Spectral methods have been developed for analyzing the equilibrium and kinetics of the complexation process of the known photosensitizer, meta-tetrakis(hydroxyphenyl)chlorine (mTHPC), with monomeric and polymeric derivatives of β-cyclodextrin (β-CD). The study of the binding isotherms showed that mTHPC has a higher affinity for the polymeric derivatives of β-CD studied, namely, carboxymethyl-β-cyclodextrin polymer (CM-β-CDPD) and β-cyclodextrin polymer (β-CDPD), than for monomeric methyl-β-cyclodextrin (M-β-CDMD). Profiles for the change in the relative content of mTHPC inclusion complexes with β-CDs in solution with and without the presence of lipid vesicles were obtained and the dissociation constants of the photosensitizer (PS) molecules were calculated from the content of the inclusion complexes with cyclodextrins. The dissociation of mTHPC from the inclusion complexes with M-β-CDMD takes 1–2 min, while this process takes more than one hour with polymeric CDs, (CM-β-CDPD and β-CDPD). These findings suggest that the complexation of the title chlorine with polymeric and monomeric cyclodextrins may play an essential role in the delivery of photosensitizer to cellular/tissue structures.

Now polymeric sorbents are used as basic environmental protection agents. They are used as filter elements for air and water purification. The application of stimulus-dependent polymers opens up new possibilities for the adsorption and desorption of different classes of substances. It was shown that the phase change behavior of dextran70-poly(N-isopropylacrylamide) copolymers at temperatures above 34-35 °C can be used for reversible adsorption/desorption of porphyrins. The interaction of meso-tetra(m-hydroxyphenyl)-porphine with the polymer at temperatures above the Lower Critical Solution Temperature leads to the binding of its molecule to the polymer matrix. The resulting complexes are stable. The results obtained suggest that the process of porphyrin-polymer complexation depends strongly on the physico-chemical properties of porphyrins.

Сравнительный анализ структурных и кинетических характеристик комплексов фотосенсибилизатора мета-тетрагидроксифенилхлорина с различными типами / В. П. Зорин, Т. Е. Зорина, И. Е. Кравченко, И. В. Коблов // Физико-химическая биология как основа современной медицины : тез. докл. Междунар. науч. конф., посвящ. 75-летию со дня рождения проф. Е. В. Барковского, Минск, 21 мая 2021 г. / под ред. В. В. Хрусталёва, А. Д. Тагановича, Т. А. Хрусталёвой. – Минск, 2021. – С. 110-111.

Термочувствительные липосомальные носители фотосенсибилизаторов / Т. Е. Зорина, И. Е. Кравченко, Т. И. Ермилова, Т. В. Шман, В. П. Зорин // Физико-химическая биология как основа современной медицины : тез. докл. Междунар. науч. конф., посвящ. 75-летию со дня рождения проф. Е. В. Барковского, Минск, 21 мая 2021 г. / под ред. В. В. Хрусталёва, А. Д. Тагановича, Т. А. Хрусталёвой. – Минск, 2021. – С. 113-115.

Photodynamic therapy represents a more targeted and less invasive alternative cancer treatment to traditional modalities. Temoporfin, as with many photosensitizers, is given by injection into a vein, and its subsequent fate is largely determined by the binding to plasma proteins and interaction with endothelial and blood cells. Thus, it is essential to be able to control and to alter the biodistribution of temoporfin in blood. In the present study, we evaluated the effect of co-administration of temoporfin with randomly methylated β-CD (Me-β-CD) on the distribution of temoporfin in the main subpopulations of blood cells of healthy donors using absorbance spectrophotometry and flow cytometry. We showed that cell-bound temoporfin fraction in blood strongly depends on the concentration of Me-β-CD. In fact, the accumulation of temoporfin in white blood cells was more sensitive than that in red blood cells, due to the higher volume of membranous organelles in white blood cells. Finally, we demonstrated that Me-β-CD significantly increases cellular uptake of temoporfin cancer human Burkitt′s lymphoma Raji cells. The presence of Me-β-CD resulted in a spotted pattern of temoporfin distribution in the plasma membrane compartment. Our results clearly demonstrated that β-CDs derivatives provide new options to modulate temoporfin biodistribution in blood.

Thermosensitive polymer poly-N-isopropylacrylamide (PNIPAM) having a conformational transition in the interval of physiological temperatures was discussed last years as a novel drug delivery system. Chlorin e6 (Ce6) is a photosensitizer used in the photodynamic anticancer therapy. The comparative study of the encapsulation of Ce6 and its derivative, dimethylether of chlorine e6 (DME Ce6), into a water-soluble star-like PNIPAM-based copolymer to prevent the aggregation of a photosensitizer in the water medium is carried out. The photophysical properties of the copolymer/photosensitizer complexes as functions of the temperature in the region of the conformational transition of the polymer matrix have been studied and discussed. It is shown that Ce6 at low temperatures interacts weakly with the polymer phase. As a result, the absorption and fluorescence properties of Ce6 in aqueous and polymer solutions are practically identical. Fluorescence characteristics of Ce6 in a copolymer solution remain unchanged, when it is heated, which indicates the lack of a possibility for this sensitizer to bind in the bulk of the polymer phase. Following fluorescence data, all DME Ce6 molecules are bound with the polymer matrix, when a temperature is higher than the Lower Critical Solution Temperature (LCST) of the polymer. The formed complexes are quite stable. In the presence of serum proteins, the molecules of the photosensitizer remain associated for a long time with the polymer. At temperatures below LCST, DME Ce6 is not bound by the polymer. Moreover, the cooling of a solution of DME Ce6/polymer complexes leads to the rapid dissociation of photosensitizer molecules with subsequent aggregation or binding to biological structures in an aqueous medium. The obtained results show that the possibility of using the polymer PNIPAM as a temperature-dependent nanocarrier strongly depends on the properties of the loaded drug.

Аминопроизводные хлорина е6 — эффективные фотосенсибилизаторы для фотодинамической терапии / Т. Е. Зорина [и др.] // Физико-химическая биология как основа современной медицины : тез. докл. Респ. конф. с междунар. участием, посвящ. 110-летию В.А. Бандарина, Минск, 24 мая 2019 г. : в 2 ч. / под ред. В. В. Хрусталёва, Т. А. Хрусталёвой. - Минск, 2019. - Ч. 1. - С. 113-114.

—Confocal microscopy and colocalization analysis using Pearson correlation coefficients were used to show that esterified chlorin e 6 derivatives and their liposomal forms are mainly localized in the endoplasmic reticulum, Golgi complexes, cell mitochondria, and levels of their localization in lysosomes are low. Cellular uptake and accumulation kinetics of chlorin e 6 derivatives were strongly depended on the type of pharmacological formulation used for photosesitizers administration, while intracellular localization was independent on the formulation. Differences in the photodynamic activity and sensitization mechanisms for chlorin e 6 derivatives and their liposomal forms were shown when compared to those of chlorin e 6 photosensitizers in K562 cells. It is assumed that the observed differences in the mechanisms of cellular damage are to a greater extent due to specific photosensitizer localization.

By extrusion of phospholipids stable nanoparticles loaded with photosensitizers a chlorin e6 derivatives were obtained. The structural and physico-chemical characteristics of the liposomal forms of chlorins were estimated. The use of nanoscale liposomes as carriers of hydrophobic photosensitizers has been studied.

We studied the effects of medium pH on steady-state distribution of chlorine e6 and its derivatives between the main transport proteins of human blood plasma. The decrease in medium pH from weakly alkaline (pH 7.4) to acid (pH 5.0) was followed by an increase in relative affinity of chlorines to lipoproteins and reduced their affinity to serum albumin. pH-Dependent changes in the parameters of distribution of photosensitizers between the plasma and blood cells was revealed. We discussed the role of charge and polarity degree of photosensitizer molecule in the mechanism of binding to serum albumin. A possible role of changes in hydrogen ion activity in the processes of selective accumulation of chlorines by tumor cells is discussed.

Photophysical characteristics and photosensitizing activity were studied for dimethyl (DME) and trimethyl ester (TME) derivatives of chlorin e6 (Chl e6) in various solutions and liposomal forms. Incorporation in liposomes rendered the Chl e6 ester derivatives monomeric in aqueous solutions keeping intact photophysical properties and high photochemical activity. The redistribution rate of Chl e6 DME from lipid vesicles to cells was substantially higher than that of Chl e6 TME. Serum proteins affected the intracellular accumulation of liposomal forms for the DME and TME derivatives of Chl e6 differently. Cell-culture experiments showed that liposomal forms of the DME and TME derivatives of Chl e6 had significantly lower cytotoxicity, while preserving a high cytotoxic effect of photodynamic activity.

Three approaches to analyzing the rate of release of the photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC) from unilaminar lipid vesicles (ULV) in model biological systems are studied: by excitation energy transfer from probe diphenylhexatriene to mTHPC, by the fluorescence anisotropy of mTHPC, and by photoinduced quenching of the fluorescence of mTHPC. Each of these methods has its characteristic range of sensitivity for measurements of the local concentration of mTHPC in ULV. Fluorescence anisotropy can be used for quantitative determination of the mTHPC yield from ULV for mTHPC:lipid ratios of 1:100 to 1:1000, determining the efficiency of fluorescence quenching of diphenylhexatriene for ratios <1:200, and photoinduced quenching for ratios of 1:10–1:500.

Liposomal formulations of meso-tetra(hydroxyphenyl)chlorin (mTHPC) have already been proposed with the aim to optimize photodynamic therapy. Spectral modifications of these compounds upon irradiation have not yet been investigated. The objective of this study was to evaluate photobleaching properties of mTHPC encapsulated into dipalmitoylphosphatidylcholine (DPPC) liposomes, Foslip. Fluorescence measurements in DPPC liposomes with different DPPC:mTHPC ratios demonstrated a dramatic decrease in fluorescence anisotropy with increasing local mTHPC concentration, thus suggesting strong interactions between mTHPC molecules in lipid bulk medium. Exposure of Foslip suspensions to small light doses (< 50 mJ/cm(2)) resulted in a substantial drop in fluorescence, which, however, was restored after addition to the sample of a non-ionic surfactant Triton X-100. We attributed this behavior to photoinduced fluorescence quenching. This effect depended strongly on the molar DPPC:mTHPC ratio and was revealed only for high local mTHPC concentrations. The results were interpreted supposing energy migration between closely located mTHPC molecules with its subsequent dissipation by the molecules of photoproduct acting as excitation energy traps. We further assessed the effect of photoinduced quenching in plasma protein solution. Relatively slow kinetics of photoinduced Foslip response during incubation in the presence of proteins was attributed to mTHPC redistribution from liposomal formulations to proteins. Therefore, changes in mTHPC distribution pattern in biological systems would be consistent with changes in photoinduced quenching and would provide valuable information on mTHPC interactions with a biological environment.

The distribution of porphyrin pigments between plasma proteins and blood cells was studied. It was shown that the relative fraction of sensitizer bound by blood cells changed significantly depending on the physicochemical features of pigment molecules. This parameter strongly correlates with porphyrin polarity. Polar watersoluble tetraphenylporphin derivatives, chlorine e6 and hematoporphyrin are bound by plasma proteins only. The decrease in pigment polarity by substitution of polar side groups results in a drastic increase of pigment affinity to blood cells. The binding of extremely apolar pigments by cells in blood occurs for a long period of time, probably as a result of a low rate of pigment redistribution between serum proteins and cellular membrane. The data obtained show that blood cells may be involved into the control of pigment transport and distribution in organism during photodynamic therapy. The parameters of porphyrin distribution between plasma proteins and cells in blood are of certain importance when the pharmacokinetic behavior of various sensitizers is compared.