Carbon fiber felt scaffold from Brazilian textile PAN fiber for regeneration of critical size bone defects in rats: A histomorphometric and microCT study.

The objective of the present study was to evaluate the carbon fiber obtained from textile PAN fiber, in its different forms, as a potential scaffolds synthetic bone. Thirty-four adult rats were used (Rattus norvegicus, albinus variation), two critical sized bone defects were made that were 5 mm in diameter. Twenty-four animals were randomly divided into four groups: control (C)-bone defect + blood clot, non-activated carbon fiber felt (NACFF)-bone defect + NACFF, activated carbon fiber felt (ACFF)-bone defect + ACFF, and silver activated carbon fiber felt (Ag-ACFF)-bone defect + Ag-ACFF, and was observed by 15 and 60 days for histomorphometric, three-dimensional computerized microtomography (microCT) and mineral apposition analysis. On histomorphometric and microCT analyses, NACFF were associated with higher proportion of neoformed bone and maintenance of bone structure. On fluorochrome bone label, there was no differences between the groups. NACFF has shown to be a promising synthetic material as a scaffold for bone regeneration.

Dental implant and abutment in PEEK: stress assessment in single crown retainers on anterior region.

OBJECTIVE: Stress distribution assessment by finite elements analysis in poly(etheretherketone) (PEEK) implant and abutment as retainers of single crowns in the anterior region. MATERIALS AND METHODS: Five 3D models were created, varying implant/abutment manufacturing materials: titanium (Ti), zirconia (Zr), pure PEEK (PEEKp), carbon fiber-reinforced PEEK (PEEKc), glass fiber-reinforced PEEK (PEEKg). A 50 N load was applied 30o off-axis at the incisal edge of the upper central incisor. The Von Mises stress (σvM) was evaluated on abutment, implant/screw, and minimum principal stress (σmin) and maximum shear stress (τmax) for cortical and cancellous bone. RESULTS: The abutment σvM lowest stress was observed in PEEKp group, being 70% lower than Ti and 74% than Zr. On the implant, PEEKp reduced 68% compared to Ti and a 71% to Zr. In the abutment screws, an increase of at least 33% was found in PEEKc compared to Ti, and of at least 81% to Zr. For cortical bone, the highest τmax values were in the PEEKp group, and a slight increase in stress was observed compared to all PEEK groups with Ti and Zr. For σmin, the highest stress was found in the PEEKc. Stress increased at least 7% in cancellous bone for all PEEK groups. CONCLUSION: Abutments and implants made by PEEKc concentrate less σvM stress, transmitting greater stress to the cortical and medullary bone. CLINICAL RELEVANCE: The best stress distribution in PEEKc components may contribute to decreased stress shielding; in vitro and in vivo research is recommended to investigate this.

An inexpensive paracetamol sensor based on an acid-activated carbon fiber microelectrode.

Paracetamol, a contaminant of emerging concern, has been detected in different bodies of water, where it can impact ecological and human health. To quantify this paracetamol, electroanalytical methods have gained support. Thus, the present study developed a simple, inexpensive, and environmentally friendly method for paracetamol quantification using a carbon fiber microelectrode based on commercial carbon fiber. To improve the carbon fiber microelectrode's paracetamol sensitivity and selectivity, it was subjected to an activation process via electrochemical oxidation in an acid medium (H2SO4 or HNO3), using 20 consecutive cycles of cyclic voltammetry. The treated (activated) carbon fiber microelectrode was characterized using scanning electron microscopy and electrochemical techniques, including chronoamperometry and electrochemical impedance spectroscopy. The H2SO4-activated carbon fiber microelectrode exhibited enhanced figures of merit, with a linear dynamic range of paracetamol detection from 0.5 to 11 µmol L-1 and a limit of detection of 0.21 µmol L-1 under optimized conditions. The method was optimized by quantifying paracetamol in commercial pharmaceutical tablets, spiked running tap water, and river water (Pita River, Quito, Ecuador, latitude -0.364955°, longitude -78.404538°); the respective recovery values were 102.89, 103.93, and 112.40%. The results demonstrated an acceptable level of accuracy and the promising applicability of this carbon fiber microelectrode as a sensor to detect paracetamol.

Evaluation of a gold-nanoparticle-modified carbon-fiber microelectrode to quantify mercury in canned tuna sold in Ecuador.

Seafood consumption is the primary exposure route for trace metals like mercury. Accordingly, canned tuna meat has been focused on by researchers because of the potential bioaccumulation of high amounts of mercury. This study aimed to test a novel and reliable electroanalytical method employing a working electrode consisting of gold-nanoparticle-modified carbon microfibers to quantify total mercury in canned tuna samples. Determination was achieved via differential pulse anodic stripping voltammetry. The proposed method had a limit of detection of 3.9781 ± 0.0001 µg L-1 and a limit of quantification of 33.6634 ± 0.0001 µg L-1, with a sensitivity of 0.3275 nA µg L-1. The modified electrode was evaluated in samples taken from three canned tuna brands sold in the Sangolquí parish in Rumiñahui, Ecuador. These brands, coded A, B, and C, represent 47.92%, 27.08%, and 11.98% of all canned tuna sold in the Ecuadorian market, respectively. The resulting respective total mercury concentrations were 0.5999 ± 0.0001 mg kg-1; 0.9387 ± 0.0001 mg kg-1; and 0.3442 ± 0.0001 mg kg-1 for A, B, and C. Method accuracy was determined through the recovery percentages of ≥98%, which indicated acceptable accuracy for the final optimized method. Mean mercury concentrations for all samples did not represent a carcinogenic risk for consumers. However, the values obtained for potential no-carcinogenic risk and daily consumption rate suggest that consumers of tuna canned in water, particularly brand C, may be at risk.

Multiple Pulse Amperometry-An Antifouling Approach for Nitrite Determination Using Carbon Fiber Microelectrodes.

Nitrite is a ubiquitous pollutant in modern society. Developing new strategies for its determination is very important, and electroanalytical methods present outstanding performance on this task. However, the use of bare electrodes is not recommended because of their predisposition to poisoning and passivation. We herein report a procedure to overcome these limitations on carbon fiber microelectrodes through pulsed amperometry. A three-pulse amperometry approach was used to reduce the current decay from 47% (after 20 min under constant potential) to virtually 0%. Repeatability and reproducibility were found to have an RSD lower than 0.5% and 7%, respectively. Tap water and synthetic inorganic saliva samples were fortified with nitrite, and the results obtained with the proposed sensor were in good agreement with the amount added.

Fibra de carbono ativada: avaliação das interações biológicas in vitro / Activated carbon fiber: evaluation of biological interactions in vitro

Devido a constante necessidade de desenvolver materiais biocompatíveis com propriedades osteocondutores e osteoindutoras, a presente tese conta com o desenvolvimento de dois estudos in vitro com fibra de carbono obtida a partir de fibra PAN têxtil, incorporada com diferentes íons de metais, na osteogênese com vistas à compreensão das necessidades da engenharia tecidual no desenvolvimento desse biomaterial com adequadas propriedades biológicas. As células foram obtidas dos fêmures de 09 ratos machos adultos (Wistar) pesando 300g, com 90 dias.Estudo 1: A partir da preparação da fibras foram obtidos corpos de prova de 4 mm de diâmetro e 2 mm de altura, dos seguintes grupos: fibra de carbono não ativada (FCNA), fibra carbono ativada (FCA) e fibra carbono ativada com prata (FCAAg). Após plaqueamento (n=5) em meio suplementado (MTS) e meio suplementado osteogênico (MTSO) foram analisados: viabilidade celular, conteúdo de proteína total (PT), atividade de fosfatase alcalina (ALP), interaçãocelular e formação de nódulos de mineralização. Foi avaliada a formação de biofilme nos corpos de prova, utilizando cepas de S. aureus, P. aeruginosa e E. coli. Na viabilidade celular, houve diferença estatística entre grupo controle celular (C) e FCA-MTS, FCAAg-MTS e FCAAg-MTSO. Em PT, não houvediferença, na ALP houve diferença entre C-MTS e as fibras, C-MTSO se mostrou semelhante. Em nódulos, houve diferença entre C-MTS e C-MTSO e as fibras do MTSO. Houve redução de formação de biofilme do S. aureus na FCAAg.Estudo 2: Foram obtidos corpos de prova da mesma dimensão do estudo 1 (n=5) dos seguintes grupos: fibra carbono ativada com prata (FCAAg), fibra carbono ativada com ouro (FCAAu), fibra carbono ativada com cobre (FCACu), fibra carbono ativada com paládio (FCAPd) e fibra carbono ativada com platina (FCAPt). Foram quantificadas a proliferação celular, viabilidade celular, formação de nódulos de mineralização, conteúdo de PT e ALP. Todas as amostras mostraram-se semelhantes quanto a proliferação celular, com exceção do grupo FCAAg comparado ao grupo controle (C). Sobre viabilidade celular, C obteve maior viabilidade que os outros grupos, e FCA obteve maior taxa que os grupos FCAAg, FCACu, FCAPt, sendo semelhante aos grupos FCAAu e FCAPd. Já os grupos FCAAu e FCAPd apresentaram diferença aos grupos FCAAg e FCACu. Na análise de expressão de PT apenas houve diferença entre FCA e FCAAu, sendo FCAAu com menor expressão de produção de PT. Na avaliação da ALP os grupos FCAAg e FACu mostraram diferença estatística e inferior com os grupos C, FCAAu, FCAPd e FCAPt, além disso, o grupo FCA mostrou menor taxa que C.Conclusões: As fibras utilizadas de base para a incorporação dos íons demonstraram grande potencial para uso como scaffold para reparação óssea, isso porque em ambos os estudos, na forma ativada e não ativada, as fibras apresentaram viabilidade celular e quantificação de cálcio satisfatórias. Sendo a versão não ativada mais econômica no que diz respeito ao tempo e custo de preparação. Mais estudos devem ser empregados a fim de assegurar sua segurança clínica em relação à citotoxicidade da incorporação de íons de ouro e paládio.(AU)

Due to the constant need to develop biocompatible materials with osteoconductive and osteoinductive properties, this thesis involves the development of two in vitro studies with carbon fiber obtained from textile PAN fiber, incorporated with different metal ions, in osteogenesis with a view to understanding the needs of tissue engineering in the development of this biomaterial with adequate biological properties. The cells were obtained from the femurs of 9 adult male rats (Wistar) weighing 300g, aged 90 days. Study 1: From the fiber preparation, specimens measuring 4 mm in diameter and 2 mm in height were obtained from the following groups: non-activated carbon fiber (FCNA), activated carbon fiber (FCA) and silver-activated carbon fiber (FCAAg). After plating (n=5) in supplemented medium (MTS) and supplemented osteogenic medium (MTSO), cell viability, total protein content (PT), alkaline phosphatase (ALP) activity, cell interaction and formation of mineralization nodules were analyzed. . Biofilm formation was evaluated in the specimens, using strains of S. aureus, P. aeruginosa and E. coli. In cell viability, there was a statistical difference between the cell control group (C) and FCAMTS, FCAAg-MTS and FCAAg-MTSO. In PT, there was no difference, in ALP there was a difference between C-MTS and fibers, C-MTSO was similar. In nodules, there was a difference between C-MTS and C-MTSO and MTSO fibers. There was a reduction in S. aureus biofilm formation on FCAAg. Study 2: Specimens of the same size as in study 1 (n=5) were obtained from the following groups: carbon fiber activated with silver (FCAAg), carbon fiber activated with gold (FCAAu), carbon fiber activated with copper (FCACu), palladium-activated carbon fiber (FCAPd) and platinum-activated carbon fiber (FCAPt). Cell proliferation, cell viability, formation of mineralization nodules, PT and ALP content were quantified. All samples were similar in terms of cell proliferation, with the exception of the FCAAg group compared to the control group (C). Regarding cell viability, C obtained higher viability than the other groups, and FCA obtained a higher rate than the FCAAg, FCACu, FCAPt groups, being similar to the FCAAu and FCAPd groups. The FCAAu and FCAPd groups showed differences to the FCAAg and FCACu groups. In the analysis of PT expression, there was only a difference between FCA and FCAAu, with FCAAu having lower expression of PT production. In the ALP assessment, the FCAAg and FACu groups showed a lower statistical difference compared to the C, FCAAu, FCAPd and FCAPt groups, in addition, the FCA group showed a lower rate than C. Conclusions: The fibers used as the basis for the incorporation of ions demonstrated great potential for use as a scaffold for bone repair, because in both studies, in activated and non-activated form, the fibers showed satisfactory cell viability and calcium quantification. The non-activated version is moreeconomical in terms of preparation time and cost. More studies must be carried out to ensure its clinical safety in relation to the cytotoxicity of the incorporation of gold and palladium ions. (AU)

Miniaturized Carbon Fiber Paper Electrodes for In Situ High Resolution NMR Analyses.

Combining spectroscopic techniques with electrochemistry is a promising strategy, as it allows the detailed investigation of the species that are consumed and produced by the reaction in real time. However, as with any in situ coupling technique, the junction between NMR and electrochemistry presents some challenges, notably the distortion of NMR signals due to the placement of electrodes close to or within the detection region. In this work, miniaturized electrodes made of carbon fiber paper were developed and later modified with platinum. Platinum decoration by cathodic deposition was chosen, as platinum is a prominent element in electrocatalysis, able to catalyze a large variety of reactions. To evaluate the efficiency of this electrochemical system, the oxidation of ascorbic acid was used as a model reaction. It was observed that the electrodes caused substantial signal distortion when placed within the detection region (full width at half-maximum equal to 1.46 Hz), whereas no distortion was observed when the electrodes were placed 1 mm above the detection region (full width at half-maximum equal to 0.95 Hz). With this system, it was also possible to monitor the magnetoelectrolysis effect, caused by the interaction of the magnetic field with the flowing ions, leading to a doubling of the ascorbic acid oxidation rate, compared to the reaction performed without a magnetic field. In addition to its low cost and simplicity in preparation, the developed electrode system allows the electrode surface to be easily modified with other suitable catalysts.

Synergistic Effect of Composite Nickel Phosphide Nanoparticles and Carbon Fiber on the Enhancement of Salivary Enzyme-Free Glucose Sensing.

An electrospinning method was used for the preparation of an in situ composite based on Ni2P nanoparticles and carbon fiber (FC). The material was tested for the first time against direct glucose oxidation reaction. The Ni2P nanoparticles were distributed homogeneously throughout the carbon fibers with a composition determined by thermogravimetric analysis (TGA) of 40 wt% Ni2P and 60 wt% carbon fiber without impurities in the sample. The electrochemical measurement results indicate that the GCE/FC/Ni2P in situ sensor exhibits excellent catalytic activity compared to the GCE/Ni2P and GCE/FC/Ni2P ex situ electrodes. The GCE/FC/Ni2P in situ sensor presents a sensitivity of 1050 µAmM-1cm-2 in the range of 5-208 µM and a detection limit of 0.25 µM. The sensor was applied for glucose detection in artificial saliva, with a low interference observed from normally coexisting electroactive species. In conclusion, our sensor represents a novel and analytical competitive alternative for the development of non-enzymatic glucose sensors in the future.

Fibra de carbono: caracterização e avaliação da resposta inflamatória e toxicidade em ratos / Carbon Fiber from PAN textile fIibers: characterization and evaluation of the inflammatory response and toxicity in rat

Este estudo teve como objetivo avaliar a Fibra de Carbono obtida a partir da fibra PAN têxtil e de fibra de algodão, nas suas diferentes formas de apresentação: Feltro Fibra de Carbono Não Ativado (FFCNA), Feltro Fibra de Carbono Ativado (FFCA), Feltro de Fibra de Carbono Ativado com Prata (FFCAAg) e Tecido Fibra de Carbono Ativado (TFCA), com vistas à obtenção de scaffolds como potencial material com propriedades relativas à enxerto ósseo sintético. Foram realizados testes de caracterização: molhabilidade de superfície, ensaio de tração, ensaio de intumescimento e testes in vivo: avaliação da resposta inflamatória pela implantação dos materiais no tecido subcutâneo de quatorze ratos Wistar, avaliação das fibras colágenas pela coloração Picrosirius Red e avaliação da toxicidade nos seguintes órgãos: coração, baço, fígado e rim. No teste de molhabilidade, FFCNA e TFCA se mostraram hidrofóbicos (ɵ124º e 114º), FFCA e FFCAAg hidrofílicos. Para tensão máxima FFCA se apresentou mais resistente (2.983 ± 1.059). No ensaio de intumescimento os grupos FFCAAg e FFCA se mostraram com maior porcentagem de absorção para a solução PBS e água destilada. Os animais não apresentaram sinais clínicos de intoxicação. Os órgãos não apresentaram sinais de toxicidade sistêmica aguda. As regiões dos implantes apresentaram infiltrado inflamatório de leve a moderado em 7 e 21 dias. Apenas o grupo TFCA não apresentou maturação de fibras colágenas tipo I em 21 dias. Por meio das análises relizadas constatou-se que o TFCA se apresentou hidrofóbico, pouco resistente a tração e baixo potencial para maturação de fibras colágenas. Portanto o TFCA mostra-se com pouco potencial para ser indicado como possível scaffold para engenharia tecidual óssea. Conclui-se que FFCNA, FFCA e FFCAAg, possuem potencial para serem consideradas scaffolds, devido as seguintes características que foram apresentadas: boa taxa de absorção, hidrofilicidade e atóxicas. (AU)

This study aimed to evaluate the Carbon Fiber obtained from PAN textile fiber and cotton fiber, in its different forms of presentation: Non-Activated Carbon Fiber Felt (FFCNA), Activated Carbon Fiber Felt (FFCA), Activated Carbon Fiber with Silver (FFCAAg) and Activated Carbon Fiber Tissue (TFCA), with a view to obtaining scaffolds as a potential material with properties related to synthetic bone graft. Characterization tests were performed: surface wettability, traction test, swelling test and in vivo tests: evaluation of the inflammatory response by implanting the materials in the subcutaneous tissue of fourteen Wistar rats, evaluation of collagen fibers by Picrosirius Red staining and evaluation of toxicity in the following organs: heart, spleen, liver and kidney. In the wettability test, FFCNA and TFCA were hydrophobic (ɵ124º and 114º), FFCA and FFCAAg were hydrophilic. For maximum stress FFCA was more resistant (2.983 ± 1.059). In the swelling test, the FFCAag and FFCA groups showed the highest percentage of absorption for the PBS solution and distilled water. The animals did not show clinical signs of intoxication. The organs showed no signs of acute systemic toxicity. The implant regions showed mild to moderate inflammatory infiltrate at 7 and 21 days. Only the TFCA group did not show maturation of type I collagen fibers in 21 days. Through the analyzes carried out, it was found that the TFCA was hydrophobic, with little resistance to traction and low potential for collagen fiber maturation. Therefore, TFCA shows little potential to be indicated as a possible scaffold for bone tissue engineering. It is concluded that FFCNA, FFCA and FFCAAg have the potential to be considered scaffolds, due to the following characteristics that were presented: good absorption rate, hydrophilicity and non-toxic. (AU)

Fibra de carbono em defeitos ósseos de tamanho crítico: estudo in vivo em ratos / Carbon fiber in critical size bone defects: an in vivo study in rats

Materiais a base de carbono têm sido utilizado em várias áreas como química, engenharia, ciência dos materiais, ciências biomédicas, entre outras. Além disso, por serem quimicamente estáveis, mecanicamente fortes, acessíveis economicamente, e biologicamente compatíveis, chamaram a atenção como material de arcabouço para a engenharia tecidual óssea. Assim, o presente estudo teve como objetivo principal avaliar a fibra de carbono obtida a partir de fibra PAN têxtil, nas suas diferentes formas, com vistas à obtenção de scaffolds como potencial enxerto ósseo sintético. Foram utilizados 34 ratos adultos (Rattus norvegicus, variação albinus, Wistar), e realizados dois defeitos ósseos críticos na calvária de cada animal com 5 mm de diâmetro. Vinte e quatro animais foram divididos aleatoriamente em 4 grupos: Defeito ósseo + coágulo sanguíneo, Defeito ósseo + Feltro Fibra de Carbono Não Ativado (FFCNA), Defeito ósseo + Feltro Fibra de Carbono Ativado (FFCA), Defeito ósseo + Feltro Fibra de Carbono Ativado com Prata (FFCAAg), e foram observados por períodos distintos de 15 e 60 dias para análise histomorfométrica e micro CT. Dez animais foram divididos aleatoriamente nos mesmos 4 grupos para aplicação de marcadores fluorocromáticos e análise de aposição mineral (em andamento). Após o período de observação dos subgrupos, os animais foram eutanasiados por sobredose de anestesia geral. Em seguida, as calvárias foram removidas para as análises. Na avaliação dos dois períodos (15 e 60 dias), o FFCNA mostrou-se melhor para os parâmetros de Área de Neoformação óssea, Área de Neoformação Lamelar e Área de Neoformação Intramembranosa. Em 60 dias, o grupo FFCNA apresentou maior volume ósseo, volume tecidual e maior número de trabéculas, mostrando-se um material sintético promissor como scaffold para regeneração óssea (AU)

Carbon based materiais have been used in some areas like chemistry, engineering, materials science, biomedical science, among others. In addition, because they are chemically stables, mecanically strongs, economically acessibles, and biologically compatibles, they have drawn attention as a scaffold material for bone tissue engineering. Thus, the present study had a main objetive to evaluate the carbon fiber obtained from textile PAN fiber, in its diferents forms, as a scaffolds potential synthetic bone. Thirty four adult rats was used (Rattus norvegicus, albinus variation, Wistar), and two critical bone defects was made with 5mm in diameter. Thenty for animals was ramdoly divided in 4 groups: Bone deffect + blood clot; Bone deffect + Unactivated Carbon Fiber Felt (FFCNA); Bone deffect + Activated Carbon Fiber Felt (FFCA); Bone deffect + Carbon Fiber Felt Activated with Silver (FFCAAg), and was observed for different periods of 15 and 60 days for histomorfometrical analisys and micro CT. Ten animals was ramdoly divided in the same four groups for aplication of fluorochromatic markers and mineral apposition analisysis (in progress). After the observation period of the subgroups, the animals was euthanized by general aneshtesia overdose. Then, the calvarias was removed for the analysis. In the evaluation of the two periods (15 and 60 days), the FFCNA was better for the parameters of Bone Neoformation Area, Lamelar Neoformation Area and Intramembranous Neoformation Area. In 60 days, the FFCNA group presented higher bone volume, tissue volume and higher number of trabeculae, showing a promising synthetic material as scaffold for bone regeneration. (AU)

Recycling of polymeric composites from industrial waste by pyrolysis: Deep evaluation for carbon fibers reuse.

The use of polymeric composite on transport applications as reinforcement material has been increased due to the low fuel consumption when replacing heavier materials. It is estimated that 170,000 tons of polymeric composites will be discarded by 2025, and recycling processing for carbon fibers recovery is required to save primary energy and reduce waste. Among the current techniques, pyrolysis processing has been most effective. On the other hand, innovation must maintain the structure for reuse since physical and mechanical properties are important for recycled materials. For this reason, the goal of the present study was the recycling of polymeric composite by pyrolysis. The recovered carbon fibers were analyzed in SEM and EDS to verify surface defects compared with virgin carbon fibers. The effect of temperature, time, and atmosphere were investigated. Results showed that at 550 °C for 1 h, it was possible to obtain free carbon fibers from the polymeric matrix. After the pyrolysis process in this condition, the fibers had no pores, material fracture, and carbonization. This paper contributes to the widening and systematizing knowledge on effectiveness and understanding polymeric composites recycling for carbon fiber recovery, maintaining its structure for reuse.

Superficial properties of activated carbon fiber catalysts produced by green synthesis and their application in water purification.

Catalysts of Pd-In supported on activated carbon fiber were synthesized, characterized, and evaluated for the removal of nitrogen oxyanions from water. The work was carried out aiming the development of a green synthesis process, and the studies were accomplished with the following objectives: (a) to evaluate whether catalysts produced by wet impregnation (WI) and autocatalytic deposition (AD) have enough catalytic activity for the removal of oxyanions in water; (b) to determine the efficiency of ion removal using formic acid as a reducing agent; (c) to determine which synthesis method produces less waste. It was found that the two synthesis processes modified the properties of the support and that the distribution of the particles of the metallic phase was of the nanometric order, being these particles found predominantly at the support surface. By using formic acid as a reducing agent, although low nitrate conversions were obtained (32%), a selectivity to N2 higher than 99% was achieved. These findings were attributed to the low decomposition of formic acid on the catalyst surface. The Pd:In (0.45:0.2) catalyst prepared by WI was the most suitable for the catalytic reduction of both nitrate and nitrite oxyanions. Regarding the green point of view of the synthesis method, catalysts prepared by WI generated less waste. Graphical abstract.

Efeito da concentração de tensão em compósitos sob flexão em quatro pontos para a confecção de infraestruturas de próteses fixas odontológicas sobre implantes / Effect of stress concentration in composites under four points bending test for the manufacture of infrastructures for fixed dental prostheses on implants

Com advento dos implantes osseointegráveis gerou se a possibilidade de pacientes edêntulos adquirirem próteses fixas. Para tanto são necessários procedimentos de conexão destes implantes à prótese fixa implantossuportada, como furos e entalhes, além de materiais que confiram maior rigidez ao sistema. Dentre os materiais mais usados como infraestrutura destas próteses estão as ligas metálicas como o cobalto-cromo (Co-Cr) fundido, o titânio (Ti) e compósitos. Os compósitos poliméricos reforçados por fibras de carbono (CPRFC) vêm ganhando destaque, porém interrupções nas fibras como furos podem gerar redução das suas propriedades mecânicas. Atualmente, com o desenvolvimento de novas propostas de tratamento de maxila e mandíbula edêntulas, como o tratamento All on Four®, existe a sobre extensão das próteses, gerando cantiléveres mais longos causando maiores tensões sobre o sistema protético, quando perfuradas para a adaptação de munhões. O objetivo deste trabalho é analisar o efeito da concentração de tensão nos CPRFC submetidos a cargas de flexão, com furo.. Para isso, foram confeccionados dois laminados compósitos em fibra de carbono. Um CPRFC foi produzido com matriz termoplástica de poli(sulfeto de fenileno) PPS, processado por Moldagem de Compressão a Quente, e outro da com matriz termorrígida de epóxi, processado via Moldagem por Transferência de Resina (RTM). Após a produção tanto o laminado termoplástico (TP) quanto o termorrígido (TR) foram perfurados e ensaiados em flexão de quatro pontos. O laminado carbono/PPS foi testado com furo de 4 mm, 5 mm e 6 mm. O carbono/epóxi foi testado com furo de 4 mm e 6 mm. Realizou-se então o ensaio de flexão em quatro pontos para determinação da resistência e módulo em flexão. Foi também realizada análise de fratura em flexão. Como resultados houve uma maior resistência e módulo de elasticidade para os laminados TR em todos os grupos comparados aos TP. A presença de furos nas dimensões estudadas não apresentou diferenças significativas no módulo de elasticidade, porém houve diferenças entre a força máxima de ruptura nos compósitos com furo. Portanto, o uso de CPRFC, apesar de que suas propriedades mecânicas em flexão serem menores que ligas metálicas, estes podem ser usados em infraestruturas protéticas devido ao seu alto módulo de elasticidade(AU)

With the advent of osseointegrated implants, the possibility of edentulous patients to acquire fixed prostheses was created. Therefore, procedures are required to connect these implants to the implant-supported fixed prosthesis, such as holes and notches, in addition to materials that provide greater stiffness to the system. Among the materials most used as infrastructure for these prostheses are metallic alloys such as molten cobalt-chromium (Co-Cr), titanium (Ti) and composites. Polymeric composites reinforced by carbon fibers (CPRFC) have been gaining prominence, however interruptions in fibers such as holes can reduce their mechanical properties. Currently, with the development of new proposals for the treatment of edentulous maxilla and mandible, such as the All on Four® treatment, there is an over extension of the prostheses, generating longer cantilevers, causing greater stress on the prosthetic system. The objective of this work is to carry out the analysis of the stress concentration in the CPRFC subjected to bending loads with hole. One of the possibilities of using CPRFC is the acquisition of pre-molded arc-shaped bars, to be drilled for the adaptation of trunnions, which serves as an infrastructure in Bränemark protocols, to be later screwed to the implants. Two carbon fiber composite laminates were manufactured. One CPRFC was produced with the association of thermoplastic matrix of poly (phenylene sulphide) PPS, processed by Hot Compression Molding, and another of the association of carbon fibers with epoxy matrix, processed via Resin Transfer Molding (RTM). After production, both the thermoplastic (TP) and the thermo-rigid (TR) laminates were cut and drilled. The TP laminate was tested without hole, with 4 mm hole, with 5 mm hole and with 6 mm hole. The TR material were divided into three groups, without hole, with a 4 mm hole and with a 6 mm hole. The four-point bending test was then performed to determine the strength and stiffness of laminates. A fracture analysis of delamination was also performed. As a result, there was a greater resistance and modulus of elasticity for the TR laminates in all groups compared to TP. The presence of holes in the studied dimensions did not present significant differences in the modulus of elasticity, however there were differences between the maximum breaking force in composites with a hole. Therefore, the use of CPRFC even though its mechanical properties in bending are less than metallic alloys, these can be used in prosthetic infrastructures due to their high modulus of elasticity(AU)

Determination of polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives in coffee brews using an efficient cold fiber-solid phase microextraction and gas chromatography mass spectrometry method.

Polycyclic aromatic hydrocarbons (PAHs) are food contaminants; besides, their oxygenated (oxy-PAHs) and nitrated (nitro-PAHs) derivatives have also been detected in some foods. This is worrying because these derivatives may be more toxic than PAHs. This study presents a new method for the determination of PAHs and their oxygenated and nitrated derivatives in coffee brew. The analytes were extracted by cold fiber solid phase microextraction (CF-SPME) with analysis by gas chromatography/mass spectrometry. The developed method presented good precision with intra-assay and inter-assay, ranged from 4.5 to 16.4%, and from 9.8 to 19.8%, respectively. Recovery ranged from 82.1 to96.3% and linearity showed good adjustment presenting determination coefficients (R2) from 0.980 to 0.999. The limits of quantification ranged from 0.025 to 0.224 µg L-1. The proposed method is simple, versatile, allows simultaneous extraction of PAHs, nitrated and oxygenated derivatives and was successfully applied to the analysis of commercial coffee samples. Benzo(k)fluoranthene, benzo(b)fluoranthene, pyrene, acenaphthylene and acenaphthene are the most abundant PAHs found in samples. In addition, 5,12-naphthacenequinone was the most abundant oxy-PAH and 1-nitropyrene was the most abundant nitro-PAH.

Ethanol generation, oxidation and energy production in a cooperative bioelectrochemical system.

Integrating in situ biofuel production and energy conversion into a single system ensures the production of more robust networks as well as more renewable technologies. For this purpose, identifying and developing new biocatalysts is crucial. Herein, is reported a bioelectrochemical system consisting of alcohol dehydrogenase (ADH) and Saccharomyces cerevisiae, wherein both function cooperatively for ethanol production and its bioelectrochemical oxidation. Here, it is shown that it is possible to produce ethanol and use it as a biofuel in a tandem manner. The strategy is to employ flexible carbon fibres (FCF) electrode that could adsorb both the enzyme and the yeast cells. Glucose is used as a substrate for the yeast for the production of ethanol, while the enzyme is used to catalyse the oxidation of ethanol to acetaldehyde. Regarding the generation of reliable electricity based on electrochemical systems, the biosystem proposed in this study operates at a low temperature and ethanol production is proportional to the generated current. With further optimisation of electrode design, we envision the use of the cooperative biofuel cell for energy conversion and management of organic compounds.

Kinetics of Acid Orange 7 oxidation by using carbon fiber and reticulated vitreous carbon in an electro-Fenton process.

In this study, a micro-scale parallel plate reactor was built to electrochemically generate hydrogen peroxide (H2O2) and to develop the Fenton reaction in situ, for the treatment of toxic organic pollutants. Two types of carbon materials were compared and used as cathodes: unidirectional carbon fiber (CF) and reticulated vitreous carbon (RVC). As anode, a stainless steel mesh was used. The results of H2O2 were experimentally compared by means of electrogeneration process. RVC cathode with dimensions of 2.5 × 1 × 5 cm (170 mA and variable voltage V = 2.0-2.7) and 180 min produced 5.3 mM H2O2, with an H2O2 production efficiency of 54%. Unidirectional carbon fiber cathode produced 7.5 mM of H2O2 (96% of H2O2 production efficiency) when a voltage of 1.8 V was applied during 180 min to a total area of 480 cm2 of this material. Acid Orange 7 (AO7) was degraded to a concentration of 0.16 mM during the first 40 min of the process, which represented 95% of the initial concentration. Electrolysis process removed nearly 100% of the AO7 using both cathodes at the end of these experiments (180 min).

Adsorption of caffeine on mesoporous activated carbon fibers prepared from pineapple plant leaves.

The present work reports the preparation of activated carbon fibers (ACFs) from pineapple plant leaves, and its application on caffeine (CFN) removal from aqueous solution. The preparation procedure was carried out using the H3PO4 as activating agent and slow pyrolysis under N2 atmosphere. The characterization of materials was performed from the N2 adsorption and desorption isotherms, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Boehm titration and pHpzc method. ACFs showed high BET surface area value (SBET = 1031m2 g-1), well-developed mesoporous structure (mesopore volume of 1.27cm³ g-1) and pores with average diameter (DM) of 5.87nm. Additionally, ACFs showed features of fibrous material with predominance of acid groups on its surface. Adsorption studies indicated that the pseudo-second order kinetic and Langmuir isotherm models were that best fitted to the experimental data. The monolayer adsorption capacity was found to be 155.50mgg-1. thermodynamic studies revealed that adsorption process is spontaneous, exothermic and occurs preferably via physisorption. The pineapple leaves are an efficient precursor for preparation of ACFs, which were successful applied as adsorbent material for removal of caffeine from the aqueous solutions.

Bio-electro oxidation of indigo carmine by using microporous activated carbon fiber felt as anode and bioreactor support.

The bioremediation and electro-oxidation (EO) processes are included among the most promising cleaning and decontamination mechanisms of water. The efficiency of bioremediation is dictated by the biological actuator for a specific substrate, its suitable immobilization and all involved biochemical concepts. The EO performance is defined by the anode efficiency to perform the complete mineralization of target compounds and is highlighted by the low or null use of reagent. Recently, the combination of both technologies has been proposed. Thus, the development of high efficient, low cost and eco-friendly anodes for sustainable EO, as well as, supporting devices for immobilization of biological systems applied in bioremediation is an open field of research. Therefore, the aim of this work was to promote the bio-electrochemical remediation of indigo carmine dye (widely common in textile industry), using new anode based on a microporous activated carbon fiber felt (ACFF) and ACFF with immobilized Laccase (Lcc) from Pycnoporus sanguineus. The results were discolorations of 62.7% with ACFF anode and 83.60% with ACFF-MANAE-Lcc anode, both for 60 min in tap water. This remediation rates show that this new anode has low cost and efficiency in the degradation of indigo dye and can be applied for other organic pollutant.

Electrochemical determination of arsenic in natural waters using carbon fiber ultra-microelectrodes modified with gold nanoparticles.

We have developed an anodic stripping voltammetry method that employs carbon fiber ultra-microelectrodes modified with gold nanoparticles to determine arsenic in natural waters. Gold nanoparticles were potentiostatically deposited on carbon fiber ultra-microelectrodes at -0.90V (vs SCE) for a time of 15s, to form the carbon fiber ultra-microelectrodes modified with gold nanoparticles. Cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy coupled to an X-ray microanalysis system were used to check and confirm the presence of gold nanoparticles on the carbon fiber ultra-microelectrodes. Arsenic detection parameters such as deposition potential and deposition time were optimized allowing a detection range between 5 to 60µgL-1. The developed modified electrodes allowed rapid As determination with improved analytical characteristics including better repeatability, higher selectivity, lower detection limit (0.9µgL-1) and higher sensitivity (0.0176nAµgL-1) as compared to the standard carbon electrodes. The analytical capability of the optimized method was demonstrated by determination of arsenic in certified reference materials (trace elements in water (NIST SRM 1643d)) and by comparison of results with those obtained by hydride generation atomic absorption spectrometry (HG-AAS) in the determination of the analyte in tap and well waters.

Adsorption of SOx and NOx in activated viscose fibers.

SOx and NOx are emissions resulting from combustion processes and are the main agents that contribute to the formation of acid rain, which causes harm to humans and the environment. Several techniques for removing these pollutants are applied in i.e. oil refineries, thermoelectric that use petroleum oils and vehicular pollution. Among these, highlight the adsorption of contaminants by the usage of activated carbon fibers and activated carbon, which are characterized by high surface area and uniform distribution of pores, providing appropriate conditions for application in processes of removing environmental contaminants. In the present work, activated viscose fibers (AVF) were prepared and applied in adsorption experiments of NO and SO2. The materials produced showed high values of surface area, with a predominance of micro pores with diameters in the range of 1.0 nm. The AVF had satisfactory performance in the removal of contaminants and are compatible with other synthetic fibers. Thus, the formation of active sites of carbon provides contaminants adsorption, demonstrating that carbon fibers cloth can be applied for the removal of pollutants.