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The spectral-luminescent properties of symmetrical indotricarbocyanine dyes with the same cation and different anions (Br − , BF 4 − ) in cancerous HeLa cells, an isotonic solution of NaCl, and organic solvents have been investigated. It is shown that when these dyes are present in cells in nontoxic concentrations, they are in a monomeric state, they are localized in the region with a low dielectric permeability, bonded to biological macromolecules, and do not make contact with an aqueous medium. It has been established for the first time that the molecules of the polymeric dyes are present in cells predominantly in the form of contact ion pairs, and in a dye with the Br − anion the presence of free cations or solvately separated ionic pairs is revealed. It is shown that the shift of the ion equilibrium toward contact ion pairs for the dyes in the cells (as compared to the low-polarity organic solvents) can be due to the fairly high concentration of salts in the biosystem.

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The absorption and fl uorescence spectra of a new styryl derivative of thiofl avin T 2-{(1E,3E)-4- in solvents with diff erent polarity and viscosity and also incorporated in the structure of amyloid fi brils and bovine serum albumin were investigated. A characteristic feature of the dye is an extremely low quantum yield of fl uorescence in low-viscosity solvents (10 -4 in water) which, however, increases signifi cantly in viscous solutions and when it is incorporated in the structure of proteins or amyloid fi brils. In the latter case the quantum yield increases by 8•10 3 times. On the basis of the experimental studies and quantum chemical calculations it was shown that Th-C23 exhibits the properties of a molecular rotor. The increase of the fl uorescence quantum yield in viscous solutions and in the biopolymers results from limitation of the torsional rotation of the molecular fragments, leading to fl uorescence quenching. The longwavelength location of the absorption spectrum and the fl uorescence spectrum of the new dye in the red region of the spectrum (520 and 600 nm) makes it possible to use it as a fl uorescent marker that is sensitive to the viscosity (hardness) of the microenvironment not only in vitro but also in vivo.

We have established that the shape and position of the maximum in the fluorescence spectrum of an indotricarbocyanine dye in tumor and normal tissues in vivo change over time after intravenous injection of the dye. Based on analysis of the spectral properties of the dye in vivo and in blood plasma, the dependence of the properties on the time since injection has shown that in the living body, the environment of the dye molecule changes as the photosensitizer goes from the skin into the tissue. We have established that in tissues in vivo, the dye molecules are localized in a region with low dielectric constant of the medium. We have shown that the change in the ratio of the concentrations of the different forms of hemoglobin in the blood has an effect on the absorption and shape of the fluorescence spectrum of the dye in tissues in vivo. Introduction.Polymethine dyes (PDs) are promising for use as photosensitizers for photochemotherapy (also called photodynamic therapy, PDT) [1]. This is first of all due to the presence of absorption bands in their spectra in a range in which biological tissues have greatest transparency (the phototherapeutic window) [2]. For a number of dyes in this class, high photoactivity was found in experiments on cell cultures and also on animals with tumors [1, 3, 4]. The prospects for using a specific photosensitizer mainly depend on how efficiently the molecules in the excited state can generate active intermediates. The probabilities of intramolecular processes for dissipation of the electronic excitation energy for tricarbocyanine dyes depend on the nature of the surrounding molecules [5]. In low-polarity organic solvents, cationic PDs may be found in the form of ions or a mixture of several types of ion pairs [6]. As shown in [7], cationic PDs in a HeLa cell culture are localized in a region with low dielectric constant, and are found mainly in the contact ion pair state. The nature of the environment of the PD molecules in biological tissues in vivo has not been studied to date.In this paper, we present the results of a study of the spectral luminescence properties of a symmetric indotricarbocyanine dye in a culture of HeLa tumor cells and in tissues in vivo in animals with tumors.Objects and Methods of Investigation. As the object of investigation, we used an indotricarbocyanine dye synthesized in the spectroscopy laboratory of the A. N. Sevchenko Research Institute of Applied Physical Problems: 2-{7-[3-methyl-3-ethyl-1-trimethylenecarbo-(6-O-D-glucosyl)-2(1H)-indolenylidene]-4-chloro-3,5-(O-phenyleno)-1,3,5-hexatrien-1-yl}-3-methyl-3-ethyl-1-trimethylenecarbo-(6-O-D-glucosyl)indolenylium bromide (PD1).In vivo experiments were conducted on mongrel white rats with subcutaneously grafted tumors of the sarcoma 45 (S-45) and sarcoma M1 (SM-1) strains. We used a group of 6-8 animals for the studies. The drug was injected intravenously in the ratio of 1-5 mg per kg of the animal's weight. The fluorescence spectra of PD1 in vivo was recorded using a spectrometer developed at the A. N. Sevc...