Antimicrobial photodynamic therapy—a promising treatment for prosthetic joint infections

Periprosthetic joint infection (PJI) is associated with high patient morbidity and a large financial cost. This study investigated Photodynamic Therapy (PDT) as a means of eradicating bacteria that cause PJI, using a laser with a 665-nm wavelength and methylene blue (MB) as the photosensitizer. The effectiveness of MB concentration on the growth inhibition of methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Pseudomonas aeruginosa and Acinetobacter baumannii was investigated. The effect of laser dose was also investigated and the optimized PDT method was used to investigate its bactericidal effect on species within planktonic culture and following the formation of a biofilm on polished titanium and hydroxyapatite coated titanium discs. Results showed that Staphylococci were eradicated at the lowest concentration of 0.1 mM methylene blue (MB). With P. aeruginosa and A. baumannii, increasing the MB concentration improved the bactericidal effect. When the laser dose was increased, results showed that the higher the power of the laser the more bacteria were eradicated with a laser power?≥?35 J/cm² and an irradiance of 35 mW/cm², eradicating all S. epidermidis. The optimized PDT method had a significant bactericidal effect against planktonic MRSA and S. epidermidis compared to MB alone, laser alone, or control (no treatment). When biofilms were formed, PDT treatment had a significantly higher bactericidal effect than MB alone and laser alone for all species of bacteria investigated on the polished disc surfaces. P. aeruginosa grown in a biofilm was shown to be less sensitive to PDT when compared to Staphylococci, and a HA-coated surface reduced the effectiveness of PDT. This study demonstrated that PDT is effective for killing bacteria that cause PJI.     

Inactivation of Proteolytic Enzymes from Porphyromonas gingivalis Using Light-activated Agents

. Previous studies have shown one of the causative agents of periodontitis, Porphyromonas gingivalis, can be killed by red light in the presence of the light-activated antimicrobial agent toluidine blue O (TBO). The purpose of this study was to determine the effects of irradiating the organism with red light in the presence of TBO on its proteolytic enzyme activity. Suspensions of P. gingivalis were exposed to light with a wavelength of 633 nm in the presence of various concentrations of TBO. Samples were taken at various times and their proteolytic activity determined by assay of azocasein hydrolysis. On exposure to 126 J of red light in the presence of 12.5 μg/ml of TBO the proteolytic enzyme activity was reduced by 100%. The results of this study have shown that the main virulence factor of P. gingivalis, its proteolytic activity, can be inactivated by red light in the presence of TBO. This, together with the known bactericidal activity of the TBO/light combination, suggests that photodynamic therapy may prove important in reducing the effectiveness of P. gingivalis as a periodontopathogen in vivo. Paper received 24 June 1998; accepted after revision 20 June 1999.     

Nd:YAG laser clinical assisted in class II furcation treatment

The Nd:YAG laser efficacy associated with conventional treatment for bacterial reduction has been investigated throughout literature. The purpose of this study was to evaluate the bacterial reduction after Nd:YAG laser irradiation associated with scaling and root planning in class II furcation defects in patients with chronic periodontitis. Thirty-four furcation lesions were selected from 17 subjects. The control group received conventional treatment, and the experimental group received the same treatment followed by Nd:YAG laser irradiation (100 mJ/pulse; 15 Hz; 1.5 W, 60 s, 141.5 J/cm²). Both treatments resulted in improvements of most clinical parameters. A significant reduction of colony forming unit (CFU) of total bacteria number was observed in both groups. The highest reduction was noted in the experimental group immediately after the treatment. The number of dark pigmented bacteria and the percentage of patients with Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans reduced immediately after the treatment and returned to values close to the initial ones 6 weeks after the baseline for both groups. The Nd:YAG laser associated with conventional treatment promoted significant bacterial reduction in class II furcation immediately after irradiation, although this reduction was not observed 6 weeks after the baseline.     

Effect of 308-nm excimer laser light on peri-implantitis-associated bacteria—an in vitro investigation

Dental implants are becoming increasingly important in prosthodontic rehabilitation. Bacterial infections, however, can induce bone loss and jeopardize clinical success. Recent literature has demonstrated that infrared CO₂ laser light is suitable for the decontamination of exposed implant surfaces. The aim of the present study was to investigate the influence of 308-nm excimer laser irradiation on peri-implantitis-associated bacteria in vitro. In this study, a XeCl excimer laser (308 nm) was used (Summit Technology, Boston, USA). Both aerobe (Streptococcus mutans, S. sanguis, Actinomyces naeslundii) and anaerobe microorganisms (A. odontolyticus, Prevotella melaninogenica) were tested. According to previous studies, a constant energy of 0.8 J/cm² and a constant frequency of 20 Hz were used for all irradiations. Colony-forming units after laser irradiation were counted. Excimer laser irradiation showed significant influence on the growth of all microorganisms. As compared to S. mutans and S. sanguis, A. naeslundii demonstrated higher sensitivity to laser irradiation. Anaerobe microorganisms, in contrast, demonstrated that a total of 200 pulses were sufficient to reduce the replication of these germs for more than 99.9%. Excimer laser irradiation (λ = 308 nm) can significantly reduce both aerobe and anaerobe microorganisms. Depending on the parameters chosen, 200 pulses are sufficient for sterilization. New studies are necessary to evaluate if this wavelength is more of value in the treatment of peri-implantitis than other wavelengths or conventional therapies.     

Study of the direct bactericidal effect of Nd:YAG and diode laser parameters used in endodontics on pigmented and nonpigmented bacteria

Laser light can be used during endodontic procedures to sterilize the root canal by destroying bacteria. Previous in-vitro studies that investigated the mechanism of the destruction of bacteria inhabiting the root canal by 1,064-nm Nd:YAG and 808-nm diode laser light used substrates that absorb light in the near-infrared (NIR) spectrum. These substrates heat the bacterial microenvironment, which possibly contributes to cell death. To determine the direct effect of laser light on the bacterial sample in the absence of detrimental heating, a sapphire substrate, which is virtually transparent in NIR spectrum, was inoculated with bacterial samples and subjected to laser irradiation at 1,064 nm (1.5 W, 15 Hz) and at 808 nm (1.5 W, 20 Hz). Enterococcus faecalis, Escherichia coli, and Porphyromonas gingivalis bacteria were used. E. faecalis and E. coli were largely unaffected by laser light. The viability of P. gingivalis, a pigmented bacterium, was directly affected by both NIR wavelengths (a 57% decrease of viability at 1,064 nm and a 31% decrease at 808 nm). Our results indicate that the primary mediator of cell death appears to be the interaction between NIR laser light and the bacterial microenvironment, most likely in the form of heating. Our research suggests that when optimizing the efficacy of laser-assisted endodontic sterilization of the root canal, the optical characteristics of the bacterial microenvironment play a key role, as nonpigmented bacteria appear to be virtually transparent at 808 nm and 1,064 nm.     

Semiconductor diode laser endophotocoagulation

We successfully used a semiconductor diode laser to deliver endophotocoagulation burns to the retina of a rabbit. The diode laser employed emits light at a wavelength of 817 nm (near infrared). It has a power output of up to 1.0 W in the continuous-wave mode, equivalent to the capability of current argon laser endophotocoagulators. A standard, commercially available fiberoptic endophotocoagulation probe was used to deliver the laser burns. We used power settings ranging from 300 mW to 400 mW and exposure times of 0.1 to 0.2 seconds to produce chorioretinal burns that appeared clinically and histopathologically indistinguishable from those induced with conventional wavelengths. This new laser system has the decided advantages over traditional endophotocoagulators of being much smaller, less costly, and requiring no water cooling, without sacrificing power output or ease of delivery.     

Preliminary evaluation of a novel side-fire diode laser emitting light at 940 nm, for the potential treatment of benign prostatic hyperplasia: ex-vivo and in-vivo investigations

OBJECTIVES

To evaluate, ex vivo and in vivo, the tissue‐removal capacity and coagulation properties of a diode laser emitting light at 940 nm, as in the search for potential therapeutic strategies for benign prostatic hyperplasia that cause less morbidity than transurethral resection of the prostate (TURP), various types of lasers have been tested.

MATERIALS AND METHODS

A diode laser system (prototype; wavelength 940 nm, Dornier MedTech, Wessling, Germany) was evaluated in an isolated, blood‐perfused ex‐vivo porcine kidney model at 10–60 W (five kidneys). An in‐vivo beagle model was used to investigate the effects on six prostate lobes at a generator output power level of 200 W. After the laser treatment tissue were examined histologically to compare the depth of coagulation and vaporization.

RESULTS

With increasing generator output power levels there was an increasing vaporization and coagulation ability for the diode laser at 940 nm in the ex‐vivo model. At 60 W the mean (sd ) vaporization depth was 1.72 (0.47) mm with a coagulation zone of 9.56 (0.26) mm. In vivo, the diode laser caused rapid ablation with no intraoperative haemorrhage. Histologically, the zone of coagulation had a mean (sd ) depth of 4.25 (0.15) mm at 200 W. The tissue removal capacity was estimated at 0.874–1.583 g/min in vivo.

CONCLUSIONS

Our findings indicate that diode‐laser vaporization at 940 nm is feasible and might be effective for acutely relieving bladder outlet obstruction in an in‐vivo setting. Due to its mean coagulation zone of 4.25 mm the diode laser seems to have effective haemostatic properties.     

Laser phototherapy effect on protein metabolism parameters of rat salivary glands

The aim of this study was to evaluate the effects of infrared diode laser phototherapy (LP) on tissues of the submandibular gland (SMG) and parotid gland (PG). Wistar rats were randomly divided into experimental (A and B) and control (C) groups. A diode laser, 808 nm wavelength, in continuous wave mode, was applied to the PG, SMG and sublingual gland in the experimental groups on two consecutive days. The doses were 4 J/cm² and 8 J/cm², and total energy was 7 J and 14 J, respectively. The power output (500 mW) and power density (277 mW/cm²) were the same for both experimental groups. In order to visualize the area irradiated by the infrared laser, we used a red pilot beam (650 nm) with 3 mW maximum power for the experimental groups. For the control group, the red pilot beam was the only device used. The SMG and PG were removed after 1 week of the first irradiation. Total protein concentration, amylase, peroxidase, catalase and lactate dehydrogenase assays were performed, as well as histological analysis. Statistical tests revealed significant increase in the total protein concentration for groups A and B in the parotid glands (P < 0.05). Based on the results of this study, LP altered the total protein concentration in rats’ parotid glands.     

Helium-neon laser: A contraindication for infected wounds? In vitro study on pseudomonas aeruginosa

The purpose of this investigation was to examine the susceptibility ofPseudomonas aeruginosa to helium-neon (He-Ne) laser in order to gain an insight into the clinical implications for this type of low-level laser therapy (LLLT) in the treatment of infected wounds. Suspensions, in the presence and the absence of methylene blue (MB, 0.001% w/v), were exposed to the light from a 9 mW He-Ne laser for 5 and 50 min. Exposure of samples without MB did not affect the viability of this organism based on the lack of significant differences in the number of colony forming units (CFU) between irradiated and control samples. In the presence of MB, statistically significant mean reductions in CFU of 39.5% (22.6 J cm^-2) and 58.2% (226 J cm^-2) were found, and growth-free zones in irradiated confluent platings could be observed. Since no logarithmic reductions were achieved, the clinical implementation of He-Ne laser as a bactericidal agent seems to be of no relevance yet. Otherwise, no stimulation of bacterial growth was observed. Therefore, infection as a contraindication for LLLT should be excluded.     

Organic light emitting diode improves diabetic cutaneous wound healing in rats

A major complication for diabetic patients is chronic wounds due to impaired wound healing. It is well documented that visible red wavelengths can accelerate wound healing in diabetic animal models and patients. In vitro and in vivo diabetic models were used to investigate the effects of organic light emitting diode (OLED) irradiation on cellular function and cutaneous wound healing. Human dermal fibroblasts were cultured in hyperglycemic medium (glucose concentration 180 mM) and irradiated with an OLED (623 nm wavelength peak, range from 560 to 770 nm, power density 7 or 10 mW/cm² at 0.2, 1, or 5 J/cm²). The OLED significantly increased total adenosine triphosphate concentration, metabolic activity, and cell proliferation compared with untreated controls in most parameters tested. For the in vivo experiment, OLED and laser (635 ± 5 nm wavelength) treatments (10 mW/cm², 5 J/cm² daily for a total of seven consecutive days) for cutaneous wound healing were compared using a genetic, diabetic rat model. Both treatments had significantly higher percentage of wound closure on day 6 postinjury and higher total histological scores on day 13 postinjury compared with control. No statistical difference was found between the two treatments. OLED irradiation significantly increased fibroblast growth factor‐2 expression at 36‐hour postinjury and enhanced macrophage activation during initial stages of wound healing. In conclusion, the OLED and laser had comparative effects on enhancing diabetic wound healing.     

Comparison of the methylene blue and toluidine blue photobactericidal efficacy against gram-positive and gram-negative microorganisms

BACKGROUND AND OBJECTIVE: Studies on the photobactericidal efficacy of methylene blue (MB) and toluidine blue (TB) have shown inconsistent results in the literature. This study evaluated the bactericidal efficacy of MB and TB against different bacteria under light and dark conditions to determine the most effective bactericidal dye. STUDY DESIGN/MATERIALS AND METHODS: Suspensions of Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis, Hemophilus influenzae, Escherichia coli, and Pseudomonas aeruginosa in saline were treated in dark and red laser light conditions in the presence of each dye using an argon pumped-dye and a diode laser emitting light at 630 and 664 nm, respectively. The effect of dye concentration, dark incubation time, the fluence and intensity of laser light on the destruction of different bacteria were compared. RESULTS: Both dyes eradicated all examined bacteria under laser light. The complete photodestruction of microorganisms was reached at TB concentrations of 1.5-7-fold less than that of MB. CONCLUSION: TB exhibits a greater bactericidal activity than MB against most bacteria in dark and light conditions. Mostly, these results are consistent with their respective dye partition coefficients.     

Acute Effects of Photodynamic Treatment on Elastic Fibre Network in Atherosclerotic Plaques of Rabbit Aorta

Our objective was to demonstrate the acute effects of photodynamic treatment on the elastic framework in the atherosclerotic plaque. The photosensitiser, mono-l-aspartyl chlorin 5₆ (NP5₆), was administered intravenously, at a dose of 5 mg/kg of body weight, to cholesterol-fed, atherosclerotic rabbits. Six hours later, visible atherosclerotic lesions of the abdominal aorta were irradiated with a diode laser, wavelength 664 nm. The energy administered ranged from 50 J/cm² to 200 J/cm². The abdominal aorta was then excised and digested by a modified hot alkaline method. Scanning electron microscopy revealed the destruction of the architecture of the elastic fibre network in the atherosclerotic plaque, whereas no change was seen in the non-atheromatous aortic wall. Damage to the elastic fibre network was more obvious in plaque that was exposed to higher energy levels. No significant changes were observed in laser-treated plaques in animals that did not receive the NP5₆ pretreatment. Findings suggest that atherosclerotic plaques of the abdominal aorta can be selectively degraded by laser irradiation following pretreatment with the photosensitiser, NP5₆. Received for publication 23 July 1997; accepted following revision 20 January 1998.     

Sensitization ofStreptococcus sanguis to killing by light from a helium/neon laser

Solutions of various photosensitizers were added to suspensions of the dental plaqueforming organism,Streptococcus sanguis. These were then exposed to light from a 7.3 mW Helium/Neon (He/Ne) laser for various time periods and the numbers of surviving cells determined by viable counting. Toluidine blue O, haematoporphyrin ester, thionin and methylene blue enabled substantial kills of the organism after irradiation times as short as 10 s which corresponds to an energy dose of 73 mJ. However, haematoporphyrin ester and, to a lesser extent, methylene blue were toxic to the organism in the absence of He/Ne light. Aluminium disulphonated phthalocyanine and crystal violet were ineffective as photosensitizers under the experimental conditions employed. The killing of sensitizedS. sanguis by light from a low-power laser suggests the possibility of a new approach to the control of dental plaque bacteria.     

Diode laser and microvascular carotid anastomosis: A preliminary study

A crossed carotid end-to-end anastomosis was performed in 20 Wistar rats by means of a diode laser device (wavelength 830 nm and power output 3 W in continuous wave). The diode laser energy was delivered into a micromanipulator coupled to an OPMI 1 Zeiss operating microscope with a focused spot of 300 μm diameter. The vessel sealing was effected on common carotids (0.8–1.2 mm) using laser shots (average 9) of 680 mW power and 4.5 s duration and 962 W cm⁻² irradiance each. The good vascular flow was confirmed by Doppler spectral analysis and angiography performed on days 0, 10 and 30. Light and scanning electron microscopy showed that reendothelialization was complete on day 10 whilst collagenous fusion of media and adventitia was obvious. The patency rate was 90% impaired by a lethal thrombosis. The efficiency of the diode laser was compared to that of other types of LAVA and to manual microanastomosis.     

The photodynamic effect of a pulsed dye laser on human bladder carcinoma cells in vitro

Summary The photodynamic effect of a pulsed flashlamp pumped dye laser on cultured human bladder carcinoma cells was studied. MGH-U1 cells were incubated for 1 h in dihaematoporphyrin ether (DHE) and then exposed to green laser light (504 nm, 20 Hz) for varying laser power densities (50–100 mW/cm² and exposure times (2–15 s), representing incident pulse energy fluences of 2.5–5 mJ/cm² and energy densities of 0.1–1.5 J/cm². The cell survival was measured by clonogenic assay and controls exposed to either laser light alone or DHE in the dark showed no cytotoxicity. Sensitised cells were killed by energy densities of less than 1 J/cm² (LD₉₀=0.54 J/cm²). This demonstrates the probable effectiveness of a pulsed dye laser for photodynamic therapy provided that pulse fluence are below the saturation threshold of the photosensitiser (10 mJ/cm²).     

Wavelength-dependent effect of tetra(m-hydroxyphenyl)chlorin for photodynamic therapy in an ‘early’ squamous cell carcinoma model

The purpose of the present study was to correlate the wavelength of the irradiation source with the phototoxic activity of tetra(m-hydroxyphenyl)chlorin (mTHPC) in healthy and neoplastic mucosae. The hamster tumour model for early squamous cell carcinoma was used in these experiments. In vitro and in vivo studies have shown that mTHPC absorbs significantly at 652 nm (1, 2). This wavelength is used currently in clinical mTHPC photodynamic therapy (PDT) trials. In order to study the wavelength dependence of the phototoxic effect on normal and tumour tissues, irradiation tests were performed 4 days after injection of 0.5mg kg^-1 mTHPC. An argon-ion pumped dye laser was used as the light source. The light dose of 12 J cm^-2 was delivered at a light dose rate of 150 mW cm^-2. The wavelength was varied between 642.5 and 665 nm at 2.5-nm increments. The PDT damage was evaluated in serial Haematoxylin and Eosin stained sections using a tissue-damage scale. Light between 647.5 and 652.5 nm induced the highest damage to both the healthy and tumour mucosae. At wavelengths equal to or below 645 nm, and equal to or above 655 nm, tissue damage decreased. Wavelengths below 642 nm and above 660 nm did not induce any visible tissue damage. These results suggest that the in vivo optimal wavelength range for PDT with mTHPC is between 647 and 652 nm. This information is essential for selecting an appropriate light source.     

Effect of blood on lethal photosensitization of bacteria in subgingival plaque from patients with chronic periodontitis

The purpose of this study was to determine whether bacteria in subgingival plaque samples from patients with chronic periodontitis could be sensitized to killing by low-power laser light in the presence of blood. Toluidine blue O (45 μg ml⁻¹) was added to the plaque samples which were then exposed to light from a 7.3 mW HeNe laser for 30 or 120 s in the presence and absence of 10% horse blood. Viable counts of various groups and species of bacteria were determined before and after irradiation. A substantial bactericidal effect was obtained after irradiation for 30s regardless of whether or not blood was present. However, in most cases irradiation in the absence of blood resulted in greater decreases in the viable counts of aerobes, anaerobes, streptococci and blackpigmented anaerobes. When the samples were irradiated for 120s, 10% blood had little effect on the kills attained and elimination of periodontopathogenic species (black-pigmented anaerobes andFusobacterium nucleatum) was achieved both in the presence and absence of blood.     

Clinical application of helium neon (632 nm) plus infrared diode laser GaAIAs (830 nm) and CO2laser in treatment of onychomycotic nails

Onychomycosis (fungal infection of the toe nail) is difficult to cure. The aim of this study was to evaluate the method of surgical avulsion using a CO₂laser (7W, 0.1 mm) and using a new protocol of low level laser therapy Helium Neon (632 nm, 1.5 mW, 2 J cm^–2) plus infrared diode laser GaAIAs (830 nm, 50 mW, 4 J cm^–2) every other day to improve the recurrence rate, pain score and healing time. Seventy-eight patients were divided into three groups (A, B and C). The ANOVA statistical tests showed that there was a significant difference between the group A, B and B, C (P<0.005) in the measured mean healing time and pain score but no statistical difference between the group A and C (P<0.01). It was concluded that low level laser therapy reduced pain, improved the healing time and had a lower recurrence rate.     

Effects of photodynamic laser and violet-blue led irradiation on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> biofilm and <Emphasis Type="Italic">Escherichia coli</Emphasis> lipopolysaccharide attached to moderately rough titanium surface: in vitro study

Effective decontamination of biofilm and bacterial toxins from the surface of dental implants is a yet unresolved issue. This study investigates the in vitro efficacy of photodynamic treatment (PDT) with methylene blue (MB) photoactivated with λ 635 nm diode laser and of λ 405 nm violet-blue LED phototreatment for the reduction of bacterial biofilm and lipopolysaccharide (LPS) adherent to titanium surface mimicking the bone-implant interface. Staphylococcus aureus biofilm grown on titanium discs with a moderately rough surface was subjected to either PDT (0.1% MB and λ 635 nm diode laser) or λ 405 nm LED phototreatment for 1 and 5 min. Bactericidal effect was evaluated by vital staining and residual colony-forming unit count. Biofilm and titanium surface morphology were analyzed by scanning electron microscopy (SEM). In parallel experiments, discs coated with Escherichia coli LPS were treated as above before seeding with RAW 264.7 macrophages to quantify LPS-driven inflammatory cell activation by measuring the enhanced generation of nitric oxide (NO). Both PDT and LED phototreatment induced a statistically significant (p?<?0.05 or higher) reduction of viable bacteria, up to ?99 and ?98% (5 min), respectively. Moreover, besides bactericidal effect, PDT and LED phototreatment also inhibited LPS bioactivity, assayed as nitrite formation, up to ?42%, thereby blunting host inflammatory response. Non-invasive phototherapy emerges as an attractive alternative in the treatment of peri-implantitis to reduce bacteria and LPS adherent to titanium implant surface without causing damage of surface microstructure. Its efficacy in the clinical setting remains to be investigated.     

Transmission of laser energy and assessment of target temperature in an experimental model of laser balloon angioplasty

The potential application of laser balloon angioplasty (LBA) is limited because of difficulties in temperature control and dosimetry during trans-balloon laser irradiation. An experimental model of LBA was designed to help understand the polymer membrane effects of two materials on tissue temperature. The durability of two types of polymer films with different optical properties, polyethylene terephthalate (PET), a low scattering polymer and polyetheretherketone (PEEK), a high scattering polymer, were examined as potential balloon material. The PEEK film (thickness: 50 μm) was melted and perforated by light from a diode laser (wavelength: 808±10 nm, irradiance: 1469 W cm⁻², mean exposure time: 30±7 s). On the other hand, the PET film with the same thickness was completely intact after 1 min exposure at the same irradiance. Diode laser irradiation was applied to indocyanine green stained human aortic media in three different exposure methods; directly, through the free PET and through the pressed PET film. Temperatures of laser-irradiated specimens were measured using an infra-red thermal camera with an 8–12 μm bandwidth, and corrected for the emissivity of the tissue and the PET film. Results demonstrated underestimation of surface temperature because of low transmittance of radiated intensity through the free PET film and a significant (p<0.001) increase of corrected temperature (δT=169±32°C) through the pressed-PET exposure compared with the direct exposure (ΔT=81±7°C), even though the same laser irradiance (18.6W cm⁻²) was applied for 5s. That is, the tightly PET-covered tissue develops a significantly higher temperature during diode laser irradiation, and this increased thermal effect can be advantageous for laser welding with less power in laser balloon angioplasty.