ABSTRACT
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).
ABSTRACT
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.
ABSTRACT
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.
