This study includes the synthesis of a new natural plasticizer obtained through esterification reaction of rice fatty acid and polyols, its physicochemical characterization and its preliminary application in polyvinyl chloride (PVC). Monopropylene glycol, octanol and diethylene glycol were used as polyols for esterification reaction. Catalyst Fascat® 4100, was also added. Viscosity, acidity and hydroxyl index, moisture content, molar mass, chemical composition (by FTIR) and color were determined to characterize the natural plasticizer synthesized. The results were compared with a commercial plasticizer (DOA: di-octyl adipate) derived from petrochemical source and synthesized in laboratory. According to the results, except from color, the natural plasticizer presented similar properties of commercially available plasticizers, such as DOA. Mechanical tests indicated that the addition of the natural plasticizer to PVC films resulted in a significant increase on its elongation at break (371.2%) compared to pure PVC film, indicating a possible application for this plasticizer.

The marine algae Sargassum filipendula was collected from São Paulo seashore (Brazil) and submitted to treatment with acid. The biosorption mechanisms of Cu2+ and Ni2+ ions onto acidic algae Sargassum filipendula were examined using various analytical techniques: Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and potentiometric titration (pH ZPC). The effect of acidic treatment on algae by hydrochloric acid (pH 2.0, 3.0, 4.0 and 5.0) was evaluated for Cu2+ and Ni2+ adsorption. Alginate was extracted from raw algae and the two types of acids present in the biomass (β-D-mannuronic (M) and α-L-guluronic (G) acid) were characterized by 13C NMR. The M/G ratio was found to be 0.50. According to the pH ZPC analysis, at a pH higher than 5.5 the acidified algae surface presents a negative charge. The FT-IR analyses showed that the main chemical groups involved in the biosorption were carboxylic, alcoholic, sulfonate and amino groups.

Water pollution with heavy metals is a matter of major concern for public health and also for natural resource management. The present study investigated the effect of chemical modifications on biopolymeric adsorbents (based on chitosan membranes) for chromium removal using fixed-bed dynamic adsorption technique. Parameters such as flow rate, initial concentration and crosslinking agents were evaluated, from a practical point-of-view, in order to optimize the adsorption capacity of natural, glutaraldehyde and epichlorohydrin crosslinked chitosan membranes. The adsorption capacity of natural and epiclorohydrin-crosslinked chitosan membranes were very close to each other; however, glutaraldehyde-crosslinked chitosan membranes presented nearly twice the adsorption capacity compared to the other membranes, being the most promising adsorbent in such mass-transfer systems.

O pericárdio bovino é um material utilizado na fabricação de biopróteses. A liofilização é um método de secagem que vem sendo estudado para a conservação de válvulas cardíacas. A preservação das características do biomaterial é de fundamental importância no bom funcionamento das válvulas. Este artigo é a primeira etapa do desenvolvimento do ciclo de liofilização do pericárdio bovino. Liofilização é o processo de secagem no qual a água é removida do material congelado por sublimação e desorção da água incongelável, sob pressão reduzida. O congelamento influencia o tamanho do cristal de gelo e, consequentemente, a secagem primária e secundária. O objetivo deste estudo foi verificar a influência das taxas de congelamento nos parâmetros de liofilização do pericárdio bovino. Determinou-se a temperatura de transição vítrea e o comportamento estrutural do pericárdio bovino liofilizado. Determinou-se o tempo da secagem primária e secundária. O protocolo de liofilização utilizando-se congelamento lento com annealing apresentou os melhores resultados.

The bovine pericardium has been used as biomaterial in developing bioprostheses. Freeze-drying is a drying process that could be used for heart valve's preservation. The maintenance of the characteristics of the biomaterial is important for a good heart valve performance. This paper describes the initial step in the development of a bovine pericardium tissue freeze-drying to be used in heart valves. Freeze-drying involves three steps: freezing, primary drying and secondary drying. The freezing step influences the ice crystal size and, consequently, the primary and secondary drying stages. The aim of this work was to investigate the influence of freezing rates on the bovine pericardium tissue freeze-drying parameters. The glass transition temperature and the structural behaviour of the lyophilized tissues were determined as also primary and secondary drying time. The slow freezing with thermal treatment presented better results than the other freeze-drying protocols.

Silk fibroin is a fibrous protein that has been extensively studied for application in the biomedical field, and has been used as a scaffold for bone tissue engineering. Biomaterials made of proteins are prone to physical and chemical degradation during storage; lyophilization, a drying method that consists of freezing and drying steps, is known to promote minimal changes in structure and biological activity of biomaterials. This study evaluates the effect of freezing methods on the properties of lyophilized porous silk fibroin membranes. The membranes were obtained from silk fibroin solution, frozen in liquid nitrogen or ultrafreezer, lyophilized, and then characterized by XRD, FTIR, TGA, DSC and SEM. Although the membranes presented similar physical, chemical and microstructural characteristics, quench freezing with liquid nitrogen, followed by lyophilization, promoted collapse of the membranes, while slow cooling performed by ultrafreezer preserved membrane integrity.

Chitosan microspheres can be used in several applications, as biomaterials, in biotechnology processes and as adsorbents. The control of particle size in microsphere production is important to make these applications viable. This study focuses on the production and morphological characterization of chitosan microspheres. Microspheres were prepared by a spraying and coagulation process. Particles underwent chemical modifications with glutaraldehyde, epichlorohydrin or acetic anhydride treatments. The microspheres presented a fairly good sphericity (0.74) but an irregular micro-surface morphology. The mean particle size (MPS) ranged from 140 to 281 mum and the mean standard deviation (MSD) from 119 to 238 mm. The conditions were modelled to provide desired MPS and MSD by using the response surface methodology (RSM).