Photodynamic activity of the boronated chlorin e6 amide in artificial and cellular membranes

Photodynamic therapy of the experimental tumors of different morphological types with liposomal boronated chlorin е6

The article summarizes the results of studies of the effectiveness of photodynamic therapy using a new domestic photosensitizer liposomal borated chlorin e6 (LBC) after its parenteral administration (intraperitoneal and intravenous). Antitumor efficacy was evaluated in rats with M-1 sarcoma and PC-1 alveolar liver cancer and mice with B16 melanoma and Ehrlich’s carcinoma, which were transplanted subcutaneously into the thigh area of the animals. The aim of the study was to determine the optimal regimes of photodynamic therapy that would allow achieving the maximum antitumor effect up to 21 days after the photodynamic therapy. The therapy was carried out under the control of the accumulation of the photosensitizer in the tumor and surrounding tissues of the thigh by selecting the doses of the drug and the parameters of laser radiation (energy density and power density). The effectiveness of therapy was assessed by the inhibition of tumor growth, by the percentage of animals with complete tumor regression, by the absolute growth rate in animals with continued tumor growth compared to controls. The results of our studies have shown that the domestic photosensitizer liposomal borated chlorin e6 has high antitumor activity in vivo. In an experimental study of the photosensitizer under certain PDT modes, the maximum antitumor effect (complete tumor regression in 100% of animals) was obtained up to 21 days after PDT in all tumor models used.

Dimeric derivatives of chlorophyll a with fragments of oligoethylene glycols as spacers between macrocycles: Synthesis, dark and photoinduced cytotoxic activity

In the present work, new dimeric derivatives of chlorophyll [Formula: see text] with oligoethylene glycol fragments as spacers between macrocycles were synthesized and their dark and photoinduced cytotoxic activities were studied in experiments in vitro. Dimeric derivatives were found to have a relatively low dark cytotoxic activity. It should be noted that most of the studied dimeric derivatives exhibited photoinduced cytotoxic activity at concentrations that were several times lower than those for dark cytotoxic activity. The photoinduced action of one of the most active compounds, a phorbin-chlorin dimer with the triethylene glycol fragment as a spacer between the macrocycles (13), was analysed in more detail in experiments in vitro. Compound (13) was shown to rapidly enter HeLa cells, however, its cytotoxic effect on these cells develops rather slowly. The results of the analysis of the activity of caspase-3 showed that Compound (13) does not cause apoptosis of HeLa cells. Analysis of the degree of hemolysis of mammalian erythrocytes as a result of exposure to Compound (13) showed that plasma membranes are a probable target of this substance.

Cellular compartments challenged by membrane photo-oxidation

The lipid composition impacts directly on the structure and function of the cytoplasmic as well as organelle membranes. Depending on the type of membrane, specific lipids are required to accommodate, intercalate, or pack membrane proteins to the proper functioning of the cells/organelles. Rather than being only a physical barrier that separates the inner from the outer spaces, membranes are responsible for many biochemical events such as cell-to-cell communication, protein-lipid interaction, intracellular signaling, and energy storage. Photochemical reactions occur naturally in many biological membranes and are responsible for diverse processes such as photosynthesis and vision/phototaxis. However, excessive exposure to light in the presence of absorbing molecules produces excited states and other oxidant species that may cause cell aging/death, mutations and innumerable diseases including cancer. At the same time, targeting key compartments of diseased cells with light can be a promising strategy to treat many diseases in a clinical procedure called Photodynamic Therapy. Here we analyze the relationships between membrane alterations induced by photo-oxidation and the biochemical responses in mammalian cells. We specifically address the impact of photosensitization reactions in membranes of different organelles such as mitochondria, lysosome, endoplasmic reticulum, and plasma membrane, and the subsequent responses of eukaryotic cells.

Coupling Chlorin e6 to the surface of Nanoscale Gas Vesicles strongly enhance their intracellular delivery and photodynamic killing of cancer cells

Protein-based nanobubbles such as halophilic archaeabacterial gas vesicles (GVs) represent a new class of stable, homogeneous nanoparticles with acoustic properties that allow them to be visualized by ultrasound (US) waves. To design GVs as theranostic agents, we modified them to respond to light, with a view to locally generate reactive oxygen species that can kill cancer cells. Specifically, up to 60,000 photoreactive chlorin e6 (Ce6) molecules were chemically attached to lysine ε-amino groups present on the surface of each purified Halobacterium sp. NRC-1 GV. The resulting fluorescent NRC-1 Ce6-GVs have dimensions comparable to that of native GVs and were efficiently taken up by human breast [MCF-7] and human hypopharyngeal [FaDu-GFP] cancer cells as monitored by confocal microscopy and flow cytometry. When exposed to light, internalized Ce6-GVs were 200-fold more effective on a molar basis than free Ce6 at killing cells. These results demonstrate the potential of Ce6-GVs as novel and promising nanomaterials for image-guided photodynamic therapy.

Green synthesis of silver nanoparticles via Cynara scolymus leaf extracts: The characterization, anticancer potential with photodynamic therapy in MCF7 cells

In this study, we report on the synthesis of silver nanoparticles (AgNPs) from the leaf extracts of Cynara scolymus (Artichoke) using microwave irradiation and the evaluation of its anti-cancer potential with photodynamic therapy (PDT). Silver nanoparticles formation was characterized by scanning electron microscopy with energy dispersive x-ray spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Silver nanoparticles formation was also investigated the surface charge, particle size and distribution using zetasizer analysis. The cytotoxic effect of AgNPs and/or PDT was studied by MTT assay and migration by the scratch assay. The apoptotic inducing ability of the AgNPs and/or PDT was investigated by intracellular ROS analysis, antioxidant enzyme levels (SOD, CAT, GPx and GSH), Hoechst staining and Bax/Bcl-2 analysis using western blotting. The mean particle size of produced AgNPs was found 98.47±2.04 nm with low polydispersity (0.301±0.033). Zeta potential values of AgNPs show -32.3± 0.8 mV. These results clearly indicate the successful formation of AgNPs for cellular uptake. Mitochondrial damage and intracellular ROS production were observed upon treatment with AgNPs (10μg/mL) and PDT (0.5 mJ/cm²) showed significant reducing cell migration, expression of Bax and suppression of Bcl-2. Significantly, biosynthesized AgNPs showed a broad-spectrum anti-cancer activity with PDT therapy and therefore represent promoting ROS generation by modulating mitochondrial apoptosis induction in MCF7 breast cancer cells.

Diphytanoyl lipids as model systems for studying membrane-active peptides

The branched chains in diphytanoyl lipids provide membranes with unique properties, such as high chemical/physical stability, low water permeability, and no gel-to-fluid phase transition at ambient temperature. Synthetic diphytanoyl phospholipids are often used as model membranes for electrophysiological experiments. To evaluate whether these sturdy lipids are also suitable for solid-state NMR, we have examined their interactions with a typical amphiphilic peptide in comparison with straight-chain lipids. First, their phase properties were monitored using ³¹P NMR, and the structural behaviour of the antimicrobial peptide PGLa was studied by ¹⁹F NMR and circular dichroism in oriented membrane samples. Only lipids with choline headgroups (DPhPC) were found to form stable lipid bilayers in oriented samples, while DPhPG, DPhPE and DPhPS display non-lamellar structures. Hence, the experimental temperature and hydration are crucial factors when using supported diphytanoyl lipids, as both parameters must be maintained in an appropriate range to avoid the formation of non-bilayer structures. For the same reason, a high content of other diphytanoyl lipids besides DPhPC in mixed lipid systems is not favourable. Unlike the situation in straight-chain membranes, we found that the α-helical PGLa was not able to insert into the tightly packed fluid bilayer of DPhPC but remained in a surface-bound state even at very high peptide concentration. This behaviour can be explained by the high cohesivity and the negative spontaneous curvature of the diphytanoyl lipids. These characteristic features must therefore be taken into consideration, both, in electrophysiological studies, and when interpreting the structural behaviour of membrane-active peptides in such lipid environment.

Carboranyl-Chlorin e6 as a Potent Antimicrobial Photosensitizer

Antimicrobial photodynamic inactivation is currently being widely considered as alternative to antibiotic chemotherapy of infective diseases, attracting much attention to design of novel effective photosensitizers. Carboranyl-chlorin-e₆ (the conjugate of chlorin e₆ with carborane), applied here for the first time for antimicrobial photodynamic inactivation, appeared to be much stronger than chlorin e₆ against Gram-positive bacteria, such as Bacillus subtilis, Staphyllococcus aureus and Mycobacterium sp. Confocal fluorescence spectroscopy and membrane leakage experiments indicated that bacteria cell death upon photodynamic treatment with carboranyl-chlorin-e₆ is caused by loss of cell membrane integrity. The enhanced photobactericidal activity was attributed to the increased accumulation of the conjugate by bacterial cells, as evaluated both by centrifugation and fluorescence correlation spectroscopy. Gram-negative bacteria were rather resistant to antimicrobial photodynamic inactivation mediated by carboranyl-chlorin-e₆. Unlike chlorin e₆, the conjugate showed higher (compared to the wild-type strain) dark toxicity with Escherichia coli ΔtolC mutant, deficient in TolC-requiring multidrug efflux transporters.

Synthesis of amide derivatives of chlorin e6 and investigation of their biological activity

In this work there is a synthesis of new photosensitizers which is based on amide derivatives of chlorin е6 . For the disclosure of an extra ring of the initial compound - pheophorbide a 1, we used primary aliphatic amines with 4-12 carbon atoms in the alkyl chain. The reaction is carried out under mild conditions in chloroform with heating to 40 ºС. The structure of all compounds obtained was confirmed by means of electronic, IR, 1Н-NMR spectroscopy and mass-spectrometry. The photoactivity and the dark toxicity of the compounds 2b-2h were investigated on two cancer cell lines: P-388 and K-562. The biological investigations revealed a good photoactivity and low dark toxicity of all compounds 2b-2f. The amide derivatives of chlorin е6 with 6 and 7 carbon atoms in the alkyl part showed the best results in our research. Thus, in this paper we propose a reliable scheme of synthesis of chlorin's photosensitizers which are promising agents for PDT.

Unsaturated lipids protect the integral membrane peptide gramicidin A from singlet oxygen

In contrast to expectations that unsaturated fatty acids contribute to oxidative stress by providing a source of lipid peroxides, we demonstrated the protective effect of double bonds in lipids on oxidative damage to membrane proteins. Photodynamic inactivation of gramicidin channels was decreased in unsaturated lipid compared to saturated lipid bilayers. By estimating photosensitizer (boronated chlorine e6 amide) binding to the membrane with the current relaxation technique, the decrease in gramicidin photoinactivation was attributed to singlet oxygen scavenging by double bonds in lipids rather than to the reduction in photosensitizer binding. Gramicidin protection by unsaturated lipids was also observed upon induction of oxidative stress with tert-butyl hydroperoxide.