Murat Gulsoy
Bogazici University, Institute of Biomedical Engineering, Faculty Member
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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... more
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. 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 second exposure times and different PS/Potentiator concentrations. The biofilm formation capability of E.faecalis was observed by calculating Optical Density (OD) of samples 24,48, and 72 hours post-PDI treatment. Scanning Electron Microscopy (SEM) was used as a qualitative measure of bacterial biofilm growth. More than 4 LOGS of photokilling was obtained for experimental groups with the highest PS/KI concentrations at 1...
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... more
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 propa...
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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.... more
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/cm(2) 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 3r...
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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... more
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/cm(2), at three different energy densities (0.5, 1, and 2 J/cm(2) 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 an...
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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.... more
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 ma...
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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... more
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/cm(2). 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.
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Research Interests: Biomedical Engineering, Wound Healing, Near Infrared, Fiber Laser, Laser Welding, and 15 moreAnimals, Male, Skin, Cattle, Granulation Tissue, Rats, Diode Laser, Indexation, Bovine Serum Albumin, Tensile Strength, Infrared Rays, Tensile Test, Experimental Group, Indocyanine green, and Suture techniques
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... more
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/cm(2) 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/cm(2) 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.
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In this study, tissue welding with 980-nm laser system, which is first-time in the literature, was performed. Hence, a preliminary study was done to determine optimal parameters for further studies. 1 cm long incisions done on the Wistar... more
In this study, tissue welding with 980-nm laser system, which is first-time in the literature, was performed. Hence, a preliminary study was done to determine optimal parameters for further studies. 1 cm long incisions done on the Wistar rat's dorsal skin were welded. Tissue ...
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Removal of brain tissue by 1940-nm Tm-Fiber laser. [Proceedings of SPIE 7901, 79010L (2011)]. Burcu Tunç, Murat Gülsoy. Abstract. The aim of the study was to investigate the thermal effects of the 1940-nm Tm-fiber laser on the dead brain... more
Removal of brain tissue by 1940-nm Tm-Fiber laser. [Proceedings of SPIE 7901, 79010L (2011)]. Burcu Tunç, Murat Gülsoy. Abstract. The aim of the study was to investigate the thermal effects of the 1940-nm Tm-fiber laser on the dead brain tissue. ...
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The aim of this study was to develop a microcontroller based surgical diode laser system and to test it at two different modes (continuous [CW] and modulated) in vitro on lamb liver tissue. In laser surgery, depending on the properties of... more
The aim of this study was to develop a microcontroller based surgical diode laser system and to test it at two different modes (continuous [CW] and modulated) in vitro on lamb liver tissue. In laser surgery, depending on the properties of laser source (wavelength, power, application time, and mode of operation), the effects observed on the tissue may change from carbonization to hyperthermia. The aim is to remove the target tissue without giving any thermal damage to the surrounding tissue. Carbonization should be avoided, thus controlling the mode of operation is very crucial. The system consisted of a microcontroller based control unit, 980-nm high-power diode laser source, and fiber delivery unit. This system has the capability of delivering different modes of laser energy to the target tissue ranging from CW to 20-Hz modulated beams. The surgical diode laser system was tested on liver tissue in vitro. Efficiency of laser-tissue interaction was quantified in terms of thermal alteration per unit energy and corresponding carbonization level. Modulated mode resulted in larger coagulated area with minimum carbonizations. Carbonized area/thermally altered area (CarbA/TAA) ratio for CW mode of operation at 16 J is 0.35; however, this ratio was found to be 0.05 at modulated mode, when even 10 times higher energy (160 J) was delivered to the target tissue. Results emphasized the significance of mode of operation as well as the other laser parameters. Modulated mode was found to be a promising regime for safer laser surgery.
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To avoid the side effects of the suture usage by welding amniotic membrane (AM) to contact lens (CL) with laser. AM was taken from pregnant women and cleaned from blood clots with sterile phosphate-buffered physiological saline solution... more
To avoid the side effects of the suture usage by welding amniotic membrane (AM) to contact lens (CL) with laser. AM was taken from pregnant women and cleaned from blood clots with sterile phosphate-buffered physiological saline solution which included antibiotics. Stromal side of the AM was spread inside of the CL and it was welded to CL by 1470 nm diode laser. 600 µm diameter fiber tip of the laser was contacted with the epithelial side of the AM from 4 separate points. After welding excess amniotic membrane around the CL was cut with a scalpel. Stromal side of the AM was spread inside of the CL and then with laser fiber, different power levels and exposure times were applied on the epithelium of AM and 340 mW for seven seconds was found optimal. CL and AM attached with the spot welding effect in 4 points by touching fiber tip. CL-AM welded complex did not separated from each other while holding AM that extend beyond the CL with the help of two forceps. As a conclusion, it was aime...
Research Interests: Ophthalmology and Welding
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The use of a laser in surgical procedures involving the soft tissues is advantageous due to its sterile and hemostatic nature. Several different lasers are in use for intraoral soft tissue surgery; however, small, efficient, and... more
The use of a laser in surgical procedures involving the soft tissues is advantageous due to its sterile and hemostatic nature. Several different lasers are in use for intraoral soft tissue surgery; however, small, efficient, and fibre-coupled lasers are favoured due to the tightly confined nature of the intraoral environment. This study proposes the use of a 1940-nm thulium fibre laser (Tm:fibre laser) for intraoral soft tissue procedures. Its thermal effects when used to make incisions were investigated. This laser was chosen due to its output wavelength, which is absorbed well by water in biological tissues. Lamb tongues were used in the experiments. The laser was coupled to a 600-μm silica fibre and incisions were made in contact mode with a continuous wave. The extent of ablation and coagulation produced were measured at three different speeds, powers, and numbers of passes. The thermal effects of laser power, movement speed, and number of passes on incision depth and ablation e...
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ABSTRACT
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We present experimental and theoretical investigations of the temperature dependence of self-pulsation in CD laser diodes. We use a rate equation model to predict the device dynamic behavior over a large temperature range and identify the... more
We present experimental and theoretical investigations of the temperature dependence of self-pulsation in CD laser diodes. We use a rate equation model to predict the device dynamic behavior over a large temperature range and identify the role of carrier diffusion. We show experimentally and by calculating that the temperature dependence of the threshold current is driven by the carrier diffusion--particularly at low temperature. We experimentally show that for several temperatures the self-pulsation variation with respect to normalized bias current is highly linear. These results call into question whether pulsations in CD laser structures are undamped relaxation oscillations. Our results also suggest that the highly temperature dependent carrier diffusion does not play a first order role in CD laser diode self- pulsation.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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... more
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 hematoxylin–eosin 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.
Research Interests: Biomedical Engineering, Wound Healing, Biomedical Optics, Lasers, Female, and 12 moreAnimals, Skin, Optical physics, Anti-Bacterial Agents, Optometry and Ophthalmology, Rats, Photochemotherapy, Wistar Rats, Skin Temperature, Methicillin Resistant Staphylococcus Aureus, Wound infection, and Indocyanine green
Endovenous Laser Ablation (EVLA) has become a popular minimally invasive alternative to stripping in the treatment of saphenous vein reflux. Several wavelengths have been proposed; of which 810, 940 and 980-nm are the most commonly used.... more
Endovenous Laser Ablation (EVLA) has become a popular minimally invasive alternative to stripping in the treatment of saphenous vein reflux. Several wavelengths have been proposed; of which 810, 940 and 980-nm are the most commonly used. However, the most appropriate ...
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Laser tissue welding is a potential medical treatment method especially on closing cuts implemented during any kind of surgery. Photothermal effects of laser on tissue should be quantified in order to determine optimal dosimetry... more
Laser tissue welding is a potential medical treatment method especially on closing cuts implemented during any kind of surgery. Photothermal effects of laser on tissue should be quantified in order to determine optimal dosimetry parameters. Polarized light and phase contrast techniques reveal information about extend of thermal change over tissue occurred during laser welding application. Change in collagen structure in
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Laser skin welding is an invasive method of bonding skin tissues by temperature increase due to laser energy. In this study, a continuous-wave Tm:YAP laser at 1980 nm was designed as a versatile laser system for laser tissue welding. Due... more
Laser skin welding is an invasive method of bonding skin tissues by temperature increase due to laser energy. In this study, a continuous-wave Tm:YAP laser at 1980 nm was designed as a versatile laser system for laser tissue welding. Due to higher water absorption near 1980 nm, lower power levels of Tm:YAP lasers (compared to smaller wavelength lasers) are enough for tissue welding and no solder is necessary to increase the absorption effect. This decreases the operation time and adverse effects due to solders. 2-mum lasers are also considered to be in the "eye-safe" region, which makes them more suitable for clinical applications.
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In this study, tissue welding with 980-nm laser system, which is first-time in the literature, was performed. Hence, a preliminary study was done to determine optimal parameters for further studies. 1 cm long incisions done on the Wistar... more
In this study, tissue welding with 980-nm laser system, which is first-time in the literature, was performed. Hence, a preliminary study was done to determine optimal parameters for further studies. 1 cm long incisions done on the Wistar rat's dorsal skin were welded. Tissue welding with 980-nm wavelength depends on the degree of photothermal interaction. Thus, different power levels and exposure schedule were investigated. Dorsal sides of all animals were photographed from the date of surgery until they were sacrificed. The clinical examination - opening of wound and presence of infection - was noted. The rats did not show any abnormality on their health, behavior and nutrition manner. As a result, 980-nm diode laser was concluded to be a good candidate for tissue welding applications.
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Photodynamic therapy (PDT), due to its positive outcomes in clinical applications, easiness of practice and few side effects, is a good candidate for an efficient treatment of cancer. Indocyanine green (ICG), a water-soluble, anionic... more
Photodynamic therapy (PDT), due to its positive outcomes in clinical applications, easiness of practice and few side effects, is a good candidate for an efficient treatment of cancer. Indocyanine green (ICG), a water-soluble, anionic tricarbocyanine and non-toxic molecule is a promising photosensitive agent for PDT applications on tumor cells. ICG exhibits strong maximum absorption at around 805 nm which will be an advantage for its use in PDT; light at that wavelength can be used to treat deeper tumors. In this study the inhibitory growth effects of ICG-PDT on MDA-MB231 human breast cancer cells were investigated in a time course experiment. Cells were irradiated with a continuous wave diode laser (lambda=809 nm, 60 mW, 24 J cm(-2)). Cell viability was measured by MTT assay 0, 3, 6, 9, 12, 24 and 48h after light irradiation. The results showed that ICG-PDT application exerted its photo-oxidative effect on MDA-MB231 breast cancer cells immediately. Relative cell viability was determined throughout the 48h time course, and a consistent decrease was observed after ICG-PDT applications. In conclusion, ICG when used in combination with near-infrared light showed a very fast (within 3h) and persistent (up to 48h) photo-toxic effect on MDA-MB231 human breast cancer cells.
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ABSTRACT The emergence of antibiotic resistant bacteria causes significant increase in deaths due to wound infections around the world. Nowadays, it could be impossible to find appropriate antibiotics to treat some bacterial strains,... more
ABSTRACT The emergence of antibiotic resistant bacteria causes significant increase in deaths due to wound infections around the world. Nowadays, it could be impossible to find appropriate antibiotics to treat some bacterial strains, especially multidrug resistant types. The aim of this study is to use photodynamic therapy that destroys these kinds of bacteria with the interaction of Indocyanine green (ICG) and 808-nm diode laser. In this study, antibacterial Photodynamic Therapy technique that we call ICG-IR Laser PDT was applied on antibiotic-resistant strains of Staphylococcus aureus that infected two different types of wound model (excisional and abrasion wound model) in vivo. Wistar albino rats were used to create animal wound models. Excisional or abrasion wounds were formed on the dorsal skin of the rats. They were infected with Staphylococcus aureus. 300 mW and 500 mW of 808-nm diode laser were applied on the wounds for 30 minutes and 15 minutes of exposure duration, respectively. ICG concentrations applied topically were 500, 1000, 1500 and 2000 mu g/ml. Then the tissue was dissected properly and homogenized in buffer solution. From this solution, bacterial cell count was determined by serial dilution method. 1-2 log reduction in viable cell count was observed after these applications. The temperature increase in the tissue was between 6-8 degrees C during these applications. From these findings, it was understood that this method with 808-nm and ICG is promising but it must be improved by further dosimetry studies.
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ABSTRACT Photodynamic therapy (PDT) is a safe and alternative antimicrobial treatment that consists of a chemical agent, called photosensitizer, which can be activated by light of an appropriate wavelength to produce reactive oxygen... more
ABSTRACT Photodynamic therapy (PDT) is a safe and alternative antimicrobial treatment that consists of a chemical agent, called photosensitizer, which can be activated by light of an appropriate wavelength to produce reactive oxygen species (ROS). PDT can be used for photoinactivation of bacteria in an attempt to overcome the problem of bacterial multidrug resistance. In particular, it is an effective antimicrobial treatment against infected wounds that have antibiotic resistance and wound infections would otherwise lead to mortality and morbidity. The main purpose of this study was to demonstrate the importance of PDT dosimetry (light dose and concentration of photosensitizer). If the dosimetry of PDT was not optimized properly, photoinactivation of bacteria cannot be achieved and even worse biostimulation on pathogens could be observed. This study investigated whether there is a biostimulative effect due to free oxygen radicals of PDT when light dose and photosensitizer concentration are too low. In this study, the biostimulative effect on P. aeruginosa strain was observed instead of the PDT effect, when 84 J/cm2 of energy dose (809-nm diode laser) was applied with 20, 50, 100 and 150 μg/ml of ICG concentrations. The killing effect of PDT was observed with higher ICG concentrations, such as 200, 250 μg/ml of ICG. However the killing effect was not enough to destroy pathogen efficiently with these high concentrations of ICG.
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ABSTRACT The emergence of antibiotic resistant bacteria causes significant increase in deaths due to infections around the world. Nowadays, it could be impossible to find appropriate antibiotics to treat some bacterial strains, especially... more
ABSTRACT The emergence of antibiotic resistant bacteria causes significant increase in deaths due to infections around the world. Nowadays, it could be impossible to find appropriate antibiotics to treat some bacterial strains, especially multidrug resistant types. Therefore, there is an urgent need to develop new and safe treatment techniques for multidrug resistant bacteria associated morbidity and mortality. In this study, Photodynamic Therapy was used to destroy these kinds of bacteria with near infrared light and Indocyanine Green. Different wavelengths of lasers mostly in the visible spectrum have been investigated for Photodynamic Therapy; however near infrared lasers have been used in very few studies. The main motivation to test photodynamic therapy with near infrared light and indocyanine green is that the near infrared laser (around 800-nm) has more penetration depth in the biological tissue than the other lasers have. Therefore it is supposed that it will show more antibacterial effect. And also indocyanine green has a very low toxicity and an FDAapproved drug. This study investigated optimum parameters for PDT with 809-nm laser and Indocyanine green (ICG) to kill P. aeruginosa in vitro. We were able to optimize the laser power and ICG concentration to non-toxic levels and achieved 99% decrease in bacterial load with 252 J/cm2 laser light and 125 μg/ml ICG concentration. This study demonstrates that PDT with near-infrared light and ICG can be powerful and non-hazardous treatment strategy for untreatable pathogens.
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ABSTRACT Photodynamic therapy (PDT) is an alternative antimicrobial treatment method. Different wavelengths of light sources mostly in the visible spectrum have been investigated for antimicrobial Photodynamic Therapy. Even though the... more
ABSTRACT Photodynamic therapy (PDT) is an alternative antimicrobial treatment method. Different wavelengths of light sources mostly in the visible spectrum have been investigated for antimicrobial Photodynamic Therapy. Even though the wavelengths in near infrared spectrum have the advantage of higher penetration capability in biological tissue, they have not been preferred for PDT because of their possible photothermal effect in biological tissues. In our previous studies, the desired PDT effect was achieved with 809-nm diode laser and indocyanine green (ICG) on drug resistant pathogens. In this study, it was aimed to investigate the influence of different output powers during PDT applications with 809-nm diode laser to clarify whether there is a photothermal effect to kill the pathogens or only the photochemical effect of photodynamic therapy. 4 different output powers (500 mW, 745 mW, 1000 mW, 1500 mW) were examined in Laseronly and PDT groups of P. aeruginosa ATCC 27853 in vitro. In the PDT groups, a non-phototoxic ICG concentration (50 μl/ml) has been chosen to eliminate the toxic effect of ICG and evaluate only the thermal effect of laser. Applied energy dose (252 J/cm2) was kept constant by increasing the exposure duration (300, 240, 180 and 120 seconds respectively). These output powers in Laser-only or PDT groups did not seem to cause photothermal effect. There was not any significant decrease or increase on bacterial load after the applications with different output powers. Higher output powers in PDT groups with the same ICG concentration did not cause any higher killing effect.
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In this study, photon propagation is simulated by Monte Carlo algorithm, using absorption and scattering coefficients of histologically different human tissues (bone, brain white matter, liver, prostate, myocardium); fluence distribution... more
In this study, photon propagation is simulated by Monte Carlo algorithm, using absorption and scattering coefficients of histologically different human tissues (bone, brain white matter, liver, prostate, myocardium); fluence distribution is calculated by the convolved data, and comparisons are reported
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ABSTRACT The aim of the study was to find a relationship between laser power, exposure time, ablation efficiency and temperature increase during laser brain ablation by Thulium fiber laser. The thermal effects of the 1940-nm Tm-fiber... more
ABSTRACT The aim of the study was to find a relationship between laser power, exposure time, ablation efficiency and temperature increase during laser brain ablation by Thulium fiber laser. The thermal effects of the 1940-nm Tm-fiber laser on the brain tissue was also investigated in terms of ablation efficiency. These experiments are very important in order to model temperature increase-ablation efficiency during lasing with different power and exposure time. 4-5 mm coronal sections were taken from lamb brains. Laser was applied at cortical and subcortical tissue with 0-0.1 mm distance, in both continuous and pulsed modes with 400 mW and 600 mW which were chosen by a predosimetric study. In continuous and pulse mode doses were changed with exposure time and on-off cycle respectively, in order to achive the tissue to absorb same energy. During lasing temperature increases were recorded by a thermoprobe (thermoprobe is a system which a 300 micrometer fiber was embedded into a thermocouple). The radius of ablation and coagulation for each laser application was recorded by a microscope. By calculating ablation efficiency (100xablation/calculation radius) the appropriate laser doses were determined for both cortical and subcortical tissue. The maximum ablation efficiency for cortical and subcortical tissue in both continous and pulsed mode was found for 600 mW. Ablation efficiencies for continuous mode was superior than the pulsed mode for all laser doses which were studied. Temperature increases showed a significant differences for continuous and pulse mode operating systems and effect the ablation efficiencies.
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ABSTRACT Orthodontics is a branch of dentistry which related in correction of maloccculsions Bracket are small attachments and the part of the braces that attach to each tooth, After treatment they usually debond by conventional methods... more
ABSTRACT Orthodontics is a branch of dentistry which related in correction of maloccculsions Bracket are small attachments and the part of the braces that attach to each tooth, After treatment they usually debond by conventional methods but this can cause mechanical damage on the enamel. Using lasers in debonding is a new kind of research area in debonding of ceramic brackets. Using lasers while debonding reduces the force of the bonds in adhesive resin that application easier and reduces the risk of enamel damage. However, the heat produced by some lasers can damage the tooth pulp. 5.5°C is accepted as the threshold value for difference in intrapulpal temperature. In this study 1940-nm Thulium Fiber Laser in CW (Continious mode) applied on polycrystalline ceramic brackets which are bonded on bovine teeth by Bis-GMA type adhesive resin. Breaking time and the load at the breaking point were measured. During that time, the changes in intrapulpal temperatures were recorded by a K-type Thermocouple. Laser parameters are determined such that intrapulpal temperature changes below the threshold value.
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980-nm laser skin welding studies have been performed since 2005 by our group and promising results were obtained. As a continuation of that study, in this current research, it was aimed to compare 2 different application methods by... more
980-nm laser skin welding studies have been performed since 2005 by our group and promising results were obtained. As a continuation of that study, in this current research, it was aimed to compare 2 different application methods by histological and mechanical tests. 1-cm long, 6 incisions were welded with 980-nm diode laser by two different applications: high power (6W-400 ms)
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... References [1] Corner, D. T; Comer DJ; Gonzalez, IR: A high frequency integrable band-pass filter configuration. ... 947-955. [4] Cam, U.; Cicekoglu, O.; Kuntman, H.: A new FTFN-based single input three output (SITO) current-mode... more
... References [1] Corner, D. T; Comer DJ; Gonzalez, IR: A high frequency integrable band-pass filter configuration. ... 947-955. [4] Cam, U.; Cicekoglu, O.; Kuntman, H.: A new FTFN-based single input three output (SITO) current-mode filter, Microelectronics Journal, vol. 30, no. ...