Anna B. Solovieva

Development of novel formulations for photodynamic therapy on the basis of amphiphilic polymers and porphyrin photosensitizers. Pluronic influence on photocatalytic activity of porphyrins

Effect of ethylene and propylene oxide tri-block copolymers (Pluronics) on the photocatalytic activity of tree porphyrins differing by their hydrophobicity was studied. It was shown that Pluronics induce considerable increase in the photocatalytic activity of the tetraphenylporphyrin, hematoporphyrin disodium salt (Dimegine) and relatively hydrophilic N-methyl-bis-glucamine salt of chlorine e6 (Photoditazine) in the reaction of photooxidation of tryptophan in water solution. This effect was maximal for Pluronics F127 and P85 with intermediate hydrophobicity, while more hydrophilic F68 and more hydrophobic L61 were less effective. Pluronic effect on the photocatalytic activity of tetraphenylporphyrin and dimegine is attributed to their disaggregation in water solution, while PD activity is elevated due to the local concentrating of the photocatalyst and the substrate within micellar volume. It was found by AFM that the structure of Pluronic F127 thin films prepared by water solution evaporation on mica surface significantly changed in the presence of porphyrin. This effect can be attributed to the interaction of Pluronics with porphyrins in water solution.

Development of novel formulations for photodynamic therapy on the basis of amphiphilic polymers and porphyrin photosensitizers. Porphyrin-polymer complexes in model photosensitized processes

We have studied the effect of amphiphilic polymers with different structure (polyvinylpyrrolidone, polyethyleneoxide and a triblock copolymer of ethylene- and propyleneoxide—(Pluronic F127)) on the photoactivity of a hematoporphyrin derivative (dimegin). It has been shown that such polymers can cause a considerable increase in the porphyrin photosensitizer (PPS) activity both in the process of singlet oxygen photogeneration and in the reaction of a substrate photooxidation in D2O and water. Among the studied polymers, polyvinylpyrrolidone appeared to have a most significant influence onto the photoactivity of dimegin. We attribute the observed effect of the amphiphilic polymers on the photoactivity of dimegin to the presence of polymer-porphyrin interactions resulting in the porphyrin disaggregation in aqueous phase. Using 1H NMR spectroscopy, we have found that dimegin binds to the polymers via the PPS interaction mainly with the hydrophobic fragments of polymeric macromolecules. However, in the case of polyvinylpyrrolidone we observed also PPS interactions with the hydrophilic fragments of macromolecules.

Specific Features of Early Stage of the Wound Healing Process Occurring Against the Background of Photodynamic Therapy Using Fotoditazin Photosensitizer–Amphiphilic Polymer Complexes

There is a growing demand on the studies of the wound healing potentials of photodynamic therapy. Here we analyze the effects of Fotoditazin, an e6 chlorine derivative, and its complexes with amphiphilic polymers, on the early stage of wound healing in a rat model. A skin excision wound model with prevented contraction was developed in male albino rats divided into eight groups according to the treatment mode. All animals received injections of one of the studied compositions into their wound beds and underwent low‐intensity laser irradiation or stayed un‐irradiated. The clinical monitoring and histological examination of the wounds were performed. It has been found that all the Fotoditazin formulations have significant effects on the early stage of wound healing. The superposition of the inflammation and regeneration was the main difference between groups. The aqueous solution of Fotoditazin alone induced a significant capillary hemorrhage, while its combinations with amphiphilic polymers did not. The best clinical and morphological results were obtained for the Fotoditazin–Pluronic F127 composition. Compositions of Fotoditazin and amphiphilic polymers, especially Pluronic F127, probably, have a great potential for therapy of wounds. Their effects can be attributed to the increased regeneration and suppressed reactions changes at the early stages of repair.

Polymers as enhancers of photodynamic activity of chlorin photosensitizers for photodynamic therapy

Abstract: The impact of water-soluble and amphiphilic polymers with different structures, namely carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), was studied on the photoactivity of chlorin photosensitizers (PSs) in photodynamic therapy (PDT). It was shown that such polymers can cause a considerable increase in the PS activity, both in the process of singlet oxygen photogeneration in cell experiments, and in the model reaction of a substrate photooxidation in water. Amongst the studied polymers, CMC and PVP appeared to have the most significant influence on the photoactivity of PSs. The observed effect of the polymers on the photosensitizing activity of PSs can be attributed to the presence of chlorin-polymer interactions resulting in the porphyrin disaggregation in aqueous phase. The effect of the polymers on the photocytotoxicity of PSs is attributed to the absence of interactions between chlorin and polypeptide or lipoproteins which results in a decrease of the photoactivity of chlorins in cell culture. The PS/polymer systems appear to be a new effective dosage form of PDT drugs. Zusammenfassung: Die Wirkung von wasserlöslichen und amphiphilen Polymeren mit unterschiedlichen Strukturen (Carboxymethylcellulose, CMC; Polyvinylalkohol, PVA; Polyvinylpyrrolidon, PVP), auf die Photoaktivität von Chlorin-Photosensibilisatoren (PS) in der photodynamischen Therapie (PDT) wurde untersucht. Es wurde gezeigt, dass solche Polymere eine erhebliche Steigerung der PS-Aktivität bewirken können, sowohl im Prozess der Singulett-Sauerstoff-Generation in Zellexperimenten als auch in der Modellreaktion einer Substrat-Photooxidation in Wasser. Unter den untersuchten Polymeren schienen CMC und PVP den größten signifikanten Einfluss auf die Photoaktivität der PS zu haben. Die beobachtete Wirkung der Polymere auf die photosensibilisierende Aktivität der PS kann auf das Vorhandensein von Chlorin-Polymer-Wechselwirkungen zurückgeführt werden, die in einer Porphyrin-Disaggregation in wässriger Phase resultieren. Die Wirkung der Polymere auf die Photozytotoxizität der PS wiederum ist auf das Fehlen von Wechselwirkungen zwischen Chlorin und Polypeptid bzw. Lipoproteinen zurückzuführen, die zu einer Abnahme der Photoaktivität von Chlorin in der Zellkultur führt. Die PS/Polymer-Systeme scheinen eine neue wirksame Darreichungsform von PDT-Medikamenten zu sein.

Quantitative evaluation of atherosclerotic plaques using cross-polarization optical coherence tomography, nonlinear, and atomic force microscopy

Abstract. A combination of approaches to the image analysis in cross-polarization optical coherence tomography (CP OCT) and high-resolution imaging by nonlinear microscopy and atomic force microscopy (AFM) at the different stages of atherosclerotic plaque development is studied. This combination allowed us to qualitatively and quantitatively assess the disorganization of collagen in the atherosclerotic arterial tissue (reduction and increase of CP backscatter), at the fiber (change of the geometric distribution of fibers in the second-harmonic generation microscopy images) and fibrillar (violation of packing and different nature of a basket-weave network of fibrils in the AFM images) organization levels. The calculated CP channel-related parameters are shown to have a statistically significant difference between stable and unstable (also called vulnerable) plaques, and hence, CP OCT could be a potentially powerful, minimally invasive method for vulnerable plaques detection.

The influence of temperature on the photo-oxidation rate of tryptophan in the presence of complexes of porphyrins with amphiphilic polymers*

The influence of temperature on the photocatalytic activity of the complexes of water-soluble porphyrin photosensitizers with amphiphilic polymers, such as poly-4-vinylpyrrolidone, polyethylene oxide, and Pluronic F127 (triblock copolymers of ethylene oxide and propylene oxide) in photo-oxidation reaction of tryptophan in the aqueous solution has been investigated. It has been shown that in the temperature range of 10–40 °C the addition of these polymers increases the activity of triglucamine salt of chlorine e6, tertrasodium salt of tetrasulfophenilporfirina and dimegin. The greatest influence on the rate of photo-oxidation appears to be rendered by the introduction of poly-4-vinylpyrrolidone in the presence of which the value of the rate constant increased by 30–70%. The strongest effect of the polymers is observed at 20–23 °C for dimegin, triglucamine salt of chlorine e6, and for tertrasodium salt of tetrasulfophenilporfirina at 30 °C. We suggest that the effect of the polymer on the effective rate constant relates to the restructuring of the supramolecular structure of polymers during temperature changes.

Atomic Force Microscopy Study of Atherosclerosis Progression in Arterial Walls.

Cardiovascular disease remains the leading cause of mortality worldwide. Here we suggest a novel approach for tracking atherosclerosis progression based on the use of atomic force microscopy (AFM). Using AFM, we studied cross-sections of coronary arteries with the following types of lesions: Type II-thickened intima; Type III-thickened intima with a lipid streak; Type IV-fibrotic layer over a lipid core; Type Va-unstable fibrotic layer over a lipid core; Type Vc-very thick fibrotic layer. AFM imaging revealed that the fibrotic layer of an atherosclerotic plaque is represented by a basket-weave network of collagen fibers and a subscale network of fibrils that become looser with atherosclerosis progression. In an unstable plaque (Type Va), packing of the collagen fibers and fibrils becomes even less uniform than that at the previous stages, while a stable fibrotic plaque (Vc) has significantly tighter packing. Such alterations of the collagen network morphology apparently, led to deterioration of the Type Va plaque mechanical properties, that, in turn, resulted in its instability and propensity to rupture. Thus, AFM may serve as a useful tool for tracking atherosclerosis progression in the arterial wall tissue.

Comparative Study of Tissue Distribution of Chlorin e6 Complexes with Amphiphilic Polymers in Mice with Cervical Carcinoma

Many photosensitizers, including chlorins, are highly hydrophobic, which makes intravenous administration problematic and affects their delivery to the tumor and uptake in the cells. Moreover, self-aggregation of the photosensitizer in aqueous solution reduces fluorescence quantum yield, triplet state, and singlet oxygen generation, and consequently diminishes photosensitizing activity. To address these issues, it was proposed to use biocompatible water-soluble polymers. However, animal studies of the photosensitizer-polymer systems are still very limited. In this work, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and pluronic F108 were used for dissolution of chlorin e6 (Ce6). Dynamics of accumulation of the formulations in a mouse cervical carcinoma and clearance from normal tissue, drug plasma concentrations and tissue distribution after intravenous injection were investigated. Ce6 alone and clinically used photosensitizer Photoditazine served as a control. The results showed that none of the polymers significantly changed fluorescence kinetics in the tumor. Concentration of the Ce6 formulated with polymers in the tumor tissue was comparable with Photoditazine, but uptake in the skin was less. At the same time, tumor-toskin ratios of the Ce6-polymer complexes were similar to free Ce6. We concluded that the use of the polymeric formulation is reasonable for fluorescence diagnosis and PDT of cancer.

Chitosan impregnation with biologically active tryaryl imidazoles in supercritical carbon dioxide

The presented paper is focused on impregnation of chitosan and its derivatives with a biologically active triaryl imidazole model compound ((2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole) in the supercritical carbon dioxide medium. Since initial chitosan represents a polycation-exchange resin and does not swell in supercritical carbon dioxide, the impregnation was carried out in the presence of water (0.15–3.0 vol%). The maximum 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole concentration in a chitosan film was achieved at the ~5 × 10−3 g/cm3 water content in the reactor. We also used hydroxy carboxylic acid derivatives of chitosan and its copolymer with polylactide as matrices for introduction of hydrophobic 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole. We have shown that unmodified chitosan contains the greatest amount of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole, as compared with its hydrophobic derivatives. The kinetics of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole diffusion from a chitosan matrix was studied in acidified water with pH 1.6. We found that the complete release of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole into the aqueous phase from unmodified chitosan films occurred in 48 h, while its complete release from chitosan modified with hydroxy carboxylic acids occurred in 5 min or less.

Optimization of Photosensitized Tryptophan Oxidation in the Presence of Dimegin-Polyvinylpyrrolidone-Chitosan Systems

By the example of a model process of tryptophan photooxidation in the aqueous medium in the presence of a three-component photosensitizing complex (porphyrin photosensitizer-polyvinylpyrrolidone- chitosan, PPS-PVP-CT) in the temperature range of 20–40 °С, we have demonstrated a possibility of modification of such a process by selecting different molar ratios of the components in the reaction mixture. The actual objective of this selection is the formation of a certain PPS-PVP-CT composition in which PVP macromolecules would coordinate with PPS molecules and at the same time practically block the complex binding of PPS molecules with chitosan macromolecules. Such blocking allows utilization of the bactericidal properties of chitosan to a greater extent, since chitosan is known to depress the PPS photosensitizing activity in PPS-PVP-CT complexes when using those in photodynamic therapy (PDT). The optimal composition of photosensitizing complexes appears to be dependent on the temperature at which the PDT sessions are performed. We have analyzed the correlations of the effective rate constants of tryptophan photooxidation with the photophysical characteristics of the formed complexes.