Systematic review of photobiomodulation for the management of oral mucositis in cancer patients and clinical practice guidelines.

PURPOSE: To systematically review the literature and update the evidence-based clinical practice guidelines for the use of photobiomodulation (PBM), such as laser and other light therapies, for the prevention and/or treatment of oral mucositis (OM). METHODS: A systematic review was conducted by the Mucositis Study Group of the Multinational Association of Supportive Care in Cancer/International Society for Oral Oncology (MASCC/ISOO) using PubMed and Web of Science. We followed the MASCC methods for systematic review and guidelines development. The rigorously evaluated evidence for each intervention, in each cancer treatment setting, was assigned a level-of-evidence (LoE). Based on the LoE, one of the following guidelines was determined: Recommendation, Suggestion, or No Guideline Possible. RESULTS: Recommendations are made for the prevention of OM and related pain with PBM therapy in cancer patients treated with one of the following modalities: hematopoietic stem cell transplantation, head and neck (H&N) radiotherapy (without chemotherapy), and H&N radiotherapy with chemotherapy. For each of these modalities, we recommend 1-2 clinically effective protocols; the clinician should adhere to all parameters of the protocol selected. Due to inadequate evidence, currently, No Guideline Possible for treatment of established OM or for management of chemotherapy-related OM. The reported clinical settings were extremely variable, limiting data integration. CONCLUSIONS: The evidence supports the use of specific settings of PBM therapy for the prevention of OM in specific patient populations. Under these circumstances, PBM is recommended for the prevention of OM. The guidelines are subject to continuous update based on new published data.

Eradication of multi-drug resistant bacteria by a novel Zn-doped CuO nanocomposite.

Zinc-doped copper oxide nanoparticles are synthesized and simultaneously deposited on cotton fabric using ultrasound irradiation. The optimization of the processing conditions, the specific reagent ratio, and the precursor concentration results in the formation of uniform nanoparticles with an average size of ≈30 nm. The antibacterial activity of the Zn-doped CuO Cu0.88Zn0.12O in a colloidal suspension or deposited on the fabric is tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) bacteria. A substantial enhancement of 10,000 times in the antimicrobial activity of the Zn-CuO nanocomposite compared to the pure CuO and ZnO nanoparticles (NPs) is observed after 10 min exposure to the bacteria. Similar activities are observed against multidrug-resistant bacteria (MDR), (i.e., Methicillin-resistant S. aureus and MDR E. coli) further emphasizing the efficacy of this composite. Finally, the mechanism for this enhanced antibacterial activity is presented.

Visible light-induced OH radicals in Ga2O3: an EPR study.

Reactive oxygen species (ROS) were found to exist in water suspensions of several metal oxide nanoparticles (NPs), such as CuO, TiO2 and ZnO. Visible light irradiation enhanced the capability of TiO2 and ZnO NPs to generate ROS, thus increasing their antibacterial effects. Because of the possible toxic effects on the host tissue it is desired to find nano-metal oxides which do not produce ROS under room light, but only upon a strong external stimulus. Using the technique of electron-spin resonance (ESR) coupled with spin trapping, we examined the ability of Ga2O3 submicron-particle suspensions in water to produce reactive oxygen species with and without visible light irradiation. We found that in contrast to ZnO and TiO2 NPs, no ROS are produced by Ga2O3 under room light. Nevertheless blue light induced hydroxyl radical formation in Ga2O3. This finding might suggest that NPs of Ga2O3 could be used safely for infected skin sterilization.

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

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 7.2 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.

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

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.

A Novel Facial Cream Based on Skin-penetrable Fibrillar Collagen Microparticles.

Background: Collagen protein plays a notable role maintaining firm skin. Topical creams containing collagen fibers are widely available, but their usefulness is questionable due to limited skin penetration. When applied in a cream, collagen does not penetrate the skin leaving the skin structure unaffected. Objective: We formulated micronized collagen in a cream base. Using human skin samples, we sought to investigate the ability of the micronized collagen cream to penetrate human skin. Methods: Particle sizes of micronized marine collagen were evaluated using electron microscopy. Optical profilometry was conducted to evaluate skin topography and roughness. The antioxidant activity of the collagen was evaluated using the electron paramagnetic resonance technique by measuring the changes in free radical production. Collagen penetration depth in human skin samples was monitored using a non-invasive optical technique known as iterative multiplane optical property extraction, which works based on the detection of laser light phase changes following the presence of collagen particles in deep skin layers. Results: According to the electron microscopy, collagen particles were found to be of various sizes, the smallest being about 120nm in diameter. Skin topography measurements revealed that the treated collagen cream increased skin smoothness of the samples. Our results derived from the iterative multiplane optical property extraction indicated that micronized collagen in a cream base penetrates both the stratum corneum and the deep epidermal layers toward the dermis. Conclusion: Our investigation suggests that the collagen in the studied cream formulation was able to penetrate the stratum coreum and deep epidermal layers in human skin samples.

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

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.

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

BACKGROUND: 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. PURPOSE: The aim of the present study was to examine the bactericidal properties of nano-TiO(2) and ZnO combined with visible light on S. aureus and S. epidermitis, known for their high prevalence in infected wounds. STUDY: Using the technique of electron-spin resonance (ESR) coupled with spin trapping, we examined the ability of TiO(2) and ZnO nanoparticle suspensions in water to produce reactive oxygen species (ROS) with and without visible light irradiation. The possibility of exciting these nanoparticles with visible light in order to enhance their antimicrobial activity was also tested. RESULTS: Electron-spin resonance measurements revealed that ZnO and TiO(2) nanoparticles are able to produce ROS in water suspension. A remarkable enhancement of ROS production was found following illumination with blue light. In addition, illumination significantly enhanced the antibacterial activity of the nanoparticles. CONCLUSION: The results suggest that nanoparticles combined with visible light can be used for sterilization purposes and may be effective for treating infected wounds.

A novel explanation for the healing effect of the Er:YAG laser during skin rejuvenation.

In the present short communication, we would like to suggest a possible mechanism for the healing effects exerted by the erbium:yttrium-aluminum-garnet (Er:YAG) laser with a wavelength of 2940 nm (which surprisingly is the exact vibrational OH stretch frequency of water).

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

BACKGROUND AND OBJECTIVE: 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. EXPERIMENTAL: ROS production in Staphylococcus aureus and Escherichia coli as a function of wavelengths in the visible range (400-500, 500-800, 415, and 455 nm) was studied using the electron paramagnetic resonance (EPR) spin trapping technique. The phototoxicity of 415 and 455 nm light at different fluencies on the survival of S. aureus and E. coli was assessed by colony count of the bacteria following irradiation. RESULTS: ROS production following blue (400-500 nm) light illumination was found to be higher than that of red (500-800 nm). Within the blue range, light of 415 nm induced more ROS than 455 nm, which correlated with results obtained for the reduction in colony count of S. aureus and E. coli following illumination using equal intensities of these two wavelengths. At low fluencies, both 415 and 455 nm enhanced proliferation of S. aureus but reduced viability of E. coli. CONCLUSION: Intense blue light, preferably at 415 nm, could be used for bacterial eradication. However, it should be noted that low intensity of visible light can be dangerous since it may promote proliferation of the microorganisms.

Estimation of the optimal wavelengths for laser-induced wound healing.

BACKGROUND AND OBJECTIVES: According to earlier in vitro low level laser therapy (LLLT) studies, wavelengths in the red and near infrared range, that are absorbed by cytochrome oxidase, stimulate cell growth and hence wound healing. Wavelengths in the blue region that are absorbed by flavins were found to exert a bactericidal effect that is very important for treating infected wounds. However, as far as therapeutic application of light is concerned, penetration into the tissue must be considered. For this purpose we estimated the penetration depth as a function of the relevant wavelengths, using the formulae of the photon migration model for skin tissue. METHODS: We use the photon diffusion model, which is an analytical model for describing light transfer in biological tissues. We refer to the most common chromophores in human tissue and evaluate their volume fraction and concentration in skin cells. These empirically estimated mean wavelength-dependent absorption coefficients are then substituted in the theoretical expressions for the optical penetration depth in the tissue. The wavelengths, for which the penetration depth is the highest, are the optimal wavelengths to be used in wound healing treatments. RESULTS: Our model suggests that the optimal wavelengths for therapeutic treatments are in the red region with a local maximum at 730 nm. As to the blue region, a local maximum at 480 nm was found. CONCLUSION: Light at 480 nm should be used for treating infected wounds followed by 730 nm light for enhancing wound closure.

Visible light induces nitric oxide (NO) formation in sperm and endothelial cells.

BACKGROUND: Visible light-based stimulation using low-intensity lasers, LEDs, and broadband visible light devices has been recently introduced for therapy of human tissues in the absence of exogenous photosensitizers. Nitric oxide (NO) formation might be a potential mechanism for photobiomodulation because it is synthesized in cells by nitric oxide synthase (NOS), which contains both flavin and heme groups that absorb visible light. NO synthesis may also result from increased reactive oxygen species (ROS), which are found in various cell cultures following visible light illumination. NO is mainly known for inducing blood vessel dilation by endothelial cells, and in sperm cells NO is considered as an important agent in acrosome reaction and capacitation process, which are essential for successful fertilization. PURPOSE: To study NO formation in endothelial and sperm cells following visible light irradiation. MATERIALS AND METHODS: Sperm and endothelial cells were illuminated with broadband visible light, 400-800 nm, 130 mW/cm(2), for 5 minutes. During illumination, the endothelial cells were incubated in PBS free of Ca(+2) and Mg(+2), and the sperm cells were incubated in NKM buffer, to induce "stress conditions." NO production was quantified by using the Griess reagent which reacts with nitrite in the medium to yield an Azo compound which has an absorption band at 540 nm. RESULTS: Visible light illumination increased NO concentration both in sperm and endothelial cells. Blue light was more effective than red. Light-induced NO occurred only when endothelial cells were incubated in PBS free of Ca(+2) and Mg(+2), and in sperm cells, only when incubated in NKM. CONCLUSION: Light induces NO formation in endothelial and sperm cells. In endothelial cells, NO formation may explain previous results demonstrating enhanced wound healing and pain relief following illumination. In illuminated sperm cells, NO formation may account for the enhanced fertilization rate.

Detailed analysis of reactive oxygen species induced by visible light in various cell types.

BACKGROUND AND OBJECTIVE: Light in the visible and near infrared region stimulates various cellular processes, and thus has been used for therapeutic purposes. One of the proposed mechanisms is based on cellular production of reactive oxygen species (ROS) in response to illumination. In the present study, we followed visible light (VL)-induced hydroxyl radicals in various cell types and cellular sites using the electron paramagnetic resonance (EPR) spin-trapping technique. MATERIALS AND METHODS: Fibroblasts, sperm cells, cardiomyocytes, and skeletal muscle cells were irradiated with broadband (400-800 nm) VL. To detect ROS, the EPR spin-trapping technique coupled with the spin-traps 5,5-dimethyl pyrroline-N-oxide (DMPO) or 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) were used. To investigate the cellular sites of ROS formation, the cell-permeable molecule, isopropanol, or the nonpermeable proteins, bovine serum albumin (BSA) and superoxide dismutase (SOD), were introduced to the cells before irradiation. ROS production in mitochondria was measured using the fluorescent probe, MitoTracker Red (MTR). RESULTS AND CONCLUSIONS: The concentration of .OH increased both with illumination time and with cell concentration, and decreased when N(2) was bubbled into the cell culture, suggesting that VL initiates a photochemical reaction via endogenous photosensitizers. VL was found to stimulate ROS generation both in membrane and cytoplasm. In addition, fluorescent measurments confirmed the mitochondria to be target for light-cell interaction. The findings support the hypothesis that ROS are generated in various cellular sites following light illumination.

A novel explanation for the healing effect of the Er:YAG laser during skin rejuvenation.

The popularity of cutaneous laser resurfacing has soared in recent years. Ablative laser skin rejuvenation with carbon dioxide (CO2) and erbium:yttrium-aluminum-garnet (Er:YAG) lasers has been popularized and their side effects individually reported. It has been suggested that initial collagen contraction and thermal damage modulate wound healing. Progress in laser technology permits precise tissue removal and minimal thermal damage. However, mechanisms for cosmetic improvement have not yet been completely determined. In the present short communication, we would like to suggest a possible mechanism for the healing effects exerted by the Er:YAG laser.

Sensitivity of Staphylococcus aureus strains to broadband visible light.

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.

Topical Hyaluronic Acid Facial Cream with New Micronized Molecule Technology Effectively Penetrates and Improves Facial Skin Quality: Results from In-vitro, Ex-vivo, and In-vivo (Open-label) Studies.

Background: Topical hyaluronic acid (HA) has shown effectiveness in maintaining skin hydration. Topical creams containing HA are widely available, but their efficacy is limited by their lack of penetration into the skin due to the large molecule size of HA, the result of being formulated into a cream base. Objective: In this three-part study (in vitro, ex vivo, and in vivo), molecule sizes, penetration levels, and antiaging qualities of a topical HA facial cream that was formulated using a new technology that micronizes HA molecules (m-HA) were assessed. Methods and Results: Particle sizes of m-HA were evaluated using electron microscopy, which showed varying sizes, the smallest of which was 100nm in diameter. The antioxidation capabilities of m-HA were measured using electron spin resonance and were found to be higher than original HA. Skin penetration of the m-HA formulation was evaluated via immunohistochemical staining of porcine skin samples, which demonstrated penetration of the formulation into the stratum corneum and the deep epidermal layers toward the dermis. Antiaging qualities of the m-HA formulation were assessed in an open-label clinical study that included 36 healthy adult women. Skin parameters were measured objectively (e.g., Corneometer, Cutometer) and subjectively via patient questionnaire, results of which indicated significant improvements in facial skin hydration, elasticity, and wrinkle depth. Conclusion: The topical HA facial cream with m-HA technology demonstrated penetration into the epidermal skin layer, and, to our knowledge, our formulation is the first HA facial cream to achieve this. Clinical application of the facial cream demonstrated objective and subjective improvements in facial skin quality of healthy adult female subjects. Our results support the use of this new HA facial cream with m-HA technology as an effective antiaging topical therapy. Larger randomized, controlled studies are needed to confirm our findings.

A possible mechanism for visible light-induced wound healing.

BACKGROUND AND OBJECTIVES: 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. STUDY DESIGN/MATERIALS AND METHODS: In the present study, we examined the phototoxicity of broadband (400-800 nm, 120 J/cm(2)) visible light on the survival of several pathogenic bacteria: Staphylococcus aureus 195, Pseudomonas aeruginosa 1316, Escherichia coli 1313, and Serratia marcescens. These bacteria were chosen due to their high prevalence in infected wounds. The survival of bacterial cells following illumination was monitored by counting the number of colony forming units before and after exposure to light. RESULTS: Illumination with white light, 120 J/cm(2), caused a reduction of 62%, 83%, and 56% in the colony count of E. coli 1313, S. aureus 195 and S. marcescens, respectively, though no reduction in the viability of P. aeruginosa 1316 was demonstrated. The phototoxic effect was found to involve induction of ROS production by the bacteria. It was also found that illumination of S. aureus 195 and E. coli 1313 in the presence of pyocyanin, known to be secreted by P. aeruginosa, had a stronger bactericidal effect compared to illumination alone. CONCLUSION: Visible light at high intensity can kill bacteria in infected wounds. Thus, illumination of infected wounds with intense visible light, prior to low intensity illumination for stimulating wound closure, may reduce infection and promote healing.

Red light-induced redox reactions in cells observed with TEMPO.

OBJECTIVE: The aim of this study was to determine the wavelength dependence of light-induced redox reactions in cells, particularly whether there is any contribution by red wavelengths. An additional aim was to assess the potential of 2,2,6,6-tetramethyl piperidine-N-oxyl (TEMPO) as a tool for measuring these redox reactions. BACKGROUND DATA: Visible light has been shown to affect cells, and redox reactions, which have been detected previously using spin traps, have been proposed as a mechanism. However, there is little evidence that red light, which is used in most such experiments, is redox active in cells. METHODS: Redox activity was observed by measuring the decay of the electron paramagnetic resonance signal of TEMPO that occurs in the presence of illuminated cells. Color filters were used to generate blue, green, and red light, and the decay resulting from these wavelengths was compared to the decay caused by white light. RESULTS: Shorter wavelengths have a considerably stronger effect than longer wavelengths, although red light has some effect. Creation of reactive oxygen species by red light was confirmed with the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). CONCLUSION: Red light can induce redox reactions in illuminated cells. However, shorter wavelengths are more efficient in this regard. In addition, TEMPO was found to be a more sensitive probe than DMPO for detecting light-induced cellular redox reactions.

Chemiluminescent analysis of light-irradiated leukocytes as a diagnostic tool for fast identification of pathological states.

OBJECTIVE: Reactive oxygen species (ROS), mainly produced by polymorphonuclear neutrophils (PMN), are a significant part of host defense in pathologic states. We attempted to relate numbers of PMN and ROS generated within PMN to develop an alternative photochemical approach for evaluation of the potential of these cells to resist the development of inflammatory pathology. BACKGROUND DATA: Lack of sensitivity to light has been reported in healthy cells, while sensitivity to light characterizes cell pathology. METHODS: Human leukocytes from 34 donors were isolated and irradiated with a non-laser blue light (2 and 5 mW/cm(2) for 2 minutes), and a luminol-dependent chemiluminescence assay that reflects intracellular production of ROS was applied thereafter. The levels of basal chemiluminescence (BCL) were related to respective numbers of PMN. RESULTS: A light-insensitive cluster was discovered within the total sample and was considered to be a discrete nonpathological group. Following elimination of this group, the rest of the sample was divided into three well-defined light-sensitive groups, which were attributed to various pathological states, and differed in PMN numbers and BCL counts. Within these groups the two traits were interrelated, and each PMN range was associated with a respective level of intracellular ROS. CONCLUSIONS: Leukocyte responsiveness to light can be used for discrimination between pathological and nonpathological states and prognostic evaluation of pathological development. Patients exhibiting similar clinical symptoms could be divided into separate groups with potentially different outcomes. A novel definition of nonpathological states as well as the mechanism underlying the bell-shaped curve that delineates the relationship between PMN number and intracellular ROS is suggested in pathological states.

Photochemistry and photobiology of light absorption by living cells.

In this review, we summarize a part of our research concerning photobiostimulative effects on cardiomyocytes, sperm cells, and nerve cells. We concentrate on results demonstrating that photobiostimulation can be described by the Arndt-Schultz (A.S.) curve. Results monitoring an increase in reactive oxygen species (ROS) concentration following visible light irradiation describe the ascending part of the A.S. curve, whereas those that describe the antioxidant role of photobiostimulation represent the descending part of the curve.