Composites formed by poly(3,4-ethylenedioxythiophene) and alumina (PEDOT/Al2O3) have been prepared by in situ anodic polymerization. For this purpose, the stability of 1:1 and 4:1 monomer:alumina aqueous solutions has been examined as a function of the pH (2.3, 4.0, 7.0, 8.8, or 10.8). Results indicate that the monomer behaves as a dispersant that remains stable at the studied basic pHs despite they are close to the isoelectric point of alumina. Although the thermal stability of the composites is considerably affected by the pH of the reaction medium, its influence on the surface morphology is very small. Independently, of the synthetic conditions, the electrochemical properties were better for PEDOT/Al2O3 than for pure PEDOT, reflecting that alumina particles promote the charge mobility. The highest specific capacitance (SC; 141 F/g), which was 55% higher than that obtained for pure PEDOT, was achieved for the composite prepared at pH¿=¿8.8 using a 4:1 monomer:alumina ratio. These conditions favor the participation of OH– groups as secondary doping agents without degrading the polymer matrix and enhance the specific surface of the films, facilitating the ionic mobility. On the other hand, application of a multi-step polymerization strategy has shown that interfaces originated by consecutive steps enhance the SC.
We report the simple and fast fabrication of a bioactive integrated platform based on poly(3,4-ethylenedioxythiophene) and ¿-poly(glutamic acid)-cystamine hydrogel for the simultaneous delivery and electrochemical detection of dopamine. As shown in Figure 1, the different steps involved in the development of bioactive integrated platform consist of (i) anodic polymerization of 3,4-ethylenedioxythiophene on screen printed carbon electrodes, (ii) synthesis of biodegradable hydrogel in an aqueous environment on the surface of poly(3,4-ethylenedioxythiophene) film and gelatin which act as an anchor point, (iii) incorporation of dopamine into hydrogel by immersing method in acidic medium and finally (iv) release and electrochemical detection of dopamine in physiological buffer commonly used in biological research. The preliminary findings suggest that dopamine release rates from ¿-poly(glutamic acid)-cystamine hydrogels were dependent on the molecular weight of ¿-poly(glutamic acid), the cross-linking degree of the hydrogels, pH and ionic strength of the medium. On the other hand, the electrochemical assays indicate that we have successfully obtained high sensitive sensors (8·10-5 mA/µM dopamine) with a lower limit detection (0.45 µM).
Figure 1. Schematic representation of the different steps involved in the development of bioactive platform for the simultaneous drug delivery and electrochemical detection.
Fabregat, G.; Osorio, J.; Castedo, A.; Armelin, E.; Buendía, J.; Llorca, J.; Aleman, C. International Symposium Frontiers in Polymer Science Data de presentació: 2017-05-18 Presentació treball a congrés
We have fabricated potentially generalizable sensors based on polymeric-modified electrodes for the electrochemical detection of dopamine. Sensitive and selective sensors have been successfully obtained by applying a cold-plasma treatment during 1-2 minutes not only to conducting polymers (Figure 1) but also to electrochemically inert plastics, such as polyethylene, polypropylene, polyvinylpyrrolidone, poly(4-vinylphenol), polycaprolactone and polystyrene. The effects of the plasma in the electrode surface activation, which is an essential requirement for the dopamine detection when inert plastics are used, have been extensively investigated using X-ray photoelectron spectroscopy. Results clearly indicate that exposure of polymer-modified electrodes to cold-plasma produces the formation of a large variety of reactive species adsorbed on the electrode surface, which catalyse the dopamine oxidation promoting its detection. With this technology, which is based on the application of a very simple physical treatment rather than on the sophisticated chemical methods typically employed (e.g. functionalization, incorporation of catalytic nanoparticles and processing of the nanocomposites), we have defined a paradox-based paradigm for the fabrication of electrochemical sensors by using inert and cheap plastics.
Figure 1. SEM micrographs of (a) PEDOT and (b) PNCPy before (left) and after (right) plasma treatment using tcp= 2 min.
Figure 2. Control voltammogram of 10 ¿M DA in 0.1 M PBS at (a) polypropylene-, (b) polyvinylpyrrolidone-, (c) polycaprolactone- and (d) polystyrene-modified GCE.
Poly(1,4-disubstituted 1,2,3-triazoles) made by copper-catalyzed azide-alkyne cycloaddition form strongly bonded interfaces with several metal substrates. In this work, a variety of alkyne and azide monomers were explored as precursors to anticorrosion coatings for a standard high-strength aluminum-copper alloy (tradename AA2024). Monomers of comparatively low functionality (diazide and trialkyne) were found to act as superior barriers for electrolyte transfer to the aluminum surface. These materials showed excellent resistance to corrosive pitting due to the combination of three complementary properties: good formation of highly crosslinked films, as observed by FTIR and DSC; good adhesion to the aluminum alloy substrate, as shown by pull-off testing; and excellent impermeability, demonstrated by electrochemical impedance spectroscopy (EIS).
The best result was obtained with 1A21B3 polymer (Fig. 1), which has an azide monomer with six methylene groups and one alkyne with triazine aromatic ring. This composition helped moderate the degree of crosslinking among polymer chains, offering a beneficial flexibility to the polymer film (Fig. 2A). Thus, the presence of bi-azide (A2) and tri-alkyne (B3) functionalities in poly(1,4-disubstituted 1,2,3-triazoles) coating has fulfilled the expected role by offering improved adhesion to the metal substrate and protective barrier properties at the film surface simultaneously (Figs. 2B-C).
Figure 1. Molecular formulas of azide (1A2) and alkyne (1B3) with schematic representation of hyperbranched poly(1,4-disubstituted 1,2,3-triazole).
Figure 2. A) Polytriazole 1A21B3 fabricated as flexible thin film, B) Pull-off adhesion values (*obtained from literature), and C) Corrosion potential evolution in NaCl 0.05M.
Reference: Armelin et. al ACS Applied Materials & Interfaces 2017, 9, 4231-4243.
Dielectric spectroscopy measures the dielectric properties of a medium as a function of frequency.
Beginning in the 1970s, research electrochemists and materials scientists began to discover the power of
Electrochemical Impedance Spectroscopy (EIS) as a tool for studying difficult and complicated systems.
Currently the EIS technique is much more accessible and widely used in research areas beyond the world
of electrochemistry. It requires an impedance analyser with frequency range from 106Hz to 10-2Hz
equipped with appropriate software. The development of modern technique of Broadband Dielectric
Spectroscopy (BDS), during the mid-nineties, with extremely wide frequency range (1012 Hz to 10-6 Hz)
allowed the study of molecular fluctuations and collective phenomena, charge and polarization effects in
amorphous, semi-crystalline, liquid crystalline polymers as well as in polymer composites.
In the present work, some examples of a variety of polymeric materials (Fig. 1), characterized with EIS at
Innovation in Materials and Molecular Engineering Group (IMEM’s Group), will be showed.
The characterization of electrical properties with impedance spectroscopy requires the interpretation of
the data with the help of suitable models, which are divided into two broad categories: equivalent circuit
models and process models. From Nyquist, Bode and permittivity plots (Figs. 2A-C) it is possible extract
quantitative parameters related to the polymer resistance, capacitance, conductivity, relative permittivity,
using the electrical equivalent circuit (EEC, Fig. 2D). Additionally, qualitative observations regarding
blistering formation under coating or permeability of organic coatings can be performed. Results can vary
depending on types of polymers, film thickness, number of polymer layers; and the nature and surface
treatment of the metal substrate used as working electrode.
The versatility of dielectric spectroscopy has made it to become a fundamental tool in multidisciplinary
design, characterization and application of advanced functional materials and systems applied in such
diverse fields as those ranging from nanotechnology to biology.
References: 1) Müller et. al, J. Phys. Chem. B, 118 (2014) 1102-1112.2) González et. al, Eur. Polym. J.,
75 (2015) 210–222. 3) Dalmoro et. al, Prog. .Org. Coat. 88 (2015) 181–190. 4) Pérez-Madrigal et al., ACS
Appl. Mater. Interfaces, 7 (2015) 1632-1643.
Unusual gelation of acidic solutions was achieved using polycations bearing quaternary ammonium moieties. These ionene polymers are based on a disubstituted phenylene dibenzamide core, which allows the construction of different topomers (i.e. ortho-1, meta-2 and para-3). The topology of the polymers was found to play a key role on their aggregation behaviour both in pure water and in a variety of aqueous acidic solutions leading to the formation of stable acidic gels. Specifically, ortho-1 showed superior gelation ability than the analogues meta-2 and para-3 in numerous solutions of different pH and ionic strengths. Lower critical gelation concentrations, higher gel-to-sol transition temperatures and faster gelation were usually observed for ortho-1 regardless the solvent system. Detailed computational molecular dynamic simulations revealed a major role of the counterion (Cl-) and specific polymer¿polymer interactions. In particular, hydrogen bonds, N–H¿p interactions and intramolecular p–p stacking networks are distinctive in ortho-1. In addition, counterions located at internal hydration regions also affect to such polymer¿polymer interactions, acting as binders and, therefore, providing additional stability.
Mayans, E.; Casanovas Salas, Jordi; Gil, A.; Jimenez, A.; Cativiela, C.; Puiggali, J.; Aleman, C. Langmuir Vol. 33, p. 1-13 DOI: 10.1021/acs.langmuir.7b00622 Data de publicació: 2017-04-25 Article en revista
Microstructures from small phenylalanine-based peptides have attracted great attention lately because these compounds are considered to be a new class of tunable materials. In spite of the extensive studies on uncapped diphenylalanine and tetraphenylalanine peptides, studies on the self-assembly of uncapped triphenylananine (FFF) are very scarce and nonsystematic. In this work, we demonstrate that FFF assemblies can organize in a wide number of well-defined supramolecular structures, which include laminated helical-ribbons, leaflike dendrimers, doughnut-, needle-, and flower-shapes. These organizations are produced by the attractive or repulsive interactions between already formed assemblies and therefore can be controlled through the choice of solvents used as the incubation medium. Thus, the formation of the desired supramolecular structures is regulated through the protonation/deprotonation of the terminal groups, the polarity of the incubation medium, which affects both peptide···solvent interactions and the cavity solvation energy (i.e., solvent···solvent interactions), and the steric interactions between own assemblies that act as building blocks. Finally, the ß-sheet disposition in the latter structural motifs has been examined using both theoretical calculations and Fourier transform infrared spectroscopy. Results indicate that FFF molecules can adopt both parallel and antiparallel ß-sheets. However, the former one is the most energetically favored because of the formation of p–p stacking interactions between the aromatic rings of hydrogen-bonded strands.
The effect of counterions and multiple polymer chains on the properties and structure of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with ClO4- has been examined using density functional theory (DFT) calculations with periodic boundary conditions (PBCs). Calculations on a one-dimensional periodic model with four explicit polymer repeat units and two ClO4- molecules indicate that the latter are separated as much as possible, with the salt structure and band gap obtained from such ClO4- distribution being in excellent agreement with those determined experimentally. On the other hand, DFT calculations on periodic models that include two chains indicate that neighboring PEDOT chains are shifted along the molecular axis by a half of the repeat unit length, with dopant ions intercalated between the polymer molecules acting as cement. In order to support these structural features, classical molecular dynamics (MD) simulations have been performed on a multiphasic system consisting of 69 explicit PEDOT chains anchored onto a steel surface, explicit ClO4- anions embedded in the polymer matrix, and an acetonitrile phase layer onto the polymer matrix. Analyses of the radial distribution functions indicate that the all-anti conformation, the relative disposition of adjacent PEDOT chains and the distribution of ClO4- dopant ions are fully consistent with periodic DFT predictions. The agreement between two such different methodologies allows reinforcing the microscopic understanding of the PEDOT film structure.
Poly(N-methylpyrrole)/molybdenum trioxide composites have been prepared by in situ anodic polymerization using a 75:25 acetonitrile:water monomer solution, exfoliated molybdenum trioxide particles, and supporting electrolyte as reaction medium. The incorporation of molybdenum trioxide increases the ability of poly(N-methylpyrrole) to exchange charge reversibly (i.e., the electroactivity) by 47%. This has been attributed to the structural changes induced by the molybdenum trioxide, which transforms the uniform and compact surface morphology of poly(N-methylpyrrole) into a more open structure with distinctive topographic features at different levels. These trends facilitate the access and escape of dopant ions during oxidation and reduction processes, respectively, with respect to poly(N-methylpyrrole).
Mazzier, D.; Grassi, L.; Moretto, A.; Aleman, C.; Formaggio, F.; Toniolo, C.; Crisma, M. Journal of peptide science Vol. 23, num. 4, p. 346-362 DOI: 10.1002/psc.2957 Data de publicació: 2017-04-01 Article en revista
We performed the solution-phase synthesis of a set of model peptides, including homo-oligomers, based on the 2-aminoadamantane-2-carboxylic acid (Adm) residue, an extremely bulky, highly lipophilic, tricyclic, achiral, Ca-tetrasubstituted a-amino acid. In particular, for the difficult peptide coupling reaction between two Adm residues, we took advantage of the Meldal's a-azidoacyl chloride approach. Most of the synthesized Adm peptides were characterized by single-crystal X-ray diffraction analyses. The results indicate a significant propensity for the Adm residue to adopt ¿-turn and ¿-turn-like conformations. Interestingly, we found that a -CO-(Adm)2-NH- sequence is folded in the crystal state into a regular, incipient ¿-helix, at variance with the behavior of all of the homo-dipeptides from Ca-tetrasubstituted a-amino acids already investigated, which tend to adopt either the ß-turn or the fully extended conformation. Our density functional theory conformational energy calculations on the terminally blocked homo-peptides (n = 2–8) fully confirmed the crystal-state data, strongly supporting the view that this rigid Ca-tetrasubstituted a-amino acid residue is largely the most effective building block for ¿-helix induction, although to a limited length (anti-cooperative effect).
Fabregat, G.; Osorio-Madrigal, J.; Castedo, A.; Armelin, E.; Buendía-Morales, J.J.; Llorca, J.; Aleman, C. Applied surface science Vol. 399, p. 638-647 DOI: 10.1016/j.apsusc.2016.12.137 Data de publicació: 2017-03-31 Article en revista
We have fabricated potentially generalizable sensors based on polymeric-modified electrodes for the electrochemical detection of dopamine. Sensitive and selective sensors have been successfully obtained by applying a cold-plasma treatment during 1–2 min not only to conducting polymers but also to electrochemically inert polymers, such as polyethylene, polypropylene, polyvinylpyrrolidone, polycaprolactone and polystyrene. The effects of the plasma in the electrode surface activation, which is an essential requirement for the dopamine detection when inert polymers are used, have been investigated using X-ray photoelectron spectroscopy. Results indicate that exposure of polymer-modified electrodes to cold-plasma produces the formation of a large variety of reactive species adsorbed on the electrode surface, which catalyse the dopamine oxidation. With this technology, which is based on the application of a very simple physical functionalization, we have defined a paradox-based paradigm for the fabrication of electrochemical sensors by using inert and cheap plastics.
Rivas, M.; Franco, M.; del Valle, LJ.; Turon, P.; Aleman, C.; Puiggali, J. International Conference on Multifunctional, Hybrid and Nanomaterials p. P3-170 Data de presentació: 2017-03-06 Presentació treball a congrés
The influence of the preparation method in the properties of poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes used to manufacture organic energy storage devices, as for example supercapacitors, have been examined by considering a reduction of both monomer and supporting electrolyte concentrations during the anodic polymerization reaction. Thus, the excellent electrochemical properties of PEDOT films prepared using quiescent solutions have been preserved by applying controlled agitation to the polymerization process, even though the concentration of monomer and supporting electrolyte were reduced 5 and 2 times, respectively. For example, the charge stored for reversible exchange in a redox process, the electrochemical stability and the current productivity of films achieved using quiescent solutions have been preserved using a dynamic reaction medium in which the concentrations of monomer and supporting electrolyte are several times lower. The excellent properties of PEDOT electrodes prepared using optimized dynamic conditions have also been proved by constructing a symmetric supercapacitor. This energy storage device, which has been used as power source for a LED bulb, is rechargeable and exhibits higher charge-discharge capacities than supercapacitors prepared with electrodes derived from quiescent solutions. In addition of bring an efficacious procedure for preparing cost-effective PEDOT films with excellent properties, the proposed dynamic conditions reduce the environmental hazards of depleted reaction media.
Pérez-Madrigal, Maria M.; Edo, M.; Diaz, A.; Puiggali, J.; Aleman, C. Journal of Physical Chemistry C Vol. 121, num. 6, p. 3182-3193 DOI: 10.1021/acs.jpcc.6b10693 Data de publicació: 2017-02-16 Article en revista
Biosynthetic poly-¿-glutamic acid (¿-PGA) has been used to produce hydrogels using cystamine as cross-linker and 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide methiodide (EDC methiodide) as condensing agent. Eight different hydrogels with different properties were formulated by varying both the molecular weight of ¿-PGA and the ¿-PGA/EDC/cystamine ratio and subsequently characterized. The most appropriate ¿-PGA hydrogel was selected to perform as solid electrolytic medium in organic electrochemical supercapacitors (OESCs) using poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes based on their mechanical behavior (consistency and robustness to hold the PEDOT electrodes), morphology, and influence on the electrochemical response of the organic electrode (i.e., specific capacitance and both maximum energy and power density values). Hence, PEDOT/¿-PGA energy storage devices fabricated using the most adequate hydrogel formulation displayed a supercapacitor response of 168 F/g and a capacitance retention of 81%. Moreover, after evaluating the maximum energy and power densities (Ragone plot), cyclability, long-term stability, leakage current, and self-discharging response of PEDOT/¿-PGA OESC devices, results allow us to highlight the merits and great potential of ¿-PGA hydrogels as sustainable ion-conductive electrolytes for environmentally friendly energy storage technologies.
The conformational preferences of the Arg-GlE-Asp sequence, where GlE is an engineered amino acid bearing a 3,4-ethylenedioxythiophene (EDOT) ring as side group, have been determined combining density functional theory calculations with a well-established conformational search strategy. Although the Arg-GlE-Asp sequence was designed to prepare a conducting polymer–peptide conjugate with excellent electrochemical and bioadhesive properties, the behavior of such hybrid material as adhesive biointerface is improvable. Results obtained in this work prove that the bioactive characteristics of the parent Arg-Gly-Asp sequence become unstable in Arg-GlE-Asp because of both the steric hindrance caused by the EDOT side group and the repulsive interactions between the oxygen atoms belonging to the backbone amide groups and the EDOT side group. Detailed analyses of the conformational preferences identified in this work have been used to re-engineer the Arg-GlE-Asp sequence for the future development of a new electroactive conjugate with improved bioadhesive properties. The preparation of this new conjugate is in progress.
Armelin, E.; Whelan, R.; Martinez, Y.; Aleman, C.; Finn, M.; Díaz-Díaz, D. ACS applied materials and interfaces Vol. 9, num. 4, p. 4231-4243 DOI: 10.1021/acsami.6b14174 Data de publicació: 2017-02-01 Article en revista
Organic polymers are widely used as coatings and adhesives to metal surfaces, but aluminum is among the most difficult substrates because of rapid oxidative passivation of its surface. Poly(1,4-disubstituted 1,2,3-triazoles) made by copper-catalyzed azide–alkyne cycloaddition form strongly bonded interfaces with several metal substrates. In this work, a variety of alkyne and azide monomers were explored as precursors to anticorrosion coatings for a standard high-strength aluminum–copper alloy. Monomers of comparatively low valency (diazide and trialkyne) were found to act as superior barriers for electrolyte transfer to the aluminum surface. These materials showed excellent resistance to corrosive pitting due to the combination of three complementary properties: good formation of highly cross-linked films, as observed by Fourier transform infrared spectroscopy and differential scanning calorimetry; good adhesion to the aluminum alloy substrate, as shown by pull-off testing; and excellent impermeability, as demonstrated by electrochemical impedance spectroscopy.
Peptides homing tumor vasculature are considered promising molecular imaging agents for cancer detection at an early stage. In addition to their high binding affinity, improved tissue penetrating ability, and low immunogenicity, they can deliver targeted anticancer drugs, thus expanding therapeutic treatments. Among those, CREKA, a linear peptide that specifically binds to clotted-plasma proteins in tumor vessels, has been recently employed to design bioactive systems able to target different cancer types. Within this context, this paper explores the biorecognition event between CR(NMe)EKA, an engineered CREKA-analog bearing a noncoded amino acid (N-methyl-Glu) that is responsible for its enhanced activity, and clotted-plasma proteins (fibrin and fibrinogen) by nanomechanical detection. Specifically, the tumor-homing peptide was covalently attached via epoxysilane chemistry onto silicon microcantilever chips that acted as sensors during dynamic mode experiments. Before that, each step of the functionalization process was followed by contact angle measurements, interferometry, X-ray photoelectron spectroscopy, and atomic force microscopy, thus revealing the applied protocol as a suitable strategy. The fibrin(ogen)-binding induced by CR(NMe)EKA was detected by the resonance frequency shift of the cantilevers, and a detection limit of 100¿ng/mL was achieved for both proteins. Even though further development is required, this work reflects the promising application of emerging technologies capable of assisting in the comprehension of biological interactions and their implications in the biotechnological field.
Maione, S.; Pérez-Madrigal, M.M.; del Valle, LJ.; Diaz, A.; Catiavela, C.; Franco, M.; Puiggali, J.; Aleman, C. Journal of applied polymer science Vol. 134, num. 22 DOI: 10.1002/app.44883 Data de publicació: 2017 Article en revista
The encapsulation of amino acids (AAs) and their correct preservation before they are ingested are challenging tasks. Nonpolar (l-alanine and l-phenylalanine), polar (l-cysteine hydrochloride and l-asparagine), and charged (l-lysine hydrochloride and l-aspartic acid) AAs were loaded into biodegradable and nontoxic poly(tetramethylene succinate) (PE44) nanofibers (NFs) with electrospinning. The loading of AAs considerably affected the morphology, topography, thermal properties, and wettability of the PE44 NFs. Furthermore, although the AAs crystallized in a phase separated from the polymeric matrix, the distribution of such crystals changed into PE44 NFs and depended on their chemical nature. Release assays in enzyme-free solutions provided evidence that very significant amounts of AAs were retained in the NFs after 7 days, whereas assays in the lipase-containing solution (because lipase performs essential roles in the digestion) showed almost complete release after a few hours. Lipase preferentially attacked the PE44 regions responsible for the retention of AAs in the biphasic system and favored the almost immediate release of the biomolecules. The results displayed in this study, combined with the biocompatibility, biodegradability, and potential use of the PE44 NFs as edible nonnutritional elements, suggest that the loaded PE44–AA NFs could be used to supply essential and conditional AAs.
We report the noticeable control exerted by the surface in the self-assembly of a highly hydrophobic triphenylalanine peptide with fluorenyl functionalities blocking the two ends. The remarkable differences observed among the polymorphic hierarchical assemblies obtained onto silanized glass, scratched glass, stainless steel, exfoliated mica, silicon wafer, carbon, polytetrafluoroethylene, plasma-functionalized, polystyrene and nitrocellulose substrates are consequence of the balance between peptide···peptide and peptide···surface interactions. This balance is greatly influenced by the surface characteristics, as defined by the wettability (hydrophobicity or hydrophilicity) and roughness (degree of flatness and regularity). Furthermore, very stable dendritic structures, in which primary frameworks nucleated from the center grow according to a 4-fold pseudo-symmetry branching, have been obtained onto hydrophilic treated polystyrene.
Puiggali, A.; Pérez-Madrigal, M.M.; del Valle, LJ.; Armelin, E.; Casas, M.; Michaux, C.; Perpete, E.; Estrany, F.; Aleman, C. Nanoscale Vol. 8, num. 38, p. 16922-16935 DOI: 10.1039/c6nr04948f Data de publicació: 2016-10-14 Article en revista
Bioinspired free-standing nanomembranes (FSNMs) for selective ion transport have been tailored by immobilizing the Omp2a ß-barrel membrane protein inside nanoperforations created in flexible poly(lactic acid) (PLA) nanomembranes. Perforated PLA FSNMs have been prepared by spin-coating a 99 : 1 PLA : poly(vinyl alcohol) mixture, and through a phase segregation process nanofeatures with dimensions similar to the entire nanomembrane thickness (~110 nm) were induced. These nanofeatures have subsequently been transformed into nanoperforations (diameter: ~51 nm) by selective solvent etching. The protein confined inside the nanopores of PLA FSNMs preserves the ß-barrel structure and organizes in ovoid aggregates. The transport properties of Na+, K+, and Ca2+ across non-perforated PLA, nanoperforated PLA, and Omp2a-filled nanoperforated PLA have been monitored by measuring the nanomembrane resistance with electrochemical impedance spectroscopy (EIS). The incorporation of nanoperforations enhances the transport of ions across PLA nanomembranes, whereas the functionality of immobilized Omp2a is essential to exhibit effects similar to those observed in biological nanomembranes. Indeed, Omp2a-filled nanoperforated PLA nanomembranes exhibit stronger affinity towards Na+ and Ca2+ ions than towards K+. In summary, this work provides a novel bioinspired strategy to develop mechanically stable and flexible FSNMs with channels for ion transport, which are precisely located inside artificial nanoperforations, thus holding great potential for applications in biofiltration and biosensing
The properties as biointerfaces of electroactive conducting polymer–peptide biocomposites formed by poly(3,4-ethylenedioxythiophene) (PEDOT) and CREKA or CR(NMe)EKA peptide sequences (where Glu has been replaced by N-methyl-Glu in the latter) have been compared. CREKA is a linear pentapeptide that recognizes clotted plasma proteins and selectively homes to tumors, while CR(NMe)EKA is an engineer to improve such properties by altering peptide–fibrin interactions. Differences between PEDOT-CREKA and PEDOT-CR(NMe)EKA reflect dissemblance in the organization of the peptides into the polymeric matrix. Both peptides affect fibrinogen thrombin-catalyzed polymerization causing the immediate formation of fibrin, whereas in the absence of thrombin this phenomenon is only observed for CR(NMe)EKA. Consistently, the fibrin-adsorption capacity is higher for PEDOT-CR(NMe)EKA than for PEDOT-CREKA, even though in both cases adsorbed fibrin exhibits round-like morphologies rather than the characteristic fibrous structure. PEDOT-peptide films coated with fibrin are selective in terms of cell adhesion, promoting the attachment of metastatic cells with respect to normal cells.
The properties as biointerfaces of electroactive conducting polymer-peptide biocomposites formed by poly(3,4-ethylenedioxythiophene) (PEDOT) and CREKA or CR(NMe)EKA peptide sequences (where Glu has been replaced by N-methyl-Glu in the latter) have been compared. CREKA is a linear pentapeptide that recognizes clotted plasma proteins and selectively homes to tumors, while CR(NMe)EKA is an engineer to improve such properties by altering peptide-fibrin interactions. Differences between PEDOT-CREKA and PEDOT-CR(NMe)EKA reflect dissemblance in the organization of the peptides into the polymeric matrix. Both peptides affect fibrinogen thrombin-catalyzed polymerization causing the immediate formation of fibrin, whereas in the absence of thrombin this phenomenon is only observed for CR(NMe)EKA. Consistently, the fibrin-adsorption capacity is higher for PEDOT-CR(NMe)EKA than for PEDOT-CREKA, even though in both cases adsorbed fibrin exhibits round-like morphologies rather than the characteristic fibrous structure. PEDOT-peptide films coated with fibrin are selective in terms of cell adhesion, promoting the attachment of metastatic cells with respect to normal cells.
Pérez-Madrigal, Maria M.; Ochoa, D. A.; Garcia, J. E.; Armelin, E.; Aleman, C. Journal of polymer science. Part B, polymer physics Vol. 54, num. 18, p. 1896-1905 DOI: 10.1002/polb.24095 Data de publicació: 2016-09-15 Article en revista
Dielectric elastomer actuators (DEAs) transform electrical energy into mechanical work. However, despite displaying exceptional features, the low permittivity of elastomers restricts their application. Hence, to overcome this limitation, DEAs are fabricated by dispersing poly(3-methylthiophene acetate) (P3TMA), a polarizable conducting polymer, into poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS), a thermoplastic elastomer with excellent mechanical properties. Although high-quality SEBS:P3TMA films are obtained for all compositions (between 0.5 and 20 wt % P3TMA), their thickness and surface roughness increase with the nano-sized filler content. Moreover, the conducting particles are well integrated into the SEBS network with no evidence of aggregation or significant change in the mechanical properties of the composites. P3TMA, which forms encapsulated conductive domains within the polymeric matrix, improves the dielectric behavior of SEBS:P3TMA by increasing their dielectric constant with low dielectric losses and no current leakage. Thus, indicating the potential future application of these nanocomposites as elastomer actuators or high energy density capacitors.
The structural and electronic properties of all-thiophene dendrimers and dendrons in solution have been evaluated using very different theoretical approaches based on quantum mechanical (QM) and hybrid QM/molecular mechanics (MM) methodologies: (i) calculations on minimum energy conformations using an implicit solvation model in combination with density functional theory (DFT) or time-dependent DFT (TD-DFT) methods; (ii) hybrid QM/MM calculations, in which the solute and solvent molecules are represented at the DFT level as point charges, respectively, on snapshots extracted from classical molecular dynamics (MD) simulations using explicit solvent molecules, and (iii) QM/MM-MD trajectories in which the solute is described at the DFT or TD-DFT level and the explicit solvent molecules are represented using classical force-fields. Calculations have been performed in dichloromethane, tetrahydrofuran and dimethylformamide. A comparison of the results obtained using the different approaches with the available experimental data indicates that the incorporation of effects associated with both the conformational dynamics of the dendrimer and the explicit solvent molecules is strictly necessary to satisfactorily reproduce the properties of the investigated systems. Accordingly, QM/MM-MD simulations are able to capture such effects providing a reliable description of electronic properties–conformational flexibility relationships in all-Th dendrimers.
Estrany, F.; Sanchez, M.; Borras, N.; Aleman, C.; Saborío, M. Reunión del Grupo de Electroquímica de la Real Sociedad Española de Química p. 112 Data de presentació: 2016-07-18 Presentació treball a congrés
Activación de la capacitancia de films de PEDOT por adición de nanopartículas de alúmina
Se han preparado nanocomposites de partículas de alúmina dispersa en una matriz de PEDOT electrogenerado sobre electrodo de acero a partir del monómero (3,4-etilendioxitiofeno ó EDOT) en medio acuoso con una suspensión partículas de alúmina, empleando LiClO4 como dopante. Se han generado capas simples y tricapas de PEDOT de microespesor, tanto puro como en forma de nanocomposite a partir de medios de EDOT y partículas de Al2O3 en proporciones 1:1 y 4:1, respectivamente.
Se ha verificado el comportamiento electroquímico (VC y carga-descarga galvanostática) de los films de composites obtenidos, así como la morfología superficial a micro- y a nano- escala con las técnicas SEM y AFM.
Los films de nanocomposites PEDOT/Al2O3 tienen una capacitancia específica mucho mayor que la de los de PEDOT puro, de forma similar a los films de nanocomposites de PEDOT/montmorillonita preparados en un trabajo anterior .
Es destacable que el mayor incremento de capacitancia específica se da en los nanocomposites generados con la menor proporción de partículas de alúmina, revelando que existe una composición óptima que maximiza la capacidad de almacenamiento de carga del film. El resultado es coherente con la morfología superficial de los films observada a micro- y nanoescala, que es más abierta (y por tanto permite una mayor movilidad interfacial de los iones) en el caso de los nanocomposites preparados a partir de la proporción. 4:1 EDOT/Al2O3.
Los autores agradecen al MCI, la financiación obtenida del Proyecto: MAT2012-34498.
 D. Aradilla, F Estrany, D. S. Azambuja et al. Eur. Polym. J. 46 (2010). 977-983.
Estrany, F.; Sanchez, M.; Borras, N.; Aleman, C.; Saborío, M. Reunión del Grupo de Electroquímica de la Real Sociedad Española de Química p. 116 Data de presentació: 2016-07-18 Presentació treball a congrés
Estudio de un sistema de tres capas de polímero conductor
para aplicaciones en baterías orgánicas
El propósito primordial de este proyecto, es el desarrollo de una batería orgánica usando electrodos de tres capas de polímeros conductores. Los monómeros de partida son el 3,4-polietilendioxitiofeno (EDOT) y el N-metilpirrol (NMPy), y cada capa de polímero se ha sintetizado sobre electrodo de acero inoxidable por electrodeposición cronoamperométrica, a 1,40 V, a partir de una disolución 10mM de cada monómero con 0,1 M de LiClO4 como electrolito. Se obtiene una estructura dopada, en general mucho más conductora que el polímero neutro.
Se han preparado films de PEDOT y de PNMPy puros, y también se ha ensayado la
preparación electroquímica del copolímero PEDOT/PNMPy. El PEDOT tiene una conductividad mucho mayor (con gran diferencia) que el PNMPy y que el copolímero, lo que nos ha llevó a proponer la estructura de un capacitor plano de dos capas-armaduras exteriores de PEDOT (como conductor) y una capa intermedia de PNMPy, o bien de copolímero (con la función de pseudo-dieléctrico), para obtener electrodos de gran capacidad redox de almacenamiento de carga.
Se prepararon baterías en forma de celdas galvánicas con electrodos tricapa, y se realizó el seguimiento de la fuerza electromotriz entre electrodos y la intensidad de corriente que atraviesa la celda, calculando también la potencia del sistema. Estas variables fueron estudiadas en circuito cerrado, siguiendo varios ciclos de carga y descarga electródica.
El estudio se complementó con el efecto del grosor de cada una de las tres capas de
los diferentes films, que conformaron la batería. Se estudió el efecto del puente salino y se varió el voltaje aplicado por la fuente de alimentación.
Se estudió la respuesta de los electrodos tricapa ante ciclos redox consecutivos en
celda de control, así como al someterlos a corriente constante a diferentes tiempos. Finamente se realizó también el estudio de su micro- y nanomorfología superficial mediante la técnica AFM.
Como conclusión es destacable la interesante respuesta eléctrica de la arriba indicada estructura tricapa tipo capacitor plano (armaduras conductoras – intermedio pseudodieléctrico).
Revilla-López, G.; Bertran, O.; Casanovas Salas, Jordi; Turon, P.; Puiggali, J.; Aleman, C. RSC advances Vol. 6, p. 69634-69640 DOI: 10.1039/c6ra10660a Data de publicació: 2016-07-13 Article en revista
Advanced Molecular Dynamics (MD) simulation protocols have been used to assess the ring puckering of cyclic D-ribose when the sugar is adsorbed on the most stable (0001) facet of calcium hydroxyapatite (HAp). In addition, sugar¿mineral interactions, which are crucial for transfection processes and prebiotic chemistry, have been studied for systems in which the Ca2+ ions of the above mentioned HAp facet were totally or partially replaced by Mg2+. The latter replacement is spatially and quantitatively limited and has been found to cause important alterations in the conformational behavior of D-ribose that are similar to those suffered in hairpin RNA from A to B helical structures. Accordingly, replacement of Ca2+ by Mg2+ has a dramatic effect on the functionality of the nucleic acid. These changes have been related to both the substitution site on the surface and the amount of ions. Our results show that when replacement by Mg2+ occurs in OH--coordinated Ca2+ ions, Mg2+¿D-ribose interactions are strong enough to prevent the interactions between the hydroxyl groups of the sugar and the remaining Ca2+ ions.
Electrochemical detection of glucose using simple polymeric electrodes without the assistance of enzymatic or inorganic catalysts (i.e. metals or metal oxides) has been issued a challenge to the scientific community. In this work we present the development of a potentiometric glucose sensor based on nanometric films of a very electroactive polythiophene derivative bearing a hydroxyl substituent per repeat unit. The sensor, which is enzyme free and does not require from additional catalytic nanoparticles, exhibits excellent tolerance against interferents, a low detection limit, and a deviation lower than 2% with respect to measures in human blood samples with commercial sensors. The excellent response of this highly electroactive polythiophene derivative, which exhibits a very simple chemical structure, has been attributed to the closeness between the hydroxyl substituents and the aromatic groups contained in the linear and rigid backbone. This particular chemical distribution favors the activation of the hydroxyl substituents, inducing their participation in the oxidation of glucose molecules. (C) 2016 Elsevier Ltd. All rights reserved.
Progress in the chemical sciences has formed the world we live in, both on a macroscopic and on a nanoscopic scale. The last decade witnessed the development of high performance materials that storage charge on many ways, from solar cells to fuel cells, from batteries to supercapacitors devices. One could argue that inorganic hybrid materials have played a central, starring role for the assemble of various electrochemical energy conversion systems. However, energy conversion systems fabricated from biopolymers has just emerged as new prospect. Here we summarize the main research highlights on the attactive employment of bio-hydrogels for the fabrication of either conductive electrolytes or electrodes for battery science and technology.
Electrocompatible interfaces formed by electroactive conducting polymers combined with biohydrogels towards sustainable solid-state supercapacitors
Maria M. Pérez-Madrigal,1,2,3 Francesc Estrany,3,4 Elaine Armelin,1,2,3 David Diaz-Diaz,1,* and Carlos Alemán2,3,*
1 Institut für Organische Chemie Fakultät für Chemie und Pharmazie Universität Regensburg Universitätsstr. 31 , 93053 Regensburg , Germany
2 Departament d’Enginyeria Química, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, Barcelona E-08028, Spain
3 Center for Research in Nano-Engineering, Universitat Politècnica de Catalunya, Campus Sud, Edifici C’, C/Pasqual i Vila s/n, Barcelona E-08028, Spain
4 Departament d’Enginyeria Química, Escola Universitària d’Enginyeria Tècnica Industrial de Barcelona, Universitat Politècnica de Catalunya, Comte d’Urgell 187, 08036 Barcelona, Spain
* firstname.lastname@example.org and email@example.com
Electro compatible interfaces have been prepared with films of poly (3,4-ethylenedioxythiophene) (PEDOT) and biohidrogel, in order to prepare organic solid state electrochemical supercapacitors (OESCs). The electroactive surface of the conductive polymer film acts as an electrode and electrolyte biohidrogel acts as electron transfer, It has tried several hydrogels based on biomolecules (sodium alginate, ¿-carrageenan, chitosan and gelatin biohydrogels). In addition to performing tests morphological characterization by SEM microscopy, the degree of electrocompatibilidad of the prepared interface is characterized by assessing their electrical response to electrochemical techniques (Cyclic voltammetry and galvanostatic charge-discharge Assays), and the results have revealed that biohidrogel obtained based ¿-carrageenan is the most appropriate, because as the highest specific capacity and the highest electroestabilidad to consecutive redox cycles, added to a small leakage current and low self-discharging tendency. Good electrochemical results described, together with this biohidrogel has a good mechanical stability, is easy to prepare and no water loss, has become the ¿-carrageenan the best candidate for preparing OESCs. Based on these good properties, four OESC devices were connected in series and used to power on a red LED (Fig. 1), confirming that the system has clear expectations of being constitute a direct practical application.
Finally, it was tested adding polyaniline nanofibers dispersed in the matrix of biohidrogel, determining that the dispersed polyaniline is a redox additive which interacts with biomolecules to form the biohidrogel and changes the electrical response of the system. This allows to consider the improvement of future OESCs design with the ability to modulate the speed of charge and discharge of the device, using different concentrations of dispersed polyaniline.
Fig. 1. - LED powered using the system described
Authors are indebted to supports from MICINN and FEDER (MAT2012-34498)
After exhibiting the important limitations of the template-assisted approach when electropolymerization on simple stainless steel electrodes and electrospinning of insulating polymeric templates are combined, hollow poly(3,4-ethylenedioxythiophene) (PEDOT) nano- and microtubes have been successfully prepared using an alternative approach. In this procedure, which is based on a two-step electropolymerization process, electrospun fibers are collected onto a relatively flat PEDOT film that plays a crucial role in complete coating of the template in the second electropolymerization process. Once the insulating fiber templates have been eliminated by solvent etching, the ability to exchange charge reversibly of the resulting hollow tubes is very similar to that observed for films while the amount of the electroactive surface is noticeably higher. The diameter and density of hollow tubes can be easily controlled through this multistep template-assisted approach, allowing to collect such PEDOT structures onto simple steel electrodes. The multi-step strategy overcomes the limitations of the conventional approach, which was restricted to the use of neural electrode sites and restricted to applications related with neural prostheses, opening the door to the use of PEDOT hollow nano- and microtubes in many important applications, as for example the detection of biomolecules and the fabrication of organic and bio-organic batteries.
Gstrein, C.; Zhang , B.; Abdel-Rahman, M.A; Bertran, O.; Aleman, C.; Wegner, G.; Schlüter, A. Chemical Science num. 7, p. 4644-4652 DOI: 10.1039/c5sc04609b Data de publicació: 2016-04-06 Article en revista
Two series of dendronized polymers (DPs) of generations g=1-4 with different levels of dendritic substitution (low and high) and a solvatochromic probe at g=1 level are used to study their swelling behavior in a collection of solvents largely differing in polarity as indicated by the Kamlet-Taft parameters. This is done by measuring the UV-Vis spectra of all samples in all solvents and determining the longest wavelength absorptions (¿max). The ¿max values fall into a range defined by the extreme situations, when the solvatochromic probe is either fully surrounded by solvent or completely shielded against it. The former situation is achieved in a model compound and the latter situation is believed to be reached when in a poor solvent the dendritic shell around the backbones is fully collapsed. We observe that solvent penetration into the interior of the DPs decreases with increasing g and does so faster for the more highly dendritically substituted series than for the less highly substituted one. Interestingly, the swelling of the more highly substituted DP series already at the g=4 level has decreased to approximately 20% of that at the g=1 level which supports an earlier proposal that high g DPs can be viewed as nano-sized molecular objects. Furthermore, when comparing these two DP series with a g=1-6 series of dendrimers investigated by Fréchet et al. it becomes evident that even the less substituted series of DPs is much less responsive to solvent changes that are assessed by the solvatochromic probe than the dendrimers, suggesting the branches around the (polymeric) core in DPs to be more densely packed compared to those in dendrimers, thus, establishing a key difference between these two dendritic macromolecules.
Bertran, O.; Revilla-López, G.; Casanovas Salas, Jordi; del Valle, LJ.; Turon, P.; Puiggali, J.; Aleman, C. Chemistry: a european journal Vol. 22, num. 19, p. 6631-6636 DOI: 10.1002/chem.201600703 Data de publicació: 2016-04-01 Article en revista
In spite of the clinical importance of hydroxyapatite (HAp), the mechanism that controls its dissolution in acidic environments remains unclear. Knowledge of such a process is highly desirable to provide better understanding of different pathologies, as for example osteoporosis, and of the HAp potential as vehicle for gene delivery to replace damaged DNA. In this work, the mechanism of dissolution in acid conditions of HAp nanoparticles encapsulating double-stranded DNA has been investigated at the atomistic level using computer simulations. For this purpose, four consecutive (multi-step) molecular dynamics simulations, involving different temperatures and proton transfer processes, have been carried out. Results are consistent with a polynuclear decalcification mechanism in which proton transfer processes, from the surface to the internal regions of the particle, play a crucial role. In addition, the DNA remains protected by the mineral mold and transferred proton from both temperature and chemicals. These results, which indicate that biomineralization imparts very effective protection to DNA, also have important implications in other biomedical fields, as for example in the design of artificial bones or in the fight against osteoporosis by promoting the fixation of Ca2+ ions.
Pérez-Madrigal, M.M.; Llorens, E.; del Valle, LJ.; Puiggali, J.; Armelin, E.; Aleman, C. Express polymer letters Vol. 10, num. 8, p. 628-646 DOI: 10.3144/expresspolymlett.2016.58 Data de publicació: 2016-02-25 Article en revista
Nanoperforated poly(lactic acid) (PLA) free-standing nanomembranes (FsNMs) have been prepared using a two-step process: (1) spin-coating a mixture of immiscible polymers to provoke phase segregation and formation of appropriated nanofeatures (i.e. phase separation domains with dimensions similar to the entire film thickness); and (2) selective solvent etching to transform such nanofeatures into nanoperforations. For this purpose, PLA has been mixed with polyethylene glycol (PEG) and poly(vinyl alcohol) (PVA). Unfortunately, the characteristics of PLA:PEG mixtures were not appropriated to prepare nanoperforated FsNMs. In contrast, perforated PLA FsNMs with pores crossing the entire film thickness, which have been characterized by scanning electron microscopy and atomic force microscopy, were obtained using PLA:PVA mixtures. The diameter (¿) of such pores has been controlled through both the PLA:PVA ratio and the processing conditions of the mixtures, FsNMs with pores of ¿ ˜ 0.8 µm, 170 nm and 65 nm being achieved. Investigations on nanoperforated FsNMs (i.e. those with ¿ ˜ 170 and 65 nm), which are the more regular, reveal that pores crossing the entire membrane thickness do not affect the surface wettability of PLA but drastically enhances the cellular response of this biomaterial. Thus, cell proliferation assays indicate that cell viability in PLA with perforations of ¿ ˜ 170 nm is ~2.6 and ~2.2 higher than in non-perforated PLA and PLA with perforations of ¿ ˜ 65 nm, respectively. This excellent response has been attributed to the similarity between the nanoperforations with ¿ ˜ 170 nm and the filopodia filaments in cells (¿ ˜ 100–200 nm), which play a crucial role in cell migration processes. The favorable interaction between the perforated membrane nanofeatures and cell filopodia has been corroborated by optical and scanning electron microscopies.
En esta tesis doctoral se propone una metodología para el control de la calidad durante el proceso de fabricación de una estructura de plástico reforzado con fibra de vidrio, utilizando el método de ensayo no destructivo de los ultrasonidos mediante impulso-eco y ondas longitudinales por contacto directo.La metodología que se presenta se basa en la monitorización en tiempo real de la evolución de la señal ultrasónica reflejada durante el proceso de curado- maduración de un laminado de resina de poliéster reforzada con fibra de vidrio (PRFV), que es con diferencia el materialmás ampliamente utilizado en la construcción de cascos de embarcaciones de la náutica de recreo y gran parte de la flota pesquera. Un posterior procesamiento de los datos registrados en continuo durante un período de 15 días, han permitido representar la evolución de la amplitud de la señal o eco de fondo en función del tiempo, obteniéndose de esta forma una curva sigmoide patrón característica delproceso de fabricación que puede utilizarse como indicador cualitativo del grado de curado maduración del laminado.Simultáneamente a la medición ultrasónica, se han real zado ensayos de dureza Barco!, en probetas fabricadas en series homólogas , observándose una similitud entre las curvas obtenidas por ultrasonidos y las de dureza, donde los valores de amplitud de la señal ultrasónica y los datos de dureza registrados van en aumento según evoluciona el proceso de maduración. Finalmente se ajusta matemáticamente la curva ultrasónica obtenida.Por su versatilidad, su naturaleza no destructiva niintrusiva del sensor y la posibilidad de utilizar un equipo convencional de ultrasonidos junto a la gran disponibilidad de palpadores comerciales existentes actualmente en el mercado, la metodología propuesta puede facilitar en gran medida la inspección en el proceso de fabricación de embarcaciones.
In this PhD thesis a methodology for the quality control of reinforced fiberglass plastic manufacturing process is proposed. The system is based on the ultrasonic pulse-echo nondestructive method and longitudinal waves on direct contact.
The presented methodology is based on the in-line monitoring of the reflected ultrasonic signal during the laminate curing of the polyester resin reinforced with fiber glass, which is the most widely used material in the construction of pleasure boat hulls and fishing fleet. Further data processing over a period of fifteen days has allowed the representation of the ultrasonic amplitude from the back-wall echo on a function of time, obtaining in this way the characteristic sigmoid curve of growth and maturation of the tested material.
Simultaneously to the ultrasonic measurements, a hardness measurements (Barcol test) have been performed on a series of homologous manufactured samples. A relation between the ultrasonic curing curve and the hardness curve has been obtained where the ultrasonic amplitude and the hardness measurements increases by the days. A final mathematical fitting has been applied.
Due to its versatility, its nondestructive nature and the property of the transducers of being non-invasive in addition to the possibility to use a standard ultrasonic equipment together with a broad selection of existing transducers, this methodology might help to the inspection of the boat building process.
En esta tesis doctoral se propone una metodología para el control de la calidad durante el proceso de fabricación de una estructura de plástico reforzado con fibra de vidrio, utilizando el método de ensayo no destructivo de los ultrasonidos mediante impulso-eco y ondas longitudinales por contacto directo.
La metodología que se presenta se basa en la monitorización en tiempo real de la evolución de la señal ultrasónica reflejada durante el proceso de curado- maduración de un laminado de resina de poliéster reforzada con fibra de vidrio (PRFV), que es con diferencia el material más ampliamente utilizado en la construcción de cascos de embarcaciones de la náutica de recreo y gran parte de la flota pesquera. Un posterior procesamiento de los datos registrados en continuo durante un período de 15 días, han permitido representar la evolución de la amplitud de la señal o eco de fondo en función del tiempo, obteniéndose de esta forma una curva sigmoide patrón característica del proceso de fabricación que puede utilizarse como indicador cualitativo del grado de curado-maduración del laminado.
Simultáneamente a la medición ultrasónica, se han realizado ensayos de dureza Barcol, en probetas fabricadas en series homólogas, observándose una similitud entre las curvas obtenidas por ultrasonidos y las de dureza, donde los valores de amplitud de la señal ultrasónica y los datos de dureza registrados van en aumento según evoluciona el proceso de maduración. Finalmente se ajusta matemáticamente la curva ultrasónica obtenida. Por su versatilidad, su naturaleza no destructiva ni intrusiva del sensor y la posibilidad de utilizar un equipo convencional de
ultrasonidos junto a la gran disponibilidad de palpadores comerciales existentes actualmente en el mercado, la metodología propuesta puede facilitar en gran medida la inspección en el proceso de fabricación de embarcaciones.
We describe the 3D supramolecular structure of Fmoc–RGDS fibrils, where Fmoc and RGDS refer to the hydrophobic N-(fluorenyl-9-methoxycarbonyl) group and the hydrophilic Arg-Gly-Asp-Ser peptide sequence, respectively. For this purpose, we performed atomistic all-atom molecular dynamics simulations of a wide variety of packing modes derived from both parallel and antiparallel ß-sheet configurations. The proposed model, which closely resembles the cross-ß core structure of amyloids, is stabilized by p–p stacking interactions between hydrophobic Fmoc groups. More specifically, in this organization, the Fmoc-groups of ß-strands belonging to the same ß-sheet form columns of p-stacked aromatic rings arranged in a parallel fashion. Eight of such columns pack laterally forming a compact and dense hydrophobic core, in which two central columns are surrounded by three adjacent columns on each side. In addition to such Fmoc¿Fmoc interactions, the hierarchical assembly of the constituent ß-strands involves a rich variety of intra- and inter-strand interactions. Accordingly, hydrogen bonding, salt bridges and p–p stacking interactions coexist in the highly ordered packing network proposed for the Fmoc–RGDS amphiphile. Quantum mechanical calculations, which have been performed to quantify the above referred interactions, confirm the decisive role played by the p–p stacking interactions between the rings of the Fmoc groups, even though both inter-strand and intra-strand hydrogen bonds and salt bridges also play a non-negligible role. Overall, these results provide a solid reference to complement the available experimental data, which are not precise enough to determine the fibril structure, and reconcile previous independent observations.
Pérez-Madrigal, M.M.; Estrany, F.; Armelin, E.; Díaz-Díaz, D.; Aleman, C. Journal of materials chemistry A Vol. 4, num. 5, p. 1792-1805 DOI: 10.1039/c5ta08680a Data de publicació: 2016-01-04 Article en revista
Solid-state organic electrochemical supercapacitors (OESCs) have been fabricated using poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes, a biohydrogel as electrolyte system, and polyaniline fibers as redox additive. The effectivity of sodium alginate, kappa-carrageenan, chitosan and gelatin hydrogels as electrolytic media has been evaluated considering different criteria. Results indicate that kappa-carrageenan-based hydrogel is the most suitable to perform as electrolyte due to the appropriate combination of properties: mechanical stability, ease of preparation, lack of water leaking, and good medium for the electrochemical response of PEDOT electrodes. Cyclic voltammetry and galvanostatic charge-discharge assays indicate that OESCs based on PEDOT electrodes and kappa-carrageenan hydrogel as electrolyte exhibits a good supercapacitor response in terms of specific capacitance, cycling stability, small leakage current and low self-discharging tendency. On the basis of these good properties, four OESC devices were assembled in series and used to power a red LED, confirming that, in addition to advantageous characteristics (e.g. elimination of liquid leaking and enhancement of the device compactness), the designed biohydrogel-containing OESC exhibits potential for practical applications. On the other hand, preliminary assays have been performed loading the kappa-carrageenan hydrogel with polyaniline nanofibers, which act as a redox additive. OESC devices prepared using such loaded biohydrogel have been found to be very promising and, therefore, future work is oriented towards the improvement of their design.
Schiller, J.; Alegre-Requena, J.; Herrera, R.; Casanovas Salas, Jordi; Aleman, C.; Díaz-Díaz, D. Soft matter Vol. 12, num. 19, p. 4361-4374 DOI: 10.1039/c5sm02997j Data de publicació: 2016 Article en revista
Chiral N, N'-disubstituted squaramide 1 has been found to undergo self-assembly in a variety of alcoholic solvents at low concentrations leading to the formation of novel nanostructured supramolecular alcogels. The gels responded to thermal, mechanical, optical and chemical stimuli. Solubility studies, gelation ability tests and computer modeling of a series of structurally related squaramides proved the existence of a unique combination of non-covalent molecular interactions and favorable hydrophobic/hydrophilic balance in 1 that drive the anisotropic growth of alcogel networks. The results have also revealed a remarkable effect of ultrasound on both the gelation kinetics and the properties of the alcogels.
Maione, S.; del Valle, LJ.; Pérez-Madrigal, Maria M.; Cativiela, C.; Puiggali, J.; Aleman, C. RSC advances Vol. 6, num. 77, p. 73045-73055 DOI: 10.1039/c6ra11056h Data de publicació: 2016 Article en revista
Gramicidin (GA), a very hydrophobic pentadecapeptide with important biological activities (i.e. in addition to its well-known antimicrobial and antibiotic activities, GA has been recently identified as a potent therapeutic agent against different carcinomas), has been loaded by electrospraying in poly(tetramethylene succinate) (PE44), a biodegradable and biocompatible aliphatic polyester. Microspheres (average diameter: 5.0 +/- 0.7 mm) were successfully obtained from the mixture of GA and PE44 solutions in ethanol and chloroform, respectively. The loading of the peptide, which has been proved by FTIR and X-ray photoelectron spectroscopies, essentially occurred at the surface of the microspheres, as was reflected by scanning electron microscopy micrographs and atomic force microscopy phase images. In spite of this, the thermal stability of the polyester matrix remained essentially unaltered, even though the wettability decreased. The release of GA in phosphate buffer saline (PBS) was limited by the very low solubility of the peptide in aqueous solution, a fast burst effect followed by the establishment of equilibrium after 5 days of being observed in this hydrophilic environment. The release behaviour was very different when the hydrophilicity of the medium was reduced by adding ethanol. In this case, a very fast but sustained release was identified during the first few hours. On the other hand, biological tests have demonstrated that GA retains its antimicrobial activity after loading and does not alter the biocompatibility of PE44. Our results prove that, despite its hydrophobicity and relatively large number of residues, the loading of GA in a polymeric matrix represents an alternative strategy for the release of this versatile peptide in cancer therapy.
Mayans, E.; Ballano, G.; Casanovas, J.; del Valle, LJ.; Pérez-Madrigal, Maria M.; Estrany, F.; Jimenez, A.; Puiggali, J.; Cativiela, C.; Aleman, C. Soft matter Vol. 12, num. 24, p. 5475-5488 DOI: 10.1039/c6sm00337k Data de publicació: 2016 Article en revista
Homopeptides with 2, 3 and 4 phenylalanine (Phe) residues and capped with fluorenylmethoxycarbonyl and fluorenylmethyl esters at the N-terminus and C-terminus, respectively, have been synthesized to examine their self-assembly capabilities. Depending on the conditions, the di-and triphenylalanine derivatives self-organize into a wide variety of stable polymorphic structures, which have been characterized: stacked braids, doughnut-like shapes, bundled arrays of nanotubes, corkscrew-like shapes and spherulitic microstructures. These highly aromatic Phe-based peptides also form incipient branched dendritic microstructures, even though they are highly unstable, making their manipulation very difficult. Conversely, the tetraphenylalanine derivative spontaneously self-assembles into stable dendritic microarchitectures made of branches growing from nucleated primary frameworks. The fractal dimension of these microstructures is similar to 1.70, which provides evidence for self-similarity and two-dimensional diffusion controlled growth. DFT calculations at the M06L/6-31G(d) level have been carried out on model beta-sheets since this is the most elementary building block of Phe-based peptide polymorphs. The results indicate that the antiparallel beta-sheet is more stable than the parallel one, with the difference between them growing with the number of Phe residues. Thus, the cooperative effects associated with the antiparallel disposition become more favorable when the number of Phe residues increases from 2 to 4, while those of the parallel disposition remained practically constant.
In recent years, significant research has aimed at developing environmentally friendly supercapacitors by introducing biopolymeric materials, such as polysaccharides or proteins. In addition to the sustainability and recyclability of such novel energy storage devices, these polymers also provide flexibility, lightweight nature and stable cycling performance, which are of tremendous importance for applications related to wearable electronics. Among the different sustainable natural polymers, cellulose deserves special consideration since it is the most abundant and is extensively recycled. Consequently, research on electrically active cellulose-based supercapacitors has noticeably increased since 2012, which makes this review on the field timely. Specifically, recent advances in preparing high performance cellulose supercapacitors are summarized. Moreover, the key roles of cellulose in improving the specific capacitance and cycling stability of cellulose-based devices are compiled to offer important fundamental guidelines for designing the next generation of all-cellulose energy storage devices that are to come. Finally, challenges and perspectives in this exciting area of study are also discussed.