Ozgur Tabakoglu

Photo-toxic effects of 809-nm diode laser and indocyanine green on MDA-MB231 breast cancer cells.

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.

Low-power skin welding by thulium (Tm:YAP) laser at 1980-nm

Laser skin welding is an invasive method of bonding skin tissues by temperature increase due to laser energy [1]. 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-µm lasers are also considered to be in the “eye-safe” region, which makes them more suitable for clinical applications [2].

Skin tissue ablation by thulium (Tm:YAP) laser at 1980nm

The 1.9-µm lasers can be used in an efficient way in superficial tissue ablation with minimal coagulation depth [1]. Among the possible candidates, Tm:YAP is one of the most suitable candidates due to the availability of high-quality host crystals and possibility of efficient laser performance near 2 µm. In addition, Tm:YAP lasers offer easy pumping with 800-nm diode lasers, benefit from crystal durability at high powers, can be coupled to conventional fibers for invasive operations, and operate in the eye-safe region [2]. In this study, a Tm:YAP laser system with power output up to 1 W and emission wavelength of 1980 nm was established and its ablation parameters on Wistar rat skin tissues were analyzed to determine the optimum skin ablation dose.

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.

Fluence of Thulium laser system in skin ablation

Tm:YAP laser system at power levels up to 1.2 W at 1980 nm was established in both continuous-wave and modulated modes of operation. The fluence effect of the laser system for skin ablation was analyzed by histology analysis with Wistar rat skin tissues. Thermally altered length, thermally altered area, ablation area, and ablation depth parameters were measured on histology images of skin samples just after the laser operation and after four-day healing period. Continuous-wave mode of operation provided higher thermal effects on the skin samples. Lower fluence levels were found for efficient ablation effect.

Modulated and continuous-wave operations of Thulium (Tm:YAP) laser in tissue welding

Modulated and continuous-wave (CW) operations of Thulium (Tm:YAP) laser are compared for tissue welding by histology analysis study. Higher thermal effects but better closure on skin samples is obtained for CW mode.

Welding by Thulium laser system: Tensile strength tests

Laser tissue welding tensile strength tests were performed on Wistar rat skin by using diode-pumped and fiber-coupled Thulium (Tm:YAP) laser system emitting at 1980-nm, which is developed for medical applications. The success of laser tissue welding at 100 mW and 5 s in both continuous wave and modulated operation modes were compared with the results by suture technique. Tm:YAP laser at 100 mW, 5 second (34,66 W/cm2) was found successful for tissue welding studies.

Investigation of different modalities of laser delivery for skin welding

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-400ms) and low power (0.5W–5s). Throughout 21-day healing period, incision were removed from dorsal skin of Wistar rats under anesthesia on control days (1st, 4th, 7th, 14th and 21st) for histology and mechanical tests. Closure index, thermally altered areas, epidermal thickness and granulation areas of H&E stained samples were calculated. Breaking point of incisions during mechanical tensile test that has 5 mm / min crosshead speed was noted. In this study, effects of high (6W–400ms) and low power (0.5W–5s) applications of same energy level (2.5J) 980-nm diode laser irradiation on skin tissue was shown.