Silver nanoprisms as plasmonic enhancers applied in the photodynamic inactivation of Staphylococcus aureus isolated from bubaline mastitis.

Mastitis is a bacterial infection that affects all lactating mammals, and in dairy cattle, it leads to a reduction in their milk production and, in worse cases, it may lead to animal death. One viable therapeutic modality for overcoming bacterial resistance can be photodynamic inactivation (PDI), a therapeutic modality for bacterial infection treatment. One of the main factors that can lead to an efficient PDI process is the association of metallic nanoparticles in the close vicinity of photosensitizers, which has shown promising results due to localized surface plasmon resonance phenomena. In this work, methylene blue (MB) molecules were associated with Ag prismatic nanoplatelets (AgNPrs) to use as PDI photosensitizer against Staphylococcus aureus isolated from bubaline mastitis. The optical plasmonic activity of AgNPrs was tuned to the MB absorption region (600-700 nm) by inducing their growth into prismatic shapes by a seed-mediated procedure, using poly (sodium 4-styrene sulfonate) as the surfactant. A simulation on the plasmonic properties of the nanoprisms, applying particle size within the dimensions determined by TEM image analysis (d = 32 ± 6 nm), showed a 30 % increase of the incident field on the prismatic tips. Photodynamic results showed that the electrostatic AgNPr-MB conjugates promoted enhancement (ca. 15 %) of the reactive oxygen species production. Besides, PDI mediated by AgNPrs-MB led to the complete inactivation of the mastitis S. aureus strain after 6 min inactivation, in contrast to PDI mediated by MB, which reduced less than a 0.5 bacterial log. Thus, the results show this plasmonic enhanced photodynamic tool's potential to be applied in the inactivation of multi-resistant bacterial strains.

Assessment of simulated osteoporosis in alveolar bone using optical coherence tomography.

Steoporosis is a skeletal disorder that compromises bone resistance and its diagnosis is usually performed using dual energy X-ray absorptiometry. Thus, the search for efficient diagnostic methods that do not involve the emission of ionizing radiation is necessary. This study proposed to use the Optical Coherence Tomography (OCT) to evaluate osteoporosis in alveolar bone. Osteoporosis lesions is simulated in vitro in porcine bones, and imaging is performed by OCT and micro-computed tomography (micro-CT). A developed algorithm is proposed to calculate the optical attenuation coefficient ( µ t ), mean optical attenuation coefficient ( µ¯t ), integrated reflectivity (ΔR) and bone density ( BD). The µ¯t , ΔR and BD parameters shows a good correlation to micro-CT parameters (bone volume/tissue volume and total porosity). The µ t and µ¯t methods are negatively impacted by non-uniform intensities distribution in osteoporosis images. In conclusion, BD and ΔR analysis demonstrates to be potential techniques for diagnosis and monitoring of osteoporosis using OCT.

Remineralizing Potential of Nano-Silver-Fluoride for Tooth Enamel: An Optical Coherence Tomography Analysis

Objective: To evaluate the use of nanosilver fluoride in the enamel remineralization process through optical coherence tomography. Material and Methods: All samples were submitted to demineralization process by pH cycling during 14 days and randomly distributed into three groups (n = 11): Nanosilver Fluoride (NSF), Sodium fluoride (NaF), and negative control. Optical coherence tomography images were acquired at three different moments: initial stage (T0), post caries formation (T1), and post pH cycling (T2). The integrity of the enamel surface and the measurement of the volume loss for the tissue after pH cycling in comparison to initial images were obtained from optical coherence tomography images. Results: After analyzing the exponential decay of A-scans from each group, it was possible to identify differences in light propagation among samples. In T1 it is not possible to visualize the dentin-enamel junction, probably due to the higher back scattering of the demineralized enamel, which does not allow light to reach the dentin. The decay curves obtained from NaF and nanosilver fluoride groups showed similar behavior, while the negative group showed lower extinction coefficient. Conclusion: Nanosilver fluoride showed the best effect against caries compared to conventional fluoride treatments.

A novel 785-nm laser diode-based system for standardization of cell culture irradiation.

OBJECTIVE: The purpose of this study was to develop a novel device that concatenates alignment of infrared lasers and parallel procedure of irradiation. The purpose of this is to seek standardization of in vitro cell irradiation, which allows analysis and credible comparisons between outcomes of different experiments. BACKGROUND DATA: Experimental data obtained from infrared laser therapies have been strongly dependent upon the irradiation setup. Although further optical alignment is difficult to achieve, in contact irradiation it usually occurs. Moreover, these methods eventually use laser in a serial procedure, extending the time to irradiate experimental samples. METHODS: A LASERTable (LT) device was designed to provide similar infrared laser irradiation in 12 wells of a 24 well test plate. It irradiated each well by expanding the laser beam until it covers the well bottom, as occurs with unexpanded irradiation. To evaluate the effectiveness of this device, the spatial distribution of radiation was measured, and the heating of plain culture medium was monitored during the LT operation. The irradiation of LT (up to 25 J/cm(2) - 20 mW/cm(2); 1.250 sec) was assessed on odontoblast-like cells adhered to the bottom of wells containing 1 mL of plain culture medium. Cell morphology and metabolism were also evaluated. RESULTS: Irradiation with LT presented a Gaussian-like profile when the culture medium was not heated >1°C. It was also observed that the LT made it 10 times faster to perform the experiment than did serial laser irradiation. In addition, the data of this study revealed that the odontoblast-like cells exposed to low-level laser therapy (LLLT) using the LT presented higher metabolism and normal morphology. CONCLUSIONS: The experimental LASERTable assessed in this study provided parameters for standardization of infrared cell irradiation, minimizing the time spent to irradiate all samples. Therefore, this device is a helpful tool that can be effectively used to evaluate experimental LLLT protocols.

Thermography applied during exercises with or without infrared light-emitting diode irradiation: individual and comparative analysis.

OBJECTIVE: The aim of our study was to evaluate the cutaneous temperature during an exercise on a treadmill with or without infrared light-emitting diode (LED) irradiation in postmenopausal women. BACKGROUND DATA: Thermography is an imaging technique in which radiation emitted by a body in the middle and far infrared spectrum is detected and associated with the temperature of the body's surface. MATERIALS AND METHODS: Eighteen postmenopausal women were randomly divided into two groups: (1) the LED group, which performed the exercises on a treadmill associated with phototherapy (n=9) and; (2) the exercise group, which performed the exercises on a treadmill without additional phototherapy (n=9). The irradiation parameters for each women's thigh were: array of 2000 infrared LEDs (850 nm) with an area of 1,110 cm(2), 100 mW, 39 mW/cm(2), and 108 J/cm(2) for 45 min. The submaximal constant-speed exercise on the treadmill at intensities between 85% and 90% maximal heart rate (HRmax) with or without phototherapy were performed during 45 min, to perform the thermographic analysis. Thermography images were captured before the exercise (t=0), after 10, 35, and 45 min of exercising (t=10, t=35, and t=45) and at 5 min post-exercising (t=50). RESULTS: The LED group showed an increased cutaneous thigh temperature during the exercise (from 33.5±0.8°C to 34.6±0.9°C, p=0.03), whereas the exercise group showed a reduced cutaneous temperature (from 33.5±0.6 to 32.7±0.7°C, p=0.02). The difference between the groups was significant (p<0.05) at t=35, t=45, and t=50. CONCLUSIONS: These data indicate an improved microcirculation, and can explain one possible mechanism of action of phototherapy associated with physical exercises.

Chemiluminescence as a PDT light source for microbial control.

The photodynamic therapy (PDT) is a combination of using a photosensitizer agent, light and oxygen that can cause oxidative cellular damage. This technique is applied in several cases, including for microbial control. The most extensively studied light sources for this purpose are lasers and LED-based systems. Few studies treat alternative light sources based PDT. Sources which present flexibility, portability and economic advantages are of great interest. In this study, we evaluated the in vitro feasibility for the use of chemiluminescence as a PDT light source to induce Staphylococcus aureus reduction. The Photogem® concentration varied from 0 to 75 µg/ml and the illumination time varied from 60 min to 240 min.The long exposure time was necessary due to the low irradiance achieved with chemiluminescence reaction at µW/cm² level. The results demonstrated an effective microbial reduction of around 98% for the highest photosensitizer concentration and light dose. These data suggest the potential use of chemiluminescence as a light source for PDT microbial control, with advantages in terms of flexibility, when compared with conventional sources.

Construção e caracterização de um sistema de imagens / Construction and characterization of a hyperspectral imaging system

O uso de interação da luz com a matéria não é um conceito novo em biologia para a detecção de processos físico-químicos, embora ainda seja utilizado de uma forma rudimentar. Já é sabido que imagens de refletância e fluorescência podem revelar informações importantes sobre tais processos em amostras biológicas. Apesar deste potencial, os sistemas experimentais disponíveis para a obtenção de tais imagens costumam serem complexos e de difícil implementação. Neste trabalho é descrita a construção e a caracterização de uma montagem experimental para produção de imagens hiperespectrais entre 400 e 1.000 nm. O sistema é composto de um espectrômetro, um conjunto de lentes para formação da imagem e uma câmera CCD para capturá-la. São descritos em detalhes o procedimento de calibração do sistema, o qual envolve os parâmetros largura da imagem, campo de visão, resolução espectral e espacial. O sistema de iluminação utiliza diodos emissores de luz de alta potência, tanto de luz branca quanto em 470 e 405 nm. Demonstramos que o sistema construído é capaz de obter imagens de fluorescência e/ou refletância de amostras biológicas. Como exemplos de aplicações, o instrumento aqui desenvolvido foi utilizado em dois campos distintos, a agricultura e a odontologia. Foram obtidas imagens de fluorescência de folhas de citros contaminadas com cancro cítrico, e de processos de desmineralização em dentes. Os resultados demonstram que o sistema construído está operando como projetado.

The use of light-mater interaction for the detection of chemicalphysical processes is not a new concept in biology, though it is still used in a rudimentary form. It is already known that reflectance as well as fluorescence images can reveal important information on such processes in biological samples. In spite of this potential, the experimental available image systems usually are complexes and of difficult implementation. In this work, we describe the construction and characterization of an experimental device to produce hyperspectral images between 400 and 1,000 nm. The system is composed of a spectrometer, a set of lenses for image formation and a CCD camera to capture it. We describe in details also the calibration procedure of the system, which involves parameters as image width, field of view, spectral and space resolution. The illumination system uses high power light emitting diodes, either at white light or at 470 and 405 nm. We demonstrate that our system is able to obtain reflectance as well as fluorescence images of biological samples. As examples of applications, we use it into two different fields, agriculture and dentistry. We obtained fluorescence images of citrus leaves contaminated with citrus canker and demineralization processes in teeth. Our results demonstrate that our system isoperating as designed.

Evaluation of fluorescence of dental composites using contrast ratios to adjacent tooth structure: a pilot study.

STATEMENT OF THE PROBLEM: Fluorescence is an optical signal that is present in natural teeth and some dental restorative materials as a consequence of its molecules energetic decrease. Restorative materials need to match the fluorescence properties of surrounding tooth structure to achieve the best esthetics and appear undetectable. PURPOSE: The fluorescence of 10 commercial composites (shade A2 or equivalent) was tested against that of tooth structure using contrast differences. MATERIALS AND METHODS: Thirty-three standard preparations (3.0-mm wide and 2.00-mm depth) were done on mean maxillaries incisors and divided into 10 groups containing three test samples each. High-definition images of the restored areas and adjacent tooth structure were obtained both under white light of the visible spectrum (control) and ultraviolet light (UV-A=300/ 400 nm). The contrast between composites and tooth structure, expressed in absolute values, was analyzed through digital processing Matlab and Origin softwares and by one-way analysis of variance and Tukey's test (p