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Background Contemporary medicine does not concern the issue of dosimetry in photodynamic diagnosis (PDD) but follows the photosensitizer (PS) producers recommendation. Most preclinical and clinical PDD studies indicate a considerable variation in the possibility of visualization and treatment, as e.g. in case of cervix lesions. Although some of these variations can be caused by the different histological subtypes or various tumor geometries, the issue of varying PS concentration in the tumor tissue volume is definitely an important factor. Therefore, there is a need to establish the objective and systematic PDD dosimetry protocol regarding doses of light and photosensitizers. Methods Four different irradiation sources investigated in PDD (literature) were used for PS excitation. The PS luminescence was examined by means of the non-imaging (spectroscopic) and imaging (wide- and narrow-field of view) techniques. The methodology for low-level intensity photoluminescence (PL) characterization and dedicated image processing algorithm for PS luminescence images analysis were proposed. Further, HeLa cells' cultures penetration by PS was studied by a confocal microscopy. Results Reducing the PS dose with the choice of proper photoexcitation conditions decreases the PDD procedure costs and the side effects, not affecting the diagnostic efficiency. We determined in vitro the minimum incubation time and photosensitizer concentration of Photolon for diagnostic purposes, for which the Photolon PL can still be observed. It was demonstrated that quantification of PS concentration, choice of proper photoexcitation source, appropriate adjustment of light dose and PS penetration of cancer cells may improve the low-level luminescence photodynamic diagnostics performance. Conclusions Practical effectiveness of the PDD strongly depends on irradiation source parameters (bandwidth, maximum intensity, half-width) and their optimization is the main conditioning factor for low-level intensity and low-cost PDD. [ABSTRACT FROM AUTHOR]

We have studied the feasibility of using an indotricarbocyanine dye as a marker for the efficacy of photodynamic therapy (PDT) of cancers with the photosensitizer Photolon. We have established that on exposure to laser emission at λ = 667 nm with an exposure dose of 100 J/cm, we observe that the Photolon concentration drops by about a factor of two in the exposed part of the tumor, while the concentration of the indotricarbocyanine dye does not change in any region of the tumor node. We have observed a correlation between the change in the shape of the fluorescence spectra of the indotricarbocyanine dye in vivo in the 780-880 nm resulting from a PDT session with the photosensitizer Photolon and the extent of damage to the tumor tissues. Changes in the shape of the fluorescence spectrum of the dye are interpreted in terms of a model involving the appearance of absorption by different forms of hemoglobin, and changes in their ratio in the exposed part of the tumor due to consumption of molecular oxygen. [ABSTRACT FROM AUTHOR]

Abstract: It is recognized that chlorin e6–polyvinylpyrrolidone (Ce6–PVP) formulations are characterized by a high efficacy in photodynamic therapy of malignant tumors. Currently, a commercially available formulation of this type is Photolon® (Fotolon®) with Ce6:PVP=1:1 (w/w) and the weight-average molecular weight of PVP is 1.2×104. To gain a better understanding of the role played by PVP in Ce6–PVP formulations, we carry out experiments on IR and UV–VIS absorption, steady-state and time-resolved fluorescence, time-resolved triplet–triplet absorption, octanol–water partitioning, and solubility of chlorin e6 in buffer solutions at pH 6.3, 7.4, and 8.5 in presence of PVP with Ce6:PVP ratios ranging from 1:0 to 1:1000 (w/w) for PVP samples with weight-average molecular weights of 8×103, 1.2×104, and 4.2×104. We show that Ce6 interacts with PVP by forming molecular complexes via hydrophobic interactions and determine the Ce6–PVP binding constant, as well as the mean number of PVP monomers per binding site. We find that complexation of Ce6 with PVP prevents Ce6 aggregation in aqueous media and leads to an enhancement of Ce6 fluorescence quantum yield, while keeping the quantum yield of the intersystem crossing essentially unchanged. Possible scenarios of how the presence of PVP can favorably affect the PDT efficacy of chlorin e6 in Ce6–PVP formulations are discussed. [Copyright &y& Elsevier]

Abstract: Photolon is one of the new photosensitisers that has found application in photodynamic therapy (PDT). Its chemical structure has a partially reduced porphyrin moiety and its molecular structure is comparable to chlorin e6, which can be isolated after hydrolysis of the 5-membered exocyclic β-ketoester moiety of pheophorbide a. For this study, a Photolon doped sol–gel matrix was produced in the form of coatings deposited on silica fibers cores. The material was produced from sols prepared from the silicate precursor TEOS mixed with ethyl alcohol. The sol–gel films were prepared with factor R =20, where R denotes the solvent-to-precursor molar ratio. Hydrochloric acid was added as a catalyst in the correct proportion to ensure acid hydrolysis (pH ≈2). The mixture was stirred at room temperature for 4h using a magnetic stirrer (speed 400rpm). The coated fibers were examined in different environments, liquid and gaseous, at different pH values and with various zinc cation concentrations. The chemical reactions were studied by means of spectroscopic methods, whereby the fluorescence response was studied. It was demonstrated that Photolon immobilized in a sol–gel matrix is accessible for the environment and shows visible response to the external changes. Furthermore, it was observed that these reactions are reversible. These biomaterials are also examined as carriers for PDT. It was also proved that a toxic effect is observed an environment with microorganisms, meaning that doped coatings have photodynamic activity. [Copyright &y& Elsevier]

Abstract: The tetrapyrrolic compound chlorin e6 is currently used as a pharmaceutical substance for Photolon formulation, which is utilized in photodynamic therapy of various diseases. It was found that chlorin e6 could contain both process- and degradation-related impurities. In order to understand their origin, the most abundant impurities were prepared by liquid extraction, preparative chromatography or chemical synthesis. By means of HPLC-PDA–MS, 1D and 2D NMR spectroscopy, these impurities were identified as chlorin e6 174-ethyl ester, chlorin e4, 15-hydroxyphyllochlorin, rhodochlorin, 151-hydroxymethylrhodochlorin δ-lactone, rhodochlorin-15-oxymethyl δ-lactone, rhodochlorin-15-oxymethyl δ-lactone 174-ethyl ester, 151-hydroxymethylrhodoporphyrin δ-lactone, rhodoporphyrin-15-oxymethyl δ-lactone and purpurin 18. The possible routes of formation of the chlorin derivatives upon the production and storage of chlorin e6 are discussed. [Copyright &y& Elsevier]

Abstract: The study was carried out on Escherichia coli strains isolated from poultry and cows. The bacteria were incubated and treated by Photolon, a plant-based photosensibilizator, and exposed after that to laser light at 662nm. Additionally, the photosensitizer was immobilized in fiberoptic sol–gel coating, constructed as an 8-layer applicator. It was demonstrated that Photolon inhibits bacteria growth. Photolon entrapped into the sol–gel matrix also exhibits photodynamic activity and no bacteria were seen near the doped sol–gel applicator. [Copyright &y& Elsevier]

Using the methods of steady‐state absorption and fluorescence spectroscopy and flash‐photolysis, the new photosensitizer “Photolon” (Stock Company “Belmedpreparaty”) and its basic chromophore part — the substance chlorin e6 — have been studied under model conditions. It has been shown that there are no considerable differences between the spectral‐luminescent characteristics of Photolon and chlorin e6 at a concentration not exceeding 2.5·10-5 M in ethanol, phosphate‐saline buffer (pH 8.5), and isotonic solution. That is, the polyvinyl‐pyrrolidone (PVP) entering into the composition of Photolon does not influence the chromophore characteristics being investigated. It has been found that an increase in the mass fraction of PVP in the buffer solution of chlorin e6 leads to an increase in the degree of polarization of chlorin e6 fluorescence and to a change in the spectral‐luminescent and kinetic characteristics, pointing to the fact that the pigment is built into the hydrophobic portions of the polymer. Using the method of multiple scattering of light, it has been shown that both Photolon and chlorin e6 are present in the whole blood of donors and oncological patients mainly in the monomeric form; Photolon is quickly removed from the blood of patients (after 24 h, C ≤ 10-3 mg/ml). [ABSTRACT FROM AUTHOR]

The worldwide increase in bacterial resistance and healthcare-associated bacterial infections pose a serious threat to human health. The antimicrobial photodynamic method reveals the opportunity for a new therapeutic approach that is based on the limited delivery of photosensitizer from the material surface. Nanoporous inorganic–organic composites were obtained by entrapment of photosensitizer Photolon in polysiloxanes that was prepared by the sol–gel method. The material was characterized by its porosity, optical properties (fluorescence and absorbance), and laser-induced antimicrobial activity against Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The permanent encapsulation of Photolon in the silica coating and the antimicrobial efficiency was confirmed by confocal microscope and digital holotomography. The generation of free radicals from nanoporous surfaces was proved by scanning Kelvin probe microscopy. For the first time, it was confirmed that Kelvin probe microscopy can be a label-free, noncontact alternative to other conventional methods based on fluorescence or chemiluminescence probes, etc. It was confirmed that the proposed photoactive coating enables the antibacterial photodynamic effect based on free radicals released from the surface of the coating. The highest bactericidal efficiency of the proposed coating was 87.16%. This coating can selectively limit the multiplication of bacterial cells, while protecting the environment and reducing the risk of surface contamination. [ABSTRACT FROM AUTHOR]

Liposomal technologies are used in order to improve the effectiveness of current therapies or to reduce their negative side effects. However, the liposome–erythrocyte interaction during the intravenous administration of liposomal drug formulations may result in changes within the red blood cells (RBCs). In this study, it was shown that phosphatidylcholine-composed liposomal formulations of Photolon, used as a drug model, significantly influences the transmembrane potential, stiffness, as well as the shape of RBCs. These changes caused decreasing the number of stomatocytes and irregular shapes proportion within the cells exposed to liposomes. Thus, the reduction of anisocytosis was observed. Therefore, some nanodrugs in phosphatidylcholine liposomal formulation may have a beneficial effect on the survival time of erythrocytes. [ABSTRACT FROM AUTHOR]

Background: Liposomes serve as delivery systems for biologically active compounds. Existing technologies inefficiently encapsulate large hydrophilic macromolecules, such as PVP-conjugated chlorin e6 (Photolon). This photoactive drug has been widely tested for therapeutic applications, including photodynamic reduction of atherosclerotic plaque. Methods: A novel formulation of Photolon was produced using "gel hydration technology". Its pharmacokinetics was tested in Sus scrofa f. domestica. Its cellular uptake, cytotoxicity, and ability to induce a phototoxic reaction were demonstrated in J774A.1, RAW264.7 macrophages, and vascular smooth muscle (T/G HA-VSMC) as well as in vascular endothelial (HUVEC) cells. Results: Developed liposomes had an average diameter of 124.7 ± 0.6 nm (polydispersity index (PDI) = 0.055) and contained >80% of Photolon). The half-life of formulation in S. scrofa was 20 min with area under the curve (AUC) equal to 14.7. The formulation was noncytotoxic in vitro and was rapidly (10 min) and efficiently accumulated by macrophages, but not T/G HA-VSMC or HUVEC. The accumulated quantity of photosensitizer was sufficient for induction of phototoxicity in J774A.1, but not in T/G HA-VSMC. Conclusions: Due to the excellent physical and pharmacokinetic properties and selectivity for macrophages, the novel liposomal formulation of Photolon is a promising therapeutic candidate for use in arteriosclerosis treatment when targeting macrophages but not accompanying vascular tissue is critical for effective and safe therapy. [ABSTRACT FROM AUTHOR]