Bio-based electrospun mats composed of aligned and nonaligned fibers from cellulose nanocrystals, castor oil, and recycled PET.

Cellulose nanocrystals (CNCs), castor oil (CO), and recycled poly(ethylene terephthalate) (rPET), were used to add value to renewable raw materials and to a recycled polymer produced worldwide, producing mats composed of fibers on the nano- and submicrometric (ultrathin) scales through a sustainable process. Bio-based electrospun mats composed of aligned (rotary collector) and nonaligned (static collector) nanofibers/ultrathin fibers were produced from the electrospinning of solutions prepared from rPET (mixed with CO, CNCs, or CNCs/CO). The contact angle results showed that the CNC mat surfaces composed of nonaligned fibers were hydrophilic, and in contrast, these surfaces were hydrophobic when composed of aligned fibers. Among the mats composed of nonaligned fibers, PET/CO/CNC exhibited storage and Young's moduli approximately eleven and ten times, respectively, better than those of neat rPET. The PET/CO/CNC mat showed both modulus and tensile strength values higher than those of PET/CNC, when characterized in the preferential direction of fiber alignment. Electrospun mats were obtained from environmentally sound raw materials with diversified properties, which were modulated by the type of collector used, as well as whether CO and CNC were mixed with rPET, and have the potential for use in applications such as membrane separation processes and biomedical applications.

Synthesis of bio-based polyurethanes from Kraft lignin and castor oil with simultaneous film formation.

Kraft lignin (KL) and castor oil (CO) were used as polyols in the synthesis of bio-based polyurethanes (PUs) in the absence of both solvents and catalysts at room temperature with simultaneous film formation. KL was purified (PKL), and both KL and PKL were fully characterized. CO was mixed with different percentages of PKL (0%, 10%, 30%, and 50%), as well as with polymeric methyl phenyl diisocyanate. After degassing, the reaction mixture was stirred; when the medium viscosity was suitable for spreading, it was poured onto a glass plate, and the thickness was adjusted using an extender. The storage modulus (E', 25 °C) and tensile strength of the lignopolyurethane films (LignoPUCOPKL) were higher than those of the control film (PUCO). LignoPUCOPKL30 and LignoPUCOPKL50 did not break under the conditions that the other films broke under. It was noted phase segregation (rigid and flexible domains) for LignoPUCOPKL30 and LignoPUCOPKL50, and the glass transition temperature (Tg) of the flexible domains (96.2 °C and 52.3 °C, respectively) was higher than that of PUCO (8.4 °C). The formed films were also characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, contact angles, and swelling tests. To our knowledge, the approach of this study is unprecedented.

Renewable Resources and a Recycled Polymer as Raw Materials: Mats from Electrospinning of Lignocellulosic Biomass and PET Solutions.

Interest in the use of renewable raw materials in the preparation of materials has been growing uninterruptedly in recent decades. The aim of this strategy is to offer alternatives to the use of fossil fuel-based raw materials and to meet the demand for materials that are less detrimental to the environment after disposal. In this context, several studies have been carried out on the use of lignocellulosic biomass and its main components (cellulose, hemicelluloses, and lignin) as raw materials for polymeric materials. Lignocellulosic fibers have a high content of cellulose, but there has been a notable lack of investigations on application of the electrospinning technique for solutions prepared from raw lignocellulosic biomass, even though the presence of cellulose favors the alignment of the fiber chains during electrospinning. In this investigation, ultrathin (submicrometric) and nanoscale aligned fibers were successfully prepared via electrospinning (room temperature) of solutions prepared with different contents of lignocellulosic sisal fibers combined with recycled poly(ethylene terephthalate) (PET) using trifluoroacetic acid (TFA) as solvent. The "macro" fibers were deconstructed by the action of TFA, resulting in solutions containing their constituents, i.e., cellulose, hemicelluloses, and lignin, in addition to PET. The "macro" sisal fibers were reconstructed at the nanometer and submicrometric scale from these solutions. The SEM micrographs of the mats containing the components of sisal showed distinct fiber networks, likely due to differences in the solubility of these components in TFA and in their dielectric constants. The mechanical properties of the mats (dynamic mechanical analysis, DMA, and tensile properties) were evaluated with the samples positioned both in the direction (dir) of and in opposition (op) to the alignment of the nano and ultrathin fibers, which can be considered a novelty in the analysis of this type of material. DMA showed superior values of storage modulus (E' at 30 °C) for the mats characterized in the preferential direction of fiber alignment. For example, for mats obtained from solutions prepared from a 0.4 ratio of sisal fibers/PET, Sisal/PET0.40dir presented a high E' value of 765 MPa compared to Sisal/PET0.40op that presented an E' value of 88.4 MPa. The fiber alignment did not influence the Tg values (from tan δ peak) of electrospun mats with the same compositions, as they presented similar values for this property. The tensile properties of the electrospun mats were significantly impacted by the alignment of the fibers: e.g., Sisal/PET0.40dir presented a high tensile strength value of 15.72 MPa, and Sisal/PET0.40op presented a value of approximately 2.5 MPa. An opposite trend was observed regarding the values of elongation at break for these materials. Other properties of the mats are also discussed; such as the index of fiber alignment, average porosity, and surface contact angle. To our knowledge, this is the first time that the influence of fiber alignment on the properties of electrospun mats based on untreated lignocellulosic biomass combined with a recycled polymer, such as PET, has been evaluated. The mats obtained in this study have potential for diversified applications, such as reinforcement for polymeric matrices in nanocomposites, membranes for filtration, and support for enzymes, wherein the fiber alignment, together with other evaluated properties, can impact their effectiveness in these applications.

Rabdomiólise induzida por esforço físico intenso com altos níveis de creatinoquinase / Rhabdomyolysis induced by intense physical effort with high creatinoquinase levels

Rabdomiólise é uma síndrome que afeta a musculatura estriada esquelética que apresenta um amplo espectro de sintomas clínicos e achados laboratoriais. Decorre, basicamente, da lesão das células musculares, com liberação do conteúdo citoplasmático para a corrente sanguínea e devido a essa situação gerar complicações com alto potencial de morbi-mortalidade, como insuficiência renal aguda. O diagnóstico, baseado em suspeita clínica e em achados laboratoriais, deve ser feito o mais precocemente possível, para buscar a redução das complicações inerentes à síndrome. É relatado caso de paciente com rabdomiólise secundária a exercício físico intenso, que apresentou resolução, sem repercussões de maior morbidade com o tratamento adequado.

Rhabdomyolysis is a syndrome that affects the skeletal striated musculature and presents a wide range of clinical symptoms and laboratory findings. It is primarily a result of injury to muscle cells with release of the cytoplasmic content into the blood flow and thereby generating complications with a high risk of morbidity and mortality including acute kidney failure. The diagnosis, based on clinical suspicion and laboratory findings, must be made as early as possible in order to reduce the complications inherent in the syndrome. Here we report the case of a patient with rhabdomyolysis secondary to intense physical effort, which was successfully resolved with proper treatment without any repercussions of major morbidity.

Determination of atenolol at a graphite-polyurethane composite electrode.

A bare graphite-polyurethane composite was evaluated as an alternative electrode in the determination of atenolol (ATN) in pharmaceutical formulations. Using a DPV procedure, a linear analytical curve was observed in the 4-100mumolL(-1) range with a LOD=3.16mumolL(-1), without need of surface renewing between successive runs, with recoveries between 95.5 and 108%. Interference of other antihypertensive drugs was observed, but not from the usual components of tablets. The results of the proposed method agreed with HPLC ones within 95% confidence level.

Evaluation of the electrochemical behavior and analytical potentialities of a carbon paste electrode modified with a ruthenium (III) piperidinedithiocarbamate complex.

The preparation and electrochemical characterization of a carbon paste electrode modified with bis(N,N-piperidinedithiocarbamate)-mu-tris(N,N-piperidinedithiocarbamate)diruthenium(III) complex, alpha-[Ru2(Pip)5]Cl are described. The best voltammetric response was obtained for a 10% (m/m) alpha-[Ru2(Pip)5]Cl content in the paste, potassium acid phthalate solution pH 4.0 as supporting electrolyte and scan rate of 100 mV s-1. The analytical potentialities of the electrode have been evaluated using L-ascorbic acid (vitamin C) as a probe. A sensitive linear voltammetric response for L-ascorbic acid was obtained in the concentration range 4.50-113x10(-5) mol l-1 (7.92-200 mg l-1) with a slope of 1.12x10(4) microA mol-1, and a detection limit (3sigma/slope) of 7.00x10(-6) mol l-1 using cyclic voltammetry. The concentrations of L-ascorbic acid in pharmaceutical formulations (tablets and liquid) were determined using the modified electrode and compared with an iodimetric procedure with good agreement at the 95% confidence and relative error lower than 1%.

A zucchini-peroxidase biosensor applied to dopamine determination.

A biosensor modified with peroxidase from crude extract of zucchini (Cucurbita pepo) was developed for the determination of dopamine in pharmaceutical samples. This enzyme catalyses the oxidation of dopamine to dopaminequinone, in presence of hydrogen peroxide, which the electrochemical reduction can be followed at a peak potential of -0.02 V. The recovery of dopamine from the samples ranged from 94.8% to 106% and a rectilinear analytical curve for dopamine concentration from 5.0 x 10(-4) to 3.0 x 10(-3) mol L-1 (r=0.9982) was obtained. The detection limit was 2.6x10(-5) mol L-1 and the relative standard deviation was less than 1.2% for 7.9 x 10(-4) mol L-1 dopamine in 0.1 mol L-1 phosphate buffer solution at pH 6.0 (n=10).