Zamora-Mora, V, Soares PIP, Echeverria C, Hernández R, Mijangos C.
2015.
Composite chitosan/agarose ferrogels for potential applications in magnetic hyperthermia. Gels. 1:69–80., Number 1: Multidisciplinary Digital Publishing Institute
AbstractComposite 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.
Echeverria, C, Soares PIP, Robalo A, Pereira L, Novo C, Ferreira I, Borges JP.
2015.
One-pot synthesis of dual-stimuli responsive hybrid PNIPAAm-chitosan microgels. Materials & Design. 86:745-751.
AbstractThe incorporation of magnetic nanoparticles into poly(N-isopropylacrylamide) (PNIPAAm) and chitosan microgels gives rise to hybrid systems that combine the microgels swelling capacity with the interesting features presented in magnetic nanoparticles. The presence of chitosan that act as surfactant for magnetic nanoparticles provides a simplistic approach which allows the encapsulation of magnetic nanoparticles without any previous surface modification. Spherical and highly monodisperse microgels with diameters in the range of 200 to 500 nm were obtained. The encapsulation of magnetic nanoparticles in the polymer matrix was confirmed by high resolution Scanning Electron Microscopy in transmission mode. Volume phase transition of the microgels was accessed by Dynamic Light Scattering measurements. It was observed that the thermosensitivity of the PNIPAM microgels still persists in the hybrid microgels; however, the swelling ability is compromised in the microgels with highest chitosan content. The heating performance of the hybrid magnetic microgels, when submitted to an alternating magnetic field, was also evaluated demonstrating the potential of these systems for hyperthermia treatments.
Aquino, AS, Bernard FL, Borges JV, Mafra L, Dalla Vecchia F, Vieira MO, Ligabue R, Seferin M, Chaban VV, Cabrita EJ, Einloft S.
2015.
Rationalizing the role of the anion in CO2 capture and conversion using imidazolium-based ionic liquid modified mesoporous silica. RSC Advances. 5:64220-64227., Number {79}, {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}: {ROYAL SOC CHEMISTRY}
AbstractCovalently supported ionic liquids in mesoporous materials were prepared by grafting 1-methyl-3-(3-trimethoxysylilpropyl)imidazolium chloride in MCM-41. Subsequently, the {[}Cl-] anion was changed to {[}BF4-], {[}PF6-] or {[}Tf2N-]. These materials that present an advantageous combination of the properties of mesoporous solid materials and ionic liquids were evaluated for CO2 sorption as well as catalysts for CO2 conversion into cyclic carbonate using propylene oxide. The material with the {[}Cl-] anion had the best performance for both CO2 sorption and conversion. A CO2 sorption of 11 w/w% on the adsorbent was achieved and the cycloaddition reaction exhibited a conversion of 67% with 82% selectivity with the catalyst remaining active after 5 cycles, proving that the same sorbent/catalyst setup can be used for both CO2 capture and conversion. Based on the experimental data and electronic-structure numerical simulations, we have hypothesized two major reasons why chloride out performs other anions when adsorbed on MCM-41 unlike unsupported ionic liquids.
Carvalho, LCR, Ribeiro D, Seixas RSGR, Silva AMS, Nave M, Martins AC, Erhardt S, Fernandes E, Cabrita EJ, Marques MMB.
2015.
Synthesis and evaluation of new benzimidazole-based COX inhibitors: a naproxen-like interaction detected by STD-NMR. RSC Advances. 5:49098-49109., Number {61}
AbstractNon-steroidal anti-inflammatory drugs exert their pharmacological activity through inhibition of cyclooxygenase 1 and 2 (COX-1 and COX-2). Recent research suggests that a balanced inhibition of both COX-1 and COX-2 is the key to reduce the side-effects exhibited by COX inhibitors. We developed new benzimidazole-based compounds that showed a balanced COX inhibition, supported by molecular docking screening. The human whole blood assays demonstrated that the ester derivatives were potent inhibitors. Competitive saturation transfer difference (STD)-NMR experiments, in the presence of COX-2, using naproxen and diclofenac demonstrated that ester derivatives do not compete with diclofenac for the same binding site, but compete with the allosteric inhibitor naproxen. Combination of NMR spectroscopy with molecular docking has permitted us to detect a new naproxen-like inhibitor, which could be used for future drug development.
Soares, PIP, Lochte F, Echeverria C, Pereira L, Coutinho J, Ferreira I, Novo C, Borges JP.
2015.
Thermal and magnetic properties of iron oxide colloids: influence of surfactants. Nanotechnology. 26(42):425704.
AbstractIron oxide nanoparticles (NPs) have been extensively studied in the last few decades for several biomedical applications such as magnetic resonance imaging, magnetic drug delivery and hyperthermia. Hyperthermia is a technique used for cancer treatment which consists in inducing a temperature of about 41–45 °C in cancerous cells through magnetic NPs and an external magnetic field. Chemical precipitation was used to produce iron oxide NPs 9 nm in size coated with oleic acid and trisodium citrate. The influence of both stabilizers on the heating ability and in vitro cytotoxicity of the produced iron oxide NPs was assessed. Physicochemical characterization of the samples confirmed that the used surfactants do not change the particles' average size and that the presence of the surfactants has a strong effect on both the magnetic properties and the heating ability. The heating ability of Fe3O4 NPs shows a proportional increase with the increase of iron concentration, although when coated with trisodium citrate or oleic acid the heating ability decreases. Cytotoxicity assays demonstrated that both pristine and trisodium citrate Fe3O4 samples do not reduce cell viability. However, oleic acid Fe3O4 strongly reduces cell viability, more drastically in the SaOs-2 cell line. The produced iron oxide NPs are suitable for cancer hyperthermia treatment and the use of a surfactant brings great advantages concerning the dispersion of NPs, also allowing better control of the hyperthermia temperature.
Soares, PIP, Lochte F, Echeverria C, Pereira LCJ, Coutinho JT, Ferreira IMM, Novo CMM, Borges JPMR.
2015.
Thermal and magnetic properties of iron oxide colloids: influence of surfactants. Nanotechnology. 26(42):425704.
AbstractIron oxide nanoparticles (NPs) have been extensively studied in the last few decades for several biomedical applications such as magnetic resonance imaging, magnetic drug delivery and hyperthermia. Hyperthermia is a technique used for cancer treatment which consists in inducing a temperature of about 41–45 °C in cancerous cells through magnetic NPs and an external magnetic field. Chemical precipitation was used to produce iron oxide NPs 9 nm in size coated with oleic acid and trisodium citrate. The influence of both stabilizers on the heating ability and in vitro cytotoxicity of the produced iron oxide NPs was assessed. Physicochemical characterization of the samples confirmed that the used surfactants do not change the particles' average size and that the presence of the surfactants has a strong effect on both the magnetic properties and the heating ability. The heating ability of Fe3O4 NPs shows a proportional increase with the increase of iron concentration, although when coated with trisodium citrate or oleic acid the heating ability decreases. Cytotoxicity assays demonstrated that both pristine and trisodium citrate Fe3O4 samples do not reduce cell viability. However, oleic acid Fe3O4 strongly reduces cell viability, more drastically in the SaOs-2 cell line. The produced iron oxide NPs are suitable for cancer hyperthermia treatment and the use of a surfactant brings great advantages concerning the dispersion of NPs, also allowing better control of the hyperthermia temperature.
Kowacz, M, Marchel M, Juknaite L, Esperanca J, Romao MJ, Carvalho AL, Rebelo LPN.
2015.
Ionic-Liquid-Functionalized Mineral Particles for Protein Crystallization. Crystal Growth & Design. 15:2994-3003., Number 6
AbstractNucleation is a critical step determining the outcome of the entire crystallization process. Finding an effective nucleant for protein crystallization is of utmost importance for structural biology. The latter relies on good-quality crystals to solve the three-dimensional structures of macromolecules. In this study we show that crystalline barium sulfate (BaSO4) with an etched and/or ionic liquid (IL)-functionalized surface (1) can induce protein nucleation at concentrations well below the concentration needed to promote crystal growth under control conditions, (2) can shorten the nucleation time, (3) can increase the growth rate, and finally (4) may help to improve the protein crystal morphology. These effects were shown for lysozyme, RNase A, trypsin, proteinase K, myoglobin, and hemoglobin. Therefore, the use of BaSO4 particles enables us to reduce the amount of protein in crystallization trials and increases the chance of obtaining protein crystals of the desired quality. In the context of the underlying mechanism, it is shown that the protein-solid contact formation is governed by the interaction of the polar compartments of the biomacromolecule with the support. The tendency of a protein to concentrate near the solid surface is enhanced by both the hydrophobicity of the protein and that of the surface (tuned by the functionalizing IL). These mechanisms of interaction of biomacromolecules with inorganic hydrophilic solids correspond to the principles of amphiphilic IL-mineral interactions.
Corvo, M, Sardinha J, Casimiro T, Marin G, Seferin M, Einloft S, Menezes SC, Dupont J, Cabrita EJ.
2015.
A Rational Approach to CO2 Capture by Imidazolium Ionic Liquids: Tuning CO2 Solubility by Cation Alkyl Branching. ChemSusChem. 8:1935-46., Number 11
AbstractBranching at the alkyl side chain of the imidazolium cation in ionic liquids (ILs) was evaluated towards its effect on carbon dioxide (CO2 ) solubilization at 10 and 80 bar (1 bar=1x10(5) Pa). By combining high-pressure NMR spectroscopy measurements with molecular dynamics simulations, a full description of the molecular interactions that take place in the IL-CO2 mixtures can be obtained. The introduction of a methyl group has a significant effect on CO2 solubility in comparison with linear or fluorinated analogues. The differences in CO2 solubility arise from differences in liquid organization caused by structural changes in the cation. ILs with branched cations have similar short-range cation-anion orientations as those in ILs with linear side chains, but present differences in the long-range order. The introduction of CO2 does not cause perturbations in the former and benefits from the differences in the latter. Branching at the cation results in sponge-like ILs with enhanced capabilities for CO2 capture.