Abstract Bacterial nanocellulose (BNC) membranes have interconnected porous nanostructures and excellent biocompatibility. Functionalizing these with calcium phosphate sources and metal ions confers optimized properties to the biomaterial. This study aims to synthesize BNC membranes, functionalize them with copper and magnesium apatites, characterize and evaluate their cytotoxicity and antimicrobial potential. Membranes were synthesized for 8 days in Mannitol Medium. The biocomposite production was by immersion cycles. The biocomposites were characterized by porosity and swelling capacity, Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), antimicrobial properties and cytotoxicity assays. The FTIR and SEM results showed that phosphate groups were incorporated into the BNC. The TGA analysis also indicated the incorporation of the inorganic phase. The membrane functionalization with Cu promoted the antimicrobial properties of the biomaterial. However, functionalization with Mg had a more positive behavior on cell viability, proving to be more suitable for use as an implantable material.

Abstract Nanocellulose (BNC) is a natural polymer produced by bacteria. Its structure has only glucose monomer, it has various properties such as high water holding capacity, unique nanostructure, high crystallinity and high mechanical strength. Pure BNC or in combination with different components can be used for a wide range of applications. Aloe vera is a medicinal plant with polysaccharides in its composition that has a potential for tissue regeneration and repair. The aim of this study was to evaluate the effect of incorporating Aloe vera (A. vera) into BNC membranes produced with three fractions of A. vera extract (BNC-Aloe) on the behavior of epithelial cells. Human fibroblasts and keratinocytes were shown to have increased metabolic activity and proliferation when cultured on BNC-Aloe membranes compared to control. Quantification of collagen biosynthesis was significantly higher in BNC-Aloe membranes. In conclusion, BNC-Aloe membranes are suggested as a material for the purpose of skin tissue repair.

This work aimed to synthesize bacterial cellulose (BC) membranes functionalized with Ce(NO3)3 and silver nanoparticles (AgNPs) heat-treated in oven and autoclave. The AgNPs were characterized by TEM and the membranes were characterized by their rehydration capacity, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy with Dispersive Energy Spectroscopy (SEM/EDS), Wide-angle X-ray Diffractometry (XRD), Atomic Absorption Spectroscopy (AAS), antimicrobial activity and cytotoxicity. The BC membranes were white to light yellow or brown indicating functionalization with AgNps with 20 nm. XRD detected a decrease in the degree of crystallinity in functionalized membranes. The autoclaved samples exhibited the largest porosity and good rehydration capacity. AAS showed Ag presence in all samples. The best antibacterial activity was achieved for the membrane’s oven treated with 40 ppm of AgNPs. Among the functionalized membranes, the most recommended to be used as burn dressing is the Ag40A and Ag20CN1.1A since they showed good porosity, good antimicrobial activity, and better suitable cell viability.

Abstract This work investigates fluid mechanics and structural properties inside bacterial cellulose hydrogels in from of macroscopic anisotropic ellipsoid body cocoon-like 3D scaffolds. The hydrogels were evaluated by injections of iopamidol, a radiopaque medium used in medical radiological procedures. Results showed that hydromechanical behavior of BC hydrogels may be used to characterize its internal structure. It is suggested that internal barriers and flow distribution anisotropy may be used to develop novel therapeutic applications based on the tissue engineered multifunctional possibilities of the biomaterial.

Abstract Genome-scale metabolic models based on a combination of genome sequence and biochemical information have strongly influenced the field of systems biology. However, basic principles of the operation of metabolic networks, in particular the central metabolism can be easily studied in smaller metabolic (core) models. Komagataeibacter hansenii ATCC 23769 has been used for bacterial nanocellulose (BNC) biosynthesis, and the recent availability of its genome sequence allowed the development of a metabolic model. The core metabolic model was constructed from an initial draft metabolic reconstruction including 74 reactions and 68 metabolites that provides insights for a better understanding of K. hansenii metabolic pathways. The applicability of the model is finally demonstrated by applying the FBA approach, and the in silico simulation successfully predicted the minimal medium and the growing abilities on different substrates. This core model can facilitate system-level metabolic analysis as well as developments for improving BNC production.

RESUMO Queimaduras causam lesões do revestimento epitelial, a partir de um agente externo, podendo variar desde uma pequena bolha flictena até formas mais graves, capazes de desencadear respostas sistêmicas. O uso de curativos contendo substâncias cicatrizantes e antimicrobianas é uma opção para terapia local. Os curativos de nanocelulose bacteriana (BNC) já demonstraram seu grande potencial de aplicação devido às suas propriedades como alto teor de pureza, alto poder de absorção de água e ótima adaptabilidade biológica. A incorporação de metais na membrana de nanocelulose é bastante promissora. Nanopartículas de prata (NPAgs) têm sido objeto de vários estudos devido às suas propriedades antibacterianas; nitrato de cério, Ce(NO3)3, por sua vez, aumenta a eficácia no tratamento por apresentar propriedades imunomoduladoras. O objetivo deste trabalho foi sintetizar e caracterizar membranas de nanocelulose bacteriana funcionalizadas com nitrato de cério e nanopartículas de prata visando aplicação no tratamento de pele humana lesionada por queimadura. O comportamento térmico, interações entre a BNC, Ce(NO3)3 e NPAg, bem como a morfologia, capacidade de retenção de água, reidratação e potencial antimicrobiano foram analisadas por termogravimentria (TGA), microscopia eletrônica de varredura (MEV), análise de conteúdo de capacidade de água, capacidade de reidratação e atividade antimicrobiana. A membrana formada pela incorporação de Ce(NO3)3 e NPAgs simultaneamente, e submetida ao tratamento térmico, conservou as propriedades térmicas de ambos os materiais, assim como também boa capacidade de reidratação e um potencial de redução microbiana de 98% para Staphylococcus aureus. A análise de MEV apresentou alteração na morfologia, redução de poros e a presença de partículas, o que sugere adequada incorporação dos compostos.

ABSTRACT Burns cause lesions of the epithelial lining, from an external agent, and can range from a small injury to more severe forms, capable of triggering systemic responses. The use of dressings containing healing and antimicrobial substances are options for local therapy. Bacterial nanocellulose (BNC) dressings have already demonstrated their great potential due to their properties such as high purity, high water absorption capacity and optimum biological adaptability. The incorporation of metals in the nanocellulose membrane is quite promising. Silver nanoparticles (AgNPs) have been studied because of their antibacterial properties; cerium nitrate, Ce(NO3)3, on the other hand, increases the efficacy of the treatment because of its immunomodulatory properties. The objective of this work was to synthesize and characterize bacterial nanocellulose membranes functionalized with cerium nitrate and silver nanoparticles aiming the treatment of human skin that has been subject to burning injuries. Thermal behavior, interactions between BNC, Ce(NO3)3 and AgNP, as well as morphology, water retention capacity, rehydration capacity and antimicrobial potential were analyzed by thermogravimetry (TGA), scanning electron microscopy (SEM), analysis of water content, rehydration capacity and antimicrobial activity. Membranes formed by incorporation of Ce(NO3)3 and AgNPs simultaneously, and submitted to heat treatment, preserved thermal properties of both materials, as well as a good rehydration capacity and a microbial reduction potential of 98% for Staphylococcus aureus. SEM analysis showed changes in morphology, pore size reduction and the presence of particles, what suggest successful incorporation of the compounds.

Groups of genes that produce exopolysaccharide with a N-acetyl-D-glucosamine monomer are in the genome of several pathogenic bacteria. Chromobacterium violaceum, an opportunistic pathogen, has the operon hmsHFR-CV2940, whose proteins can synthesize such polysaccharide. In this work, multiple alignments among proteins from bacteria that synthesize such polysaccharide were used to verify the existence of amino acids that might be critical for pathogen activity. Three-dimensional models were generated for spatial visualization of these amino acid residues. The analysis carried out showed that the protein HmsR preserves the amino acids D135, D228, Q264 and R267, considered critical for the formation of biofilms and, furthermore, that these amino acids are close to each other. The protein HmsF of C. violaceum preserves the residues D86, D87, H156 and W115. It was also shown that these residues are also close to each other in their spatial arrangement. For the proteins HmsH and CV2940 there is evidence of conservation of the residues R104 and W94, respectively. Conservation and favorable spatial location of those critical amino acids that constitute the proteins of the operon indicates that they preserve the same enzymatic function in biofilm synthesis. This is an indicator that the operon hmsHFR-CV2940 is a possible target in C. violaceum pathogenicity.

A determinação de vias metabólicas e regulatórias de microrganismos é essencial para estudos pós-sequenciamento de DNA, com aplicações diretas em várias áreas da biotecnologia, em especial em engenharia metabólica. Neste trabalho desenvolvemos uma extensão do software IsaViz, editor de grafos RDF (Resource Description Framework), com a finalidade de criar um ambiente gráfico para a construção de modelos de vias metabólicas e regulatórias. Este ambiente, o Metabolic IsaViz, foi integrado a uma biblioteca de tipos genômicos, modelada com base em ontologias, sendo que as vias bioquímicas podem incluir dados ao nível de seqüência (como a seqüência de aminoácidos das enzimas), além de parâmetros cinéticos e termodinâmicos. Os modelos criados com o Metabolic IsaViz podem ser exportados para simuladores de vias metabólicas através da linguagem SBML (Systems Biology Markup Language) para análise da formação de metabólitos de interesse.

In this work we developed an extension of IsaViz software, a RDF (Resource Description Framework) authoring tool, designed to be a graphical environment to build models of metabolic and regulatory networks. This environment, called Metabolic IsaViz, was linked to a genomic library of types and was modeled on the basis of ontologies. Biochemical pathways included data at sequence level (e.g., the amino acid sequence of enzymes), besides kinetic and thermodynamic parameters for the reactions. Models created with Metabolic IsaViz could be exported to pathways simulators through SBML (Systems Biology Markup Language), which allowed to analyze the pathway dynamics of target chemicals.