Host-guest supramolecular chemistry in solid-state nanopores: potassium-driven modulation of ionic transport in nanofluidic diodes

We describe the use of asymmetric nanopores decorated with crown ethers for constructing robust signal-responsive chemical devices. The modification of single conical nanopores with 18-crown-6 units led to a nanodevice whose electronic readout, derived from the transmembrane ion current, can be finely tuned over a wide range of K+ concentrations. The electrostatic characteristics of the nanopore environment arising from host-guest ion-recognition processes taking place on the pore walls are responsible for tuning the transmembrane ionic transport and the rectification properties of the pore. This work illustrates the potential and versatility of host-guest chemistry, in combination with nanofluidic elements, as a key enabler to achieve addressable chemical nanodevices mimicking the ion transport properties and gating functions of specific biological channels.Fil: Perez Mitta, Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Albesa, Alberto Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; ArgentinaFil: Knoll, Wolfang. Austrian Institute of Technology; AustriaFil: Trautmann, Christina. GSI Helmholtzzentrum für Schwerionenforschung; AlemaniaFil: Toimil Molares, Maria Eugenia. GSI Helmholtzzentrum für Schwerionenforschung; AlemaniaFil: Azzaroni, Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentin

Sujetos, comunicación y poder : Entrevista a Ernesto Laclau

En 1997, Ernesto Laclau visitó la Facultad de Periodismo y Comunicación Social para dictar un seminario y participar del Segundo Congreso Nacional de Facultades de Comunicación Social que se organizó en la ciudad de La Plata. Allí pudimos encontrarnos con el pensamiento de un filósofo argentino radicado en Inglaterra, que está repensando la política y la democracia desde la revisión de las clásicas categorías de la ciencia social. Para Laclau reflexionar sobre el objeto sociedad, implica buscar las posibilidades de un proyecto social que profundice los discursos emancipatorios y libertarios abiertos por la «revolución democrática» y que evite los aspectos represivos del «imaginario jacobino». Inés Seoane Toimil, Susana Malacalza y Alberto Amato, tomaron la posta de Oficios Terrestres y realizaron esta entrevista que no ha perdido actualidad.Facultad de Periodismo y Comunicación Socia

Sujetos, comunicación y poder : Entrevista a Ernesto Laclau

En 1997, Ernesto Laclau visitó la Facultad de Periodismo y Comunicación Social para dictar un seminario y participar del Segundo Congreso Nacional de Facultades de Comunicación Social que se organizó en la ciudad de La Plata. Allí pudimos encontrarnos con el pensamiento de un filósofo argentino radicado en Inglaterra, que está repensando la política y la democracia desde la revisión de las clásicas categorías de la ciencia social. Para Laclau reflexionar sobre el objeto sociedad, implica buscar las posibilidades de un proyecto social que profundice los discursos emancipatorios y libertarios abiertos por la «revolución democrática» y que evite los aspectos represivos del «imaginario jacobino». Inés Seoane Toimil, Susana Malacalza y Alberto Amato, tomaron la posta de Oficios Terrestres y realizaron esta entrevista que no ha perdido actualidad.Facultad de Periodismo y Comunicación Socia

The Influence of Divalent Anions on the Rectification Properties of Nanofluidic Diodes: Insights from Experiments and Theoretical Simulations

During the last decade, the possibility of generating synthetic nanoarchitectures with functionalities comparable to biological entities has sparked the interest of the scientific community related to diverse research fields. In this context, gaining fundamental understanding of the central features that determine the rectifying characteristics of the conical nanopores is of mandatory importance. In this work, we analyze the influence of mono- and divalent salts in the ionic current transported by asymmetric nanopores and focus on the delicate interplay between ion exclusion and charge screening effects that govern the functional response of the nanofluidic device. Experiments were performed using KCl and K₂SO₄ as representative species of singly and doubly charged species. Results showed that higher currents and rectification efficiencies are achieved by doubly charged salts. In order to understand the physicochemical processes underlying these effects simulations using the Poisson-Nernst-Planck formalism were performed. We consider that our theoretical and experimental account of the effect of divalent anions in the functional response of nanofluidic diodes provides further insights into the critical role of electrostatic interactions (ion exclusion versus charge screening effects) in presetting the ionic selectivity to anions as well as the observed rectification properties of these chemical nanodevices.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Shape matters: Enhanced osmotic energy harvesting in bullet-shaped nanochannels

Nanofluidic reverse electrodialysis systems based on track-etched nanochannels are promising devices for new eco-friendly ways of sustainable energy generation. In recent years, several works have been focused on the influence of parameters such as pH, ionic strength, and chemical nature of the electrolyte on the device performance. However, despite the relevance of the geometry on the channel properties, the influence of the nanochannel shape on the performance of energy conversion remains almost unexplored. In this work, we present an experimental study – complemented with Poisson–Nernst–Planck simulations – that describes how the shape of the nanochannels strongly affects the energy conversion performance of single bullet-shaped nanochannels created on PET foils by the ion-track-etching method. To test optimal parameters for energy conversion and selectivity, the performance was investigated by varying the channel effective diameter as well as the pH and the electrolyte gradient. With a maximum output power of 80 pW, this system reveals the best value reported for a bare single track-etched nanochannel. Therefore, this work experimentally demonstrates that it is possible to obtain high power output by means of a careful choice of channel geometry and etching conditions, in addition to other experimental parameters such as pH and electrolyte gradient. We believe that these results offer a promising framework to explore new design concepts in nanofluidic osmotic power generators.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Host–guest supramolecular chemistry in solid-state nanopores: potassium-driven modulation of ionic transport in nanofluidic diodes

We describe the use of asymmetric nanopores decorated with crown ethers for constructing robust signal-responsive chemical devices. The modification of single conical nanopores with 18-crown-6 units led to a nanodevice whose electronic readout, derived from the transmembrane ion current, can be finely tuned over a wide range of K⁺ concentrations. The electrostatic characteristics of the nanopore environment arising from host–guest ion-recognition processes taking place on the pore walls are responsible for tuning the transmembrane ionic transport and the rectification properties of the pore. This work illustrates the potential and versatility of host–guest chemistry, in combination with nanofluidic elements, as a key enabler to achieve addressable chemical nanodevices mimicking the ion transport properties and gating functions of specific biological channels.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Phosphate-Responsive Biomimetic Nanofluidic Diodes Regulated by Polyamine–Phosphate Interactions: Insights into Their Functional Behavior from Theory and Experiment

There is currently high interest in developing nanofluidic devices whose iontronic output is defined by biological interactions. The fabrication of a phosphate responsive nanofluidic diode by using the biological relevant amine–phosphate interactions is shown. The fabrication procedure includes the modification of a track-etched asymmetric (conical) nanochannel with polyallylamine (PAH) by electrostatic self-assembly. PAH is the arcaetypical model of polyamine and it is further used to address the nanochannels with phosphate responsivity. In order to explore the influence that phosphate in solution has in the conductance of the modified nanochannels, current–voltage measurements using different concentrations of phosphates are performed. Furthermore, to have a complete physicochemical understanding of the system, experimental data is analyzed using a continuous model based on Poison–Nernst–Planck equations and compared with results obtained from stochastic Monte Carlo simulations.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Noncovalent Approach toward the Construction of Nanofluidic Diodes with pH-Reversible Rectifying Properties: Insights from Theory and Experiment

In this paper, the fabrication of a biomimetic nanofluidic diode whose ionic transport characteristics can be completely modulated with the proton concentration in solution is demonstrated. The fabrication procedure involves the electrostatic assembly of poly(allylamine hydrochloride) (PAH) into a track-etched conical nanochannel. A fully reversible, zwitterionic-like behavior with important implications for the supramolecular interactions of the PAH within confined spaces was observed. The experimental design constitutes a facile venue for the fabrication of functional nanofluidic devices and paves the way for a number of applications in nanofluidics and biosensing. Furthermore, in order to explain the experimental results and to obtain physicochemical information about the system, theoretical modeling using a continuous model based on Poisson−Nernst−Planck equations and a stochastic model using Monte Carlo simulations were performed. Good agreement between experiments and theory was found.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Aplicaciones farmacológicas y alimentarias de la microalga extremófila Coccomyxa onubensis

Las microalgas se consideran unas interesantes fuentes naturales de moléculas de alto valor añadido, muchas de las cuales presentan actividad biológica con aplicaciones en salud humana, actuando, por ejemplo, como antiinflamatorios, antitumorales y antibióticos. En la presente Tesis Doctoral se ha evaluado la capacidad antimicrobiana de algunos extractos obtenidos a partir de la microalga Coccomyxa onubensis (C. onubensis), un microorganismo extremófilo aislado de drenajes ácidos procedentes de la zona minera del río Tinto (Huelva, España). También, hemos estudiado la composición de la biomasa de esta microalga, encontrándose que es rica en proteínas, lípidos, hidratos de carbono, antioxidantes y vitaminas, por lo que se ha sugerido su utilización como alimento para animales. Nuestros resultados muestran por primera vez que una microalga acidófila es capaz de producir compuestos con actividad antibacteriana y que la biosíntesis de este tipo de compuestos se puede llevar a cabo en condiciones de pH muy bajo y en un entorno altamente oxidativo, bajo las cuales, la vida apenas es posible. En cuanto a su aplicación, como suplemento nutricional, todos los resultados obtenidos apoyan la idea de que la biomasa de C. onubensis puede ser un suplemento seguro en la dieta y que presenta las propiedades nutricionales adecuadas de los alimentos funcionales, destacando su contenido en compuestos antioxidantes como polifenoles, flavonoides, taninos y carotenoides, y en ácidos grasos poliinsaturados. En este sentido, hemos podido comprobar experimentalmente en ratas Long Evans, que la adición de C. onubensis en polvo (al 6.25% en peso) a una dieta alta en grasas, tiene un efecto protector del riesgo cardiovascular. Por lo tanto, la biomasa de C. onubensis puede ser apta tanto directamente, como alimento funcional para animales, o como fuente natural de compuestos nutracéuticos y farmacológicos.Microalgae are considered interesting natural sources of high value added molecules, many of which exhibit biological activity with applications in human health, working for instance as anti-inflammatory, anti-tumoral and antibiotic. In this Doctoral Thesis, the antimicrobial capacity of some extracts obtained from the microalgae Coccomyxa onubensis (C. onubensis), an extremophilic microorganism isolated on the basis of acid drains of the Rio Tinto’s mining area (Huelva, Spain) have been evaluated. Likewise, the biomass of this microalgae has also been studied by our research group, being found to be rich in proteins, lipids, carbohydrates, antioxidants and vitamins, so it has been suggested the possibility of its use as food for animals. Our obtained results show for the first time that an acidophilic microalga is able to produce compounds with antibacterial activity and that the biosynthesis of such compounds can be carried out under very low pH conditions and in a highly oxidative environment, under which, the life is barely possible. Regarding its application, as a nutritional supplement, all the results obtained support the idea that the biomass of C. onubensis can be a safe supplement in the diet and that it has the adequate nutritional properties of functional foods, highlighting its content in antioxidants compounds such as polyphenols, flavonoids, tannins and carotenoids, and in polyunsaturated fatty acids. In this sense, we have been able to experimentally verify in Long Evans rats, that the addition of C. onubensis powder (6.25% by weight) to a high-fat diet has a protective effect on cardiovascular risk. Therefore, C. onubensis biomass may be suitable both directly, as a functional feed for animals, or as a natural source of nutraceutical and pharmacological compounds

The acidophilic microalga Coccomyxa onubensis and atorvastatin equally improve antihyperglycemic and antihyperlipidemic protective effects on rats fed on high-fat diets

Biomass of the acidophilic green alga Coccomyxa onubensis may be used as a food source for animals without collateral toxic effects, as diet supplemented the microalga has significant hypoglycemic and hypocholesterolemic effects on healthy animals. Rats were fed for 108 days with a high-fat diet, and at the end of the experiment, they were overweight and had significantly increased serum levels of glucose (2.0-fold), total cholesterol (1.6-fold), and low-density lipoprotein (LDL)-cholesterol (7.7- fold). The supplement of C. onubensis powder (6.25% w/w dry weight) in the high-fat diet significantly protected the rats against cardiovascular risks by reducing the serum levels of glucose (38.47%), total cholesterol (22.65%), and LDL-cholesterol (26.70%). The protective effects of the microalga were comparable with that of 10 mg/kg body weight per day of atorvastatin. The high-fat diet decreased both ω–3 eicosapentaenoic and docosahexaenoic acids in the brain tissue of rats; however, C. onubensis powder could not restrict these changes. Simultaneously, the high-fat diet increased the levels of both palmitic and arachidonic (ω–6) acids in the telencephalon tissue of rats; this was prevented when microalga biomass was used in the diet of rats