Nonthrombogenic, Biodegradable Elastomeric Polyurethanes with Variable Sulfobetaine Content

For applications where degradable polymers are likely to have extended blood contact, it is often important for these materials to exhibit high levels of thromboresistance. This can be achieved with surface modification approaches, but such modifications may be transient with degradation. Alternatively, polymer design can be altered such that the bulk polymer is thromboresistant and this is maintained with degradation. Toward this end a series of biodegradable, elastic polyurethanes (PESBUUs) containing different zwitterionic sulfobetaine (SB) content were synthesized from a polycaprolactone-diol (PCL-diol):SB-diol mixture (100:0, 75:25, 50:50, 25:75 and 0:100) reacted with diisocyanatobutane and chain extended with putrescine. The chemical structure, tensile mechanical properties, thermal properties, hydrophilicity, biodegradability, fibrinogen adsorption and thrombogenicity of the resulting polymers was characterized. With increased SB content some weakening in tensile properties occurred in wet conditions and enzymatic degradation also decreased. However, at higher zwitterionic molar ratios (50% and 75%) wet tensile strength exceeded 15 MPa and breaking strain was >500%. Markedly reduced thrombotic deposition was observed both before and after substantial degradation for both of these PESBUUs and they could be processed by electrospinning into a vascular conduit format with appropriate compliance properties. The mechanical and degradation properties as well as the acute in vitro thrombogenicity assessment suggest that these tunable polyurethanes could provide options appropriate for use in blood contacting applications where a degradable, elastomeric component with enduring thromboresistance is desired

Pirólise lenta de capim-elefante (Pennisetum purpureum shum): valorização do bio-óleo e do potencial absorvido do biochar ativado.

O capim elefante é uma das culturas que mais produzem biomassa e que pode gerar produtos, como biocombustíveis, etanol lignocelulósico, adsorventes, entre outros. Como forma de investigação, o capim-elefante (Pennisetum purpureum Schum) foi analisado pelo processo de pirólise, produzindo bio-óleo e biochar. A influência de parâmetros como umidade, temperatura, análise elementar (CHN) e química (GC/MS) são discutidas objetivando o uso na indústria química. O biochar ativado termoquimicamente com K2CO3 foi avaliado para a remoção do hormônio 17β-estradiol em solução. A caracterização do adsorvente foi realizada através da Microscopia eletrônica de varredura (MEV), pH no ponto de carga zero (pHpcz) e Isoterma de Adsorção/Dessorção N2 (BET). O resultado para análise da área superficial mostrou perfil de isoterma (tipo I) característica de materiais microporosos, com uma área superficial específica de 223,044 m2/g. A escolha do hormônio como contaminante foi motivada pela crescente presença desses compostos em mananciais de abastecimento e causa de danos à saúde humana e vida marinha

Briquetagem da biomassa do capim-elefante variedade Madeira com diferentes granulometrias de partículas.

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Reciclagem das cascas de coco verde no contexto da economia circular: briquetagem e pirólise.

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Gene-Trap Mutagenesis Identifies Mammalian Genes Contributing to Intoxication by Clostridium perfringens ε-Toxin

The Clostridium perfringens ε-toxin is an extremely potent toxin associated with lethal toxemias in domesticated ruminants and may be toxic to humans. Intoxication results in fluid accumulation in various tissues, most notably in the brain and kidneys. Previous studies suggest that the toxin is a pore-forming toxin, leading to dysregulated ion homeostasis and ultimately cell death. However, mammalian host factors that likely contribute to ε-toxin-induced cytotoxicity are poorly understood. A library of insertional mutant Madin Darby canine kidney (MDCK) cells, which are highly susceptible to the lethal affects of ε-toxin, was used to select clones of cells resistant to ε-toxin-induced cytotoxicity. The genes mutated in 9 surviving resistant cell clones were identified. We focused additional experiments on one of the identified genes as a means of validating the experimental approach. Gene expression microarray analysis revealed that one of the identified genes, hepatitis A virus cellular receptor 1 (HAVCR1, KIM-1, TIM1), is more abundantly expressed in human kidney cell lines than it is expressed in human cells known to be resistant to ε-toxin. One human kidney cell line, ACHN, was found to be sensitive to the toxin and expresses a larger isoform of the HAVCR1 protein than the HAVCR1 protein expressed by other, toxin-resistant human kidney cell lines. RNA interference studies in MDCK and in ACHN cells confirmed that HAVCR1 contributes to ε-toxin-induced cytotoxicity. Additionally, ε-toxin was shown to bind to HAVCR1 in vitro. The results of this study indicate that HAVCR1 and the other genes identified through the use of gene-trap mutagenesis and RNA interference strategies represent important targets for investigation of the process by which ε-toxin induces cell death and new targets for potential therapeutic intervention

From supramolecular polymers to multi-component biomaterials

The most striking and general property of the biological fibrous architectures in the extracellular matrix (ECM) is the strong and directional interaction between biologically active protein subunits. These fibers display rich dynamic behavior without losing their architectural integrity. The complexity of the ECM taking care of many essential properties has inspired synthetic chemists to mimic these properties in artificial one-dimensional fibrous structures with the aim to arrive at multi-component biomaterials. Due to the dynamic character required for interaction with natural tissue, supramolecular biomaterials are promising candidates for regenerative medicine. Depending on the application area, and thereby the design criteria of these multi-component fibrous biomaterials, they are used as elastomeric materials or hydrogel systems. Elastomeric materials are designed to have load bearing properties whereas hydrogels are proposed to support in vitro cell culture. Although the chemical structures and systems designed and studied today are rather simple compared to the complexity of the ECM, the first examples of these functional supramolecular biomaterials reaching the clinic have been reported. The basic concept of many of these supramolecular biomaterials is based on their ability to adapt to cell behavior as a result of dynamic non-covalent interactions. In this review, we show the translation of one-dimensional supramolecular polymers into multi-component functional biomaterials for regenerative medicine applications

Designing Bioactive Delivery Systems for Tissue Regeneration

The direct infusion of macromolecules into defect sites generally does not impart adequate physiological responses. Without the protection of delivery systems, inductive molecules may likely redistribute away from their desired locale and are vulnerable to degradation. In order to achieve efficacy, large doses supplied at interval time periods are necessary, often at great expense and ensuing detrimental side effects. The selection of a delivery system plays an important role in the rate of re-growth and functionality of regenerating tissue: not only do the release kinetics of inductive molecules and their consequent bioactivities need to be considered, but also how the delivery system interacts and integrates with its surrounding host environment. In the current review, we describe the means of release of macromolecules from hydrogels, polymeric microspheres, and porous scaffolds along with the selection and utilization of bioactive delivery systems in a variety of tissue-engineering strategies

A new chance of preventing winter diseases by the administration of synbiotic formulations

The efficacy of probiotics is currently well documented with regard to the improvement of gastrointestinal functions, whereas their potential role in the prevention of infectious respiratory diseases has not been sufficiently analyzed. PURPOSE OF THE STUDY AND METHODS: A 3-stage prospective, randomized, double blind, placebo-controlled study was carried out with several synbiotic preparations containing 3 to 5 strains of Lactobacillus plantarum, Lactobacillus rhamnosus, and Bifidobacterium lactis, lactoferrin and prebiotics such as either FOS (short-chain fructooligosaccharides) or GOS (galactooligosaccharides). The study was performed over 3 different winter seasons between 2003 and 2007, and was aimed at assessing the ability of the different preparations to improve intestinal functions and to increase the body's defences against respiratory infections. In 2003/04 (stage 1; 237 healthy volunteers) an active formulation (A) containing 3 probiotic strains and FOS was used versus placebo; in 2005/06 (stage 2; 234 healthy volunteers) the same formulation versus a similar preparation enriched with lactoferrin (B), and versus placebo; in 2006/07 (stage 3; 250 healthy volunteers), 2 new synbiotic formulations each containing 5 probiotics and FOS (C) or GOS (D), respectively, versus placebo