancer treatment. Conclusion: Our results indicated that the process of using the Cerenkov light emission to excite photosensitizers from 45MV photons has a similar process and efficiency as the conventional laser in PDT. Comparing the advantages of RDT with a conventional PDT, the RDT may be developed into a potential treatment modality for a wider range of cancers stages as well as for other diseases.

Influence of carbon black and indium tin oxide absorber particles on laser transmission welding

Abstract For laser transmission welding of polypropylene carbon black and indium tin oxide (ITO) are used as absorber particles. Additionally, the colorant titanium dioxide is mixed to the absorbing part, while the transparent part is kept in natural state. The absorption coefficients of ITO and carbon black particles are obtained, as well as the scattering properties of polypropylene loaded with titanium dioxide (TiO2). At similar concentrations the absorption coefficient of ITO is an order of magnitude smaller than that of carbon black. Simulations of radiation propagation show that the penetration depth of laser light is smaller for carbon black. Therefore, the density of the released heat is higher. Adding TiO2 changes the distribution of heat in case of ITO, whereas for carbon black the effect is negligible. Thermal simulations reveal the influence of the two absorbers and TiO2 on the heat affected zone. The results of the thermal simulations are compared to tensile test results.

Comparison of wavelength-dependent penetration depths of lasers in different types of skin in photodynamic therapy

The determination of the penetration depth of laser light with different sources wavelengths into human skin is one of the preconditions of improving the photodynamic therapy (PDT) procedure for skin diseases. This research is planned to explore which wavelengths would be the most advantageous for use in PDT for superficial skin diseases, and to demonstrate that the red laser exposure of 635 nm wavelength is a suitable choice for all skin types in PDT. A realistic skin model (RSM) in the Advanced Systems Analysis Program (ASAP) software has been used to create different types of skin and to simulate laser sources with wavelengths of 635, 532, 405, 365, 308 and 295 nm. The penetration depths of different kinds of laser into the skin as well as their transmission have been calculated. Comparison of the depth of penetration of different wavelengths for all types of skin has been made. A large variation is found in the penetration depth of laser lights in all skin types. The transmission of lasers on the epidermis and dermis in different skin types occur, and the transmission dose changes significantly with the skin depths. The results of the present study provide a basis for understanding the penetration depth of laser in various skin colors and the responses of the skin to laser to improve dose–drug activation in PDT. The differences in spectral transmission between the red laser and the other lasers suggest that the red laser could be a suitable laser for all skin types.

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.

Penetration depth of laser Doppler flowmetry beam in teeth

The aim of this study was to determine the penetration depth of laser light in teeth for contact and noncontact probe tip. Fifty-one freshly extracted human mature maxillary and mandibular single rooted teeth were selected for the study. A laser Doppler flowmeter was used as a laser source. A digital camera was used to take pictures (with "night shot" mode in total darkness). When probe tip was in contact and when it was 1 mm away from the tooth, the depths of the areas illuminated in high and low density were measured. In contact probe, root was illuminated to 4.28 +/- 0.14 mm depth with high density and 13.27 +/- 0.27 mm depth with low density. In noncontact probe, 4.36 +/- 0.16 mm with high density and 13.28 +/- 0.30 mm with low density of illumination were seen on the root. Between contact and noncontact probe situations the difference was not statistically significant in the depth of illumination. On the other hand, in both groups the difference between areas illuminated in high and low density was statistically significant (P < .05). Contact or noncontact of the probe on tooth surface did not show any significant difference in light penetration. Besides, we think that, for the present, it is impossible to eliminate the contamination from periodontal tissues completely even if the necessary precautions (periodontal paste etc.) are taken.

Femtosecond pulse laser ablation of anodic oxide coatings on aluminium alloys with on-line acoustic observation

The 125-fs laser ablation behaviour (800 nm) of aluminium and anodic oxide coatings on an AlMgSi1 alloy was investigated. The multi-pulse ablation threshold of aluminium at 1.2 J cm −2 was less than that of the oxides of 2–3 J cm −2. Aluminium exhibited a single pulse modification (melting) threshold of 0.3 J cm −2. These values derived from an evaluation of the crater geometry coincided with on-line acoustic measurements. The detected microphone voltage amplitude increased linearly with the laser fluence. The morphology of the ablation craters on aluminium indicated melt formation and displacement of a homogeneous melt phase due to the recoil action of the expanding metal vapour. The laser-processed ceramic oxide phases, on the other hand, showed a spongy resolidified melt layer, which denotes a collocated in-depth formation both of a melt and a gas phase. These phenomena are discussed in terms of the relative dominance of penetration depth of laser light and heat affected zones in the investigated materials with strongly varying optical and thermodynamical properties.

Measurement of digital blood flow using the laser Doppler, impedance and strain-gauge methods

Digital volume changes and blood flow have been measured with impedance and strain-gauge plethysmography as well as with laser Doppler flowmetry. A good agreement was found between the impedance and strain-gauge flow measurements with a correlation coefficient of 0.905. The laser Doppler method recorded minor changes in finger skin blood flow following changes in posture from 30 cm below heart level to 60 cm above heart level. This result can be explained as a consequence of the limited penetration depth of laser light into the skin or as a sign of autoregulation of skin blood flow. In these experiments the total blood flow to the finger underwent major changes.