Alexander A. Stratonnikov

Absorption spectroscopy as a tool to control blood oxygen saturation during photodynamic therapy

The photodynamic therapy (PDT) is an effective method to treat cancer and other nononcological lesions by means of light action on photosensitizer in tissue. It is considered that destroying effect is mainly due to the formation of singlet oxygen resulting from the interaction of light excited photosensitizer with molecular oxygen (triplet state in the ground state). So the destroying effect will be proportional to the rate of singlet oxygen formation which is in turn depends on light intensity, photosensitizer concentration and molecular oxygen concentration. The present work deals with the investigation of blood oxygen saturation in microcircular vessels (SO2) during light irradiation in the PDT process. It has been observed that SO2 behavior strongly correlates with the light power density applied for PDT. The high power density resulted in sharp SO2 decrease. The connection of SO2 decrease with enhanced oxygen consumption rate and vessel destruction due to PDT is discussed.

Control of photosensitizer in tissue during photodynamic therapy by means of absorption spectroscopy

The data about absorption spectra properties of the photosensitized tumor tissues in vivo are very important for the evaluation photosensitizer concentration and influence of the chemical environment on photosensitizer properties in tissue. This information will help one in the appropriate choosing of irradiation light dose and wavelength in the photodynamic therapy (PDT) treatment. The interaction of photosensitizer with tumor tissue may change its absorption spectrum. Moreover the light irradiation during PDT treatment can also affect the photosensitizer chemical structure and hence change its absorption spectrum. The simple technique based on the measurement of reflection spectra by means of fiber optic spectrometer has been developed. This method allows one to evaluate the contribution to the tissue absorption properties due to the presence of photosensitizer in it. The absorption spectra of photosensitized normal and tumor tissues presented in this paper has been obtained during PDT sessions of head and neck tumors. The photosensitizer -- sulphonated aluminum phthalocyanine (Photosence) (NIOPIC, Russia) -- has been injected intravenously in doses 0.5 - 2 mg per kg of body weight. It has been observed that absorption properties of this photosensitizer are not changed significantly in tissue as compared to that of in solution. The absorption spectra widening and red shift (4 nm) has been noticed. The qualitative pharmocokinetic of photosensitizer based on absorption spectra measurements is presented.

Photosensitizer for PDT based on phosphonate phthalocyanine derivative

It is very important to develop new sensitizer which could be efficiently excited at wavelengths exceeding 685 nm where own tissue absorption can be neglected. We have synthesize water soluble phthalocyanine derivative having phosphonate groups as substituents in macrocycle. New sensitizer efficiently absorbs in spectral range 685 - 710 nm. It exhibits intense fluorescence in range 690 -720 nm. The photodynamic activity of new sensitizer is higher than in the case of sulfonated aluminum phthalocyanine.

Photobleaching of endogenous fluorochroms in tissues in vivo during laser irradiation

The photobleaching phenomenon has been previously first of all widely studied for exogenous photosensitizers applied in photodynamic therapy (PDT). The present paper deals with detailed investigation of photobleaching of endogenous fluorochroms in tissues in vivo during its laser irradiation at 532, 633 and 670 nm at different powers. The fluorescence decay curves during skin irradiation in vivo at these wavelengths have been obtained and analyzed. The similarity in bleaching behavior of endogenous fluorochroms and exogenous photosensitizers used in PDT gave us the reasons to imply the possible connection between native fluorochroms and low intensity laser therapy effects. The results obtained may be applied for tissue diagnostics and therapy control.

Photobleaching of photosensitizers applied for photodynamic therapy

It is well known that photosensitizers used for PDT are liable to photobleaching. This phenomenon should be taken into account when developing the appropriate tactics of treatment. The present paper deals with detailed investigation of photobleaching of two photosensitizers: ALA induced protoporphyrin IX (PPIX) and sulphonated aluminum phthalocyanines. The fluorescence decay curves during light irradiation in vivo and in vitro have been obtained and analyzed. The mathematical model taking into account both first and second order photobleaching as well as spatial inhomogeneity of light distribution in tissue is presented. The experimental data for fluorescence decay of ALA induced PPIX during light irradiation are fitted to this mode. As opposed to PPIX the photobleaching behavior for sulphonated aluminum phthalocyanines is rather complicated to be fitted by proposed mathematical mode. The fluorescence outburning and residual fluorescence for sulphonated aluminum phthalocyanines have been observe.d It has been shown that fluorescence maximum correlates with blood oxygen saturation decrease induced by PDT effect.

Simultaneous measurement of photosensitizer absorption and fluorescence in patients undergoing photodynamic therapy

This paper deals with photosensitizer quantification in patients undergoing photodynamic therapy. Both fluorescence and diffuse reflectance spectroscopy were applied to evaluate concentration of sulphonated aluminum phthalocyanine in different tissues. The mixtures of Intralipid, blood and photosensitizer with different concentrations were used as standard samples to solve the problem in question. While fluorescence method is more sensitive and more convenient to apply in clinics, the absorption technique may be applied to non fluorescent dyes and used to evaluate the shifts in adsorption peak position due to interaction of dye with tissues. Finally, the concentration dynamics of non fluorescent dye (cobalt phthalocyanine) in patients was obtained with the use of absorption method alone.

Influence of red laser irradiation on hemoglobin oxygen saturation and blood volume in human skin in vivo

The aim of the present work was to study the response of hemoglobin oxygen saturation and relative blood volume in human skin in vivo to laser irradiation. The hemoglobin oxygen saturation and relative hemoglobin concentration in skin were evaluated from diffuse reflectance spectra in visible wavelength range. The skin spot at human hand was irradiated with laser beam and hemoglobin oxygen saturation and relative hemoglobin concentration were sampled every two seconds from the center of the irradiated spot. It was evidently observed that hemoglobin oxygen saturation is increased after starting irradiation. During occlusion the oxygen consumption rate was higher in the presence of laser irradiation. However, these effects were observed only at sufficiently high laser fluence rates. The most probable reason is that it is due to thermal effects.

Noninvasive evaluation of absolute fluorochrom concentration in various tissues in vivo by means of standard samples with modeled optical properties

The problem of accurate determination of fluorochrome concentration in tissues from fluorescent spectra is the most important one in the spectroscopy of biological objects. Especially it is significant for the application of photodynamic therapy (PDT) when the concentration of photosensitizer (PS) in tumor and surrounding normal tissues should be known so that one could employ the appropriate treatment tactics (irradiation dose and time). It is also desirable that the screening depth be the same order as the light penetration depth used for treatment. To solve these problems we have prepared the standard samples with the optical properties close to that of tissues under investigation. The various fractions of sulphanated aluminum phtalocyanine (Al-Pc) have been used as photosensitizers. The samples with various concentration of Al-Pc have been prepared and the intensity of fluorescence excited by He-Ne laser, as well as the laser scattered line, have been measured to give a calibration curve.

Experimental study of PDT with aluminum sulphophthalocyanine using sodium ascorbate and hyperbaric oxygenation

It is well known that sulphophthalocyanine derivatives under laser irradiation induce photochemical reaction of II type with generation of cytotoxic agent - singlet oxygen. The combination of phthalocyanine and exogenic reductant - sodium ascorbate may also induce other reactions, involving the formation of free radicals, and thus intensify the antitumor effect. To improve the results of PDT we used the additional injection of sodium ascorbate, the hyperbaric oxygenation and different regimes of laser irradiation. We conducted the experimental study on 100 white mice with Erlich carcinoma. Macroscopic and microscopic data showed that sodium ascorbate significantly increases the effect of PDT in comparison with control group due to the higher tumor damage, vascular alterations, inhibition of cell proliferation and stimulation of antitumor desmoplastic reaction.

Fluorescence method for monitoring of glucose in interstitial fluids

Development of minimal invasive diagnostics methods is of great importance in todays healthcare. The present work deals with the measurements of glucose concentration in small drops, its volume being in the range of 1 (mu) L and its glucose concentration being in the range of 1-10 mM. The aim of the work was to develop robust quantitative method of glucose measurement in small volumes of interstitial fluid obtained after laser shot or by other low invasive procedures. The commercially available Amlex Red glucose assay kit was used in the present work. The glucose is detected by enzyme-coupling reactions resulting in formation of fluorescence dye resorufin. The diagnostic paper was used as a reaction medium. The fluorescence of dye in diagnostic paper was measured with the use of fiber optics spectrometer. It was shown that dye fluorescence correlates fairly well with glucose concentration. The method may be modified to involve cholesterol concentration measurement as well.