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"This is the peer reviewed version of the following article: Buendía JJ, Fabregat G, Castedo A, Llorca J, Alemán C. Plasma-treated polyethylene as electrochemical mediator for enzymatic glucose sensors: Toward bifunctional glucose and dopamine sensors. Plasma Process Polym. 2017;e1700133, which has been published in final form at https://doi.org/10.1002/ppap.201700133. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving, The application of inert and insulating low density polyethylene (LDPE) in electrochemical detection is null. However, in a recent study it was found that reactive species formed onto the surface of plasma-treated LDPE and other polymers promote the electrocatalytic oxidation of dopamine. In this work, we examine the role of plasma-treated LDPE as mediator in enzymatic glucose biosensors based on Glucose oxidase and glass carbon substrate. Results indicate that plasma-induced changes facilitate the electrocommunication between the enzyme and the substrate. The chronoamperometric response of these sensors prove their bifunctionality since the oxidation of glucose to gluconolactone, which is catalyzed by the GOx, coexists with the oxidation of dopamine that is electrocatalytized by the plasma activated LDPE surface., Peer Reviewed, Postprint (author's final draft)

The industrial process of nitrogen fixation is complex and results in a huge economic and environmental impact. It requires a catalyst and high temperature and pressure to induce the rupture of the strong N–N bond and subsequent hydrogenation. On the other hand, carbon dioxide removal from the atmosphere has become a priority objective due to the high amount of global carbon dioxide emissions (i.e. 36 200 million tons in 2015). In this work, we fix nitrogen from N2 and carbon from CO2 and CH4 to obtain both glycine and alanine (D/L racemic mixture), the two simplest amino acids. The synthesis, catalyzed by polarized hydroxyapatite under UV light irradiation and conducted in an inert reaction chamber, starts from a simple gas mixture containing N2, CO2, CH4 and H2O and uses mild reaction conditions. At atmospheric pressure and 95 °C, the glycine and alanine molar yields with respect to CH4 or CO2 are about 1.9% and 1.6%, respectively, but they grow to 3.4% and 2.4%, when the pressure increases to 6 bar and the temperature is maintained at 95 °C. Besides, the minimum temperature required for the successful production of detectable amounts of amino acids is 75 °C. Accordingly, an artificial photosynthetic process has been developed by using an electrophotocatalyst based on hydroxyapatite thermally and electrically stimulated and coated with zirconyl chloride and a phosphonate. The synthesis of amino acids by direct fixation of nitrogen and carbon from gas mixtures opens new avenues regarding the nitrogen fixation for industrial purposes and the recycling of carbon dioxide., Peer Reviewed, Postprint (published version)

QM/MM molecular dynamics simulations on the 4His-DC* protein cage have been performed using multiple active zones (up to 86 quantum regions). The regulation and nanocage stability exerted by the divalent transitionmetal ions in the monomer-to-cage conversion have been understood by comparing high level quantum trajectories obtained using Cu2+ and Ni2+ coordination ions., Peer Reviewed, Postprint (published version)

© 2017 Elsevier B.V. Outer-membrane porins are currently being used to prepare bioinspired nanomembranes for selective ion transport by immobilizing them into polymeric matrices. However, the fabrication of these protein-integrated devices has been found to be strongly influenced by the instability of the ß-barrel porin structure, which depends on surrounding environment. In this work, molecular dynamics simulations have been used to investigate the structural stability of a representative porin, OmpF, in three different environments: (i) aqueous solution at pH = 7; (ii) a solution of neutral detergent in a concentration similar to the critical micelle concentration; and (iii) the protein embedded into a neutral detergent bilayer. The results indicate that the surrounding environment not only alters the stability of the ß-barrel but affects the internal loop responsible of the ions transport, as well as the tendency of the porin proteins to aggregate into trimers. The detergent bilayer preserves the structure of OmpF protein as is found bacteria membranes, while pure aqueous solution induces a strong destabilization of the protein. An intermediate situation occurs for detergent solution. Our results have been rationalized in terms of protein ¿ water and protein ¿ detergent interactions, which makes them extremely useful for the future design of new generation of bioinspired protein-integrated devices., Peer Reviewed, Postprint (author's final draft)

The RPAR peptide, a prototype C-end Rule (CendR) sequence that binds to neuropilin-1 (NRP-1), has potential therapeutic uses as internalization trigger in anticancer nanodevices. Recently, the functionalization of gold nanoparticles with CendR peptides has been proved to be a successful strategy to target the NRP-1 receptor in prostate cancer cells. In this work, we investigate the influence of two gold surface facets, (100) and (111), on the conformational preferences of RPAR using molecular dynamics simulations. Both clustering and conformational analyses revealed that the peptide backbone becomes very rigid upon adsorption onto gold, which is a very fast and favored process, the only flexibility being attributed to the side chains of the two Arg residues. Thus, the different components of RPAR tend to adopt an elongated shape, which is characterized by the pseudo-extended conformation of both the backbone and the Arg side chains. This conformation is very different from the already known bioactive conformation, indicating that RPAR is drastically affected by the substrate. Interestingly, the preferred conformations of the peptide adsorbed onto gold facets are not stabilized by salt bridges and/or specific intramolecular hydrogen bonds, which represent an important difference with respect to the conformations found in other environments (e.g. the peptide in solution and interacting with NRP-1 receptor). However, the conformational changes induced by the substrate are not detrimental for the use of gold nanoparticles as appropriate vehicles for the transport and targeted delivery of the RPAR. Thus, once their high affinity for the NRP-1 receptor induces the targeted delivery of the elongated peptide molecules from the gold nanoparticles, the lack of intramolecular interactions facilitates their evolution towards the bioactive conformation, increasing the therapeutic efficacy of the peptide., Peer Reviewed, Postprint (published version)

Biodegradable polyester fibers have been loaded with two engineered analogues of gramicidin soviet. In these cyclic peptide derivatives, which were designed in a previous work to stabilize the bioactive conformation while enhancing the antimicrobial activity, the D-Phe was replaced by D-Pro, and the L-Pro was changed by 1-aminocyclopropanecarboxylic acid (Ac3c) or by an Ac3c derivative with two vicinal phenyl substituents in a trans relative disposition (S,S-c3diPhe). The diameter, topography, thermal stability and wettability of the polyester fibers, which have been obtained by electrospinning, strongly depend on the molecular constraints and stability of the loaded peptides. More specifically, unloaded and linear gramicidin-loaded fibers (used as control) are hydrophobic, rough and micrometric, while fibers loaded with the cyclic peptides are hydrophilic, ultra-smooth, nanometric and less thermally stable. The activity of the two cyclic peptides increases when loaded into polyester fibers, suggesting that the polymeric matrix stabilizes the bioactive β-sheet structure. The peptide with S,S-c3diPhe displays higher antibiotic potency and biocompatibility than that with Ac3c, which indicates not only that the bioactive conformation is better preserved by the former but also the significant role played by the phenyl rings in the recognition by living cells., Peer Reviewed, Postprint (published version)

Alkyne and azide, which are commonly used in the cycloaddition reaction recognized as “click chemistry”, have been used as capping groups of two engineered diphenylalanine (FF) derivatives due to their ability to form weak intermolecular interactions (i.e. dipole–π and π–π stacking). In Poc-FF-N3, alkyne and azide act as N- and C-terminal capping groups, respectively, while such positions are exchanged in N3-FF-OPrp. The self-assembly of such two synthesized peptides has been extensively studied in their “pre-click” state, considering the influence of three different factors: the peptide concentration, the polarity of the medium, and the nature of the substrate. Poc-FF-N3 assembles into microfibers that, depending on the medium and the substrate, can aggregate hierarchically in supramolecular structures with different morphologies. The most distinctive one corresponds to very stable birefringent dendritic-like microstructures, which are derived from the ordered agglomeration of microfibers. These branched supramolecular structures, which are observed under a variety of conditions, are relatively uncommon in short FF sequences. At the molecular level, Poc-FF-N3 organizes in antiparallel β-sheets stabilized by N–H⋯O intermolecular hydrogen bonds and re-enforced by weak interactions between the azide and alkyne groups of neighbouring molecules. In contrast, N3-FF-OPrp exhibits a very poor tendency to organize into structures with a well-defined morphology. Theoretical calculations on model complexes indicate that the tendency of the latter peptide to organize into small amorphous agglomerates is due to its poor ability to form specific intermolecular interactions in comparison with Poc-FF-N3. The implications of the weak interactions induced by the alkyne and azide groups, which strengthen peptide⋯peptide hydrogen bonds and π-ladders due to the stacked aromatic phenyl side groups, are discussed., Peer Reviewed, Postprint (author's final draft)

Natural rubber (NR) products are being applied in many protective tools for life-line applications, including insulating boots, blankets, sleeves, insulating gloves, or flexible coverings. Due to the inherent risk of such works it is imperative ensuring the quality of the safety products involved. The dielectric properties of NR-based products rely heavily on the compounding formulation and manufacturing processes involved. Considerable efforts are being applied to improve the dielectric performance of NR formulations to ensure that maintenance personnel work in the safer and most comfortable conditions. This work studies the addition of different weight fractions of surface-modified BaTiO3-OH nanoparticles to NR formulations to enhance dielectric properties such as breakdown strength and leakage current. The results presented in this work show that the addition of a low weight fraction of surface-modified BaTiO3-OH nanofillers (= 1 wt.%) enhances the surface and volume resistivity, crystallinity, breakdown strength under ac conditions and lowers the leakage current under dc stress., Peer Reviewed, Postprint (author's final draft)

This is the pre-peer reviewed version of the following article: E. Mayans, G. Fabregat, R. Juárez, C. Cativiela, J. Puiggalí, C. Alemán, ChemistrySelect 2017, 2, 1133, which has been published in final form at DOI 10.1002/slct.201601436. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.", 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., Peer Reviewed, Postprint (author's final draft)

The role of sulfate and nitrate in the taste of drinking water is not entirely clear. Taste threshold concentrations (TTCs) were estimated for these two species by the 3-AFC method by a trained panel, as sodium and calcium salts. In both cases TTCs for nitrate were about 100 mg NO3/L, twice the usual reference value of international recommendations. TTCs for sulfate were about 160 mg SO4/L (sodium salt) and 80 mg SO4/L (calcium); 75% detection values were also estimated for both anions. An experiment with a series of duo-trio tests plus preference showed that sulfate at low concentrations tended to improve the taste of water. However, at high concentrations it was perceived negatively: salty and bitter were the main descriptors used. The reversion concentration took place between 176 and 259 mg SO4/L. These results indicate that nitrate has to be considered an important issue for health, but with no relevant role in the taste of water. Sulfate shows a positive influence at moderate concentrations but becomes negative at high levels. The usual aesthetic-based level of 250 mg/L established by international regulations appears to be reasonable. The findings of this study with trained panellists are preliminary. Future research with consumer panels is recommended., Peer Reviewed, Postprint (published version)

A diphenylalanine (FF) amphiphile blocked at the C terminus with a benzyl ester (OBzl) and stabilized at the N terminus with a trifluoroacetate (TFA) anion was synthetized and characterized. Aggregation of peptide molecules was studied by considering a peptide solution in an organic solvent and adding pure water, a KCl solution, or another organic solvent as co-solvent. The choice of the organic solvent and co-solvent and the solvent/co-solvent ratio allowed the mixture to be tuned by modulating the polarity, the ionic strength, and the peptide concentration. Differences in the properties of the media used to dissolve the peptides resulted in the formation of different self-assembled microstructures (e.g. fibers, branched-like structures, plates, and spherulites). Furthermore, crystals of TFA·FF-OBzl were obtained from the aqueous peptide solutions for X-ray diffraction analysis. The results revealed a hydrophilic core constituted by carboxylate (from TFA), ester, and amide groups, and the core was found to be surrounded by a hydrophobic crown with ten aromatic rings. This segregated organization explains the assemblies observed in the different solvent mixtures as a function of the environmental polarity, ionic strength, and peptide concentration., Peer Reviewed, Postprint (published version)

Natural rubber (NR) nanocomposites have been prepared with hydroxylated barium titanate filler (BaTiO3-OH), employing emulsion polymerization followed by vulcanization process. The addition of barium titanate, a compound with high dielectric permittivity, was envisaged to increase the insulating properties of NR films, thereby reducing the electrical stress and the possibility of undesired arcing on their surfaces. The content of perovskite particles greatly affected both, the mechanical and the electrical properties, of the vulcanized films. It was observed that the optimum functionalized nanoparticle concentration is around 0.25–0.50 phr, range in which the elongation of break was maintained between 874–935% and the tensile strength was between 4.40–4.80 MPa; whereas the dielectric permittivity (¿') is slightly lower than the pristine NR or the NR compounded with high content of BaTiO3 nanoparticles. The dielectric study revealed the presence of two dielectric relaxation modes: (i) glass to rubber transition (a-relaxation) and (ii) interfacial polarization (IP), known as Maxwell-Wagner-Sillars (MWS) polarization. The comparison between small concentrations of non-functionalized and functionalized BaTiO3 inside NR polymeric films lead to the conclusion that the dielectric breakdown strength is high for non-functionalized fillers, supposedly due to less IP polarization phenomena., Postprint (author's final draft)

Lipoxygenases (LOXs) are nonheme iron-containing enzymes catalyzing the dioxygenation of polyunsaturated fatty acids. LOX catalytic activity depends on the presence of iron in the active site and the iron removal is also able to affect the membrane binding properties of the enzyme. Leukotrienes biosynthesis is initiated by the action of 5-LOX at the level of nuclear membrane and the mechanism of enzyme-membrane interaction is thought to involve structural flexibility and conformational changes at the level of the protein tertiary structure. In this study, we have analyzed by molecular dynamics simulations the conformational changes induced by iron removal in 5-LOX. The data indicate that the degree of enzyme flexibility is related to the presence of iron into the active site that is able to stabilize the protein increasing its rigidity. These findings provide further evidence that the conformation and the functional activity of LOXs is tuned by the presence of iron at the active site, suggesting new approaches for the design of enzyme inhibitors., Peer Reviewed, Postprint (author's final draft)

Properties related with the charge storage capacity have been evaluated for three-layered films made with two sheets of poly(3,4-ethylenedioxythiophene) separated by a sheet of poly(N-methylpyrrole) or poly(3,4-ethylenedioxythiophene-co-N-methylpyrrole) (3l-PEDOT/PNMPy or 3l-PEDOT/P(EDOT-co-NMPy), respectively). The most distinctive trend of the copolymer, which shows electrochemical properties intermediate between those of the two homopolymers, is the formation of a biphasic structure, EDOT- and NMPy-rich blocks organizing separately. The ability to exchange charge reversibly is higher for 3l-PEDOT/P(EDOT-co-NMPy) than for 3l-PEDOT/PNMPy, the electroactivity and electrostability of such two 3-layered films being significantly better than that of single-layered PEDOT. Advantages of 3l-PEDOT/P(EDOT-co-NMPy) are mainly based on the nanophase-segregated structure of the copolymer. Thus, the intermediate layer can be considered as random disposition of ultrathin dielectrics having nanometric length and width. In terms of charge storage, the intermediate layer of 3l-PEDOT/P(EDOT-co-NMPy) can be viewed as a thin reservoir filled of heterogeneously distributed nanometric supercapacitors that are connected in series among them and in parallel to the PEDOT layers. The superiority of 3l-PEDOT/P(EDOT-co-NMPy) as organic electrochemical supercapacitor compared to other 3-layered systems, has been proved by powering a red LED bulb., Peer Reviewed, Postprint (author's final draft)

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles are loaded with curcumin and piperine by in situ emulsion polymerization using dodecyl benzene sulfonic acid both as a stabilizer and a doping agent. The loaded drugs affect the morphology, size, and colloidal stability of the nanoparticles. Furthermore, kinetics studies of nonstimulated drug release have evidenced that polymer···drug interactions are stronger for curcumin than for piperine. This observation suggests that drug delivery systems based on combination of the former drug with PEDOT are much appropriated to show an externally tailored release profile. This is demonstrated by comparing the release profiles obtained in presence and absence of electrical stimulus. Results indicate that controlled and time-programmed release of curcumin is achieved in a physiological medium by applying a negative voltage of -1.25 V to loaded PEDOT nanoparticles., Peer Reviewed, Postprint (author's final draft)

This work presents the diagnosis procedure followed to determine the degree of damage of a 100-year-oldreinforced concrete building located in Barcelona city, the Sant-Manuel pavilion at Hôpital de la Santa Creui Sant-Pau. Some structural components of this building were affected by severe corrosion problems inthe reinforcing steel UPN profiles. In order to obtain a representative sample set, a preliminary inspectionof the macroscopic architectonic structure was applied at selected zones that exhibited the metallic back-bone. Gravimetric and electrochemical techniques have demonstrated that some UPN profiles presentedhigh corrosion rate. This was mainly due to the presence of water pipes installed beside the metallicstructure, which was a source of humidity, and also to the presence of calcium carbonate, calcium silicatehydrate, and calcium chloride substances inside the cement in direct contact with the metallic struc-tures, which were responsible for the steel depassivation. The work shows a practical example of howa suitable combination of chemical, physical and electrochemical techniques can be applied together tocharacterize a corrosion process, the obtained results validating and corroborating the prediction of thecorrosion rate in metallic structures., Peer Reviewed, Postprint (published version)

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., Peer Reviewed, Postprint (published version)

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)., Peer Reviewed, Postprint (author's final draft)

The aim of this work is to show the experimental results corresponding to comparative corrosion studies carried out with five commercially pure different metals (iron, lead, zinc, aluminum, and copper) together with the alloy stainless steel 316. Field tests were performed in two different environments. The first, urban environment was represented by a zone corresponding to metropolitan area of Barcelona (Spain). The second environment, a marine environment, was selected on the coast line of the same metropolitan area. The time corresponding to field tests was a half year and the subsequent results were compared with laboratory accelerated tests from robotized equipment, chosen to simulate urban and marine environments, by using aqueous sodium hydrogen sulphite and sodium chloride solutions, respectively. Equivalent time between both field and accelerated tests has been obtained. The results allow a good correlation between both types of exposures and make it possibleto study morphological and quantitative aspects of corrosion process, as well as the influence of different variables that influence the corrosion resistance of each metal and alloy. The main feature of this work is the collaboration between high school students and university faculty , to illustrate, by active participation, the concept of “research work”, in the second year of high school, just before beginning their higher education studies., Postprint (published version)

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., Peer Reviewed, Postprint (author's final draft)

This is the peer reviewed version of the following article: “Puiggalí, A., Del Valle, L.J., Aleman, C. and Pérez, M. (2017) Weighing biointeractions between fibrin (ogen) and clot-binding peptides using microcantilever sensors. Journal of peptide science, (23) 2: 162–171.” which has been published in final form at [doi: 10.1002/psc.2938]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.", 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., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

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., Postprint (author's final draft)

Postprint (published version)

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., Peer Reviewed, Postprint (author's final draft)

Amphiphilic copolymers consisting of an all conjugated polythiophene backbone and sparsely attached oligo-¿-caprolactone side chains have been prepared by anodic electropolymerization of hydroxymethyl-3,4-ethylenedioxythiophene (HMeEDOT) with a thiophene-ended oligo-¿-caprolactone macromonomer (Th-PCL), obtained by ring opening polymerization of ¿-caprolactone with thiophene methanol. The random copolymers, obtained starting from two different molar ratios of the co-monomers in the feed (HMeEDOT :&Th-PCL of 80&:&20 and 60&:&40), and the homopolymer (PHMeEDOT) were synthesized by using three different working electrodes. After structural characterization by FTIR, the electrochemical, morphological and surface properties of the obtained copolymers were examined, and the results evidenced a dependence on both the working electrode and the composition in the feed. In order to evaluate the opportunities in the copolymers's further bioapplications, biodegradability, cytotoxicity and cell proliferation investigations were carried out. By combining the results of electrochemical characterization with those of biocompatibility and dopamine sensing capability tests, it was concluded that a co-monomer feed ratio of 80&:&20 could be the optimal choice for the potential use of these amphiphilic copolymers in sensing devices. All in all, this study shows the benefit of a designed, Peer Reviewed, Postprint (author's final draft)

In this study, we performed a detailed literature survey of the ¿-turn in peptides and proteins. This three-dimensional structural feature is characterized by an eleven-membered pseudo-cycle closed by an intramolecular backbone…backbone H-bond. Interestingly, in this motif the direction of the N-H…O¿=¿C H-bond runs opposite to that of the much more popular and extensively investigated a-, ß-, and ¿-turns. We did not authenticate unequivocally the ¿-turn main-chain reversal topology in any linear short peptide. However, it is frequently observed in small cyclic peptides formed by four, five, and six amino acid residues with stringent geometric requirements. Rather surprisingly, ¿-turns do occur in proteins, although to a relatively moderate extent, as an isolated feature or in the turn segment of hairpin motifs based on two antiparallel, pleated ß-strands. Moreover, the ¿-turn may also host not only the seven-membered, intramolecularly H-bonded, pseudo-cycle termed ¿-turn, either of the classic or inverse type, but also one (or even two) cis peptide bond(s) or a ß-bulge conformation. Based on their ¿, ¿ backbone torsion angles, we were able to classify the protein ¿-turns in six different families. Conformational energy computations using the DFT methodology were also performed on the ¿-turns adopted by the amino acid triplet -Gly-Gly-Gly- (Gly is the most commonly found residue at each of the three positions in our analysis of proteins). Again, in this computational study, six families of turns were identified, but only some of them resemble rather closely those extracted from our investigation on proteins., Postprint (published version)

This manuscript describes a new route to prepare rapidly Ca2+-free hydrogels from unmodified sodium alginate by simply mixing with small organic molecules such as poly(carboxylic acid) compounds as cross-linker agents instead of classical divalent metal salts such as CaCl2. Dimethyl sulfoxide (DMSO) was also found to induce the rapid gelation of aqueous alginate solutions. The gelation process takes place at room temperature, and depending on the composition, gels with good thermal (90-100 °C) and mechanical properties compared to classical metal-containing analogs are obtained. DMSO-based gels showed remarkable self-supporting and thixotropic properties, which can be tuned by the biopolymer concentration. Furthermore, oxalic acid-based gels show superior elasticity than HCl, CaCl2 and DMSO-based gels. The possibility to prepare monoliths, beads, and films of these gels provide them with significant versatility. In particular, films made of alginate and oxalic acid show good potential as synergistic anticancer drug delivery carrier. Computational studies using both quantum mechanical and classical force-field methodologies reveal that hydrogen bonding networks between water and DMSO molecules located close to the alginate chains are responsible for the stability of DMSO-based gels. In contrast, the cohesion of oxalic acid-based gels is a consequence of the coexistence of multiple ionic associations involving oxalate, alginate, and Na+ counterions, which stabilize the system and keep all the interacting species grouped., Peer Reviewed, Postprint (author's final draft)

The novelty of the present study relies on the straightforward sonication of ZnO and TiO2 and incorporation to a complex formulation of latex, with other several organic-inorganic additives that influences the cross-linking reactions. The new elastomer with particles carefully sonicated exhibit improved electrical and mechanical properties. Strong interaction among the nanoparticles and the polymer amorphous phase has been proved by means of FTIR, SEM and XRD analyses. The synergistic effect of hybrid fillers with nanometric dimensions can be used to design high-performance natural rubber nanocomposites with enhanced electrical resistance and good cross-linking degree., Peer Reviewed, Postprint (author's final draft)

Tryptophan 7-halogenase catalyzes chlorination of free tryptophan to 7-chlorotryptophan, which is the first step in the antibiotic pyrrolnitrin biosynthesis. Many biologically and pharmaceutically active natural products contain chlorine and thus, an understanding of the mechanism of its introduction into organic molecules is important. Whilst enzyme-catalyzed chlorination is accomplished with ease, it remains a difficult task for the chemists. Therefore, utilizing enzymes in the synthesis of chlorinated organic compounds is important, and providing atomistic mechanistic insights about the reaction mechanism of tryptophan 7-halogenase is vital and timely. In this work, we examined a mechanism for the reaction of tryptophan chlorination, performed by tryptophan 7-halogenase, by calculating potential energy and free energy surfaces using two different Combined Quantum Mechanical/Molecular Mechanical (QM/MM) methods both employing Density Functional Theory (DFT) for the QM region. Both computational strategies agree on the nature of the rate-limiting step and provided close results for the reaction barriers of the two reaction steps. The calculations for both the potential energy and the free energy profiles showed very similar geometric features and hydrogen bonding interactions for the characterized stationary points., Peer Reviewed, Postprint (published version)

Las empresas de abastecimiento de agua potable precisan de métodos selectivos y suficientemente sensibles para la determinación del desinfectante dióxido de cloro. El método más utilizado, la determinación colorimétrica con DPD ha sido puesto en entredicho por su falta de selectividad frente a otro desinfectante, el cloro elemental. En el presente artículo se evalúa el comportamiento de dos métodos alternativos, el amaranto y el rojo de clorofenol. Contrariamente al DPD, los dos métodos no se basan en la formación de color sino en la degradación de un colorante. Se ha comprobado que los dos métodos son aplicables con restricciones: en ausencia de cloro o cuando la concentración de este interferente es moderada. Los errores de exactitud para concentraciones de hasta 0.8 mg/L de cloro han sido inferiores al 25 y 20 % para el amaranto y rojo de clorofenol respectivamente., Peer Reviewed, Postprint (published version)

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., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

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)., Postprint (author's final draft)

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., Preprint

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., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

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. Introduction, Peer Reviewed, Postprint (published version)

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., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

Thermodynamics and the solvent role in the acceleration of the Diels–Alder reaction between cyclopentadiene (CPD) and methyl vinyl ketone (MVK) have been revisited. In this work we use an ab initio hybrid QM/MM-MD scheme combined with multiple steered molecular dynamics to extract the free energy pofile in water and methanol using the bidirectional Minh–Adib estimator. We obtain 18.7 kcal mol–1 and 20.8 kcal mol–1 free energy barrier for the reaction in water and methanol, respectively. This methodology reproduces experimental values with an absolute error of about 0.8 kcal mol–1. The experimental difference between the activation free-energy barriers of water and methanol is also reproduced with an absolute error of about 0.1 kcal mol–1. We explore the charge transfer evolution along reaction coordinates to characterize the electronic behavior for this reaction. It is shown that the solvent molecules around the reaction system produce a global polarization along the reaction coordinate which is consistent with the solvent polarity. The results highlight the role of hydrogen bonding formed in the transition state to stabilize the system charge reorganization in the reaction process., Peer Reviewed, Postprint (author's final draft)

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., Postprint (published version)

The structural characterization of chiral nylon-3 derivative, poly (3-ethyl-3-phenyl-2- azetidinone) (PEPA) has been carried out using FTIR, thermal analysis, X-ray diffraction and electron microscopy. X-ray diffraction of power and fiber samples were analyzed together with electron diffraction patterns of single crystals obtained from isothermal crystallization in solution. Two different crystalline forms were found in accordance with DSC traces, FTIR spectra and X-ray diffraction diagrams. Electron microscopy corroborates the morphological and crystallographic differences between both crystalline forms. Molecular modeling was applied to characterize the two crystalline forms, which were related to different conformation and consequent space symmetry into the crystal unit cell, Peer Reviewed, Postprint (published version)

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., Peer Reviewed, Postprint (published version)

© BME-PT. In this work we present the drug release properties and morphological studies of fibers formed by mixing different ratios of poly(lactic acid) (PLA) and poly(3-thiophene methyl acetate) (P3TMA) loaded with four drugs (ciprofloxacin, chlorhexidine dihydrochloride, triclosan and ibuprofen sodium salt). Thus, the main aim of this study is to prove that the excellent cellular response of PLA-P3TMA biocompatible scaffolds can be successfully combined with essential applications as drug carrier and delivery systems. Atomic force microscopic (AFM) and scanning electron microscopic (SEM) micro-graphs of PLA-P3TMA fibers indicate that the presence of the conducting polymer inside the PLA matrix affects the surface morphology, resulting in a significant increment of the bulk conductivity with respect to PLA fibers. Electrospun hybrid fibers of PLA and P3TMA successfully load both hydrophilic and hydrophobic drugs, the release profiles depending on the release environment (i.e. the release rate increases with the hydrophobicity of the medium). Finally, our results prove that the antibacterial activity of the drugs is not affected by their interactions with the PLA-P3TMA matrix., Postprint (published version)

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., Postprint (author's final draft)

Natural rubber matrix, reinforced with several conventional stabilizer additives, was further charged with perovskite nanoparticles. Although the addition of BaTiO3 ceramic particles usually transforms a non-conducting pristine polymer into a more conductive polymer composite, in this case we use the addition of a few percent of BaTiO3 (less than 1 wt.%) to decrease the effective electrical conductivity of natural rubber (NR). This reduction has been attributed to the synergistic effect between ceramic particles and the amorphous phase of the polymer matrix, which allowed decreasing the interfacial polarisation among the NR/oxide particles interfaces. Electrical tests clearly indicate that the breakdown voltage increases and the leakage current decreases, whereas the mechanical and hydrophobicity properties of solid films improve after accurate sonication of all solid particles before pre-vulcanization process. Therefore, the dielectric elastomer becomes more insulating with the addition of nanometric oxide particles., Peer Reviewed, Postprint (author's final draft)