Synergistic effect of mesoporous silica nanocarrier-assisted photodynamic therapy and anticancer agent activity on lung cancer cells.

Investigating combined treatment methodologies is crucial for addressing the complex nature of cancer. As an emerging strategy, nano-biotechnology encourages the design of unique nanocarriers possessing simultaneous therapeutic application properties. This study aims to explore the combined effects of photodynamic and anticancer treatments using a multifunctional nanocarrier system co-administering the photosensitizer IR780 and the anticancer agent curcumin (Cur) on lung cancer cells. Nanocarriers were prepared by encapsulation IR780 and Cur inside polyethylene glycol-capped mesoporous silica nanoparticles (Cur&IR780@MSN). Various concentrations of nanocarriers were evaluated on A549 cells following 5 min NIR laser light (continuous wave, 785 nm, 500 mW/cm2) irradiation. The internalization of nanocarriers was observed through the fluorescence of Cur. Changes in cell viability were determined using the MTT assay and AO/PI staining. A scratch assay analysis was also performed to examine the impact of combined treatments on cell migration. Characterization of the nanocarriers revealed adequate hydrophobic drug loading, temperature-inhibited feature, enhanced reactive oxygen species generation, a pH-dependent curcumin release profile, and high biocompatibility. Cur&IR780@MSN, which enabled the observation of synergistic treatment efficacy, successfully reduced cell viability by up to 78%. In contrast, monotherapies with curcumin-loaded nanocarriers (Cur@MSN) and IR780-loaded nanocarriers (IR780@MSN) resulted in a 38% and 56% decrease in cell viability, respectively. The constructed Cur&IR780@MSN nanocarrier has demonstrated remarkable performance in the application of combination therapies for lung cancer cells. These nanocarriers have the potential to inspire future studies in tumor treatment methods.

Inactivation of planktonic cells and inhibitory effect on post-treatment biofilm formation of methicillin-resistant Staphylococcus aureus by photodynamic treatment with IR780 iodide loaded mesoporous silica nanoparticles and near infrared light.

The rapid spread of antimicrobial resistance is one of the biggest threats to global health. In the search for new treatment approaches that can eradicate pathogens without inducing drug-resistant strains, photodynamic therapy stands as a promising one. The aim of this study was to investigate the antimicrobial photodynamic potential of mesoporous silica nanoparticles (MSN) loaded with IR780 iodide on one of the most common multidrug-resistant bacteria both in hospitals and in the community, which is methicillin-resistant Staphylococcus aureus (MRSA). Mesoporous silica nanoparticles loaded with IR780 iodide were synthesized, their photodynamic and photothermal properties were examined, and their antimicrobial photodynamic potential against one methicillin-susceptible Staphylococcus aureus (MSSA), and one MRSA strain was investigated. Irradiation was achieved via a 785 nm diode laser (500 mW/cm2, 5 min). Viable bacterial cells were counted by serial dilution method. The post-treatment biofilm recurring ability of MRSA was assessed 24 h post-PDT treatment using Crystal Violet assay. Scanning Electron Microscopy (SEM) of post-treatment biofilms was acquired. Data were analyzed by ANOVA followed by Tukey's test (p ≤ 0.05). Results revealed that mesoporous silica nanoparticles loaded with IR780 iodide-mediated photodynamic therapy were effective in killing both tested strains. The antimicrobial effect was stronger on MRSA, in which 99.97% of photokilling (3.54 log reduction) was observed. The killing was mainly due to the photodynamic action of the nanoparticles. Post-treatment biofilm recurring ability of MRSA was much less in the treated group than that of the control group (50% inhibition), as confirmed by both optical density at 570 nm (OD570) measurement, and Scanning Electron Microscope (SEM) imaging.

Polylactide nanoparticles encapsulating indocyanine green for photothermal therapy of prostate cancer cells.

BACKGROUND: The aim of this study is to investigate the in vitro phototherapeutic potential of indocyanine green (ICG) loaded polylactide (PLA) nanoparticles on prostate cancer cells. Many attempts at designing drug delivery systems against cancer were made that incorporates ICG as a photothermal, photodynamic or imaging agent. However, most of these systems contain at least one more drug, making it hard to assess the effects of ICG alone. METHODS: Nanoparticles (ICGNP) were prepared via nanoprecipitation. The effects of phase volume ratio and ICG concentration on size, loading capacity and encapsulation efficiency were explored. Photothermal and photodynamic properties of ICGNP were examined. PC-3 cells were used for cell viability tests. Irradiation was achieved via custom built 809-nm computer controlled diode laser at 1 W/cm2 (up to 600 J/cm2). Data were analyzed by ANOVA followed by Tukey's test (p ≤ 0.05). RESULTS: ICGNP exhibited mean size of 300 nm with low polydispersity, and zeta potential of -14 mV. Upon laser irradiation, ICGNP were capable of causing temperature increase and producing singlet oxygen. On PC-3 cells, ICGNP were proved to be as effective as free ICG in inducing cell death. The measured temperature increase in culture medium and experiments with singlet oxygen quenchers suggest that the decrease in cell viability was mainly the result of photothermal action. CONCLUSIONS: ICGNP was effective as a photothermal agent on PC-3 cells but further improvements are required to increase ICG loading capacity for it to be useful on a wide range of cell types.

Near infrared light activated upconversion nanoparticles (UCNP) based photodynamic therapy of prostate cancers: An in vitro study.

Photodynamic therapy (PDT), has a potential to cure cancerous prostate tissue with minimal side effects. Traditional PDT, however, mostly utilized visible (VIS) light range with direct application of hydrophobic photosensitizers which may not be adequate in clinical practice for especially deep-seated cancer cells because of poor penetration of VIS wavelengths. Here, we report near infrared light (NIR) induced and dual photosensitizers (PS) encapsulated PDT strategy to reduce prostate cancer cells - PC3. The designed nanoplatform (MC540/ZnPc-UCNP@Au), in this study, include upconversion nanoparticles (UCNP) synthesis to convert NIR light into multiple VIS wavelengths, porous silica coating to upload dual photosensitizers (MC540/ZnPc), and gold (Au) functionalization to enhance PDT treatment. High chemical stabilization provided MC540/ZnPc-UCNP@Au show excellent biocompatibility, and efficient PDT treatment for prostate cancer cells. In fact, the fluorescence of the synthesized nanoplatforms, upon NIR light excitation, can produce considerable amount of ROS in 5 min, as it is well matched with the absorption of MC540, ZnPc and Au nanoparticles (np). In addition, the easy visualization of cellular internalized/adsorbed nanoplatforms reveal the in situ cell imaging possibility for diagnosis. Based on the evidence of the results, NIR light activated MC540/ZnPc-UCNP@Au may offer a PDT technique for the treatment of prostate cancer.

Photobiomodulation effects on osteogenic differentiation of adipose-derived stem cells.

Increasing interest has been observed in the use of photobiomodulation (PBM) to enhance the proliferation of stem cells and induce their differentiation. The effects of PBM at two different wavelengths (635 and 809 nm) with three different energy densities (0.5, 1 and 2 J/cm2) on the osteogenic differentiation of adipose-derived stem cells (ADSC) were investigated. Cell viability and proliferation were evaluated by MTT and Alamar Blue assays. Osteoblast differentiation were assessed by alkaline phosphatase (ALP) activity, Alizarin red staining and reverse-transcription polymerase chain reaction (RT-PCR) for the expression of collagen type I (COL1A), ALP and osteocalcin. 635 nm and 809 nm laser irradiation had no effect on the cell viability on days 7 and 14, except for 0.5 J/cm2 group at 14th day after 635 nm irradiation (p < 0.05). Cell proliferation was not changed significantly. Mineralization was increased significantly in 809 nm laser groups but no enhancement was detected in the osteogenic differentiation by ALP activity and gene expression results. In 0.5 and 1 J/cm2 groups, ALP and COL1A expressions were down regulated at day 7 after 809 nm laser exposure. These results suggest that PBM may alter osteogenic differentiation of ADSC and increase mineralization but further investigation is needed to define adequate parameters.

The Comparison of Thermal Effects of a 1940-nm Tm:fiber Laser and 980-nm Diode Laser on Cortical Tissue: Stereotaxic Laser Brain Surgery.

BACKGROUND AND OBJECTIVES: The thermal damage on adjacent healthy structures is always an unwanted consequence of continuous-wave laser irradiation of soft tissues. To propose a laser as an effective alternative to traditional surgical tools, this photothermal damage due to heat conduction must be taken into account with a detailed laser dosimetry study. Two candidate lasers; a 980-nm diode and 1940-nm Tm:fiber were selected for this study. Despite the poor absorption by water, the 980-nm diode laser has been one of the most widely used lasers in soft tissue surgeries due its good absorption by hemoglobin, which provides good homeostasis. The second laser; the Tm:fiber laser was selected due to its wavelength operating at an absorption peak of water (1,940 nm), which makes it a good candidate for ablation of biological tissues, and it is readily capable of being transmitted through flexible fiber optics to deliver energy to hard-to-reach regions. The underlying motivation for the research described in this paper is that with a comprehensive comparison of ablation capabilities and a detailed dose study of infrared lasers operating at different wavelengths and temperature monitoring of the tissue during laser surgery, it may be possible to specify the optimal laser parameters for laser surgery, and propose a treatment alternative to conventional surgical techniques in clinical use. The objectives of this study were to investigate and to compare the thermal effects of 980-nm and 1940-nm lasers on cortical tissue in vivo, to find the optimum parameters for laser-brain-ablation with minimum thermal damage to the surrounding healthy tissue, and finally, to analyze laser irradiated tissue thermographically and histologically to correlate thermal events and tissue damage with laser irradiation parameters. STUDY DESIGN/MATERIALS AND METHODS: Stereotaxic laser brain surgeries were performed on 32 male Wistar rats. A t-type thermocouple was used to measure the temperature of the nearby tissue at a distance of 1 mm above and 1 mm away from the fiber tip during laser surgery. Cresyl fast violet (CFV) staining was used to expose the thermal extent of laser surgery on cortical tissue. Eight tissue samples from each laser study group were processed for histological analysis and the mean ± standard deviation for thermal damage was reported. Thermal damage was quantified as ablation (thermally removed tissue), severe and mild coagulation (irreversible thermal damage) and edematous (reversible thermal damage) areas with regard to CFV stained slices. The Pearson correlation coefficient was calculated to test if the ablation efficiencies and total damage, and edematous areas were correlated to rates of temperature change. RESULTS: No significant adverse effects were observed during surgeries. We found that both lasers investigated were successful in cortical tissue removal. Our results also revealed that irrespective of the mode of operation, laser wavelength and laser power, there is a strong correlation between the rates of temperature change and ablation efficiencies and a negative correlation between the rate of temperature change and total damage and edematous area. CONCLUSIONS: Both lasers investigated were successful in cortical tissue removal. We also reported that when the amount of energy delivered to the tissue was constant, the most important issue was to deliver this energy in a short time to achieve more efficient ablations with less edema around the lesion, regardless of mode of delivery (continuous or pulsed-modulated mode), but further studies including the healing period after laser surgeries have to be performed to compare the thermal extent of damage comprehensively. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

The effect of curcumin in antitumor photodynamic therapy: In vitro experiments with Caco-2 and PC-3 cancer lines.

BACKGROUND: Photodynamic Therapy (PDT) is a promising antitumor and anti-bacterial treatment method for its high selectivity, non-invasiveness, and minimal side effects. However, cellular mechanisms may lead to PDT resistance and thus effect efficacy. The aim of this study is to test whether Curcumin, which is a non-toxic natural compound that has antitumor characteristics, can increase PDT efficacy by overcoming the resistance of cancer cells. METHODS: 5-ALA mediated PDT was tested on two cell lines, PC-3 and Caco-2. Curcumin toxicity was evaluated at different concentrations. The determined PDT doses were applied to the cell lines together with two different Curcumin concentrations. Cell viability was evaluated by MTT assay, 24 hs after the treatments. Results were evaluated using One-Way ANOVA followed by post-hoc tests. RESULTS: Using non-toxic doses of Curcumin resulted in a significant decrease in PDT resistance in Caco-2 cells and thus increased the efficacy of 5-ALA mediated PDT, but not on PC-3. Adding Curcumin to 5-ALA mediated PDT led to more effective results on Caco-2 with a 62.4% decrease in cell viability. On the other hand, adding Curcumin to 5-ALA mediated PDT on PC-3 cells didn't produce statistically significant increase in efficacy with a 36% decrease in cell viability. CONCLUSION: 5-ALA mediated PDT combined with Curcumin synergistically enhanced antitumor PDT efficacy on Caco-2, which is considered a highly resistive cancer cell line.

Stereotaxic laser brain surgery with 1940-nm Tm:fiber laser: An in vivo study.

BACKGROUND: With exciting developments in fiber laser technology, studies investigating the use of lasers in neurosurgery have been increasing in the recent years. Fiber lasers are advantageous in many ways; first of all they are compact and they provide a more comfortable environment in the operating room due to feasibility of coupling laser light to different cross-sectioned fibers. Thulium fiber (Tm:fiber) lasers have been under investigation for medical applications since 2005 due to their spectral proximity to the water absorption peak. OBJECTIVES: The primary aim of this study is to investigate the thermal effects of the 1940-nm Tm:fiber laser on subcortical tissue and to examine the effects of laser parameters on laser-induced lesions. Secondarily, it is also aimed to reveal the importance of temperature monitoring during laser surgeries by investigating the effects of temperature change on the characteristics of laser-induced lesions. MATERIALS AND METHODS: Stereotaxic laser brain surgery was performed on 20 male Wistar rats, in order to investigate the thermal effects of Tm:fiber laser. During surgeries temperature changes in the subcortical tissue were observed with a t-type thermocouple for which a holder was designed to accomplish a 1 mm distance between the fiber tip and thermocouple tip. Histological examinations were performed on cresyl fast violet (CFV) stained slices under light microscopy. Photothermal effects of Tm:fiber laser on subcortical tissue were investigated in terms of ablated (removal of tissue), coagulated and edematous areas with a blinded micrograph evaluation. Relations between laser parameters, ablation efficiencies and rates of temperature changes were determined. Pearson's correlation coefficients between rates of temperature changes and ablation efficiencies, total laser damage and edematous area were calculated. RESULTS: No significant adverse effects were observed during surgeries. Histological examinations revealed localized ablation surrounded by coagulation areas as well as edema. Ablation efficiencies ranged from 20% to 50% with changing laser parameters. The correlation coefficient between rates of temperature change and ablation efficiencies, total laser damage and edematous area were rather high. CONCLUSION: In this study we show that Tm:fiber lasers seem to be useful tools in brain surgeries especially to vaporize and coagulate the tissue. It is also shown that temperature monitoring during laser surgery is very crucial and gives information about laser-induced lesion. Another take home message from this study is rather than the temperature increase, the rate of temperature change is more important. We found that if the temperature is changing in a short time interval, the extent of thermal damage can be minimized. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Potassium iodide potentiated photodynamic inactivation of Enterococcus faecalis using Toluidine Blue: Comparative analysis and post-treatment biofilm formation study.

BACKGROUND: Photodynamic Inactivation (PDI) has recently gained interest as an alternative modality to fight pathogenic entities and its effect can be further enhanced by using certain inorganic salts. Here, the Potassium Iodide (KI)-mediated PDI effect on Enterococcus faecalis using Toluidine Blue Ortho (TBO) as photosensitizer (PS) has been evaluated, and subsequent Biofilm formation extent is accounted for. METHODS: The comparative photoinactivation of TBO and TBO/KI on E.faecalis was investigated by quantifying surviving bacterial colonies after laser irradiation with 30,60, and 180 s exposure times and different PS/Potentiator concentrations. The biofilm formation capability of E.faecalis was observed by calculating Optical Density (OD595) of samples 24,48, and 72 h post-PDI treatment. Scanning Electron Microscopy (SEM) was used as a qualitative measure of bacterial biofilm growth. RESULTS: More than 4 LOGS of photokilling was obtained for experimental groups with the highest PS/KI concentrations at 180 s exposure time. All KI-potentiated groups showed enhancement in PDI effect when compared to non-potentiated counterparts. The degree of recurring biofilm for laser-treated groups also showed to be much less than that of control group, as confirmed by both OD595 measurement and SEM imaging.

Monitoring system for investigating the effect of temperature change on optical properties.

Knowledge about the changes in optical properties is needed for planning safer and more accurate laser treatments. A monitoring system was developed to study how the optical properties of a lipid emulsion are affected by temperature changes. A double-integrating-sphere system is modified with a controlled heating apparatus to measure the temperature-dependent diffuse reflectance and total transmittance values. The absorption and reduced scattering coefficients were estimated from the reflectance and transmittance values using an inverse adding-doubling method. The total transmittance showed positive correlation with temperature while the diffuse reflectance was found to be negatively correlated. Although the absorption coefficient did not demonstrate a statistically significant change with temperature, the reduced scattering coefficient was negatively correlated. By using the obtained optical properties, Monte Carlo simulations were performed to observe the difference in light propagation within a tissue. The results indicate that temperature-dependent changes in optical properties should be taken into consideration for a safer laser treatment.

Indocyanine green-mediated photobiomodulation on human osteoblast cells.

Photobiomodulation (PBM) and photodynamic therapy (PDT) share similar mechanisms but have opposite aims. Increased levels of reactive oxygen species (ROS) in the target tissue in response to light combined photosensitizer (PS) application may lead to cell proliferation or oxidative damage depending on the ROS amount. The purpose of the present study is to investigate the effect of indocyanine green (ICG)-mediated PBM on osteoblast cells by measuring cell viability, proliferation, alkaline phosphatase (ALP) activity, mineralization, and gene expressions of three phenotypic osteoblast markers. A diode laser irradiating at 809 nm (10 W output power, 50 mW/cm2 power density) was used at 0.5, 1, and 2 J/cm2 energy densities (10, 20, and 40 s respectively) was applied following ICG incubation. No inhibitory effect was observed in cell viability and proliferation according to the (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and Alamar Blue assays. ICG-mediated PBM did not alter cell viability but increased ALP activity and enhanced mineralization of existing osteoblasts. These results were also confirmed by real-time polymerase chain reaction (RT-PCR) analysis of osteoblastic markers. PS can be combined to PBM not only to damage the malignant cells as aimed in PDT studies, but also to promote cellular activity. The findings of this in vitro study may contribute to in vivo studies and ICG-mediated PBM can have promising outcomes in bone healing and regeneration therapies in future.

Dose-dependent photochemical/photothermal toxicity of indocyanine green-based therapy on three different cancer cell lines.

The Food and Drug Administration-approved Indocyanine Green can be used as a photosensitizer to kill cancer cells selectively. Although indocyanine green is advantageous as a photosensitizer in terms of strong absorption in the near-infrared region, indocyanine green-based cancer treatment is still not approved as a clinical method. Some reasons for this are aggregation at high concentrations, rapid clearance of the photosensitizer from the body, low singlet oxygen quantum yield, and the uncertainty concerning its action mechanism. This in vitro study focuses on two of these points: "what is the cell inhibition mechanism of indocyanine green-based therapy?" and "how the dose-dependent aggregation problem of indocyanine green alters its cell inhibition efficiency?" The following experiments were conducted to provide insight into these points. Nontoxic doses of indocyanine green and near-infrared laser were determined. The aggregation behavior of indocyanine green was verified through experiments. The singlet oxygen quantum yield of indocyanine green at different concentrations were calculated. Various indocyanine green and energy densities of near-infrared light were applied to prostate cancer, neuroblastoma, and colon cancer cells. An MTT assay was performed at the end of the first, second, and third days following the treatments to determine the cell viability. Temperature changes in the medium during laser exposure were recorded. ROS generation following the treatment was verified by using a Total Reactive Oxygen Species detection kit. An apoptosis detection test was performed to establish the cell death mechanism and, finally, the cellular uptakes of the three different cells were measured. According to the results, indocyanine green-based therapy causes cell viability decrease for three cancer cell lines by means of excessive reactive oxygen species production. Different cells have different sensitivities to the therapy possibly because of the differentiation level and structural differences. The singlet oxygen generation of indocyanine green decreases at high concentrations because of aggregation. Nevertheless, better cancer cell killing effect was observed at higher photosensitizer concentrations. This result reveals that the cellular uptake of indocyanine green was determinant for better cancer cell inhibition.

Methylene blue mediated photobiomodulation on human osteoblast cells.

Photobiomodulation (PBM) and photodynamic therapy (PDT) are two major methods, which use light in medicine and dentistry. PBM uses low-level laser light to induce cell proliferation and activity. In contrast, PDT use laser light combined with a photosensitizer (PS) to cause cell death. Due to similar, not fully understood mechanisms and biphasic response of light, unexpected and complex outcomes may be observed. In the present study, the effect of 635 nm laser light, with power density 50 mW/cm2, at three different energy densities (0.5, 1, and 2 J/cm2 which last 10, 20, and 40 s, respectively) mediated by methylene blue (MB) on the human osteoblast cell line (ATCC-CRL-11372, Rockville, MD, USA) was investigated. Cell viability (MTT assay and acridine orange/propidium iodide staining) and proliferation (Alamar Blue assay) were assessed at 24, 48, and 72 h post irradiation. Alkaline phosphatase (ALP) activity, mineralization (Alizarin Red staining) and gene expressions (RT-PCR analysis) were analyzed at 7th and 14th days after treatment. Five groups were formed as the control group (no MB, no irradiation), MB (only 0.05 µM MB), MB + 0.5 J/cm2, MB + 1 J/cm2, and MB + 2 J/cm2. Cell viability was decreased at 72 h (ANOVA; p < 0.05) for MB + 0.5 J/cm2, MB + 1 J/cm2, and MB + 2 J/cm2 groups. Although proliferation does not seem to be effected by MB-mediated laser application, osteo-anabolic activity is altered. ALP activity was significantly increased at day 7 (ANOVA; p < 0.05) for MB-combined laser groups; on the other hand, mineralization was significantly decreased (ANOVA; p < 0.05) in all treatment groups. Alkaline phosphatase and collagen-I expressions were upregulated in MB + 2 J/cm2 group at 7th and 14th days, respectively. These results may contribute to the low-dose PDT researches and understanding PBM effects on osteoblast behavior but further studies are needed since inappropriate conditions may lead to undesirable results for both therapies.

Determining the optimal dose of 1940-nm thulium fiber laser for assisting the endodontic treatment.

Insufficient cleaning, the complex anatomy of the root canal system, inaccessible accessory canals, and inadequate penetration of irrigants through dentinal tubules minimizes the success of the conventional endodontic treatment. Laser-assisted endodontic treatment enhances the quality of conventional treatment, but each laser wavelength has its own its own limitations. The optimal parameters for the antibacterial efficiency of a new wavelength, 1940-nm Thulium Fiber Laser, were firstly investigated in this study. This paper comprises of two preliminary analyses and one main experimental study, presents data about thermal effects of 1940-nm laser application on root canal tissue, effective sterilization parameters for bacteria, Enterococcus faecalis, and finally the antibacterial effectiveness of this 1940-nm Thulium Fiber Laser irradiation in single root canal. Based on these results, the optimal parameter range for safe laser-assisted root canal treatment was investigated in the main experiments. Comparing the antibacterial effects of four laser powers on an E. faecalis bacteria culture in vitro in 96-well plates showed that the most effective group was the one irradiated with 1 W of laser power (antibacterial effect corresponding to a log kill of 3). After the optimal laser power was determined, varying irradiation durations (15, 30, and 60 s) were compared in disinfecting E. faecalis. Laser application caused significant reduction in colony-forming unit values (CFU) compared with control samples in the 17% ethylenediaminetetraacetic acid (EDTA) group. The results of bacteria counts showed that 1 W with 30 s of irradiation with a 1940-nm thulium fiber laser was the optimal dose for safely achieving maximal bactericidal effect.

Photobiomodulation of wound healing via visible and infrared laser irradiation.

Fibroblast cells are known to be one of the key elements in wound healing process, which has been under the scope of research for decades. However, the exact mechanism of photobiomodulation on wound healing is not fully understood yet. Photobiomodulation of 635 and 809 nm laser irradiation at two different energy densities were investigated with two independent experiments; first, in vitro cell proliferation and then in vivo wound healing. L929 mouse fibroblast cell suspensions were exposed with 635 and 809 nm laser irradiations of 1 and 3 J/cm2 energy densities at 50 mW output power separately for the investigation of photobiomodulation in vitro. Viabilities of cells were examined by means of MTT assays performed at the 24th, 48th, and 72nd hours following the laser irradiations. Following the in vitro experiments, 1 cm long cutaneous incisional skin wounds on Wistar albino rats (n = 24) were exposed with the same laser sources and doses in vivo. Wound samples were examined on 3rd, 5th, and 7th days of healing by means of mechanical tensile strength tests and histological examinations. MTT assay results showed that 635 nm laser irradiation of both energy densities after 24 h were found to be proliferative. One joule per square centimeter laser irradiation results also had positive effect on cell proliferation after 72 h. However, 809 nm laser irradiation at both energy densities had neither positive nor negative affects on cell viability. In vivo experiment results showed that, 635 nm laser irradiation of both energy densities stimulated wound healing in terms of tensile strength, whereas 809 nm laser stimulation did not cause any stimulative effect. The results of mechanical tests were compatible with the histological evaluations. In this study, it is observed that 635 nm laser irradiations of low energy densities had stimulative effects in terms of cell proliferation in vitro and mechanical strength of incisions in vivo. However, 809 nm laser irradiations at the same doses did not have any positive effect.

Investigation of photobiomodulation potentiality by 635 and 809 nm lasers on human osteoblasts.

Photobiomodulation (PBM) describes light-induced photochemical reactions achieved by the application of red or near infrared lasers/LED light with low energy densities. This noninvasive and painless method has been used in some clinical areas but controversial outcomes demand a skeptical look for its promising and potential effects. In this detailed in vitro study, the osteoblast cells were irradiated with 635 and 809 nm diode lasers at energy densities of 0.5, 1, and 2 J/cm2. Cell viability, proliferation, bone formation, and osteoblast differentiation were evaluated by methylthiazole tetrazolium (MTT) assay, Alamar Blue assay, acridine orange/propidium iodide staining, alkaline phosphatase (ALP) activity, Alizarin red staining, and reverse-transcription polymerase chain reaction (RT-PCR) to test the expression of collagen type I, ALPL, and osteocalcin. The results indicate that studied energy doses have a transient effect (48 h after laser irradiation) on the osteoblast viability and proliferation. Similarly, laser irradiation did not appear to have any effect on ALP activity. These results were confirmed by RT-PCR analysis of osteoblast markers. This study suggests that several irradiation parameters and variations in the methods should be clearly established in the laboratory before laser treatment becomes a postulated application for bone tissue regeneration in clinical level.

Ceramic bracket debonding with Tm:fiber laser.

Lasers have the potential for reducing the required debonding force and can prevent the mechanical damage given to the enamel surface as a result of conventional debonding procedure. However, excessive thermal effects limit the use of lasers for debonding purposes. The aim of this study was to investigate the optimal parameters of 1940-nm Tm:fiber laser for debonding ceramic brackets. Pulling force and intrapulpal temperature measurements were done during laser irradiation simultaneously. A laser beam was delivered in two different modes: scanning the fiber tip on the bracket surface with a Z shape movement or direct application of the fiber tip at one point in the center of the bracket. Results showed that debonding force could be decreased significantly compared to the control samples, in which brackets were debonded by only mechanical force. Intrapulpal temperature was kept equal or under the 5.5°C threshold value of probable thermal damage to pulp. Scanning was found to have no extra contribution to the process. It was concluded that using 1940-nm Tm:fiber laser would facilitate the debonding of ceramic brackets and can be proposed as a promising debonding tool with all the advantageous aspects of fiber lasers.

Laser biostimulation of wound healing: bioimpedance measurements support histology.

Laser biostimulation in medicine has become widespread supporting the idea of therapeutic effects of photobiomodulation in biological tissues. The aim of this study was to investigate the biostimulation effect of laser irradiation on healing of cutaneous skin wounds, in vivo, by means of bioimpedance measurements and histological examinations. Cutaneous skin wounds on rats were subjected to 635 nm diode laser irradiations at two energy densities of 1 and 3 J/cm2 separately. Changes in the electrical properties of the wound sites were examined with multi-frequency electrical impedance measurements performed on the 3rd, 7th, 10th, and 14th days following the wounding. Tissue samples were both morphologically and histologically examined to determine the relationship between electrical properties and structure of tissues during healing. Laser irradiations of both energy densities stimulated the wound healing process. In particular, laser irradiation of lower energy density had more evidence especially for the first days of healing process. On the 7th day of healing, 3 J/cm2 laser-irradiated tissues had significantly smaller wound areas compared to non-irradiated wounds (p < 0.05). The electrical impedance results supported the idea of laser biostimulation on healing of cutaneous skin wounds. Thus, bioimpedance measurements may be considered as a non-invasive supplementary method for following the healing process of laser-irradiated tissues.

Antibacterial photodynamic therapy with 808-nm laser and indocyanine green on abrasion wound models.

Infections with pathogens could cause serious health problems, such as septicemia and subsequent death. Some of these deaths are caused by nosocomial, chronic, or burn-related wound infections. Photodynamic therapy (PDT) can be useful for the treatment of these infections. Our aim was to investigate the antibacterial effect of indocyanine green (ICG) and 808-nm laser on a rat abrasion wound model infected with the multidrug resistant Staphylococcus aureus strain. Abrasion wounds were infected with a multidrug resistant clinical isolate of S. aureus. ICG concentrations of 500, 1000, and 2000 µg∕ml were applied with a 450 J∕cm2 energy dose. Temperature change was monitored by a thermocouple system. The remaining bacterial burden was determined by the serial dilution method after each application. Wounds were observed for 11 days posttreatment. The recovery process was assessed macroscopically. Tissue samples were also examined histologically by hematoxylin­eosin staining. Around a 90% reduction in bacterial burden was observed after applications. In positive control groups (ICG-only and laser-only groups), there was no significant reduction. The applied energy dose did not cause any thermal damage to the target tissue or host environment. Results showed that ICG together with a 808-nm laser might be a promising antibacterial method to eliminate infections in animals and accelerate the wound-healing process.