The preferential absorption of photon energy by hemoglobin, oxyhemoglobin and water at specific wavelengths (400 nm, 560-580 nm, 800-980 nm, 1064 nm) allows the use of laser radiation for the treatment of tumors and vascular lesions. Absorption of light energy by oxyhemoglobin at a wavelength of 1060 nm creates thermal energy, allowing to selectively damaged blood vessels with minimal damage to surrounding tissues. In this paper, were developed laser irradiation regimes to selective damage the tumor vessels using a semiconductor laser «Lakhta-Milon» at wavelength of 1060 nm with maximum power 20 W and pulse duration 10-50 ms. The calculations were based on the threshold for thermal vessels damage with various vessels sizes: less 8 μm, 10-30 μm, over 30-100 μm. Histological studies of carcinoid tumor after irradiation revealed that thermal damage of tumor vessels may be localized under pulsed irradiation without causing thermal tissue necrosis. The pulse irradiation modes developed in this work have potential applications in the method of laser airways recanalization for tumoral stenosis in therapeutic bronchoscopy.
The goal of this study was to assess the ability of singlet oxygen generated at photodynamic treatment using different irradiation modes to inhibit the enzyme TAQ polymerase activity. Experimentally were determined the laser irradiation dose and the singlet oxygen concentration that results to complete inhibition of TAQ polymerase activity. The results show that using pulse mode irradiation is 1.5x more efficient then continuous wave. TAQ polymerase damage was also assessed by fluorescence spectrometry — tryptophan residues fluorescence is decreased if damaged by singlet oxygen during photodynamic treatment. It was observed that on doses, where TAQ polymerase looses its enzymatic activity the fluorescence decreases only by 7%. The fluorescence decrement of tryptophan correlates with damage to the enzyme.
In this present study we investigate the Radachlorin photosensitizer accumulation in K562 cells and Hela cells and determined the cell viability after PDT. Using the macroscopic singlet oxygen modeling and cellular photosensitizer concentration the singlet oxygen threshold doses for K562 cells and Hela cells were calculated.
Photodynamic therapy (PDT) is a clinically approved treatment that can exhibit onsite cytotoxic activity toward tumor cells. One of the main factors limiting PDT efficiency is tissue hypoxia derived from photodynamic action. PDT with pulse mode irradiation at the same peak fluence rates as in continuous wave (CW) mode and with appropriate irradiation parameters could be more effective in the potency of <sup>1</sup>O<sub>2</sub> generation and the cytotoxic effect enhancement by tissue reoxygenation. In this study, we demonstrated theoretically that the main parameter of pulse mode irradiation is the intermittency factor, which makes it possible to maintain the intended <sup>3</sup>O<sub>2</sub> concentration and to regulate the efficiency of <sup>1</sup>O<sub>2</sub> generation. We also showed experimentally that photodynamic treatment with pulse mode irradiation has congruent cytotoxicity to CW mode but induces preferable cell apoptosis. We assume that not only is cumulative 1O2 concentration is important in photodynamic cytotoxicity, but so is the temporal distribution of <sup>1</sup>O<sub>2</sub> generation, which determines the types of cell death.