The aim of the present work was to investigate the ability of inhibiting the growth of various strains of Staphylococcus aureus by low-intensity laser light. As object of research used methicillin-sensitive and methicillinresistant strains of Staphylococcus aureus. For irradiation was used a semiconductor laser, which generates linearly polarized radiation of the red spectral region (λ - 660 nm). Power density was 100 mW/cm2, irradiation time – 5, 10, 15 and 30 min, heat density respectively 30, 60, 90, and 180 J/cm2. It was established that low-intensity laser radiation has an inhibitory effect on growth of colonies of both methicillin-sensitive and methicillin-resistant strains of Staphylococcus aureus. But resistant strain is more sensitive to the action of red light, as the bacteriostatic effect is detected at the lower doses.
In this paper, a theoretical model of the formation of a local temperature field in suspensions of microorganisms with embedded plasmonic gold nanorods under irradiation by low-intensity NIR laser light was considered. The results of numerical modeling of the optical properties of plasmon nanorods used in the experiments, and the results of multiscale modeling of the parameters of local hyperthermia with various types of distribution of the concentration of plasmon nanoparticles are presented. Found that the process of concentration of nanoparticles, functionalized with human immune globulins IgA and IgG, around the cells of microorganisms with the formation of "clouds" leads to the appearance of a microscale zone of elevated temperature. This ensures a synergistic effect of a multiplicative increase in the volume of the hyperthermia zone. The results of numerical simulation provide a justification for the experimentally observed increase in the bacterium killing ability at laser hyperthermia of the cellular environment doped with functionalized nanoparticles, without a noticeable increment in the recorded average sample temperature when irradiated with a low intensity laser beam of around 100 mW/cm2.
Numerical modeling of spectral absorption and scattering properties of structures manufactured as the ordered arrays of plasmon nanoparticles is carried out in this work. The results of numerical 2D simulation of selective heating of an array of plasmon resonant gold nanodiscs irradiated by a CW NIR laser (810 or 1064 nm) are presented. Calculations fit well to experimental data received. We demonstrate the possibility to control the local amplification of a shining laser field in the space between nanodiscs, as well as plasmon resonance absorption of each individual nanodisc. The perspectives of application of such nanostructures for providing of precision dosed-up thermal effects in cells and biological tissues are discussed.
The influence of red laser irradiation on the growth of colonies of Staphylococcus aureus and photodynamic effect of the photosensitizer Photoditazine were performed. It was established that the emission of red laser light caused an inhibition of bacterial growth. This effect on standard strain of Staphylococcus aureus was evident only when relatively high doses of radiation (180 j/cm2). Photosensitivity of the methicillin-resistant strains was much higher: bacteriostatic effect of red light was observed already at the dose of 60 j/cm2 . Pre-treatment of bacterial cells by Photoditazine significantly enhances the inhibitory effect of the laser light.
The influence of red laser irradiation on the growth of colonies of methicillin-resistant strain of Staphylococcus aureus and photodynamic effects of the photosensitizers Photoditazine and Dimegin were performed. It was established that the red semiconductor laser (λ - 660 nm, 100 mW/cm2) at 10-, 15- and 30-mins exposure, has a direct bacteriostatic action on the growth of S. aureus. Pre-treatment of bacterial cells by Photoditazine significantly enhances the inhibitory effect. The photosensitizing action of Dimegin does not appear at influence on methicillin-resistant S. aureus.
The effect of NIR laser radiation (808 nm) on methicillin-sensitive and methicillin resistant strains of Staphylococcus aureus incubated with gold nanorods is studied. Nanorods having length of 44 (± 4) nm and diameter of 10 (± 3) nm with the absorption maximum in the NIR (800 nm), functionalized with human immunoglobulins IgA and IgG, were synthesized and used in the studies. The killing ability up to 97% of the microorganism populations by using this nanotechnology was shown.
The main goal of this study was to investigate the sensitivity of microorganisms to combined action of blue light and iron oxide nanoparticles. Two strains of Staphylococcus aureus – methicillin-sensitive and meticillin-resistant were used. As a blue light source LED with spectral maximum at 405 nm was taken. The light exposure was ranged from 5 to 30 min. The Fe2O3 (diameter ∼27 nm), Fe3O4 nanoparticles (diameter ∼19 nm), and composite Fe2O3/TiO2 nanoparticles (diameter ∼100 nm) were synthesized. It was shown that irradiation by blue light caused from 20% to 88% decrease in the number of microorganisms treated with nanoparticles. Morphological changes in bacterial cells after phototreatment were analyzed using scanning electron microscope.
Photodynamic inactivation of some microorganisms (St. aureus, E.coli) was investigated and their dependence on photo-physical properties of photosensitizers (PS) (cationic porphyrins and metalloporphyrins) was shown. One of the most important criteria for the effectiveness of the PS`s is the quantum yield of singlet oxygen (γΔ). Our investigations were shown that γΔ of metalloporphyrins, containing Zn, significantly higher than of metal-free porphyrins (85-97% and 77-79%, respectively). Previousl y experimentally we were found that under the action cationic porphyrins and metalloporphyrins on Gram (+) and Gram (-) microorganisms efficiency of metalloporphyrins Zn-TOEt4PyP and Zn-TBut4PyP in 3-5 times was higher than the metal-free porphyrins. In this study under the action of porphyrins and their Zn-derivatives on microorganism St. aureus such an effect was confirmed. Using the LED with a peak emission of 405 nm and a power density of 70 mW/cm2, and irradiation time of microorganisms from 5 to 30 minutes we have found, that at a concentration of 0.1 ug/ml the highest efficiency is observed of metalloporphyrin Zn-TBut3PyP. Upon irradiation of 10 and 15 min his efficiency is 3-5 times higher than the metal-free porphyrin TOEt4PyP, and irradiation for 30 min via Zn-TBut3PyP is practically completely kills microorganisms. These data correlate with the quantum yield of singlet oxygen for photosensitizers. The 30 mindirect sun exposure (power density of 70 mW/cm2) of photosensitizer solutions showed that a significant photobleaching of porphyrins and metalloporphyrins does not occur. Thus, Zn-containing cationic metalloporphyrins are highly efficient photosensitizers for photodynamic inactivation of microorganisms and PDT.
The main goal was to study the sensitivity of microorganisms to combined action of LED blue (405 nm) light and Fe2O3
nanoparticles. The bacterial strains used in this study were Staphylococcus aureus 209 P, S. simulans, Dermabacter
hominis (isolated from maxillary sinusitis). As blue light source LED with spectrum maxima at 405 nm was taken. The
light exposure was ranged from 5 to 30 min. Fe2O3 nanoparticles with average size about 8 nm in concentration of
0.001% were used. It was shown that irradiation with blue light caused 20 to 90% decrease in the number of
microorganisms treated with nanoparticles.
We assume that the effectiveness of phototherapy against microorganisms may be increased if together with the
photosensitizer a photocatalyst will be used. It was found that the combination of TiO2-nanoparticles and Brilliant
Green at two-wavelength irradiation with blue (405 nm) and red (625 nm) light provides a strong antimicrobial
effect on standard and clinical strains of Staphylococci.
We investigated the combination of near infrared (NIR) photothermolysis and photodynamic therapy against different
models of bacteria (S. aureus, S. epidermidis both methicillin susceptible and resistant), in order to discover possible
synergistic pathways in the fight against cancer. Photothermolysis was mediated by NIR light absorption from gold
nanorods, which were coated with polyethylene glycol to gain biocompatibility and provide for a convenient interface
with the bacterial cell walls. At the same time photodynamic therapy was delivered by administration of Indocyanine
Green (ICG), whose spectrum of molecular excitation overlaps the plasmonic oscillations of gold nanorods (~ 800 nm).
Therefore irradiation with NIR light from a low power diode laser resulted into simultaneous photothermolysis and
generation of reactive oxygen species and cytotoxic byproducts of ICG. We assessed the inhibition of the bacterial
colony forming ability under different NIR light exposures, and compared the performance of the combined treatment
(gold nanorods plus ICG) with the projected addition of the separate treatments (either gold nanorods or ICG). Our
preliminary results may originate from the interplay of synergistic and conflicting interactions, which may include e.g.
the enhanced intake of cytotoxic species due to permeabilization of the bacterial cell walls, quenching of ICG and
modification of the bleaching of ICG due to the noble metal surface.
Photodynamic therapy uses laser, LED or lamp light sources in combination with dyes - exogenous photosensitizers for
the enhancement and localization of photodynamic effects within the human body. We are developing a new approach of
improvement of the efficiency of antimicrobial phototherapy via combined application of photosensitizers and the
photocatalysts to pathogenic microorganisms. The main goal of the paper is to conduct experiments to study the action of
nanodyes, based on mixtures of nanoparticles and photosensitizers, in combination with LED irradiation of pathogens.
In the present work we have investigated in vitro sensitivity of microorganisms P. acnes and S. epidermidis to action of red (625 nm and 405 nm) and infrared (805 nm) radiations in combination with photosensitizes Methylene Blue and Indocyanine Green.
Acne is a genetic, hormonal disease characterized by overproduction of oil by the sebaceous glands, plugging of the
sebaceous glands to form micro- and macro- comedons and, finally, action of skin bacteria on oil trapped underneath the
skin to red inflammatory cystic lesions.
It was shown, that Propionibacterium acnes, the bacteria responsible for acne, was rather subjected to action of red and
infrared radiation. The effect of the given radiation amplified at this bacteria by various solutions of photosensitizes.
Photodynamic therapy (PDT) now is widespread for treatment of the various skin infections caused by
Propionibacterium acnes or Staphylococcii spp. We used PDT for influence on opportunistic microflora of human skin
presented by Staphylococcus hominis, S. warnery, S. epidermidis S. aureus 209 P, S. aureus 69. Species S. epidermidis,
S. aureus 209 P, S. hominis to some extent reduced colonies forming ability under action of dual wavelength LED-light
(442 nm and 597 nm). For species S. warnery, S. aureus 69 the increase in CFU number under action of light relative to
control was characteristic. Our experiments have shown, that phototherapy can be used for treatment of diseases
associated with S. aureus 209 P. The doze 8 J/cm2 caused reduction in CFU of this species on 40% relative to control.
Antimicrobial photodynamic therapy strives for creation new photosensitizes providing effective formation of singlet
oxygen at irradiation in various spectrum areas. Construction of a new generation of photosensitizes on the basis of
nanoparticles, such as TiO2, Ag, Au, SiO2 have great potential.
We have showed that different nanoparticles used as photosensitizes lead to different effects during photodynamic
action. Interaction of broadband light and Ag-SiO2 nanoparticle film decreased bacterial CFU. Irradiation of the test-cultures,
photosensitized by TiO2, stimulates microbial cell division.
Influence of infrared low-level laser irradiation (LLLI) on induction of synthesis of some cytokines such as interleykin-1
(Il-1), tumor necrosis factor-α (TNF-α), interferon-γ (INF-γ), interleykin-8 (Il-8) and interleykin-4 (Il-4) by the
neutrophils and macrophages in time of bacterial cells phagocytosis that was searched. As the object of analysis we used
peritoneal macrophages from white mice and neutrophils from peripheral blood of healthy donors. We used the laser
diod with spectrum maximum of 850 nm with doses 300, 900 and 1500 mJ (exposition -60, 180 and 300 s respectively;
capacity - 5 mW). We carried out the Enzyme-Linked Immunospot Assay (ELISA) to determine cytokine content during
phagocytosis after 3 h and 6 h. We found dynamics in production of the cytokines, which was different for the
neutrophils and macrophages. We showed that the infrared LLLI has significant stimulating activity on the
proinflammatory cytokines production by neutrophils and macrophages. Moreover we revealed dynamics changing in
the Il-8 and Il-4 production.
It was revealed that irradiation of different pathogenic microorganisms by low-coherent blue light (405 nm) decreases
population's quantity relatively to control for certain. Changing of biochemical activity is an important characteristic to
show effect of physical action. In the present study, we have investigated the effect of low-coherent light at emission
spectrum maximum near to 405 nm on bacterial metabolic activity.
Gram-negative E. coli, gram-positive facultative anaerobe cocci Staphylococcus lugdensis, Micrococcus halobius, and Stomatococcus mucilaginosus as subjects of study were chosen. LEDs with spectrum maxima at 405 nm (without any exogenous sensitizer) and 660 nm (in conjunction with methylene blue) and power densities of 23 mW/cm2 and 5.7 mW/cm2 accordingly as continuous light sources were chosen. Photosensitized light's affect by methylene blue was studied on E. coli only. The original scheme of experiment set up was developed. It permits one to increase expositions quantity in each experiment for more certain trend's construction over dose curves and decrease parasite flora sowing. As a result of accomplished studies it was established that blue low-coherent light have unalike weak light's dose depending suppressing effect on cocci whereas red low-coherent light have a moderate dose-depended suppressing effect at low irradiation doses and a moderate dose-depended stimulating effect at high irradiation doses on sensitized by MeBlue E. coli. For all ofthis, but Staphylococcus morphology changes were observed.
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