Potential of using medicinal plant extracts as photosensitizers for antimicrobial photodynamic therapy.

Antimicrobial photodynamic therapy (APDT) is a promising approach to overcome antimicrobial resistance. However, for widespread implementation of this approach, approved photosensitizers are needed. In this study, we used commercially available preparations (Calendulae officinalis floridis extract, Chamomillae recutitae floridis extract, Achillea millefolii herbae extract; Hypericum perforatum extract; Eucalyptus viminalis folia extract) as photosensitizers for inactivation of gram-negative (Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) bacteria. Spectral-luminescent analysis has shown that the major chromophores are of chlorophyll (mainly chlorophyll a and b) and hypericin nature. The extracts are efficient generators of singlet oxygen with quantum yield (Î³Δ ) from 0.40 to 0.64 (reference compound, methylene blue with Î³Δ = 0.52). In APDT assays, bacteria before irradiation were incubated with extracts for 30 min. After irradiation and 24 h of incubation, colony-forming units (CFU) were counted. Upon exposure of P. aeruginosa to radiation of 405 nm, 590 nm, and 660 nm at equal energy dose of 30 J/cm2 (irradiance - 100 mW/cm2 , exposure time - 5 min), the most pronounced effect is observed with blue light (>3 log10 reduction); in case of S. aureus, the effect is approximately equivalent for light of indicated wavelengths and dose (>4 log10 reduction).

Identification by methods of steady-state and kinetic spectrofluorimetry of endogenous porphyrins and flavins sensitizing the formation of reactive oxygen species in cancer cells.

The question about acceptor molecules of optical radiation that determine the effects of photobiomodulation in relation to various types of cells still remains the focus of attention of researchers. This issue is most relevant for cancer cells, since, depending on the parameters of optical radiation, light can either stimulate their growth or inhibit them and lead to death. This study shows that endogenous porphyrins, which have sensitizing properties, may play an important role in the implementation of the effects of photobiomodulation, along with flavins. For the first time, using steady-state and kinetic spectrofluorimetry, free-base porphyrins and their zinc complexes were discovered and identified in living human cervical epithelial carcinoma (HeLa) cells, as well as in their extracts. It has been shown that reliable detection of porphyrin fluorescence in cells is hampered by the intense fluorescence of flavins due to their high concentration (micromolar range) and higher (compared to tetrapyrroles) fluorescence quantum yield. Optimization of the spectral range of excitation and the use of extractants that provide multiple quenching of the flavin component while increasing the emission efficiency of tetrapyrroles makes it possible to weaken the contribution of the flavin component to the recorded fluorescence spectra.

Design and Realization of Polymeric Waveguide/Microring Structures for Telecommunication Domain.

Polymer-based micro-optical components are very important for applications in optical communication. In this study, we theoretically investigated the coupling of polymeric waveguide and microring structures and experimentally demonstrated an efficient fabrication method to realize these structures on demand. First, the structures were designed and simulated using the FDTD method. The optical mode and loss in the coupling structures were calculated, thereby giving the optimal distance for optical mode coupling between two rib waveguide structures or for optical mode coupling in a microring resonance structure. Simulations results then guided us in the fabrication of the desired ring resonance microstructures using a robust and flexible direct laser writing technique. The entire optical system was thus designed and manufactured on a flat base plate so that it could be easily integrated in optical circuits.

Comparative Effect of Low-intensity Laser Radiation in Green and Red Spectral Regions on Functional Characteristics of Sturgeon Sperm.

A comparative study of the effect of low-intensity laser radiation in green (λ = 532 nm) and red (λ = 632.8 nm) spectral regions at equal average irradiance (3 mW cm-2 ) on functional characteristics of Siberian sturgeon spermatozoa is carried out. Confirmation of the photobiomodulation effect of the radiation is obtained by analyzing spermatozoa motility, percentage of motile spermatozoa and fertilization rate. It is shown that, depending on the energy dose, the laser radiation in red and green spectral regions can have both stimulatory and inhibitory effects on spermatozoa motility. Contrary to popular belief that the short-wavelength radiation has great prospects in reproductive biotechnologies (due to more efficient absorption of radiation by cellular chromophores and increased generation of ROS), convincing evidence of a more pronounced stimulatory effect of radiation in the red spectral region was obtained. For the first time, metal-free porphyrins capable of acting as endogenous photosensitizers generating ROS were detected and identified in animal sperm. Using luminol-dependent chemiluminescence, it is shown that the increased production of ROS capable of exerting an inhibitory effect on biological systems at high concentrations is among the possible reasons for reduction in the stimulatory effect of radiation when moving from red to green spectral region.

Blebbistatin, a myosin inhibitor, is phototoxic to human cancer cells under exposure to blue light.

BACKGROUND: Blebbistatin is a new inhibitor of cell motility. It is used to study dynamics of cytokinesis machinery in cells. However, the potential of this inhibitor as an anticancer agent has not been studied so far. METHODS: Cytotoxicity of blebbistatin was evaluated in five human cell lines, FEMX-I melanoma, U87 glioma, androgen independent Du145 and androgen sensitive LNCaP prostate adenocarcinoma, and F11-hTERT immortalized fibroblasts. Phototoxicity of blebbistatin was assessed in these cell lines after their exposure to a blue light (390-470 nm). Photostability of blebbistatin and its reactive oxygen species (ROS) generating properties were measured during irradiation with the blue light. RESULTS: Blebbistatin at a concentration range of 10-200 µmol/L was toxic to all studied cells. Toxic concentrations (TC) were about 10-25 µmol/L corresponding to TC10, 50-100 µmol/L to TC50 and 140-190 µmol/L to TC90. Only for the U87 glioma cells TC90 could not be measured as the highest studied concentration of 200 µmol/L gave around 70% toxicity. However, after exposure to the blue light blebbistatin exhibited phototoxicity on the cells, with a cytotoxicity enhancement ratio that was greatest for the FEMX-I cells (about 9) followed by LNCaP (5), Du145 (3), U87 (2) and F11-hTERT (1.7) cells. CONCLUSIONS: Blebbistatin inhibits cell motility and viability. Under exposure to the blue light blebbistatin exhibits photodynamic action on human cancer cells. During the irradiation blebbistatin oxidizes dihydrorhodamine 123 but not Singlet Oxygen Sensor Green. GENERAL SIGNIFICANCE: Our findings offer new possibilities for blebbistatin as a potential anticancer and photodynamic agent.