Implementation of reverse electrodialysis (RED) is economically limited by the relatively high ion-exchange membranes price. Additionally, the shadow effect of non-conductive spacers reduces the membrane area available for counter-ion transport and increases the stack electric resistance. A promising alternative could be utilization of profiled membranes, since the reliefs formed on their surface keeps the membranes separated and provides channels for solutions flow. Herein, we have simulated, through computational fluid dynamics (CFD) tools, fluid behavior in channels formed by various profiled membranes. The highest net power density values were obtained for corrugations shape and arrangement in a form of chevrons due to the increase of the available membrane area and an excellent balance between enhancement of mass transfer and the increase of the pressure drop in the channel. When properly designed, corrugated membranes may offer a better performance even compared to the case of conductive spacers. The proposed membrane corrugation design in not limited to the RED application, and could be also extended to other electromembrane processes, such as electrodialysis and Donnan dialysis, in which high ionic mass transport rates are desirable at as low as possible energy costs.

Several copper complexes have been assessed as anti-tumor agents against cancer cells. In this work, a copper compound [Cu(H2O){OS(CH3)(2)}L](NO3)(2) incorporating the ligand 4'-phenyl-terpyridine antiproliferative activity against human colorectal, hepatocellular carcinomas and breast adenocarcinoma cell lines was determined, demonstrating high cytotoxicity. The compound is able to induce apoptosis and a slight delay in cancer cell cycle progression, probably by its interaction with DNA and induction of double-strand pDNA cleavage, which is enhanced by oxidative mechanisms. Moreover, proteomic studies indicate that the compound induces alterations in proteins involved in cytoskeleton maintenance, cell cycle progression and apoptosis, corroborating its antiproliferative potential.

Metalloproteases have evolved in a vast number of biological systems, being one of the most diverse types of proteases and presenting a wide range of folds and catalytic metal ions. Given the increasing understanding of protein internal dynamics and its role in enzyme function, we are interested in assessing how the structural heterogeneity of metalloproteases translates into their dynamics. Therefore, the dynamical profile of the clan MA type protein thermolysin, derived from an Elastic Network Model of protein structure, was evaluated against those obtained from a set of experimental structures and molecular dynamics simulation trajectories. A close correspondence was obtained between modes derived from the coarse-grained model and the subspace of functionally-relevant motions observed experimentally, the later being shown to be encoded in the internal dynamics of the protein. This prompted the use of dynamics-based comparison methods that employ such coarse-grained models in a representative set of clan members, allowing for its quantitative description in terms of structural and dynamical variability. Although members show structural similarity, they nonetheless present distinct dynamical profiles, with no apparent correlation between structural and dynamical relatedness. However, previously unnoticed dynamical similarity was found between the relevant members Carboxypeptidase Pfu, Leishmanolysin, and Botulinum Neurotoxin Type A, despite sharing no structural similarity. Inspection of the respective alignments shows that dynamical similarity has a functional basis, namely the need for maintaining proper intermolecular interactions with the respective substrates. These results suggest that distinct selective pressure mechanisms act on metalloproteases at structural and dynamical levels through the course of their evolution. This work shows how new insights on metalloprotease function and evolution can be assessed with comparison schemes that incorporate information on protein dynamics. The integration of these newly developed tools, if applied to other protein families, can lead to more accurate and descriptive protein classification systems.

The incorporation of small amount of highly anisotropic nanoparticles into liquid crystalline hydroxypropylcellulose (LC-HPC) matrix improves its response when is exposed to humidity gradients due to an anisotropic increment of order in the structure. Dispersed nanoparticles give rise to faster order/disorder transitions when exposed to moisture as it is qualitatively observed and quantified by stress-time measurements. The presence of carbon nanotubes derives in a improvement of the mechanical properties of LC-HPC thin films.

Cellulose and its derivatives, such as hydroxypropylcellulose (HPC) have been studied for a long time but they are still not well understood particularly in liquid crystalline solutions. These systems can be at the origin of networks with properties similar to liquid crystalline (LC) elastomers. The films produced from LC solutions can be manipulated by the action of moisture allowing for instance the development of a soft motor (Geng et al., 2013) driven by humidity. Cellulose nanocrystals (CNC), which combine cellulose properties with the specific characteristics of nanoscale materials, have been mainly studied for their potential as a reinforcing agent. Suspensions of CNC can also self-order originating a liquid-crystalline chiral nematic phases. Considering the liquid crystalline features that both LC-HPC and CNC can acquire, we prepared LC-HPC/CNC solutions with different CNC contents (1,2 and 5 wt.%). The effect of the CNC into the LC-HPC matrix was determined by coupling rheology and NMR spectroscopy - Rheo-NMR a technique tailored to analyse orientational order in sheared systems. (C) 2015 Elsevier Ltd. All rights reserved.

Chitin, the second most abundant polymer in nature, is a renewable, nontoxic, biodegradable, and antibacterial polysaccharide. This semicrystalline biopolymer exhibits hierarchical structure from nano to micro-scale and is responsible for interesting living tissue properties. Recently, the scientific interest in chitin nanofibrils for applications in biomedical and tissue engineering fields has increased due to their particular capabilities such as matrix reinforcements, bioactivity and morphology similar to natural tissues. This chapter is focused on composite materials reinforced with chitin nanofibrils and their biomedical applications.

Composite ferrogels were obtained by encapsulation of magnetic nanoparticles at two different concentrations (2.0 and 5.0 % w/v) within mixed agarose/chitosan hydrogels having different concentrations of agarose (1.0, 1.5 and 2.0% (w/v)) and a fixed concentration of chitosan (0.5% (w/v)). The morphological characterization carried out by scanning electron microscopy showed that dried composite ferrogels present pore sizes in the micrometer range. Thermogravimetric measurements showed that ferrogels present higher degradation temperatures than blank chitosan/agarose hydrogels without magnetic nanoparticles. In addition, measurements of the elastic moduli of the composite ferrogels evidenced that the presence of magnetic nanoparticles in the starting aqueous solutions prevents to some extent the agarose gelation achieved by simply cooling chitosan/agarose aqueous solutions. Finally, it is shown that composite chitosan/agarose ferrogels are able to heat in response to the application of an alternating magnetic field so that they can be considered as potential biomaterials to be employed in magnetic hyperthermia treatments.

Core shell nanoparticles (NPs) formed by superparamagnetic iron oxide NPs (SPIONs) coated with inorganic or organically modified (ORMOSIL) sol gel silica exhibited promising properties as negative contrast agents (CA) for MRI applications. The potentiality of these new core shell NPs as negative CA for MRI is demonstrated and quantified. The longitudinal and transverse relaxivities of NPs with three different coating compositions were studied at a 7 T magnetic field: silica (TEOS), (3-aminopropyl) triethoxysilane (APTES) and (3-glycidoxypropyl) methyldiethoxysilane (GPTMS). Clearly, it was found that the core shell NPs efficiency as CA was strongly depend on the SPIONs coating. All the three core shell NPs studied presented a very small effect on the longitudinal relaxation time but a pronounced one on the transverse relaxation time, leading to a very high transverse longitudinal relaxivities ratio, decisive for their efficiency as negative CA for MRI The effect of the core shell NPs on the MRI contrast enhancement is obtained and quantified in a set of MRI of agar phantoms obtained at 7 T magnetic field and with a imaging gradient field of 1.6 T/m. The core shell NPs were tested in Zebra-fish (Danio rerio) animal model. Zebra-fish MRI were obtained with animals injected with the three core shell NPs and the contrast enhancement validated. (C) 2015 Elsevier B.V. All rights reserved.

Gum arabic (GA) is a hydrophilic composite polysaccharide derived from exudates of Acacia senegal and Acacia seyal trees. It is biocompatible, possesses emulsifying and stabilizing properties and has been explored as coating agent of nanomaterials for biomedical applications, namely magnetic nanoparticles (MNPs). Previous studies focused on the adsorption of GA onto MNPs produced by co-precipitation methods. In this work, MNPs produced by a thermal decomposition method, known to produce uniform particles with better crystalline properties, were used for the covalent coupling of GA through its free amine groups, which increases the stability of the coating layer. The MNPs were produced by thermal decomposition of Fe(acac)3 in organic solvent and, after ligand-exchange with meso-2,3-dimercaptosuccinic acid (DMSA), GA coating was achieved by the establishment of a covalent bond between DMSA and GA moieties. Clusters of several magnetic cores entrapped in a shell of GA were obtained, with good colloidal stability and promising magnetic relaxation properties (r2 /r1 ratio of 350). HCT116 colorectal carcinoma cell line was used for in vitro cytotoxicity evaluation and cell-labeling efficiency studies. We show that, upon administration at the respective IC50 , GA coating enhances MNP cellular uptake by 19 times compared to particles bearing only DMSA moieties. Accordingly, in vitro MR images of cells incubated with increasing concentrations of GA-coated MNP present dose-dependent contrast enhancement. The obtained results suggest that the GA magnetic nanosystem could be used as a MRI contrast agent for cell-labeling applications.

Gum arabic (GA) is a hydrophilic composite polysaccharide derived from exudates of Acacia senegal and Acacia seyal trees. It is biocompatible, possesses emulsifying and stabilizing properties and has been explored as coating agent of nanomaterials for biomedical applications, namely magnetic nanoparticles (MNPs). Previous studies focused on the adsorption of GA onto MNPs produced by co-precipitation methods. In this work, MNPs produced by a thermal decomposition method, known to produce uniform particles with better crystalline properties, were used for the covalent coupling of GA through its free amine groups, which increases the stability of the coating layer. The MNPs were produced by thermal decomposition of Fe(acac)3 in organic solvent and, after ligand-exchange with meso-2,3-dimercaptosuccinic acid (DMSA), GA coating was achieved by the establishment of a covalent bond between DMSA and GA moieties. Clusters of several magnetic cores entrapped in a shell of GA were obtained, with good colloidal stability and promising magnetic relaxation properties (r2 /r1 ratio of 350). HCT116 colorectal carcinoma cell line was used for in vitro cytotoxicity evaluation and cell-labeling efficiency studies. We show that, upon administration at the respective IC50 , GA coating enhances MNP cellular uptake by 19 times compared to particles bearing only DMSA moieties. Accordingly, in vitro MR images of cells incubated with increasing concentrations of GA-coated MNP present dose-dependent contrast enhancement. The obtained results suggest that the GA magnetic nanosystem could be used as a MRI contrast agent for cell-labeling applications.