Obtainment and characterization of a silicon alkoxides-based coating applied to a substrate of stainless steel 316L for use in biomaterials

The silicon alkoxides-based coating is an alternative to control the release of cytotoxic ions through metal implants. This study evaluated the influence of the number of layers of a hybrid coating on the surface of austenitic stainless steel AISI 316L on the corrosion resistance. This coating was produced from the precursors of silicon alkoxides 3-(trimethoxysilyl)propyl methacrylate (MAP) and tetraethoxisylane (TEOS) obtained by sol-gel process, and easily applied by dip-coating. Results indicated that a single layer of coating in the substrate showed a better protection than two layers. This single layer developed by the combination of the precursors TEOS-MAP was enough to create a compact and uniform film with good adherence to AISI 316L and higher electrochemical development. A single layer of TEOS-MAP coating is more adequate as a protective coating for the AISI 361L than the sample subjected to two layers and the non-coated substrate, because this film ensures its integrity in an aggressive environment

Caracterización de nanofibras lignocelulósicas de tallos de tabaco para aplicaciones farmacéuticas

Lignocellulosic nanofibers derived from tobacco stalk can have countless applications in polymers composites, textile, cosmetics, and pharmaceuticals. Thus, it is important to evaluate biomass characteristics such as the presence of nicotine. In this study, nanofibers were obtained by mechanical fibrillation while cellulose content (0.5 and 2.0%) and drying methods were varied. Nanofibers were characterized by thin layer chromatography, 1H NMR, morphological analysis, α-cellulose content, Fourier transform infrared spectroscopy, X-ray diffraction and thermal analysis. Results demonstrate the absence of nicotine in tobacco stalk. The grinding mill process was efficient to produce by freeze - drying, nanofibers with fiber’s mean diameter of ~30 nm. Solid concentrations can influence the diameter of obtained fibers. Thermal stability increased and crystallinity decreased when alkali treatment was applied. The characterization techniques applied enable the evaluation of tobacco stalk and expanded its application to pharmaceutics.Nanofibras lignocelulósicas derivadas do caule do tabaco podem ter inúmeras aplicações em compósitos poliméricos, tecidos, cosméticos e produtos farmacêuticos. Assim, é importante avaliar características da biomassa como a presença de nicotina. Neste estudo, as nanofibras foram obtidas por fibrilação mecânica, enquanto o teor de celulose (0,5 e 2,0%) e os métodos de secagem foram variados. As nanofibras foram caracterizadas por cromatografia em camada delgada, 1H RMN, análise morfológica, conteúdo de α-celulose, espectroscopia de infravermelho com transformada de Fourier, difração de raios-X e análises térmicas. Os resultados demonstram a ausência de nicotina no caule do tabaco. O processo de moagem foi eficiente para produzir por liofilização, nanofibras com diâmetro médio da fibra de ~ 30 nm. As concentrações de sólidos podem influenciar o diâmetro das fibras obtidas. A estabilidade térmica aumentou e a cristalinidade diminuiu quando o tratamento alcalino foi aplicado. As técnicas de caracterização aplicadas possibilitaram a avaliação do caule do tabaco e ampliaram sua aplicação na área farmacêutica.Las nanofibras lignocelulósicas derivadas del tallo del tabaco pueden tener innumerables aplicaciones en compuestos de polímeros, textiles, cosméticos y productos farmacéuticos. Por tanto, es importante evaluar las características de la biomasa como la presencia de nicotina. En este estudio, las nanofibras se obtuvieron mediante fibrilación mecánica mientras se variaba el contenido de celulosa (0,5 y 2,0%) y los métodos de secado. Las nanofibras se caracterizaron por cromatografía en camada delgada, 1H RMN, análisis morfológico, contenido de α-celulosa, espectroscopia infrarroja por transformada de Fourier, difracción de rayos X y análisis térmicas. Los resultados demuestran la ausencia de nicotina en el tallo del tabaco. El proceso del molino fue eficiente para producir mediante liofilización, nanofibras con un diámetro medio de fibra de ~ 30 nm. Las concentraciones de sólidos pueden influir en el diámetro de las fibras obtenidas. La estabilidad térmica aumentó y la cristalinidad disminuyó cuando se aplicó un tratamiento con álcali. Las técnicas de caracterización aplicadas permiten evaluar el tallo del tabaco y ampliar su aplicación a la industria farmacéutica

Biocompatibility Assessment of Poly(lactic acid) Films after Sterilization with Ethylene Oxide in Histological Study In Vivo with Wistar Rats and Cellular Adhesion of Fibroblasts In Vitro

Biomaterials must meet certain fundamental requirements for their usage in living beings, such as biocompatibility, bifunctionality, and sterilizability, without having chemical and structural changes. The biocompatibility of poly(lactic acid) (PLA) films, shaped by compression, was evaluated after sterilization by ethylene oxide by a histological in vivo test with Wistar rats and cytotoxicity in cell adhesion in vitro. The cytotoxicity test was performed by the reduction of tetrazolium salt (MTT). Thermal and chemical changes in PLA films concerning the proposed sterilization process and characteristics were not observed to evidence polymer degradation due to sterilization. The analysis of the cytotoxicity by the MTT method has shown that the sterilized PLA films are not cytotoxic. The adhesion and proliferation of fibroblasts on PLA films were homogeneously distributed over the evaluation period, showing an elongated appearance with unnumbered cytoplasmic extensions and cell-cell interactions. By examining the biocompatibility in a histological study, a mild tissue inflammation was observed with the presence of fibrosis in the samples that had been exposed for 21 days in the rats’ bodies. PLA films sterilized with ethylene oxide did not exhibit cell adhesion in vitro and toxicity to the surrounding tissue in vivo and they may be used in future in vivo testing, according to histological findings in Wistar rats in the present study

Compatibility study of rosmarinic acid with excipients used in pharmaceutical solid dosage forms using thermal and non-thermal techniques

Rosmarinic acid (RA) is a phenolic compound that presents well-documented anti-inflammatory, antioxidant and antitumor activities, and based on its pharmacological potential and poor bioavailability, several solid dosage forms have been developed to RA delivery. Therefore, in literature, there are no reports about RA compatibility with excipients. In this regard, the aim of the present study was to evaluate, for the first time, the compatibility of RA with excipients commonly used in solid dosage forms at a 1:1 (RA: excipient) ratio using differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier-transform infrared (FTIR), solid-state nuclear magnetic resonance (ssNMR), and isothermal stress testing (IST) coupled with liquid chromatography (LC). The excipients selected were hydroxypropyl methylcellulose (HPMC), microcrystalline cellulose (MCC), lactose monohydrate (LAC), polyvinylpyrrolidone (PVP), talc (TALC), croscarmellose sodium (CCS), and magnesium stearate (MgSTE). According to DSC results, physical interactions were found between RA and HPMC, LAC, CCS, and MgSTE. The TG analyses confirmed the physical interactions and suggested chemical incompatibility. FTIR revealed physical interaction of RA with TALC and MgSTE and the ssNMR confirmed the physical interaction showed by FTIR and excluded the presence of chemical incompatibility. By IST, the greatest loss of RA content was found to CCS and MgSTE (>15%), demonstrating chemical incompatibilities with RA. High temperatures used in DSC and TG analyses could be responsible for incompatibilities in binary mixtures (BMs) with HPMC and LAC, while temperature above 25 C and presence of water were factors that promote incompatibilities in BMs with CCS and MgSTE. Overall results demonstrate that RA was compatible with MCC and PVP

Characterization of Mullite Ceramic Membranes and their Application in the Removal Escherichia Coli

This paper aims the morphological and structural characterization of ceramic membranes of mullite and their application in the removal of Escherichia coli. A complex irregular structure presented by the pores of the membrane was verified by scanning electron microscopy (SEM). The average pore size and distribution were determined by mercury intrusion porosimetry. The average pore size of the material presented was 0,39 μm. Microfiltration tests resulted in a protein retention of 46, 76 and 89% for trypsin (TR), egg albumin (EA) and bovine serum albumin (BSA), proving the efficiency of the membrane microfiltration tests for molecular weight of 69 kDa. The application of the membranes on the retention of gram-negative bacterium E. coli resulted in a 66% efficiency at a pressure of 200 kPa and a 98% efficiency when applied a pressure of 50 kPa. Therefore, the use of mullite membranes show limited efficiency towards bacteria retention. Nevertheless, they present fluxes similar to other materials proposed in the literature

Avaliação de um sistema para a predição do coeficiente de permeabilidade de água em concretos permeáveis

Proposing a system which makes it possible to determine the water permeability coefficient in pervious concretes in a practical way, without the need of devices which require complex instrumentation, is one of the aims of this work. An experimental matrix was proposed for the evaluation of the measurement system of the coefficient of permeability into pervious concrete considering three different pervious concretes obtained from different aggregate granulometric sizes, under the condition of dry sample or water saturated. The pervious concretes were characterized by their void contents, mechanical properties and later compared with the properties of a reference, control concrete made up of coarse and fine aggregates. The different properties exhibited in this study were assessed aiming at validating the experimental matrix developed for pervious concretes to provide a basis for comparison with information available in the literature. As a noticeable result, it was evidenced that the permeability coefficient of 0.21 cm.s-1 obtained for concrete with aggregate dimensions of 2.4 to 9.5 mm. It is possible to measure the coefficient of permeability of pervious concrete with the system developed in this study; the obtained results agree with the description of ACI522- 06 for pervious concretes.A proposta de um sistema que possibilita a determinação do coeficiente de permeabilidade à água em concretos permeáveis de forma prática, sem a necessidade de dispositivos que requeiram instrumentação complexa, é um dos objetivos deste trabalho. Uma matriz experimental foi proposta para a avaliação do sistema de medição do coeficiente de permeabilidade em concretos permeáveis considerando três concretos permeáveis diferentes, obtidos a partir de diferentes tamanhos granulométricos de agregados, sob condição de amostra seca e saturada de água. Os concretos permeáveis foram caracterizados por índice de vazios e propriedades mecânicas, tendo posteriormente suas propriedades comparadas às de um concreto referência, composto por agregados graúdos e miúdos. As diferentes propriedades neste estudo foram determinadas visando validar a matriz experimental desenvolvida para concretos permeáveis e propondo fornecer uma base de comparação com as informações disponíveis na literatura. Como resultado, evidenciou-se que o coeficiente de permeabilidade de 0,21 cm.s-1 foi obtido para o concreto com dimensões de agregados de 2,4 a 9,5 mm. É possível medir o coeficiente de permeabilidade do concreto permeável com o sistema desenvolvido neste estudo, sendo que os resultados obtidos estão em acordo com a descrição do ACI522-06 para concretos permeáveis

Engineering of biomaterials

This book focuses on biomaterials of different forms used for medical implants. The authors introduce the characteristics and properties of biomaterials and then dedicate special chapters to metallic, ceramic, polymeric and composite biomaterials. Case studies on sterilization methods by biomaterials are also presented. Finally, the authors describe the degradation and effects of biomaterials in living tissue