Near infra-red diode laser for photodynamic tumour therapy using bacteriochlorina

Clonogenic cell survivals were performed in order to assess the feasibility of tumour cell kill with an experimental diode laser emitting 250 mW of light at λ = 779 nm using the photosensitizer bacteriochlorina(BCA). The AlGaAs diode laser is based on organometallic vapour epitaxial crystal growth technology. The electrical to optical conversion efficiency amounts to 21% and the beam divergence is 47° by 7.0° full width at half maximum. BCA was proved to be an effective non-toxic photosensitizer in vitro and in vivo. It has a major absorption peak at 760 nm where tissue penetration of light is optimal. Clonogenic T24 human bladder carcinoma cell survivals were photosensitizer concentration and light dose dependent. A 0.1% survival rate was obtained with an illumination intensity of 50 mWcm⁻² for 90 s (4.5 Jcm⁻²) and a BCA concentration of 6 μgml⁻¹. Illumination without BCA at energy levels exceeding the PDT levels with a factor 10, or BCA alone without illumination had no effect on the cells in the clonogenic cell survivals. The combination of BCA with a near infra-red diode laser is most promising for photodynamic tumour therapy as a result of the reliability, compactness and relatively low price of the illumination device, the high transmittance of near infra-red light in tissue and the tumour killing potential of BCA.     

Colonic mucosectomy using laser photodynamic therapy

Photodynamic therapy (PDT) involves photosensitizing tissue and then activating it with monochromatic light, causing necrosis. Precise control of the extent of injury should be possible by varying the energy density of the light applied to the target tissue. We tested the sensitivity of colonic tissue to PDT by injecting 10 mg/kg Photofrin II intraperitoneally in 10 rats. After 24 hr the left colon was opened and cleansed. A 1.0-cm2 area of mucosa was exposed to 630 nm (red) light produced by an argon-pumped dye laser. Pairs of rats were treated with energy densities of either 10, 20, 40, 60, or 80 J/cm2, controlled by varying exposure times. After 48 hr, we sacrificed the rats and fixed, sectioned, and stained the left colons. The depth of injury was measured with an ocular micrometer and expressed as a percentage of normal bowel wall thickness. A curve was fit to the data points by computerized nonlinear regression. The relationship between depth of injury (Y) and energy density (X) was found to fit the equation Y = 1 - aebx, where constants a = 1.15 and b = -0.0353, (R2 = 0.93, P less than 0.001). The relationship between injury and energy density is biphasic, rising rapidly from 0 to 40 J/cm2 and more slowly after this point, suggesting that colonic mucosa is more sensitive to PDT than muscularis, providing a margin of safety against perforation. Bowel perforation did not occur in this study but is predicted by extrapolation for energy densities of 100 J/cm2 or greater. These data indicate that photodynamic colonic mucosectomy is possible.     

Preoperative laser photodynamic therapy in combination with operation in lung cancer

Fifteen patients with lung cancer were treated by combined preoperative photodynamic therapy and operation. Preoperative photodynamic therapy was performed for the purpose of either reducing the extent of resection or increasing operability. Clinically, five patients had Stage I disease, two had Stage II, seven had Stage III, and one had Stage IV. There were two cases of tracheal invasion from primary foci, three cases of intrabronchial polypoid tumor or invasion of the carina by primary lesions, eight cases of polypoid tumor or invasion of the main bronchus, and two cases of double primary foci. Argon dye lasers were used in this study. Preoperative laser photodynamic therapy was performed 48 to 72 hours after intravenous administration of hematoporphyrin derivative. Therapeutic conditions were 60 to 600 joules for the superficial invasive areas and additional 200 to 800 mW for 8 to 15 minutes for polypoid tumors. Operation was performed 1 to 9 weeks after photodynamic therapy. The initial purpose of photodynamic therapy was achieved in 11 of 15 patients treated. In four of five originally inoperable cases, conversion to an operable condition was achieved. Ten patients were originally candidates for pneumonectomy, and it became possible to reduce the extent of resection to lobectomy or bilobectomy in seven of them. This study suggests that photodynamic therapy may have an important role in combination with operation and other modalities in advanced lung cancers.     

The impact of antimicrobial photodynamic therapy in an artificial biofilm model

The susceptibility of bacterial cultures in biofilm formations is important for a variety of clinical treatment procedures. Therefore, the aim of the study was to assess the impact of laser-induced antimicrobial photodynamic therapy on the viability of Streptococcus mutans cells employing an artificial biofilm model. Using sterile chambered coverglasses, a salivary pellicle layer was formed in 40 chambers. Streptococcus mutans cells were inoculated in a sterile culture medium. Employing a live/dead bacterial viability kit, bacteria with intact cell membranes stained fluorescent green. Each pellicle-coated test chamber was filled with 0.7 ml of the bacterial suspension and analysed using a confocal laser scanning microscope within a layer of 10 μm at intervals of 1 μm from the pellicle layer. Phenothiazine chloride was used as a photosensitizer in all 40 test chambers. A diode laser (wavelength 660 nm, output power 100 mW) was used to irradiated 20 chambers for 2 min. Fluorescence values in the test chambers after laser irradiation (median 2.1 U, range 0.4–3.4 U) were significantly lower than baseline values after adding the photosensitizer (median 3.6 U, range 1.1–9.0; p?p?>?0.05). The present study indicated that laser irradiation is an essential part of antimicrobial photodynamic therapy to reduce bacteria within a layer of 10 μm. Further studies are needed to evaluate the maximum biofilm thickness that still allows a toxic effect on microorganisms.     

Treatment of residual pockets with photodynamic therapy, diode laser, or deep scaling. A randomized, split-mouth controlled clinical trial

The objective of this work was to compare the effects of antimicrobial photodynamic therapy (PDT), diode soft laser therapy (DSL), and thorough deep scaling and root planing (SRP) for treatment of residual pockets. Thirty-two subjects with a history of non-surgical treatment for chronic periodontitis were included. Residual pockets >4?mm and bleeding upon probing were debrided with an ultrasonic device and then subjected to either PDT, DSL, or SRP. Pocket probing depth (PPD), bleeding on probing (BOP), and gingival recession were monitored over 6?months. Counts of four microorganisms were determined by direct hybridization with RNA probes. PPD decreased from 5.6?±?1.0 to 3.8?±?1.1 in 6?months (p?4?mm with BOP depended on initial PPD (p?=?0.036) and was higher if treated with DSL (p?=?0.034). Frequencies of three microorganisms were significantly lower in PDT- and SRP-treated than in DSL-treated quadrants (p?=?0.02) after 14?days, but not at months 2 and 6. All three treatments resulted in a significant clinical improvement. PDT and SRP suppressed Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola stronger, and resulted in fewer persisting pockets after 6?months, than DSL application.     

Endoscopic laser therapy in malignant tracheobronchial obstruction using sequential Nd YAG laser and photodynamic therapy

BACKGROUND: Because the survival after treatment of advanced inoperable endo-tracheobronchial carcinoma is so poor, a pilot study was undertaken to evaluate the combined cumulative effect on survival of neodymium yttrium aluminium garnet (Nd YAG) laser followed by photodynamic treatment used endoscopically. METHODS: Seventeen patients who presented between January 1992 and March 1996 with inoperable tracheobronchial lesions causing more than 50% endoluminal obstruction were selected to enter the pilot study. Initially they had bronchoscopic Nd YAG laser treatment to debulk the tumour, and this was followed six weeks later by photodynamic therapy to treat the residual tumour. RESULTS: All patients had symptomatic relief and at least a partial response, and seven had a complete response for 3-6 months. Eight of the 17 (47%) survived for at least two years and 11 (65%) survived for a year or more. The median survival of the 10 patients who had died by the time of writing was 18.5 months (range 5-39), 95% confidence interval (CI) 9.9 to 29.5. CONCLUSIONS: Combined Nd YAG laser and endoscopic photodynamic therapy may be an effective palliative treatment for patients with inoperable endotracheobronchial cancer.


     

Treatment of experimental periodontitis in rats using repeated adjunctive antimicrobial photodynamic therapy

The aim of this study was to histologically and histometrically evaluate the influence of repeated adjunctive antimicrobial photodynamic therapy (aPDT) on bone loss (BL) in furcation areas in rats. Periodontitis was induced by placing a ligature around the mandibular molar in 75 rats. The animals were divided into five groups: the SS group was treated with saline solution (SS); the SRP group received scaling and root planing (SRP); the aPDT1 group received SRP as well as toluidine blue (TBO) and low-level laser therapy (LLLT; InGaAlP, 660 nm; 4.94 J/cm²/point) postoperatively at 0 h; the aPDT2 group received SRP as well as TBO and LLLT postoperatively at 0, 24, 28, and 72 h; and the aPDT3 group received SRP, TBO, and LLLT postoperatively at 0, 48, 96, and 144 h. The area of BL in the furcation region of the molar was histometrically analyzed. Data were analyzed statistically (P?<?0.05). Animals treated with a single episode of aPDT showed less BL at days 7 and 30 than those who received only SRP treatment. No significant differences were found among the aPDT groups (P?>?0.05). Repeated aPDT did not improve BL reduction when compared to a single episode of aPDT.     

Effect of antimicrobial photodynamic therapy on periodontally infected tooth sockets in rats

Lasers in Medical Science - The aim of the present study was to evaluate the antimicrobial effect of antimicrobial photodynamic therapy (aPDT) in alveolar treatment of areas with induced...     

Endoscopic diode laser therapy for chronic radiation proctitis

The purpose of this study is to determine the effectiveness of endoscopic diode laser therapy in patients presenting rectal bleeding due to chronic radiation proctitis (CRP). A retrospective analysis of CRP patients who underwent diode laser therapy in a single institution between 2010 and 2016 was carried out. The patients were treated by non-contact fibers without sedation in an outpatient setting. Fourteen patients (median age 77, range 73–87 years) diagnosed with CRP who had undergone high-dose radiotherapy for prostatic cancer and who presented with rectal bleeding were included. Six required blood transfusions. Antiplatelet (three patients) and anticoagulant (two patients) therapy was not suspended during the treatments. The patients underwent a median of two sessions; overall, a mean of 1684 J of laser energy per session was used. Bleeding was resolved in 10/14 (71%) patients, and other two patients showed improvement (93%). Only one patient, who did not complete the treatment, required blood transfusions after laser therapy; no complications were noted during or after the procedures. Study findings demonstrated that endoscopic non-contact diode laser treatment is safe and effective in CRP patients, even in those receiving antiplatelet and/or anticoagulant therapy.     

Scanning laser system for photodynamic therapy of choroidal neovascularization

BACKGROUND AND OBJECTIVES: In order to improve selectivity of photodynamic therapy (PDT) to choroidal neovascularization (CNV) associated with age-related macular degeneration, a laser scanning technique was applied to perform focal laser irradiation to the retina, and the occlusion effects of a new device to the choriocapillaris were evaluated in primate eyes. STUDY DESIGN/MATERIALS AND METHODS: The device contains lasers for fundus observation of 785 nm and for PDT of 670 nm, matching the absorption peak of a photosensitizer, ATX-S10(Na). The laser irradiated the shape on the retina specified before treatment and shut off automatically when the predetermined treatment was achieved. The occlusion of the choriocapillaris after PDT was documented by fluorescein and indocyanine green angiography and histology. RESULTS: The area designated for PDT was easily drawn on the touch-screen monitor, and occlusion of the choriocapillaris was achieved precisely in the area pre-selected for treatment with 5 J/cm(2) or more of radiance following administration of 8 mg/kg ATX-S10(Na). CONCLUSIONS: This device is useful for irradiating CNV of any shape, sparing the surrounding retina. Since our previous studies suggested that selective occlusion of CNV would decrease not only the functional disturbance caused by PDT, but also the recurrence of CNV, the present device may allow more effective PDT than the slit-lamp system presently used.     

Effect of methylene blue-mediated antimicrobial photodynamic therapy on dentin caries microcosms

Antimicrobial photodynamic therapy (aPDT) has been proposed as an adjuvant treatment of dental caries, although there are no well-defined protocols to its clinical application. This study aimed to evaluate the influence of aPDT on the viability of microorganisms, vitality of biofilms, and lactic acid production of dentin caries microcosms. Biofilms were grown on bovine dentin discs in anaerobic conditions at 37 °C for 5 days, inoculating infected carious dentin in modified McBain medium plus 1% sucrose. The biofilms were treated by the combination of deionized water or 100 mg L^?1 methylene blue (MB) with 0, 37.5, or 75 J cm^?2 LED at 630 nm. The counts of total microorganisms, total streptococci, mutans streptococci, and total lactobacilli were determined by colony-forming units (CFU). The vitality of microbial cells in intact biofilms was measured by confocal laser scanning microscope (CLSM). The lactic acid production was analyzed by enzymatic spectrophotometry at 340 nm. Statistical analysis was conducted by Kruskal-Wallis and post hoc Dunn’s tests (P < 0.05). MB and 37.5 J cm^?2 LED alone did not interfere in the viability of microorganisms, unlike 75 J cm^?2 LED alone that decreased the total microorganism and lactobacillus counts. The combination of MB and 75 J cm^?2 LED reduced the viability of all microorganisms and the vitality of intact biofilms. The production of lactic acid was statistically lower in all treatment groups in comparison with that of the control (no treatment), except for MB alone. Therefore, the MB-mediated aPDT was effective in controlling the viability, vitality and the acidogenicity of dentin caries microcosms.     

Rose bengal photodynamic antimicrobial therapy to inhibit Pseudomonas aeruginosa keratitis isolates

To evaluate the in vitro efficacy of rose bengal and riboflavin photodynamic antimicrobial therapy for inhibition the growth of four Pseudomonas aeruginosa (P. aeruginosa) isolates. Four different clinical P. aeruginosa isolates were collected from patients with confirmed keratitis. Each strain was mixed with either sterile water, 0.1% riboflavin solution, or 0.1% rose bengal solution to yield a final bacteria concentration of 1.5?×?10⁷ CFU/mL. Aliquots from each suspension were plated onto nutrient agar in triplicate. Plates were separated into two groups: (1) no irradiation and (2) 5.4 J/cm² of radiant exposure with custom-made LED irradiation sources. Separate irradiation sources were used for each photosensitizer. The riboflavin groups used a UV-A light source (375 nm) and rose bengal groups used a green light source (525 nm). Plates were photographed at 72 h and custom software measured bacterial growth inhibition. Growth inhibition to riboflavin and rose bengal PDAT showed strain-dependent variability. All four strains of P. aeruginosa showed greatest growth inhibition (89–99%) in the green irradiated-rose bengal group. The UV-A-irradiated riboflavin showed inhibition of 24–44%. UV-A irradiation only showed minimal inhibition (7–14%). There was little inhibitory effect in the non-irradiated photosensitizer groups. Rose bengal PDAT had the greatest inhibitory effect on all four P. aeruginosa isolates. In the UV-A-irradiated riboflavin group, there was moderate inhibition within the irradiation zone; however, there was no inhibition in the non-irradiated groups. These results suggest that rose bengal PDAT may be an effective alternative treatment for Pseudomonas aeruginosa infections.

     

Effectiveness of antimicrobial photodynamic therapy with indocyanine green against the standard and fluconazole-resistant Candida albicans

Lasers in Medical Science - Antimicrobial photodynamic therapy (aPDT) is an alternative approach. The current study aimed to investigate the efficacy of aPDT with indocyanine green (ICG) against...