Phototransients of 2-ethylaminodiphenylborinate generated by direct photolysis and photosensitization

Ground state interactions and excited states and transients formed after photolysis and photosensitization of 2-ethylaminodiphenylborinate (2APB) were studied by various techniques. The UV spectrum shows a large absorption band at 235 nm (epsilon = 14,500 M-1 cm(-1)) with a shoulder at 260 nm. The fluorescence spectra show increasing emission intensity with maximum at 300 nm, which shifts to the red up to 10(-3) M concentrations. At higher concentrations, the emission intensity decreases, probably due to the formation of aggregates. UV excitation in deareated solutions shows the formation of two transients at 300 and 360 nm. The latter has a lifetime of 5.7 mu s in ethanol and is totally quenched in the presence of oxygen and assigned to the triplet state of 2APB. The 300 nm peak is not affected by oxygen, has a lifetime in the order of milliseconds, and corresponds to a boron-centered radical species originated from the singlet state. A boron radical can also be obtained by electron transfer from triplet Safranine to the borinate (k(q) = 9.7 x 10(7) M-1 s(-1)) forming the semioxidized form of the dye. EPR experiments using DMPO show that dye-sensitized and direct UV-photolysis of 2ABP renders initially arylboron-centered radicals. (C) 2012 Elsevier B.V. All rights reserved.

Application of an active attachment model as a high-throughput demineralization biofilm model

Objectives: To investigate the potential of an active attachment biofilm model as a highthroughput demineralization biofilm model for the evaluation of caries-preventive agents. Methods: Streptococcus mutans UA159 biofilms were grown on bovine dentine discs in a highthroughput active attachment model. Biofilms were first formed in a medium with high buffer capacity for 24 h and then subjected to various photodynamic therapies (PACT) using the combination of Light Emitting Diodes (LEDs, Biotable (R)) and Photogem (R). Viability of the biofilms was evaluated by plate counts. To investigate treatment effects on dentine lesion formation, the treated biofilms were grown in a medium with low buffer capacity for an additional 24 h. Integrated mineral loss (IML) and lesion depth (LD) were assessed by transversal microradiography. Calcium release in the biofilm medium was measured by atomic absorption spectroscopy. Results: Compared to the water treated control group, significant reduction in viability of S. mutans biofilms was observed when the combination of LEDs and Photogem (R) was applied. LEDs or Photogem (R) only did not result in biofilm viability changes. Similar outcomes were also found for dentine lesion formation. Significant lower IML and LD values were only found in the group subjected to the combined treatment of LEDs and Photogem (R). There was a good correlation between the calcium release data and the IML or LD values. Conclusions: The high-throughput active attachment biofilm model is applicable for evaluating novel caries-preventive agents on both biofilm and demineralization inhibition. PACT had a killing effect on 24 h S. mutans biofilms and could inhibit the demineralization process. (C) 2011 Elsevier Ltd. All rights reserved.

Antimicrobial photodynamic therapy in the non-surgical treatment of aggressive periodontitis: microbiological profile

The aim of this trial was to investigate changes occurring in the subgingival microbiological composition of subjects with aggressive periodontitis, treated with antimicrobial photodynamic therapy (aPDT), in a single episode, or scaling and root planing (SRP), in a split-mouth design on -7, 0, and +90 days. Ten patients were randomly assigned to either aPDT using a laser source in conjunction with a photosensitizer or SRP with hand instruments. Subgingival plaque samples were collected and the counts of 40 subgingival species were determined using checkerboard DNA-DNA hybridization. The data were analyzed using the method of generalized estimating equations (GEE) to test the associations between treatments, evaluated parameters, and experimental times (alpha = .05). The results indicated that aPDT and SRP affects different bacterial species, with aPDT being effective in reducing numbers of A. actinomycetemcomitans than SRP. On the other hand, SRP was more efficient than aPDT in reducing the presence of periodontal pathogens of the Red Complex. Additionally, a recolonization in the sites treated by aPDT was observed, especially for T. forsythia and P. gingivalis. Under our experimental conditions, this trial demonstrates that aPDT and SRP affected different groups of bacteria, suggesting that their association may be beneficial for the non-surgical treatment of aggressive periodontitis.

Toxicity of photodynamic therapy with LED associated to Photogem (R): An in vivo study

The aims of this study were to evaluate the effects of PhotogemA (R)-mediated photosensitization on rat palatal mucosa and the biodistribution of the photosensitizer in this tissue. A solution of PhotogemA (R) (500 or 1000 mg/l) was applied to the palatal mucosa for 30 min and the exposure time to blue LED (460 nm) was 20 min (144 J/cm(2)). At 0, 1, 3, and 7 days, palatal mucosa was photographed for macroscopic analysis. After killing, the palate was removed for microscopic analysis. Thermal mapping evaluated temperature change in the tissue during irradiation. All experimental groups revealed intact mucosa in the macroscopic analysis. Tissue alterations were observed microscopically for only four out of 80 animals subjected to PDT. Fluorescence emitted by PhotogemA (R) was identified and was limited to the epithelial layer. A temperature increase from 35 to 41A degrees C was recorded. PhotogemA (R)- mediated PDT was not toxic to the rat palatal mucosa.

Local clinical phototreatment of herpes infection in Sao Paulo

The clinical use of topical photodynamic therapy in herpes simplex lesions in Sao Paulo is presented and discussed. Although previous attempts utilising this type of approach in the USA were discontinued in the early 1970s due to several presentations of post-treatment Bowen's disease, none of the cases from the clinic presented here have displayed any complications on follow-up. In addition, lesion recrudescence periods are generally much longer than with conventional approaches. This is thought to be due to improvements in the treatment protocol, viz, use of the non-toxic photosensitisers methylene blue and Hypericum perforatum extract in place of proflavine and neutral red in the original trials, differences in photosensitisation pathway and illumination of the treatment site with red rather than fluorescent/UV light. Post-treatment cosmesis is also excellent. (C) 2012 Elsevier B.V. All rights reserved.

Evidence of 5-aminolevulinic acid (ALA) penetration increase due to microdrilling in soft tissue using femtosecond laser ablation

Photodynamic therapy (PDT) is a therapeutic technique mainly applied to the treatment of malignant and pre-malignant lesions, which induces cell death by the combined effect of a photosensitizer, irradiation in a proper wavelength, and molecular oxygen. One of the main limitations of PDT using 5-aminolevulinic acid (ALA) is the superficial volume of treatment, mainly due to the limited penetration of topical photosensitization. In this context, the present study investigates if a laser micromachining producing microchannels on the tissue surface could improve ALA penetration and result in an increase in the treatment depth. The laser micromachining under femtosecond regime was performed on the tissue surface of rat livers. Conventional PDT was applied and the induced depth of necrosis with or without laser micromachining was compared. The results showed an increase of more than 20% in the depth of necrosis when the femtosecond laser micromachining was performed before the treatment with the PDT.

Photodynamic inactivation of microorganisms present on complete dentures. A clinical investigation

The aim of this study was to evaluate the effectiveness of photodynamic therapy (PDT) for the disinfection of complete dentures. Biofilm samples were collected from dentures of 60 denture users who were randomly divided into four experimental groups (n = 15 each): subjects whose maxillary dentures were sprayed with 50 and 100 mg/l of PhotogemA (R) suspension (groups P50S and P100S) and patients whose maxillary dentures were treated with 50 and 100 mg/l of PhotogemA (R) gel (groups P50G and P100G). Dentures with photosensitizers were left in the dark for 30 min (pre-irradiation time) and then irradiated with blue LED light at 37.5 J/cm(2) (26 min). Denture samples were taken with sterile cotton swab before (left side surfaces) and after (right side surfaces) PDT. All microbial material was diluted and plated on selective media for Candida spp., Staphylococcus mutans spp., streptococci and a non-selective media. After incubation (48 h/37A degrees C), the number of colony-forming units (cfu/ml) was counted. Microorganisms grown on selective media were identified using biochemical methods before and after PDT. The data were submitted to McNemar and Kruskal-Wallis tests (alpha = 0.05). No growth after PDT was observed in 60, 53, 47, and 40% of dentures from P100G, P50G, P100S, and P50S groups, respectively. When evidence of microorganisms' growth was observed, PDT regimens eliminated over 90% of microorganisms on dentures. This clinical study showed that PDT was effective for disinfecting dentures.

Photo-activated phase separation in giant vesicles made from different lipid mixtures

Using giant unilamellar vesicles (GUVs) made from POPC. DPPC, cholesterol and a small amount of a porphyrin-based photosensitizer that we name PE-porph, we investigated the response of the lipid bilayer under visible light, focusing in the formation of domains during the lipid oxidation induced by singlet oxygen. This reactive species is generated by light excitation of PE-porf in the vicinity of the membrane, and thus promotes formation of hydroperoxides when unsaturated lipids and cholesterol are present. Using optical microscopy we determined the lipid compositions under which GUVs initially in the homogeneous phase displayed Lo-Ld phase separation following irradiation. Such an effect is attributed to the in situ formation of both hydroperoxized POPC and cholesterol. The boundary line separating homogeneous Lo phase and phase coexistence regions in the phase diagram is displaced vertically towards the higher cholesterol content in respect to ternary diagram of POPC:DPPC:cholesterol mixtures in the absence of oxidized species. Phase separated domains emerge from sub-micrometer initial sizes to evolve over hours into large Lo-Ld domains completely separated in the lipid membrane. This study provides not only a new tool to explore the kinetics of domain formation in mixtures of lipid membranes, but may also have implications in biological signaling of redox misbalance. (C) 2011 Elsevier B.V. All rights reserved.