Nermin Topaloglu

Antimicrobial Photodynamic Therapy of Resistant Bacterial Strains by Indocyanine Green and 809-nm Diode Laser

OBJECTIVE This research aimed to investigate the bactericidal effect of indocyanine green (ICG) with 809-diode laser on wild type and resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa in vitro. BACKGROUND DATA ICG and 809 nm combination can be a powerful tool for the treatment of wound-infecting, antibiotic-resistant bacteria. METHODS The effect of ICG and 809 nm laser light on wild type and resistant strains of S. aureus and P. aeruginosa was examined in vitro. ICG concentrations and laser doses were initially optimized for wild type S. aureus and P. aeruginosa. After determining the most effective ICG concentrations with specified light dose, they were applied on resistant strains. Viable bacterial cells were counted by serial dilution method. RESULTS Photodynamic therapy (PDT) with ICG was totally efficient to kill all of these bacterial strains, and light/ICG alone did not cause any lethal effect on any of the strains. Optimum ICG laser doses varied with respect to the bacteria type: 84 J/cm(2) of light dose with 6 μg/mL of ICG concentration caused more than 95% killing of wild type S. aureus strains. The same bactericidal effect was achieved with a lower amount of ICG (4 μg/mL) on resistant strain S. aureus. Optimum parameters for 99% killing of wild type P. aeruginosa were 125 μg/mL ICG and 252 J/cm(2) of light dose. Similarly, their bactericidal effect was stronger on resistant strain; 100 μg/mL ICG with 252 J/cm(2) was enough to cause a 99% decrease in viable cells. CONCLUSIONS The combination of ICG and 809 nm laser light was found as an effective antibacterial method to destroy antibiotic-resistant strains of gram-positive and gram-negative bacteria.

The effect of irradiance level in 980-nm diode laser skin welding.

OBJECTIVE Current research aimed to investigate the role of irradiance in skin laser welding. BACKGROUND DATA Optical and thermal responses of tissue to infrared irradiation are highly dependent on both wavelength and tissue type. The desired effect on tissue is created by proper selection of laser power, application time, and spot size. METHODS Full-thickness skin incisions on Wistar rat dorsum were welded with 980-nm diode laser application. Two irradiance levels (200 and 16.6 W/cm(2)) were applied with high (6 W, 400 ms) and low (0.5 W, 5 s) powers of laser with the same spot size (0.03 cm(2)). Subjects were monitored throughout a 21-day recovery period; incisions were sampled for histology and mechanical tests on particular control days (1, 4, 7, 14, and 21). Closure index, thermally altered areas, epidermal thickness, and granulation areas of H&E (eosin) stained samples were calculated. The breaking point during a mechanical tensile test that ran at 5-mm/min crosshead speed was recorded. RESULTS In the suture group, there was no closure 24 h postoperation. For laser groups, immediate closure at the surface layers of the incisions was observed: Almost half-thickness (from surface to deep dermis) welding was achieved. Granulation tissue level and epidermal thickness level for all groups were similar on postoperative day 21. CONCLUSION The laser welding technique was found reliable in terms of immediate and mechanically strong closure compared with suture. Low irradiance of a 980-nm laser (16.6 W/cm(2)) yielded noticeably stronger bonds at the end of 21 days of recovery, as well as minimal thermal damage.

Modulated and continuous-wave operations of low-power thulium "Tm:YAP… laser in tissue welding

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 Wcm(2)). 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.

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

Abstract. 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 role of reactive oxygen species in the antibacterial photodynamic treatment: photoinactivation vs proliferation

Low‐level light/low concentration of reactive oxygen species (ROS) may trigger some biochemical pathways that lead to cell proliferation. Thus, there is a risk of stimulation of bacterial cell proliferation during photodynamic therapy (PDT). In this study, PDT with different doses of 809‐nm laser and indocyanine green (ICG) was investigated in vitro for safe bactericidal application. The combined effect of laser doses with ICG concentrations were examined on Pseudomonas aeruginosa in vitro. Data showed that low energy dose and ICG concentration caused bacterial cell proliferation. When these parameters were increased high enough, photoinactivation of the bacteria was achieved. Energy dose and photosensitizer concentration ranges at which proliferation, cell death or neither observed were determined. Furthermore, l‐histidine was used as a scavenger of ROS to block the mechanism of biostimulation and cell killing. It inhibited proliferation when laser dose and ICG concentrations were low. It also inhibited cell killing when dose and concentration were high. Data showed that mechanisms of proliferation and cell killing depend on the amount of ROS and antibacterial photodynamic treatment have serious biostimulative risk. Effective range might need to be determined before any therapeutic usage. The risk seems to exist specifically at lower energy doses and photosensitizer concentrations.

Influence of different output powers on the efficacy of photodynamic therapy with 809-nm diode laser and indocyanine green

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.

Comparison of 980-nm and 1070-nm in endovenous laser treatment

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.

Comparison of 980-nm and 1070-nm in endovenous laser treatment (EVLT)

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.

Optimization of parameters in photodynamic therapy to kill p. aeruginosa with 809-nm diode laser and indocyanine green

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 with TM-fiber laser

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.