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.

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.

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.

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.

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.

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.

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.

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.

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.

Effects of early and delayed laser application on nerve regeneration.

The aim of this study is to analyze the differences between early and delayed use of low-level laser therapy (LLLT) in functional and morphological recovery of the peripheral nerve. Thirty male Wistar rats were divided into three groups after the sciatic nerve was crushed: (1) control group without laser treatment, (2) early group with laser treatment started immediately after surgery and lasted 14 days, and (3) delayed group with laser treatment starting on the postoperative day 7 and lasted until day 21. A 650-nm diode laser (model: DH650-24-3(5), Huanic, China) with an output power of 25 mW exposed transcutaneously at three equidistant points on the surgical mark corresponding to the crushed nerve. The length of the laser application was calculated as 57 s to satisfy approximately 10 J/cm(2). A Sciatic Functional Index (SFI) was used to evaluate functional improvement in groups at pre- and post-surgery (on days 7, 14, and 21). Compound action potential (CAP) was measured after the sacrifice and histological examination was performed for all groups. SFI results showed that there was no significant difference between groups at different days (p > 0.05). On the other hand, the latency of CAP decreased significantly (p < 0.05) in the delayed group. Histological examination confirmed that the number of mononuclear cells was lower (p < 0.05) in both early and delayed groups. In conclusion, results supported the hypothesis that LLLT could accelerate the rate of recovery of injured peripheral nerves in this animal model. Though both laser groups had positive outcomes, delayed group showed better recovery.

Tm:fiber laser ablation with real-time temperature monitoring for minimizing collateral thermal damage: ex vivo dosimetry for ovine brain.

BACKGROUND AND OBJECTIVE: The thermal damage of the surrounding tissue can be an unwanted result of continuous-wave laser irradiations. In order to propose an effective alternative to conventional surgical techniques, photothermal damage must be taken under control by a detailed dose study. Real-time temperature monitoring can be also an effective way to get rid of these negative effects. The aim of the present study is to investigate the potential of a new laser-thermoprobe, which consists of a continuous-wave 1,940-nm Tm:fiber laser and a thermocouple measurement system for brain surgery in an ex vivo study. STUDY DESIGN/MATERIALS AND METHODS: A laser-thermoprobe was designed for using the near-by tissue temperature as a real-time reference for the applicator. Fresh lamb brain tissues were used for experiments. 320 laser shots were performed on both cortical and subcortical tissue. RESULTS: The relationship between laser parameters, temperature changes, and ablation (removal of tissue) efficiency was determined. The correlation between rate of temperature change and ablation efficiency was calculated. CONCLUSION: Laser-thermoprobe leads us to understand the basic laser-tissue interaction mechanism in a very cheap and easy way, without making a change in the experimental design. It was also shown that the ablation and coagulation (thermally irreversible damage) diameters could be predicted, and carbonization can be avoided by temperature monitoring.

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.

Ceramic bracket debonding with ytterbium fiber laser.

Since the early 1990 s, lasers have been used experimentally for debonding ceramic brackets. Lasers reduce the required debonding force and risk of enamel damage. However, the thermal effect during the laser radiation on dental tissues can cause undesirable results. The aim of this study is to develop a laser debonding technique for ceramic brackets that is better than mechanical debonding and also to minimize the side-effects of laser applications. A new fiber laser (1,070-nm ytterbium fiber laser) was tested, debonding procedure was quantified with a universal testing machine, and intrapulpal temperature was monitored for limiting the injury or pain. Experiments were performed in two sections according to the type of lasing mode: continuous wave (CW) and modulated mode. In continuous wave (CW) mode, a laser was applied on samples with different constant power levels continuously. In the second set of experiments, brackets were irradiated in modulated mode, in which the laser energy was delivered with on-and-off cycles. Laser power and duty cycles were adjusted by controlling the current, which was set to 4.99 A of current for 18 W of emission. Debonding force, debonding time, and work done by a universal testing machine were all significantly decreased for both modalities of laser irradiation compared to the control group. When laser parameters were set to proper doses, a 50% of reduction in required load for debonding and a three-fold decrease in debonding time were observed. Intrapulpal temperature changes were below the accepted threshold value (5.5°C) until the level of 3.5 W of laser power in continuous wave mode. During debonding, the work done by the universal testing machine is decreased up to five times by irradiation. Parameters were compared for both modes of operations and it was concluded that modulated mode laser application (Group 300/900) provided faster and easier debonding with less temperature change.

Development of a thulium (Tm:YAP) laser system for brain tissue ablation.

In this study, a thulium (Tm:YAP) laser system was developed for brain surgery applications. As the Tm:YAP laser is a continuous-wave laser delivered via silica fibers, it would have great potential for stereotaxic neurosurgery with highest local absorption in the IR region. The laser system developed in this study allowed the user to set the power level, exposure time, and modulation parameters (pulse width and on-off cycles). The Tm:YAP laser beam (200-600 mW, 69-208 W/cm(2)) was delivered from a distance of 2 mm to cortical and subcortical regions of ex-vivo Wistar rat brain tissue samples via a 200-µm-core optical fiber. The system performance, dosimetry study, and ablation characteristics of the Tm:YAP laser were tested at different power levels by maximizing the therapeutic effects and minimizing unwanted thermal side-effects. The coagulation and ablation diameters were measured under microscope. The maximum ablation efficiency (100 × ablation diameter/coagulation diameter) was obtained when the Tm:YAP laser system was operated at 200 mW for 10 s. At this laser dose, the ablation efficiency was found to be 71.4% and 58.7% for cortical and subcortical regions, respectively. The fiber-coupled Tm:YAP laser system in hence proposed for the delivery of photothermal therapies in medical applications.

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.

In vivo comparison of near infrared lasers for skin welding.

The skin closure abilities of near infrared lasers and suturing were compared by histological examination and mechanical tensile tests during a 21-day healing period. One-centimeter incisions on the dorsal skin of Wistar rats were treated by one of the closing techniques: (a) soldering, using an 809 nm diode laser (0.5 W, 5 s) with 25% bovine serum albumin (BSA) and 2.5 mg/ml indocyanine green (ICG); (b) direct welding with a 980 nm diode laser (0.5 W, 5 s); (c) direct welding with a 1,070 nm fiber laser (0.5 W, 5 s); (d) suturing. Six spots (79.61 J/cm(2) for each spot) were applied through the incisions. Healing was inspected on the 1st, 4th, 7th, 14th, and 21st post-operative days. The closure index (CI), thermally altered area (TAA), granulation area (GA) and epidermal thickness (ET) were determined by histological examination. Tensile tests were performed at a 5 mm/min crosshead speed up to the first opening along the incision. Immediate superficial closure with high CI values was found for the laser-irradiated incisions at the early phase of recovery. Clear welds without thermal damage were observed for the group irradiated at 1,070 nm. For the sutured group, the incisions remained unclosed for the first day, and openings through the incision were observed. At the end of the 21-day recovery period, no differences between experimental groups were observed in terms of the CI, GA and ET values. However, the tensile strength of the groups irradiated at 980 nm and 1,070 nm was found to be higher than that of the sutured incisions. The laser welding techniques were found to be reliable in terms of immediate and mechanically strong closure compared with suturing. Of them, 1,070 nm laser welding yielded noticeably stronger bonds, with minimal scarring at the end of the 21-days of recovery.

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 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.