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 PDT 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.
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 μg/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°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.
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.
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.
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.
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 wavelength is still the subject of debate. Thermal shrinkage of collagenous tissue
during EVLA plays a significant role in the early and late results of the treatment. The aim of this study is to compare the
efficacy of 980 and 1940-nm laser wavelengths in the treatment of varicose veins. In this study, 980 and 1940-nm lasers
at different power settings (8/10W for 980-nm, 2/3W for 1940-nm) were used to irradiate stripped human veins. The
most prominent contraction and narrowing in outer and inner diameter were observed with the 1940-nm at 2W,
following 980-nm at 8W, 1940-nm at 3W and finally 980-nm at 10W. The minimum carbonization was observed with
the 1940-nm at 2W. As a conclusion, 1940-nm Tm-fiber laser which has a significant effect in the management of
varicose veins due to more selective energy absorption in water and consequently in the vein is a promising method in
the management of varicose veins.
Our aim is to explore the welding capabilities of a thulium (Tm:YAP) laser in modulated and continuous-wave (CW) modes of operation. The Tm:YAP laser system developed for this study includes a Tm:YAP laser resonator, diode laser driver, water chiller, modulation controller unit, and acquisition/control software. Full-thickness incisions on Wistar rat skin were welded by the Tm:YAP laser system at 100 mW and 5 s in both modulated and CW modes of operation (34.66 W/cm2). The skin samples were examined during a 21-day healing period by histology and tensile tests. The results were compared with the samples closed by conventional suture technique. For the laser groups, immediate closure at the surface layers of the incisions was observed. Full closures were observed for both modulated and CW modes of operation at day 4. The tensile forces for both modulated and CW modes of operation were found to be significantly higher than the values found by conventional suture technique. The 1980-nm Tm:YAP laser system operating in both modulated and CW modes maximizes the therapeutic effect while minimizing undesired side effects of laser tissue welding. Hence, it is a potentially important alternative tool to the conventional suturing technique.
The use of endovenous laser treatment for varicose veins has been increasing in recent years. It is a safer technique than surgical vein stripping. Its complications (e.g. bruising, pain) are less than the complications of surgical vein stripping. But best parameters such as optimum wavelength, power, and application duration are still under investigation to clarify uncertainties about this technique. To prevent its complications and improve its clinical outcomes, the exact mechanism of it has to be known. The aim of this study is to investigate the effect of different laser wavelengths on endovenous laser therapy. In this study 980-nm diode laser and 1070-nm fiber laser were used. Human veins were irradiated with 980-nm and 1070-nm lasers at 8 W and 10 W to find the optimal power and wavelength. After laser application, remarkable
shrinkage was observed. Inner and outer diameters of the veins also narrowed for both of the laser types. 10 W of 980-nm laser application led to better shrinkage results.
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