the-synergistic-effect-visible-light-gentamycin-on-pseudomona

The Synergistic Effect of Visible Light and Gentamycin on <em>Pseudomona aeruginosa</em> Microorganisms

Recently there were several publications on the  bactericidal effect of visible light, most of them claiming that blue part of  the spectrum (400 nm-500 ...

Chronic wounds resistant to conventional therapy have been treated successfully with low energy lasers and light emitting diodes (LEDs) in the visible and near IR region. It has been proposed that production of low level reactive oxygen species (ROS) following illumination is the first step of photobiomodulation. It was also shown that white light (400-800 nm) has similar stimulatory effects as lasers and LEDs. ROS at higher levels are toxic to cells and bacteria.

A possible mechanism for visible light-induced wound healing.

The phototoxic effect of illumination with broadband visible light on the viability of two Staphylococcus aureus strains was examined in the present study. A difference in the light sensitivity of the two strains was found. Illumination of the tested strains with a fluence rate of 180 J cm(-2) caused a reduction of up to 99.8% in the colony count of one of the strains (the "sensitive" strain). Illumination of the other strain (the "resistant" strain) resulted in a 55.5% reduction in viability. Proliferation of both strains was observed at low fluence rates of light. The phototoxic effect was found to be dependent on oxy radical production. The light-sensitive strain produced higher amounts of hydroxyl and superoxide radicals than the "resistant" strain. Adaptation to oxidative stress was exhibited only by the "resistant" strain. The "sensitive" strain produced ten times more endogenous porphyrins and secreted almost nine times more porphyrins than the resistant strain. Furthermore, the "resistant" strain produced twice as many carotenoids that protect the strain from illumination than the "sensitive" strain. These results indicate that high intensities of visible light cause bacterial photoeradication, a reaction which may assist wound healing by killing the infecting bacteria. On the other hand, low intensities of white light were found to enhance bacterial proliferation and thus prolong wound infection.

Sensitivity of Staphylococcus aureus strains to broadband visible light.

Visible light (400-800 nm) at high intensity was previously found to kill bacteria that are frequently found in infected wounds, while low-power white light enhances bacterial proliferation. The phototoxic effect was found to involve induction of reactive oxygen species (ROS) production by the bacteria. The aim of the present study was to identify the most effective wavelengths in the visible range for inducing a bactericidal effect.

Visible light-induced killing of bacteria as a function of wavelength: implication for wound healing.

Non-healing ulcers represent a significant dermatological problem. Recently, conventional therapy-resistant chronic ulcers have been treated with low energy lasers or light-emitting diodes in the visible and near IR region, but only a few placebo-controlled double-blind studies have been performed to support the efficacy of this approach. The aim of the present study was to evaluate the efficacy of a broadband (400-800â€‰ nm) visible light device in the treatment of leg or foot ulcers.

Visible light-induced healing of diabetic or venous foot ulcers: a placebo-controlled double-blind study.

Metal oxide nanoparticles have marked antibacterial activity. The toxic effect of these nanoparticles, such as those comprised of ZnO, has been found to occur due to an interaction of the nanoparticle surface with water, and to increase with a decrease in particle size. In the present study, we tested the ability of ZnO nanoparticles to affect the viability of the pathogenic yeast, Candida albicans (C. albicans). A concentration-dependent effect of ZnO on the viability of C. albicans was observed. The minimal fungicidal concentration of ZnO was found to be 0.1 mg ml(-1) ZnO; this concentration caused an inhibition of over 95% in the growth of C. albicans. ZnO nanoparticles also inhibited the growth of C. albicans when it was added at the logarithmic phase of growth. Addition of histidine (a quencher of hydroxyl radicals and singlet oxygen) caused reduction in the effect of ZnO on C. albicans depending on its concentration. An almost complete elimination of the antimycotic effect was achieved following addition of 5 mM of histidine. Exciting the ZnO by visible light increased the yeast cell death. The effects of histidine suggest the involvement of reactive oxygen species, including hydroxyl radicals and singlet oxygen, in cell death. In light of the above results it appears that metal oxide nanoparticles may provide a novel family of fungicidal compounds.

Antifungal activity of ZnO nanoparticles--the role of ROS mediated cell injury.

In recent years nano-metaloxides which easily penetrate into the cells with special interest due to their higher chemical reactivity as compared to that of similar materials in the bulk form. Of particular interest are nano-TiO(2) and ZnO, which have been widely used for their bactericidal and anticancerous properties.

Enhanced inactivation of bacteria by metal-oxide nanoparticles combined with visible light irradiation.

Photoexcited TiO(2) has been found to generate reactive oxygen species, yet the precise mechanism and chemical nature of the generated oxy species especially regarding the different crystal phases remain to be elucidated. Visible light-induced reactions of a suspension of titanium dioxide (TiO(2)) in water were investigated using electron paramagnetic resonance (EPR) coupled with the spin-trapping technique. Increased levels of both hydroxyl (Ë™OH) and superoxide anion (Ë™O(2)(-)) radicals were detected in TiO(2) rutile and anatase nanoparticles (50 nm). The intensity of signals assigned to the Ë™OH and Ë™O(2)(-) radicals was larger for the anatase phase than that originating from rutile. Moreover, illumination with visible (nonUV) light enhanced Ë™O(2)(-) formation in the rutile phase. Singlet oxygen was not detected in water suspension of TiO(2) neither in rutile nor in anatase nanoparticles, but irradiation of the rutile phase with visible light revealed a signal, which could be attributed to singlet oxygen formation. The blue part of visible spectrum (400-500 nm) was found to be responsible for the light-induced ROS in TiO(2) nanoparticles. The characterization of the mechanism of visible light-induced oxy radicals formation by TiO(2) nanoparticles could contribute to its use as a sterilization agent.

The different behavior of rutile and anatase nanoparticles in forming oxy radicals upon illumination with visible light: an EPR study.

To date, there is still a lack of definite knowledge regarding the interaction of CuO nanoparticles with bacteria and the possible permeation of the nanoparticles into bacterial cells. This study was aimed at shedding light on the size-dependent (from the microscale down to the small nanoscale) antibacterial activity of CuO. The potent antibacterial activity of CuO nanoparticles was found to be due to ROS-generation by the nanoparticles attached to the bacterial cells, which in turn provoked an enhancement of the intracellular oxidative stress. This paradigm was confirmed by several assays such as lipid peroxidation and reporter strains of oxidative stress. Furthermore, electron microscopy indicated that the small nanoparticles of CuO penetrated the cells. Collectively, the results reported herein may reconcile conflicting concepts in the literature concerning the antibacterial mechanism of CuO nanoparticles, as well as highlight the potential for developing sustainable CuO nanoparticles-based devices for inhibiting bacterial infections.

Understanding the antibacterial mechanism of CuO nanoparticles: revealing the route of induced oxidative stress.

Low-level visible light irradiation was found to stimulate proliferation potential of various types of cells in vitro. Stem cells in general are of significance for implantation in regenerative medicine. The aim of the present study was to investigate the effect of low-level light irradiation on the proliferation of mesenchymal stem cells (MSCs). MSCs were isolated from the bone marrow, and light irradiation was applied at energy densities of 2.4, 4.8, and 7.2Â J/cm(2). Illumination of the MSCs resulted in almost twofold increase in cell number as compared to controls. Elevated reactive oxygen species and nitric oxide production was also observed in MSCs cultures following illumination with broadband visible light. The present study clearly demonstrates the ability of broadband visible light illumination to promote proliferation of MSCs in vitro. These results may have an important impact on wound healing.

Low-level visible light (LLVL) irradiation promotes proliferation of mesenchymal stem cells.

Abstract Objective: The purpose of this article was to review studies that use visible light instead of dangerous ultraviolet (UV) radiation, for inducing antibacterial properties in metal oxide nanoparticles (NPs). Background data: Metal oxide NPs such as ZnO, CuO, and TiO2 are frequently studied for their antibacterial effects, based on their capability to generate reactive oxygen species (ROS) in their water suspensions, following UV light absorption. Methods: Research articles on shifting metal oxide NPs absorption into the visible light region, published up to 2011, were retrieved from library sources, as well as PubMed and MEDLINE(Â®) databases. Results: The studies indicated that doping metaloxide NPs with transition metals ions, or attaching the metal oxide nanoparticles to an organic molecule, enhanced their activity in the visible and near infrared (NIR) range. Moreover, ZnO and TiO2 nanoparticles were found to have an absorption peak in UV-A, with a marked absorption in the blue region. Conclusions: It is possible to extend the absorption region of metal oxide NPs to the red/NIR, increasing their antibacterial activity without inducing damage to tissues and cells.

Article	Year
A possible mechanism for visible light-induced wound healing. Lasers in surgery and medicine\| PubMed ID: 18727022	2008
Sensitivity of Staphylococcus aureus strains to broadband visible light. Photochemistry and photobiology\| PubMed ID: 18764895	2009
Visible light-induced killing of bacteria as a function of wavelength: implication for wound healing. Lasers in surgery and medicine\| PubMed ID: 20662022	2010
Visible light-induced healing of diabetic or venous foot ulcers: a placebo-controlled double-blind study. Photomedicine and laser surgery\| PubMed ID: 21214497	2011
Antifungal activity of ZnO nanoparticles--the role of ROS mediated cell injury. Nanotechnology\| PubMed ID: 21289395	2011
Enhanced inactivation of bacteria by metal-oxide nanoparticles combined with visible light irradiation. Lasers in surgery and medicine\| PubMed ID: 21412807	2011
The different behavior of rutile and anatase nanoparticles in forming oxy radicals upon illumination with visible light: an EPR study. Photochemistry and photobiology\| PubMed ID: 21988075	2012
Understanding the antibacterial mechanism of CuO nanoparticles: revealing the route of induced oxidative stress. Small (Weinheim an der Bergstrasse, Germany)\| PubMed ID: 22888058	2012
Low-level visible light (LLVL) irradiation promotes proliferation of mesenchymal stem cells. Lasers in medical science\| PubMed ID: 23007630	2013
Visible Light-Induced Antibacterial Activity of Metaloxide Nanoparticles. Photomedicine and laser surgery\| PubMed ID: 23448383	2013

Anat Lipovsky

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