Surface-Modified Bacterial Cellulose with Mercaptosilane as a Multifunctional Platform

Cellulose synthesized by bacteria has unique properties such as high water retention capacity, biocompatibility, biodegradability and flexibility. Nevertheless, modification of this biomaterial is required in order to obtain multifunctional materials, which may be applied in several high-value added products, as catalytic and cell culture platforms. The surface of bacterial cellulose (BC) can be modified by several approaches, namely: (i) physical treatment by plasma, (ii) adsorption of molecules onto BC surface, and (iii) chemical modification. In this sense, the aim of this study was to modify the BC surface by silanization reaction at room temperature using a mixture of ethanol and water, using two different protocols. Thus, BC membranes synthesized by Komagataeibacter xylinus were modified by adding the thiol (SH) functional group with (3-mercaptopropyl)trimethoxysilane under mild conditions. The produced materials were analyzed by elemental analysis, ATR-FTIR, TGA and SEM, and the successful modification was proven by elemental analysis and SEM.

O secretariado e a modernização da administração pública: a implementação de serviços eficientes

O presente artigo pretende evidenciar a necessária mudança de paradigma no que se refere à capacidade de um profissional qualificado em secretariado, no mundo contemporâneo, bem como à necessária abrangência dos seus conhecimentos e das suas competências. Pretende-se ainda apresentar um projeto de implementação do Balcão Único de Atendimento (BUA) na Câmara Municipal de Moimenta da Beira, no sentido de adequar os seus serviços ao atual paradigma competitivo, que exige da Administração Pública uma postura moderna e dinamizadora que incremente a melhoria constante dos seus serviços, de forma a responder às exigências de eficiência, eficácia, transparência e qualidade dos seus clientes

Electrospun polylactic acid-chitosan composite: a bio-based alternative for inorganic composites for advanced application

Fabricating novel materials for biomedical applications mostly require the use of biodegradable materials. In this work biodegradable materials like polylactic acid (PLA) and chitosan (CHS) were used for designing electrospun mats. This work reports the physical and chemical characterization of the PLA-CHS composite, prepared by the electrospinning technique using a mixed solvent system. The addition of chitosan into PLA, offered decrease in fiber diameter in the composites with uniformity in the distribution of fibers with an optimum at 0.4wt% CHS. The fiber formation and the reduction in fiber diameter were confirmed by the SEM micrograph. The inverse gas chromatography and contact angle measurements supported the increase of hydrophobicity of the composite membrane with increase of filler concentration. The weak interaction between PLA and chitosan was confirmed by Fourier transform infrared spectroscopy and thermal analysis. The stability of the composite was established by zeta potential measurements. Cytotoxicity studies of the membranes were also carried out and found that up to 0.6% CHS the composite material was noncytotoxic. The current findings are very important for the design and development of new materials based on polylactic acid-chitosan composites for environmental and biomedical applications.info:eu-repo/semantics/publishedVersio

Microbial Cellulose — Biosynthesis Mechanisms and Medical Applications

Currently some principles of sustainability, eco-efficiency and green chemistry are guiding the development of a new generation of materials as an alternative to conventional polymers based on petroleum. Then, in the field of biodegradable polymers one of the most promising investigations is focused on the use of microbial cellulose (MC), biocellulose or bacterial cellulose. MC has received substantial interest since it is synthesized from the bacterium Gluconacetobacter genus from a variety of carbon sources such as glucose, fructose, galactose, etc. MC is an interesting emerging biomaterial, with no toxicity, and since its discovery has shown tremendous potential in various fields, because the structural aspect of MC is far superior to those of plant cellulose. Thus, the main focus of the chapter review involves detailed aspects about the biosynthesis and recent advances on microbial production, including mechanism for the biochemistry of the cellulose synthesis, new sources for culture medium, main aspects about static and air-reactor productions and genetic modifications. We also revised microbial cellulose devices for biomedical applications: artificial skin, artificial blood vessels and microvessels, wound dressing of second- or third-degree burn ulcers, scaffolds for tissue engineering, drug delivery systems, dental implants, among others

Orange Pectin Mediated Growth and Stability of Aqueous Gold and Silver Nanocolloids

International audienceThe role of orange based pectin in the nucleation and growth of silver and gold nanoparticles is addressed. Pectin is a complex polysaccharide found in fruits such as oranges, lemons, passion fruits or apples. It displays smooth and hairy chain regions contg. hydroxyl-​, ester-​, carboxylate- and eventually amine groups that can act as surface ligands interacting under various pH conditions more or less efficiently with growing nanometals. Here, a high methoxy pectin (>50​% esterified) was used as a stabilizer​/reducing agent in the prepn. of gold, silver and silver-​gold nanoparticles. Com. pectin (CP) and pectin extd. from orange bagasse (OP) were used. Optionally, trisodium citrate or oxalic acid we used to reduce AgNO3 and HAuCl4 in aq. environment. Characterization methods included UV-​vis absorption spectroscopy, transmission electron microscopy, electron diffraction and energy-​dispersive X-​ray spectroscopy. The results show that under different pH conditions, pectin and reducing agents allow producing various nanostructures shapes (triangles, spheres, rods, octahedrons and decahedrons) often with high polydispersity and sizes ranging between 5 nm and 30 nm. In addn., depending on Ag​/Au-​ratio and pH, the surface plasmon bands can be continuously shifted between 410 nm and 600 nm. Finally, pectin seems to be a highly efficient stabilizer of the colloidal systems that show a remarkable stability and unchanged optical spectral response even after five years

Bacterial Cellulose as a Raw Material for Food and Food Packaging Applications

Bacterial cellulose (BC) has been produced for a number of applications, mainly focused on the biomedical area. Although there is a variety of interesting applications of BC for food and food packaging, only a few have been explored to the moment, since the high cost of BC production is usually considered as a limiting factor. On the other hand, several cost-effective culture media have been proposed, contributing to reduce BC production costs. This article overviews the bioprocess conditions that affects BC production and the main possible applications of BC for food and food packaging purposes

Cashew gum (Anacardium occidentale) as a potential source for the production of tocopherol-loaded nanoparticles: formulation, release profile and cytotoxicity

Every year, more than thirty thousand tons of Cashew gum (Anacardium occidentale, family: Anacardiaceae) are produced in Brazil; however, only a small amount is used for different applications in foodstuff and in pharmaceutical industries. As a raw material for the production of drug delivery systems, cashew gum is still regarded as an innovative compound worth to be exploited. In this work, cashew gum was extracted from the crude exudate of cashew tree employing four methodologies resulting in a light brown powder in different yields (40.61% to 58.40%). The total ashes (0.34% to 1.05%) and moisture (12.90% to 14.81%) were also dependent on the purification approach. FTIR spectra showed the typical bands of purified cashew gum samples, confirming their suitability for the development of a pharmaceutical product. Cashew gum nanoparticles were produced by nanoprecipitation resulting in particles of low polydispersity (<0.2) and an average size depending on the percentage of the oil. The zeta potential of nanoparticles was found to be below 20 mV, which promotes electrostatic stability. Encapsulation efficiencies were above 99.9%, while loading capacity increased with the increase of the percentage of the oil content of particles. The release of the oil from the nanoparticles followed the KorsmeyerPeppas kinetics model, while particles did not show any signs of toxicity when tested in three distinct cell lines (LLC-MK2, HepG2, and THP-1). Our study highlights the potential added value of using a protein-, lignans-, and nucleic acids-enriched resin obtained from crude extract as a new raw material for the production of drug delivery systems.This research received funding from the Coordenação Aperfeiçoamento de Pessoal de Nivel Superior (CAPES), Fundação de Ámparo à Pesquisa do Estado de Sergipe (FAPITEC) (PROCESSO: 88887.159533/2017-00 extração, encapsulação e caracterização de bioativos para o interesse biotecnologico) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq 301964/2019-0 Chamada 06/2019, and Chamada CNPq nº 01/2019), from Portuguese Foundation for Science and Technology (FCT/MEC) through national funds, and co-financed by FEDER, under the Partnership Agreement PT2020 for the project UIDB/04469/2020.info:eu-repo/semantics/publishedVersio

Electrospun Materials for Biomedical Applications

Considered a simple and versatile technique, electrospinning has emerged as a technology for developing 3D materials for a wide range of applications [...

Flexible magnetic membranes based on bacterial cellulose and its evaluation as electromagnetic interference shielding material

Flexible magnetic membranes with high proportion of magnetite were successfully prepared by previous impregnation of the never dried bacterial cellulose pellicles with ferric chloride followed by reduction with sodium bisulfite and alkaline treatment for magnetite precipitation. Membranes were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating magnetometer, field emission scanning electron microscopy (FEG-SEM) and impedance spectroscopy. Microwave properties of these membranes were investigated in the X-band (8.2 to 12.4 GHz). FEG-SEM micrographs show an effective coverage of the BC nanofibers by Fe 3O4 nanoparticles. Membranes with up to 75% in weight of particles have been prepared after 60 min of reaction. Magnetite nanoparticles in the form of aggregates well adhered to the BC fibers were observed by SEM. The average crystal sizes of the magnetic particles were in the range of 10 ± 1 to 13 ± 1 nm (estimated by XRD). The magnetic particles in the BC pellicles presented superparamagnetic behavior with a saturation magnetization in the range of 60 emu g- 1 and coercive force around 15 Oe. These magnetic pellicles also displayed high electrical permittivity and a potential application as microwave absorber materials. © 2013 Elsevier B.V

Bacterial cellulose as a template for preparation of hydrotalcite-like compounds

Bacterial cellulose (BC) was used as a template for preparation of Hydrotalcite-type compounds or layered double hydroxides (LDHs) by co-precipitation method, and submitted to three aging times. Isolated composites containing LDH supported on BC (BC-LDH) were calcined to remove the organic matrix. Mixed metal oxides formed after thermal decomposition underwent reconstruction reaction in Na2CO3 solution producing again hydrotalcite-like materials (RBC-LDH). To evaluate the influence of BC on the LDH formation, it was also analyzed LDH fractions not attached to the BC fibers and LDH synthesized in absence of the polymeric membrane. XRD pattern of BC-LDH composites show broadened peaks related to the organic semi-crystalline matrix, indicating a deep level of interaction between organic and inorganic phases. Interaction is also evidenced by changes in the composites thermal decomposition profiles compared to pristine polymer. SEM images revealed formation of submicrometrical round-shaped LDH particles after removal of membrane (RBC-LDH), differently from the plate-habit exhibited by pristine LDH. Aging plays a key role in growth of all LDHs samples, leading to the formation of larger inorganic particles as time is increased. RBC-LDH aging for three days shows significant improvement in the surface area (more than three times) if contrasted to LDH prepared in BC absence.Celulose bacteriana (BC) foi utilizada nesse estudo como molde na preparação de compostos do tipo hidrotalcita ou hidróxidos duplos lamelares (LDHs) pelo método da co-precipitação e submetida a três tempos de envelhecimento distintos. Os compósitos isolados contendo LDH suportado na BC (BC-LDH) foram calcinados para remoção da matriz orgânica. Os óxidos metálicos mistos formados após a decomposição térmica sofreram reação de reconstrução na presença de uma solução de Na2CO3 para produzirem novamente materiais do tipo hidrotalcita (RBC-LDH). Para avaliar a influência da BC na formação do LDH, também foram analisadas as frações de LDH que não aderiram às fibras da BC e, também, o LDH sintetizado na ausência da membrana polimérica. Os difratogramas de raios X dos compósitos BC-LDH exibem picos alargados relacionados com a matriz orgânica semi-cristalina, indicando um grande nível de interação entre as fases orgânica e inorgânica. A interação também é evidenciada pelas mudanças nos perfis de decomposição dos compósitos com relação ao polímero prístino. As imagens de microscopia eletrônica de varredura mostraram a formação de partículas arredondadas submicrométricas de LDH após a remoção da membrana (RBC-LDH), diferentemente do hábito de rosetas exibido pelo LDH prístino. O envelhecimento é uma componente chave no processo de crescimento de todas as amostras de LDH produzidas, resultando na formação de partículas inorgânicas maiores à medida que o tempo aumenta. O compósito RBC-LDH envelhecido por três dias apresenta um aumento significativo na área superficial (mais do que três vezes) se comparado ao LDH preparado na ausência de BC.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES