Publications

Abstract In this work we report for the first time differential capacitance curves measured at imidazolium dicationic ionic liquid/electrode interfaces as a new strategy to understand the interfacial behaviour of ionic liquids (IL) near a charged electrode. The ionic liquid studied (1,5-bis(3-dimethylimidazolium)pentane di-bis(trifluoromethylsulfonyl)imide [C-5(MIM)(2)][Tf2N](2)) contains a cation with two positively charged imidazolium rings substituted with a methyl group connected by a pentane linkage alkyl chain length providing a new cationic structure variation. The comparison with the analogue monocationic ionic liquids showed that the dicationic liquid has a wider electrochemical polarization window and a more positive potential of zero charge at a Hg electrode. Differential capacity curves measured at dicationic ionic liquid/Hg interface show similar shape compared with analogous monocationic ionic liquids and revealed to be very sensitive to the electrode material.

Abstract The efficacy, cellular uptake and specific transport of dietary antioxidants to target organs, tissues and cells remains the most important setback for their application in the treatment of oxidative-stress related disorders and in particular in neurodegenerative diseases, as brain targeting remains a still unsolved challenge. Nanotechnology based delivery systems can be a solution for the above mentioned problems, specifically in the case of targeting dietary antioxidants with neuroprotective activity. Nanotechnology-based delivery systems can protect antioxidants from degradation, improve their physicochemical drug-like properties and in turn their bioavailability. The impact of nanomedicine in the improvement of the performance of dietary antioxidants, as protective agents in oxidative-stress events, specifically through the use of drug delivery systems, is highlighted in this review as well as the type of nanomaterials regularly used for drug delivery purposes. From the data one can conclude that the research combining (dietary) antioxidants and nanotechnology, namely as a therapeutic solution for neurodegenerative diseases, is still in a very early stage. So, a huge research area remains to be explored that hopefully will yield new and effective neuroprotective therapeutic agents in a foreseeable future.

Abstract The quantification of nitric oxide (NO) based on the quenching of the fluorescence of a nanocomposites sensor constituted by cadmium/selenium quantum dots (CdSe) stabilized by chitosan (CS) and mercaptosuccinic acid (MSA) is assessed. The optimization of the response of the CS-CdSe-MSA nanocomposites to NO was done by multivariate response surface experimental design methodologies. The highest fluorescence quenching was obtained at pH 5.5 and at room temperature. The NO quantification capability of CS-CdSe-MSA was evaluated using standard solutions and a NO donor reagent. A large linear working range from 5 to 200 mu M and a limit of detection of 1.86 mu M were obtained. Better quantification results were obtained using the NO donor reagent. Besides NO, the response of the fluorescence of CS-CdSe-MSA to the main reactive oxygen and nitrogen species and similar NO compounds was also assessed.

Abstract Bacteria can be resistant to multiple antibiotics and we are fast approaching a time when antibiotics will not work on some bacterial infections. New antimicrobial compounds are urgently necessary. Plants are considered the greatest source to obtain new antimicrobials. This study aimed to assess the antimicrobial activity of four phytochemicals-7-hydroxycoumarin (7-HC), indole-3-carbinol (I3C), salicylic acid (SA) and saponin (SP)-against Escherichia coli and Staphylococcus aureus, either as planktonic cells or as biofilms. These bacteria are commonly found in hospital-acquired infections. Some aspects on the phytochemicals mode of action, including surface charge, hydrophobicity, motility and quorum-sensing inhibition (QSI) were investigated. In addition, the phytochemicals were combined with three antibiotics in order to assess any synergistic effect. 7-HC and I3C were the most effective phytochemicals against E. coli and S. aureus. Both phytochemicals affected the motility and quorum-sensing (QS) activity, which means that they can play an important role in the interference of cell-cell interactions and in biofilm formation and control. However, total biofilm removal was not achieved with any of the selected phytochemicals. Dual combinations between tetracycline (TET), erythromycin (ERY) and ciprofloxacin (CIP) and I3C produced synergistic effects against S. aureus resistant strains. The overall results demonstrates the potential of phytochemicals to control the growth of E. coli and S. aureus in both planktonic and biofilm states. In addition, the phytochemicals demonstrated the potential to act synergistically with antibiotics, contributing to the recycling of old antibiotics that were once considered ineffective due to resistance problems. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

Abstract Templated microspheres based on the sol-gel process usually present low density, high surface area, excellent loading capacity, biocompatibility, and high thermal and mechanical stability, which make them ideal for a vast number of applications, from sensors to separation processes. The preparation of these templated microspheres, obtained by some sol-gel route, is here the subject of a review. The purposes and ways of insertion of templates inside a sol-gel matrix are diversified. Most commonly, templates are intended to produce some sort of controlled microstructure, either by simply reverting the volume occupied by the template to pore volume of identical dimensions or by directing the self-organization within the sol-gel network during the synthesis. Mesoporous spherical gels or glasses and composites have extensively been produced in this manner, using surfactants and polymeric materials as preferential templates. It is also common to find the utilization of templates related to the very process of achieving the microspheric format of the gels, which in many instances is designed to produce hollow spheres. Bulky templates in the micrometer range, such as whole cells, other microspheres or gas bubbles, are usually applied for the purpose. Molecularly imprinted microspherical gels have also been reported in the recent years. In this case, an usually small molecule of interest is added as template to the solgel mixture. It is expected that, upon removal from the final gel, the template will leave a cavity with the size and shape of the template, as well as some functionally complimentary chemical microenvironment.

Abstract The role of the electrode material on the interfacial double layer structure of a series of ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]), 1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([C4MIM][Tf2N]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM][BF4]) was investigated on gold (Au) and platinum (Pt) electrodes. The aim of this work is to contribute with experimental data to complement theoretical models that are currently under discussion in order to describe the structure of the double layer formed at the interface electrode/ionic liquid. There is still a controversy about the general shape that differential capacitance curves should present and researchers still continue making efforts to correlate the nature of the electrode/ionic liquid with the shape of the curves. Differential capacitance curves at the Au and Pt interface shows that the values of capacity follow the same order C [C4MIM][PF6] < C [C4MIM][Tf2N] < C [C4MIM][BF4]. However, the values of C are considerably lower for Pt when compared with Au for all three liquids studied. The alkyl chain length effect on the differential capacity curves was also studied at the Pt/[CnMIM][Tf2N] interface (where n = 2, 4 and 6). The results follow an expected trend except for the liquid [C6MIM][Tf2N] that shows a value of capacity near to that obtained for [C2MIM][Tf2N]. Since ionic liquids have great applicability in energy storage devices and capacitors it is of great importance to evaluate the dependence of differential capacitance as function of temperature. The results indicate that the capacity increases with increasing temperature for all systems studied in this work.