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Skin cancer diagnosis is a great challenge nowadays since it has the major incidence rates among all cancer types. Non-melanoma skin cancer is the most incident even being less aggressive, whereas melanoma is one of the most lethal cancer types due to its high metastatic potential. Early diagnosis is a main goal in new techniques development since it is responsible not only by increasing life expectancy, as well as decreasing treatment morbidity. Visual clinical inspection and then possibly dermoscopy and biopsy is the most common diagnosis procedure, being not so efficiently managed at the public health system, and can be very imprecise if not performed by a well-trained skilled dermatologist. An alternative early diagnosis technique is the label-free fluorescence since it is portable, real-time, non-invasive, not subjective, and that does not rely on exogenous fluorophores addiction. Some of the main native fluorophores are related to morpho-functional and metabolic activities on cell\'s, thus, they can act as intrinsic optical biomarkers (OB), such as collagen, elastin, Nicotinamide Adenine Dinucleotide (NADH) and Flavin Adenine Dinucleotide (FAD). Since cancer causes mitochondrial dysfunction on cells, these molecules are powerful endogenous agents for diagnosis. In order to study the effect of cells metabolic activities in autofluorescence, healthy fibroblasts cells, squamous cell carcinoma (SCC) and melanoma cancer cells were used. By two-photon excitation and multispectral steady-state and lifetime fluorescence microscopy, it was shown that optical redox ratio (ORR) and the lifetime parameters decrease in cancer cells, indicating that they may be relevant OB to distinguish cells. These OB were used in a clinical study on 119 patients with malignant lesions (melanoma, SCC, and nodular and superficial basal cell carcinoma (nBCC and sBCC)), and benign lesions (intradermal nevus (IN) and pigmented seborrheic keratosis (pSK)). Using a portable multispectral fluorescence lifetime imaging (FLIm) device, the patient skin cancer was imaged using a 355 nm excitation wavelength, and the fluorescence emission signal was detected in three channels mostly targeting collagen and elastin (390 ± 20 nm), NADH (452 ± 22 nm) and FAD (> 496 nm) emission. Using the OB extracted features, random forest, linear, and partial least square discriminant analysis classifiers were built on a training set and tested on a test set of images. As a result, to distinguish between healthy and nBCC tissue, classifiers showed that lifetime parameters are as important as steady-state fluorescence parameters, and achieved sensitivity of 88%. To distinguish between clinical similar malignant and benign lesions the models were tuned to achieve 100% sensitivity both on pigmented and non-pigmented lesions, which is very similar with the dermatologists\' biopsy accuracy (87-94%). Two-way and five-way classification models achieved accuracies around 70% and 60%, whereas dermatologists accuracies is around 66% in this clinical diagnostic classification. In general, using the machine learning models, the FLIm technique was able to provide a fast and dermatologist-level skin cancer screening, which may contribute especially in areas where there is a lack of trained professionals. O diagnóstico de câncer de pele é um grande desafio, pois este apresenta as maiores taxas de incidência entre todos os tipos de câncer. O câncer de pele não melanoma é o mais incidente, mesmo sendo menos agressivo, enquanto o melanoma é um dos tipos de câncer mais letais devido ao seu alto potencial metastático. A inspeção clínica visual seguida de dermatoscopia e possivelmente biópsia é o tipo mais comum de diagnóstico. Entretanto, este procedimento de não é de fácil adoção e gestão, além de ter baixa eficiência no sistema público de saúde, e pode ser impreciso se não for realizado por um dermatologista especialista treinado. Uma técnica alternativa de rastreio é a fluorescência sem marcador, por ser portátil, em tempo real, não invasiva e não depende da adição de fluoróforos exógenos. Alguns dos principais fluoróforos nativos estão relacionados às atividades morfo-funcionais e metabólicas das células, portanto, podem atuar como biomarcadores ópticos (BO) intrínsecos, tais como colágeno, elastina, dinucleotídeo de nicotinamida adenina (NADH) e dinucleotídeo de flavina adenina (FAD). Para estudar o efeito das atividades metabólicas na autofluorescência, foram utilizadas células saudáveis e cancerígenas. Por microscopia de estado estacionário e de tempo de vida de fluorescência, foi demonstrado que a razão óptica redox e o tempo de vida diminuem nas células cancerígenas, indicando que os BO são ideais para distinguir células. Neste contexto, os BO foram utilizados em um estudo clínico em 119 pacientes com lesões malignas (melanoma, carcinoma espinocelular e carcinoma basocelular (CBC)) e benignas (nevo intradérmico e queratose seborreica pigmentada). Usando um dispositivo portátil para aquisição de imagens de tempo de vida de fluorescência multiespectral (FLIm), o câncer de pele do paciente foi imageado usando uma excitação laser no comprimento de onda de 355 nm, e a emissão de fluorescência foi investigada em três canais: colágeno e elastina (390 ± 20 nm), NADH (452 ± 22 nm) e FAD (> 496 nm). Usando as características extraídas dos BO, os classificadores de floresta aleatória, análise de discriminante linear e de mínimos quadrados parciais foram construídos em um conjunto de treinamento e testados em um conjunto de imagens de teste. Para distinguir entre tecido saudável e CBC os classificadores mostraram que os parâmetros de tempo de vida são tão importantes quanto os parâmetros de fluorescência no estado estacionário e atingiram sensibilidade de 88%. Para distinguir entre lesões malignas e benignas clinicamente semelhantes, os modelos foram ajustados para alcançar 100% de sensibilidade nas lesões pigmentadas e não pigmentadas, o que é muito semelhante à precisão da biópsia dos dermatologistas (87-94%). Os modelos de classificação em duas e cinco vias alcançaram acurácia em torno de 70% e 60%, enquanto a precisão dos dermatologistas está em torno de 66% nesse tipo de tarefa. Em essência, usando os modelos de aprendizado de máquina, a técnica FLIm foi capaz de fornecer uma triagem rápida e em nível de dermatologista para o câncer de pele, o que pode contribuir especialmente em áreas onde há falta de profissionais treinados.

Photodynamic procedures have been used in many applications, ranging from cancer treatment to microorganism inactivation. Photodynamic reactions start with the activation of a photosensitizing molecule with light, leading to the production of cytotoxic molecules that promote cell death. However, establishing the correct light and photosensitizer dosimetry for a broadband light source remains challenging. In this study, we proposed a theoretical mathematical model for the photodegradation of protoporphyrin-IX (PpIX), when irradiated by multi-wavelength light sources. The theoretical model predicts the experimental photobleaching (temporal change in PpIX concentration) of PpIX for different light sources. We showed that photobleaching occurs independently of the light source wavelengths but instead depends only on the number of absorbed photons. The model presented here can be used as an important mathematical approach to better understand current photodynamic therapy protocols and help achieve optimization of the doses delivered.

Photosensitization of all tissue in sufficient quantity to generate damage is one of the limiting factors for Photodynamic Therapy (PDT) efficiency. Methyl nicotinate (MN) is a thermogenic and vasodilating substance that facilitates the topical tissue penetration of some compounds. The topical MAL (methyl aminolevulinate) PDT is commonly used as a precursor of protoporphyrin IX (PpIX). This study investigates the safety of topical use in NM, as well as its ability to improve the efficiency of topical PDT. For this, we investigate the cytotoxicity of MN, as well as its actions in increasing cellular metabolism and vasodilation. Besides, its ability to optimize the formation of PpIX in the tissue when associated with MAL cream was investigated, besides assessing the severity of necrosis obtained by treatments. The cytotoxicity of MN was tested for concentrations of 0, 0.1, 0.25, 0.5, 0.75 and 1% in cell culture. For the concentration of 0.5%, the cellular metabolism was evaluated using confocal microscopy to calculate the redox rate. In the Chorioallantoic Membrane Model, vasodilation was evaluated for concentrations of 0.5 and 1% MN during 1 h of incubation. In the animal model, the healthy skin of Wistar rat was used to evaluate the production of PpIX in the tissue and the degree of necrosis obtained by Photodynamic therapy when using NM associated with methyl aminolevulinate. It was observed the non-cytotoxicity in vitro of MN in the concentration used (0.5%) and its ability to increase cellular metabolism. In a chorioallantoic model, the MN vasodilation power was demonstrated for different caliber of vessels. In vivo studies are showing that the incorporation of MN in the MAL cream increases the amount of PpIX produced in the tissue causing a higher effect on the epidermis after PDT. This improvement of the protocol may make the procedure more effective both in the destruction of tumor tissue and in the treatment of deeper cells decreasing possible recurrence, in addition to allowing improvements in the protocol, such as reducing the cream's incubation time.

Basal cell carcinoma (BCC) is the most common type of skin cancer. Diagnosis and edge assessment of BCC lesions are based on clinical and dermoscopy evaluation, which are strongly dependent on the expertise and training of the physician. There is a high rate of underdiagnosis because BCC is frequently confused with certain common benign lesions and is often indistinguishable from the surrounding healthy tissue. In the present study, a multispectral fluorescence lifetime imaging (FLIm) dermoscopy system, designed for imaging and analyzing the autofluorescence emission of skin tissue, was used to image thirty-eight patients with diagnosed nodular BCC (nBCC) lesions, using clinically acceptable levels of excitation light exposure. With this system, skin autofluorescence was imaged simultaneously using three emission bands: 390 ± 20 nm, 452 ± 22 nm, and >496 nm, preferentially targeting collagen, NADH, and FAD autofluorescence, respectively. Statistical classifiers based on FLIm features developed to discriminate BCC from healthy tissue showed promising performance (ROC area-under-the-curve of 0.82). This study demonstrates the feasibility of clinically performing multispectral endogenous FLIm dermoscopy providing baseline results indicating the potential of this technology as an image-guided tool to improve the delineation of nBCC during surgical lesion resection.

Every year more than 5.4 million new cases of skin cancer are reported in the US. Melanoma is the most lethal type with only 5% occurrence rate, but accounts for over 75% of all skin cancer deaths. Non-melanoma skin cancer, especially basal cell carcinoma (BCC) is the most commonly occurring and often curable type that affects more than 3 million people and causes about 2000 deaths in the US annually. The current diagnosis involves visual inspection, followed by biopsy of the lesions. The major drawbacks of this practice include difficulty in border detection causing incomplete treatment and, the inability to distinguish between clinically similar lesions. Melanoma is often mistaken for the benign lesion pigmented seborrheic keratosis (pSK), making it extremely important to differentiate benign and malignant lesions. In this work, a novel feature extraction algorithm based on phasors was performed on the Fluorescence Lifetime Imaging (FLIM) images of the skin to reliably distinguish between benign and malignant lesions. This approach, unlike the standard FLIM data processing method that requires time-deconvolution of the instrument response from the measured time-resolved fluorescence signal, is computationally much simpler and provides a unique set of features for classification. Subsequently, FLIM derived features were selected using a double step cross validation approach that assesses the reliability and the performance of the resultant trained classifier. Promising FLIM-based classification performance was attained for detecting benign from malignant pigmented (sensitivity: ~80%, specificity: 79%, overall accuracy: ~79%) and nonpigmented (sensitivity: ~88%, specificity: 83%, overall accuracy: ~87%) lesions.

There are few published data on the relationship between loss of bone mass due to osteoporosis and poor tooth quality. This study analyzed the effects of osteoporosis on incisor teeth and femoral bones using optical techniques in rats. Twenty female Wistar rats aged 6 months (n = 20) were randomized into two groups: control group, non-ovariectomized rats (n = 10); ovariectomy group, ovariectomized rats to induce osteoporosis (n = 10). Each group was subdivided randomly into two groups containing five rats each as follows. Control group 1: non-ovariectomized rats euthanized at the age of 9 or 3 months post-ovariectomy (n = 5); Control group 2: non-ovariectomized rats euthanized at the age of 1 year or 6 months post-ovariectomy (n = 5); ovariectomy group 1: ovariectomized rats euthanized at the age of 9 months or 3 months post-ovariectomy (n = 5); ovariectomy group 2: ovariectomized rats euthanized at the age of 1 year or 6 months post-ovariectomy (n = 5). The incisor teeth and femoral bones of Wistar rats were removed to perform Raman spectroscopy using an excitation laser at 785 nm. In addition, an energy-dispersive X-ray spectrometer system was used to evaluate calcium (Ca) and phosphorus (P). The main findings included significant changes (p

A number of phosphate rocks and organomineral P fertilizers was analyzed comparatively by laser-induced breakdown spectroscopy (LIBS) in both single- and double-pulse modes associated with two chemometric methods, i.e., principal components analysis (PCA) and partial least squares regression (PLSR). PCA was demonstrated to be a valuable method for the identification of spectral differences between similar samples with only minor compositional differences. The raw and normalized LIBS spectra were able to provide effective identification and discrimination at a 95% confidence level and in good agreement with the reference concentrations. Results obtained confirm the promising potential of LIBS for the rapid classification of P fertilizers in situ.

Huanglongbing (HLB) is the most recent and destructive bacterial disease of citrus and has no cure yet. A promising alternative to conventional methods is to use laser-induced breakdown spectroscopy (LIBS), a multi-elemental analytical technique, to identify the nutritional changes provoked by the disease to the citrus leaves and associate the mineral composition profile with its health status. The leaves were collected from adult citrus trees and identified by visual inspection as healthy, HLB-symptomatic, and HLB-asymptomatic. Laser-induced breakdown spectroscopy measurements were done in fresh leaves without sample preparation. Nutritional variations were evaluated using statistical tools, such as Student's t-test and analysis of variance applied to LIBS spectra, and the largest were found for Ca, Mg, and K. Considering the nutritional profile changes, a classifier induced by classification via regression combined with partial least squares regression was built resulting in an accuracy of 73% for distinguishing the three categories of leaves.

Skin lesions are the most common human cancer diseases, usually, is it diagnosed by clinical visual inspections followed by biopsy. Early detection of these diseases is critical, depending on an accurate and trained dermatologist and can increase the survival rate. Aiming for screening and early diagnose skin lesions many techniques are presented, however, optical techniques are highlighted since they are fast and noninvasive. In this context, fluorescence steady-state and lifetime imaging show potential by being able to image metabolic changes using endogenous contrast. Here it is demonstrated an in vivo label-free multispectral fluorescence lifetime imaging system to distinguish between two types of clinically similar lesions. A pulsed Nd:YAG laser emitting at 355 nm is used to excite the endogenous fluorophores and three channels of acquisition bands are used to imaging the skin. Preliminary results showed differences in the fluorescence lifetime between Bowen and Actinic Keratosis as well as the lesion and the skin around, demonstrating a potential tool to identify the lesion and its edges.

This study investigated the effects of demineralization on teeth and bones evaluated by fluorescence spectroscopy and micro energy-dispersive X-ray fluorescence spectrometry (μ-EDXRF) in rats. For in vitro study, 20 teeth of Wistar rats were removed and decalcified to evaluate fluorescence. For in vivo study, 10 female Wistar rats aged 6months were randomized into 2 groups: Control Group (C): non-ovariectomized rats; Ovariectomy Group (OV): ovariectomized rats to induce osteoporosis. The fluorescence spectroscopy of the teeth was performed for long-term (until 180days). For ex vivo study, the tooth and femur bone of the Wistar rats were removed at 180days to perform fluorescence spectroscopy using excitation laser at 408 and 532nm and μ-EDXRF for calcium (Ca) and phosphorus (P) analysis. There were no intergroup differences in fluorescence spectra with laser at 408nm (p≥0.05), but there were changes in the fluorescence spectra using laser at 532nm which led to both the wavelength shift and changes in the band area (p0.05). The concentrations of P and Ca for the dentine and cortical bone, respectively, were significantly reduced in OV (p0.05). Demineralization leading to loss of tissue quality may be assessed by fluorescence spectroscopy using 532nm laser. These findings corroborate those obtained by μ-EDXRF.

Laser-induced breakdown spectroscopy (LIBS) is a well-known consolidated analytical technique employed successfully for the qualitative and quantitative analysis of solid, liquid, gaseous and aerosol samples of very different nature and origin. Several techniques, such as dual-pulse excitation setup, have been used in order to improve LIBS's sensitivity. The purpose of this paper was to optimize the key parameters as excitation wavelength, delay time and interpulse, that influence the double pulse (DP) LIBS technique in the collinear beam geometry when applied to the analysis at atmospheric air pressure of soil samples of different origin and texture from extreme regions of Brazil. Additionally, a comparative study between conventional single pulse (SP) LIBS and DP LIBS was performed. An optimization of DP LIBS system, choosing the correct delay time between the two pulses, was performed allowing its use for different soil types and the use of different emission lines. In general, the collinear DP LIBS system improved the analytical performances of the technique by enhancing the intensity of emission lines of some elements up to about 5 times, when compared with conventional SP-LIBS, and reduced the continuum emission. Further, the IR laser provided the best performance in re-heating the plasma.

This study clearly demonstrates that multispectral confocal microscopy images analyzed by artificial neural networks provides a powerful tool to real-time monitoring photosensitizer uptake, as well as photochemical transformations occurred.

Laser-induced breakdown spectroscopy (LIBS) is a technique increasingly used to perform fast semi-quantitative multi-elemental analyses of various materials without any complex sample preparation, being also suitable for in situ analyses. Few studies have been performed to understand the influence of laser wavelength on LIBS analytical performance on environmental samples. The main goal of this study was to perform a comparative elemental analysis of a number of soils, citrus leaves, and synthetic solid matrices using two different wavelengths, i.e., 532 and 1064 nm of Nd:YAG lasers, and a spectrometer coupled to a non-intensified charge-coupled device camera as the detection system. The emission lines with higher upper energy level, i.e., C I—193.03 (7.685 eV) and Si I—212.41 nm (6.616 eV), were more intense when using the 532 nm than the 1064 nm laser light, whereas the opposite occurred for elements with lower upper energy level, i.e., Ti I—336.12 nm (3.716 eV) and Fe I—368.75 nm (4.220 eV). The observed increase in LIBS signal between the two wavelengths is about 30–50%. The relationship between the line emission intensities and the used excitation wavelengths were associated to the upper level energy of the element.

Soil organic matter (SOM) constitutes an important reservoir of terrestrial carbon and can be considered an alternative for atmospheric carbon storage, contributing to global warming mitigation. Soil management can favor atmospheric carbon incorporation into SOM or its release from SOM to atmosphere. Thus, the evaluation of the humification degree (HD), which is an indication of the recalcitrance of SOM, can provide an estimation of the capacity of carbon sequestration by soils under various managements. The HD of SOM can be estimated by using various analytical techniques including fluorescence spectroscopy. In the present work, the potential of laser-induced breakdown spectroscopy (LIBS) to estimate the HD of SOM was evaluated for the first time. Intensities of emission lines of Al, Mg and Ca from LIBS spectra showing correlation with fluorescence emissions determined by laser-induced fluorescence spectroscopy (LIFS) reference technique were used to obtain a multivaried calibration model based on the k-nearest neighbor (k-NN) method. The values predicted by the proposed model (A-LIBS) showed strong correlation with LIFS results with a Pearson's coefficient of 0.87. The HD of SOM obtained after normalizing A-LIBS by total carbon in the sample showed a strong correlation to that determined by LIFS (0.94), thus suggesting the great potential of LIBS for this novel application.

Devido à grande preocupação com a geração de novas tecnologias mais ágeis, eficientes e de baixo custo, as reações fotodinâmicas (RF) têm ganhado destaque. Estas envolvem a ativação de um fármaco fotossensível (fotossensibilizador (FS)), pela iluminação em uma faixa específica de comprimentos de onda, gerando assim espécies reativas altamente citotóxicas levando as células à morte. As RF são divididas em duas categorias: terapia fotodinâmica (TFD) e inativação fotodinâmica (IFD). A primeira é utilizada para tratamentos oncológicos, dermatológicos, entre outros. A segunda é utilizada para descontaminação de micro-organismos em infecções localizadas. Atualmente a IFD tem sido alvo de muitos estudos pois tem diversas vantagens quando comparadas com as técnicas de descontaminação atuais. Duas das mais importantes são: a seletividade e a não geração de micro-organismos resistentes aos FSs. Apesar desta técnica ser utilizada com sucesso em diversos campos, ela ainda apresenta baixa eficiência quando comparada às técnicas tradicionais. Neste contexto, o objetivo deste trabalho foi criar um novo protocolo de aplicação da IFD visando o aumento de eficiência, bem como um estudo profundo das interações dos FSs com as células, e o monitoramento da dinâmica do FS nestas. O presente estudo utiliza-se de células da levedura Candida albicans e demonstra a interação destas células com dois FSs: Photogem® e Curcumina. Foi proposto um novo protocolo que promove o aumento da internalização de FS pelas células baseado na pré-iluminação de baixa dose durante o tempo de incubação. Foi possível demonstrar através da medida dos espectros de absorção do sobrenadante de uma solução com células e Photogem®, que as amostras que tiveram pré-iluminação internalizaram mais FS do meio do que as células mantidas no escuro. Além disso, a partir de ensaios de viabilidade com a levedura e o Photogem® foi demonstrado que as amostras que tiveram pré-iluminação apresentaram diminuição de até seis ordens de grandeza nas unidades formadoras de colônia quando comparadas com as amostras tratadas pelo protocolo tradicional de IFD. Através das técnicas de microscopia confocal de fluorescência e de imagem de tempo de vida de fluorescência foi possível compreender a interação entre os FSs e as células, bem como estudar a ligação deste FS em diferentes regiões da célula. Além disso, foi estudada ainda a mobilidade destas moléculas dentro das células sob condições com e sem iluminação de baixa dose. Através deste estudo pôde-se inferir que as moléculas de curcumina tem tempos característicos de entrada nas células mais lentos que os tempos característicos do Photogem®. Ainda foi possível tomar vantagem da fluorescência do Photogem® para monitorar a entrada deste nas células de levedura, bem como monitorar a formação do seu fotoproduto, determinando assim que 7,5 minutos é o tempo médio de iluminação durante a incubação com FS necessário para que pelo menos 80% das células tivessem o FS internalizado, sem significante formação de fotoprodutos. Conclui-se ainda que este novo protocolo de incubação com iluminação leva a maior eficiência e seletividade da IFD, abrindo caminho para uma nova linha de pesquisa nas RF em geral, possivelmente podendo este protocolo ser aplicado em diversos tipos de células. In the last years, due to the increasing need of generation of novel faster and cheaper technologies, the photodynamic reactions (PR) have been highlighted. These reactions involves the activation of a photosensitive drug, named photosensitizer (PS), by light in proper spectral window and generation of highly cytotoxic reactive species, leading cells to death. The photodynamic reactions may be divided in two categories: photodynamic therapy (PDT) and photodynamic inactivation (PDI). The first one is performed in order to treat oncologic, dermatologic and other diseases, whereas the second one is employed in the decontamination of microorganisms in localized infections. When compared with existing decontamination techniques, PDI has several advantages, among which two of the most important are its selectivity of the PS that acts only at the delivered site, as well as not inducing antibiotic resistance, for such reasons are subjected of many current studies. Althought this technique has been performed with great success in many fields, it still has a lack of efficiency. In this context, the purpose of this study was create a new application protocol of this technique in order to increase the efficiency, as well as understand the interactions of the PS with the cells and monitoring the drug dynamic in cells. In this study, Candida albicans cells were utilized and the interaction of two PSs (Photogem® and Curcumin) were demonstrated. A new protocol which promotes an increase of the PS cells uptake was proposed, this protocol is based on the low dose illumination during the incubation time. By measuring absorption spectra of the supernatant of two solutions with cells and Photogem®, in which in one of them were applied a low dose light, was demonstrated that the illuminated cells had an uptake increased when compared with the sample kept in the dark. Moreover, viability assays with the Photogem® and the cells proved that the cells that receive low dose light in the incubation stage had more damage in the PDI, showing a decrease of six orders of magnitude when compared with the traditional PDI. Through confocal and lifetime fluorescence microscopy techniques it was possible not only to comprehend the interaction between the PS and cells, as well as to study the binding of this molecules in different regions of the cells. Furthermore, the mobility of the PS molecules inside the cells was studied in conditions of illumination and dark, it could be inferred that the curcumin molecules has higher characteristic time than Photogem® molecules. Monitoring the cell Photogem® uptake, and the photoproduct formation was possible by take advantage of the PS fluorescence. Thus it was possible to determine the average illumination time (7.5 minutes) during the incubation time so at least 80% of the cells had the PS internalized, without much generation of photoproducts. It follows also that this new incubation protocol with low dose illumination leads to greater efficiency of PDI, so this study leads a new field of research in overall photodynamic reaction.

Made available in DSpace on 2018-12-11T17:25:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-02-01 The analysis of soil texture is crucial for the proper management of agricultural systems and for environmental studies. Soil texture is important as it affects erosion potential, water retention capacity, organic matter complexation, and the retention of nutrients, among others. It is usually determined by pipette or hydrometer methods, but analysis requires a preparation with chemical reagents, which can take hours and hence is unfeasible for large number of samples. Here we propose the use of laser-induced breakdown spectroscopy (LIBS) to estimate the proportions of sand, silt, and clay in 60 Brazilian soil samples of varying composition. Two calibration models were developed with the partial least square regression method: one considering the spectral region from 188 to 980 nm and the other, emission lines of the elements Si, Na, Fe, Ti, Ca, K, Al, Co, Mg, V, Ba, and Be. The Pearson correlation coefficients for the estimated values were 0.89 and 0.90 on average for the first and second models, respectively. The uncertainties were 6% on average for both models. These results demonstrate the use of LIBS for rapid scanning of the texture of soil samples with distinct composition. The procedure presented here can be extended to other chemical and physical soil properties, which makes LIBS a universal tool for rapid soil analysis without preparation with chemical reagents. Embrapa Instrumentation, R. XV de Novembro 1452 Physics Institute of São Carlos University of São Paulo IFSC-USP, Av. Trabalhador Sancarlense, 400 Pq. Arnold Schimid Physics Department São Carlos Federal University, P.O. Box 676 São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355, R. Prof. Francisco Degni, 55 São Paulo State University - UNESP Analytical Chemistry Department, P.O. Box 355, R. Prof. Francisco Degni, 55

Tooth bleaching agents may weaken the tooth structure, therefore, it is important to minimize any risks of enamel and dentine damage caused by them. In this way, different materials have been used to avoid or minimize the tooth damage during bleaching. Recently, bioactive glasses have been demonstrated to be effective in mineralization of dental structures. Therefore, this study evaluated the effect of BioSilicate® (a polycrystalline bioactive glass-ceramic) after bleaching by Laser-induced breakdown spectroscopy (LIBS) technique. Bovine dental blocks with 4 × 4 × 3 mm were obtained (n = 20), sequentially embedded in epoxy resin and then polished. Bleaching was performed using 35% hydrogen peroxide (Whiteness HP). Calcium (Ca) and phosphate (P) intensity values by LIBSwere obtained before the treatment (T0, baseline – control Group), after bleaching (T1), and after BioSilicate® application (T2). The use of BioSilicate® after bleaching showed to be an optimal way to remineralize enamel surface making BioSilicate® application a promising adjunct step to avoid or minimize the mineral loss on enamel surface after bleaching.

Liver transplantation is a well-established treatment for liver failure. However, the success of the transplantation procedure depends on liver graft conditions. The tissue function evaluation during the several transplantation stages is relevant, in particular during the organ harvesting, when a decision is made concerning the viability of the graft. Optical fluorescence spectroscopy is a good option because it is a noninvasive and fast technique. A partial normothermic hepatic ischemia was performed in rat livers, with a vascular occlusion of both median and left lateral lobes, allowing circulation only for the right lateral lobe and the caudate lobe. Fluorescence spectra under excitation at 532 nm (doubled frequency Nd:YAG laser) were collected using a portable spectrometer (USB2000, Ocean Optics, USA). The fluorescence emission was collected before vascular occlusion, after ischemia, and 24 hours after reperfusion. A morphometric histology analysis was performed as the gold standard evaluation ─ liver samples were analyzed, and the percentage of necrotic tissue was obtained. The results showed that changes in the fluorescence emission after ischemia can be correlated with the amount of necrosis evaluated by a morphometric analysis, the Pearson correlation coefficient of the generated model was 0.90 and the root mean square error was around 20%. In this context, the laser-induced fluorescence spectroscopy technique after normothermic ischemia showed to be a fast and efficient method to differentiate ischemic injury from viable tissues.

International audience; The Amazon rainforest presents one of the greater biodiversity in the world and a huge and dynamic carbon reservoir, both in the vegetation and in the soil pools, so it is an attractive subject of study. In the present paper, humic acids from a toposequence of an Oxisol-Spodosol system associated with kaolin was studied using fluorescence emission-excitation matrix combined with parallel factor analysis. The combined techniques allowed to assess the intensities of the two different fluorophores associated with humic acid with core consistency diagnoses of 84.2%. The results for the Humiluvic Spodosol seem to corroborate the model of the supramolecular structure of humic acid, because the intensity ratio of fluorophores does not remain in the profile. Therefore, the use of these combined techniques can provide information about the transformation processes of humic substances in soils, becoming an interesting analytical tool for studying these substances of different soils.

Laser-induced fluorescence spectroscopy (LIFS) has shown advantages for analyses of whole soil, providing results about chemical structure of soil organic matter (SOM) without the need for a chemical fractionating process; thus, allowing direct analysis of soils. Moreover, another advantage is the potential for the development of portable systems, which could be usable in field analyses. The aim of this paper is to evaluate the performance of a portable LIFS system to assess the humification degree (HD) of SOM. A good correlation (R > 0.8) was obtained for results (HD) achieved using the proposed portable system and a conventional fluorescence spectrometric method for humic acid. In addition, the results obtained using the portable LIFS system statistically agreed with the ones achieved using a benchtop LIFS system already described in the literature for such application (R = 0.953). Thus, the portable LIFS system constitutes an affordable option for the in situ characterization of SOM.

The C cycle in the Brazilian forests is very important, mainly for issues addressed to climate changes and soil management. Assessing and understanding C dynamics in Amazonian soils can help scientists to improve models and anticipate scenarios. New methods that allow soil C measurements in situ are a crucial approach for this kind of region, due to the costs for collecting and sending soil samples from the rainforest to the laboratory. Laser-induced breakdown spectroscopy (LIBS) is a multielemental atomic emission spectroscopy technique that employs a highly energetic laser pulse for plasma production and requires neither sample preparation nor the use of reagents. As LIBS takes less than 10 s per sample measurement, it is considered a promising technique for in situ soil analyses. One of the limitations of portable LIBS systems, however, is the common overlap of the emission lines that cannot be spectrally resolved. In this study a method was developed capable of separating the Al interference from the C emission line in LIBS measurements. Two typical forest Brazilian soils rich in Al were investigated: a spodosol (Amazon Forest) and an oxisol (Atlantic Forest). Fifty-three samples were collected and analyzed using a low-resolution LIBS apparatus to measure the intensities of C lines. In particular, two C lines were evaluated, at 193.03 and 247.86 nm. The line at 247.86 nm showed very strong interference with Fe and Si lines, which made quantitative analysis difficult. The line at 193.03 nm showed interference with atomic and ionic Al emission lines, but this problem could be solved by applying a correction method that was proposed and tested in this work. The line at 247.86 was used to assess the proposed model. The strong correlation (Pearson’s coefficient R=0.91) found between the LIBS values and those obtained by a reference technique (dry combustion by an elemental analyzer) supported the validity of the proposed method.

One of the approaches to overcome sensibility limitation of conventional LIBS system is use a double pulse (DP) configuration. The use of the DP technique allowed enhancing of line emission intensity, when compared with conventional