Marquez, Y.; Cabral, T.; Lorenzetti, A.; Franco, M.; Turon, P.; del Valle, LJ.; Puiggali, J. Materials science and engineering C. Biomimetic and supramolecular systems Vol. 71, p. 629-640 DOI: 10.1016/j.msec.2016.10.049 Data de publicació: 2017-02-01 Article en revista
A new biodegradable coating was developed for bioabsorbable monofilament sutures. Specifically, a random copolymer having 35 wt-% and 65 wt-% of lactide and trimethylene carbonate units showed appropriate flexibility, stickiness and degradation rate, as well as capability to produce a complete and uniform coating. Monofilament sutures of polyglycolide-b-poly(glycolide-co-trimethylene carbonate-co-e-caprolactone)-b-polyglycolide were loaded with chlorhexidine (CHX) and poly(hexamethylene biguanide) (PHMB) to explore the possibility to achieve antimicrobial activity without adverse cytotoxic effects. To this end, two processes based on single drug adsorption onto the suture surface and incorporation into the coating copolymer were used and subsequently evaluated. Although the second process could be considered more complex, clear benefits were observed in terms of drug loading efficiency, antimicrobial effect and even lack of cytotoxicity. In general, drugs could be loaded in an amount leading to a clear bacteriostatic effect for both Gram-negative and Gram-positive bacteria without causing significant cytotoxicity. Release profiles of PHMB and CHX were clearly different. Specifically, adsorption of the drug onto the fiber surface which prevented complete release was detected for PHMB. This polymer had advantages derived from its high molecular size, which hindered penetration into cells, thus resulting in lower cytotoxicity. Furthermore, bacterial growth kinetics measurements and bacterial adhesion assays showed greater effectiveness of this polymer.
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.
Franco, M.; Diaz, A.; del Valle, LJ.; Casas, M.; Chumburizge, G.; Katsaraba, R.; Puiggali, J. Avances en Materiales Poliméricos p. PTII-7-22- Data de presentació: 2016-09-05 Presentació treball a congrés
Although food-borne outbreaks of listeriosis are uncommon, they remain a major public health problem. We assessed the prevalence of Listeria monocytogenes in prepared foods and the influence of different factors (including type of food or presence of accompanying bacteria). Results showed that accompanying bacteria cause interference in the sensitivity of the detection method, being half Fraser
Urbano, V.; Teran, M.C.S.; Maniero, M.; Guimarães, J.; del Valle, LJ.; Pérez-Moya, M. European Meeting on Solar Chemistry & Photocatalysis: Environmental Applications p. 174 Data de presentació: 2016-06-15 Presentació treball a congrés
Sulfaquinoxaline antimicrobial has been detected on environmental samples and its side effects are still unknown. Degradation of sulfaquinoxaline sodium by Fenton and photo-Fenton processes has not been reported before. Sulfaquinoxaline degradation and the evaluation of the mineralization and toxicity reduction were studied in a laboratory scale and after tested on a pilot plant. The results obtained using a small reactor were reproducible at large scale and more than 99% of the initial sulfaquinoxaline concentration (25 mg L-1) was reached. No antimicrobial activity was observed to the Staphylococcus aureus and Escherichia coli when mineralization was higher than 50% on the pilot plant.
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.
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
Multifunctional electrospun scaffolds were prepared from two polylactide (PLA) grades having slightly different d-lactide content (4.2 wt % and 2.0 wt %). Triclosan (TCS), ketoprofen (KTP), and p-coumaric acid (CUM) were selected as bactericide, anti-inflammatory, and antioxidant agents, respectively. Single, binary, and ternary drug-loaded microfibers having a unimodal diameter distribution could be prepared using a common chloroform:acetone:dimethylsulfoxide mixture and similar operational parameters (i.e., voltage, flow rate, and tip-collector distance). FTIR spectra were sensitive to the low amount of drugs loaded and even showed slight differences in PLA conformation. DSC heating scans clearly demonstrated the ability of electrospinning to induce molecular orientation of PLA and also the nucleation effect of incorporated drugs to induce crystallization. Thus, crystallinity of binary drug-loaded scaffolds was significantly higher than observed for unloaded samples. Release behavior of the three drugs from loaded scaffolds and PLA matrices in PBS:ethanol medium was evaluated. A rapid release was always detected, together with partial drug retention which was higher when the more stereoregular PLA matrix was employed. A strong bactericidal effect was found when scaffolds were loaded with 3 wt/vol % of TCS, but incorporation of a small percentage of KTP (i.e., 1 wt/vol %) had a bacteriostatic effect even in the absence of TCS. The inherent cytotoxicity of TCS could be well neutralized by enhancing cell viability by incorporation of CUM and/or KTP.
Development of materials with an antimicrobial activity is fundamental for different sectors, including medicine and health care, water and air treatment, and food packaging. Electrospinning is a versatile and economic technique that allows the incorporation of different natural, industrial, and clinical agents into a wide variety of polymers and blends in the form of micro/nanofibers. Furthermore, the technique is versatile since different constructs (e.g. those derived from single electrospinning, co-electrospinning, coaxial electrospinning, and miniemulsion electrospinning) can be obtained to influence the ability to load agents with different characteristics and stability and to modify the release behaviour. Furthermore, antimicrobial agents can be loaded during the electrospinning process or by a subsequent coating process. In order to the mitigate burst release effect, it is possible to encapsulate the selected drug into inorganic nanotubes and nanoparticles, as well as in organic cyclodextrine polysaccharides. In the same way, processes that involve covalent linkage of bactericide agents during surface treatment of electrospun samples may also be considered.; The present review is focused on more recent works concerning the electrospinning of antimicrobial polymers. These include chitosan and common biodegradable polymers with activity caused by the specific load of agents such as metal and metal oxide particles, quaternary ammonium compounds, hydantoin compounds, antibiotics, common organic bactericides, and bacteriophages.
Electrospraying of poly(butylene succinate) and its mixture with different indole derivatives was successfully performed using chloroform as solvent and relatively low flow rates and concentrations. Morphology of particles (size, diameter distribution and surface texture) and encapsulation efficiency were dependent on the loaded drug and specifically on the type of substituent (methyl or phenyl) and its position in the indole core. In general, particles showed a raisin-like morphology caused by the shell collapsing of the resulting structurally weak microspheres. Accumulation of electrosprayed particles gave rise to consistent mats and they had a more hydrophobic surface than that determined for smooth films. The increase of hydrophobicity was mainly dependent on the porosity and the hydrophobic nature of the incorporated drugs. Indole derivatives were hardly delivered in a standard phosphate saline buffer due to their scarce solubility in aqueous media but the addition of ethanol caused a drastic change in the release behavior. This was generally characterized by a fast burst effect and followed by the establishment of an equilibrium condition that was dependent on the indole derivative. However, a clearly different behavior was found when the indole was unable to form hydrogen bonds (e.g. 1-methylindole) since in this case a slow and sustained release was characteristic. Microspheres loaded with indole derivatives showed a high antiproliferative activity that was dependent on encapsulation efficiency and the type of loaded drug. The best results were specifically attained for the indole with an aromatic substituent. Interestingly significant differences were found between cancer and immortalized cells, a feature that points out the potential use of such systems for cancer prevention and treatment. (C) 2015 Elsevier Ltd. All rights reserved.
Saccharomyces cerevisiae is industrially the most important yeast, and its growth in different concentrations of oxygen can be used to improve various application processes. The aims of this work were to study in aerobic and microaerophilic growth conditions the cell size and tendency of morphological changes in S. cerevisiae in different stages of growth and to assess the effect of the two growth conditions in the differentiation of quiescent and non-quiescent subpopulations in the stationary phase. Dissolved oxygen levels in the culture medium for aerobic and microaerophilic conditions were 6.6 and 5.2 mg L-1, respectively. In both growth conditions, similar viable cell populations were obtained, although in aerobic conditions the stationary phase was reached and the quiescent and non-quiescent subpopulations were also differentiated. The microaerophilic growth produced a significant reduction in the specific growth rate and consequently also in glucose and oxygen consumption. The most notable changes in cellular size and morphology occurred with the depletion of glucose and oxygen. The concentration of dissolved oxygen in the culture medium significantly modulated the growth kinetics of S. cerevisiae and their development and differentiation to quiescent cells. This could justify the need to readjust small variations in oxygen levels during yeast cultures in biotechnological processes.
Murase, S. K.; del Valle, LJ.; Kobauri, S.; Katsarava, R.; Puiggali, J. Polymer degradation and stability Vol. 119, p. 275-287 DOI: 10.1016/j.polymdegradstab.2015.05.018 Data de publicació: 2015-09-01 Article en revista
Fibrous mats from an alpha-amino acid based poly(ester amide) have been prepared due to the potential applications of this kind of polymers in the biomedical field thanks to the expected non-toxicity of their degradation products. Specifically, the electrospinning technique has been applied and both solution properties and operational parameters have been optimized to get continuous fibers in the micrometer range. Furthermore, fibrous mats have been loaded with biguanide compounds differing on molecular size but having a well-proved bactericide activity (i.e., chlorhexidine, CHX and poly-hexamethylenebiguanide, PHMB). The high solubility of the poly(ester amide) constituted by L-phenylalanine, adipic acid and 1,4-butanediol also allowed getting appropriate electrospinning conditions to incorporate degrading enzymes like alpha-chymotrypsin without significant denaturation.; Degradability of fibrous mats has been evaluated in distinct enzymatic media (lipase, proteinase K and alpha-chymotrypsin) being found a similar behavior that contrasts with the significant differences detected when film samples were employed. An accelerated degradation was clearly found for fibrous mats loaded with alpha-chymotrypsin even when they were exposed to a non-enzymatic aqueous medium.; Release of bactericide agents was evaluated and a specific delay was determined when the polymeric biguanide was employed. Nevertheless, PHMB showed a clearly enhanced activity. Biocompatibility of the new fibrous mats was verified being also determined an increase on the cell adhesion with respect to film samples as a consequence of the increased porosity. (C) 2015 Elsevier Ltd. All rights reserved.
Gordun, E.; del Valle, LJ.; Ginovart, M.; Carbó, R. Food science and technology international Vol. 21, num. 6, p. 428-439 DOI: 10.1177/1082013214543033 Data de publicació: 2015-09-01 Article en revista
The microbiological culture-dependent characterization and physicochemical characteristics of laboratory sourdough prepared with grape (GS) were evaluated and compared with apple (AS) and yogurt (YS), which are the usual Spanish sourdough ingredients. Ripe GS took longer than AS and YS to reach the appropriate acidity and achieved lower values of lactic acid. In all sourdoughs, the lactic acid bacteria (LAB) increased during processing and were the dominant microorganisms (>1E+8 CFU/g). GS, as well as AS, had high diversity of LAB species. In ripe YS, Pediococcus pentosaceus was the only species identified; in GS and AS, several Lactobacilli were also found, Lb. plantarum, Lb. brevis, and Lb. sakei; in addition, in GS Weisella cibaria also appeared. Regarding the yeast population, non-Saccharomyces yeasts from GS and AS showed a very high specific population (>1E+7 CFU/g), but this was reduced in ripe sourdough (<1E+4 CFU/g). Finally, the Saccharomyces group dominated in all sourdoughs. Starting ingredients or raw material provided microbiological specificity to sourdoughs, and grape could be considered one of them.
The microbiological culture-dependent characterization and physicochemical characteristics of laboratory sourdough prepared with grape (GS) were evaluated and compared with apple (AS) and yogurt (YS), which are the usual Spanish sourdough ingredients. Ripe GS took longer than AS and YS to reach the appropriate acidity and achieved lower values of lactic acid
Polylactide (PLA) electrospun microfibers were prepared and loaded with triclosan (TCS), ketoprofen (KTP), or their combination to obtain multifunctional scaffolds with bactericide and anti-inflammatory properties. Continuous and porous fibers with diameters in the micrometer scale and a unimodal distribution were successfully attained using a dual-electrospinning technique. Dual drug-loaded scaffolds showed a peculiar release that was in contrast to the single drug-loaded systems, which suggested the establishment of intermolecular interactions that delayed TCS and KTP release. Antimicrobial activity of all TCS-loaded electrospun scaffolds was demonstrated against E. coli and M. luteus bacteria; and furthermore, KTP-loaded samples slightly showed bactericide activity. Biocompatibility of scaffolds was evaluated by adhesion and proliferation assays, and interestingly, the dual drug-load systems were able to support high TCS doses without adverse effects.
Pérez-Madrigal, M.M.; Armelin, E.; Puiggali, A.; del Valle, LJ.; Michaux, C.; Roussel, G.; Perpete, E.; Aleman, C. European Polymer Congress p. 206 Data de presentació: 2015-06-22 Presentació treball a congrés
Del Valle, J.; Tapia, A.; Espejo, P.; Verne, E.; Nazario, R.; Ugarte, C.; del Valle, LJ.; Pumarola, T. Journal of medical virology Vol. 87, num. 6, p. 917-924 DOI: 10.1002/jmv.24159 Data de publicació: 2015-06-01 Article en revista
Acute respiratory infections are responsible for high morbi-mortality in Peruvian children. However, the etiological agents are poorly identified. This study, conducted during the pandemic outbreak of H1N1 influenza in 2009, aims to determine the main etiological agents responsible for acute respiratory infections in children from Lima, Peru. Nasopharyngeal swabs collected from 717 children with acute respiratory infections between January 2009 and December 2010 were analyzed by multiplex RT-PCR for 13 respiratory viruses: influenza A, B, and C virus; parainfluenza virus (PIV) 1, 2, 3, and 4; and human respiratory syncytial virus (RSV) A and B, among others. Samples were also tested with direct fluorescent-antibodies (DFA) for six respiratory viruses. RT-PCR and DFA detected respiratory viruses in 240 (33.5%) and 85 (11.9%) cases, respectively. The most common etiological agents were RSV-A (15.3%), followed by influenza A (4.6%), PIV-1 (3.6%), and PIV-2 (1.8%). The viruses identified by DFA corresponded to RSV (5.9%) and influenza A (1.8%). Therefore, respiratory syncytial viruses (RSV) were found to be the most common etiology of acute respiratory infections. The authors suggest that active surveillance be conducted to identify the causative agents and improve clinical management, especially in the context of possible circulation of pandemic viruses. J. Med. Virol. 87:917-924, 2015. (c) 2015 Wiley Periodicals, Inc.
Llorens, E.; Calderon, S.; del Valle, LJ.; Puiggali, J. Materials science and engineering C. Biomimetic and supramolecular systems Vol. 50, p. 74-84 DOI: 10.1016/j.msec.2015.01.100 Data de publicació: 2015-05-01 Article en revista
Polyhexamethylenebiguanide hydrochloride (PHMB), a low molecular weight polymer related to chlorohexidine (CHX), is a well-known antibacterial agent. In this study, polylactide (PLA) nanofibers loaded with PHMB were produced by electrospinning to obtain 3D biodegradable scaffolds with antibacterial properties. PLA fibers loaded with CHX were used as control. The electrospun fibers were studied and analyzed by SEM, FTIR, DSC and contact angle measurements. PHMB and CHX release from loaded scaffolds was evaluated, as well as their antibacterial activity and biocompatibility. The results showed that the nanofibers became smoother and their diameter smaller with increasing the amount of loaded PHMB. This feature led to an increase of both surface roughness and hydrophobicity of the scaffold. PHMB release was highly dependent on the hydrophilicity of the medium and differed from that determined for CHX. Lastly, PHMB-loaded PLA scaffolds showed antibacterial properties since they inhibited adhesion and bacterial growth, and exhibited biocompatible characteristics for the adhesion and proliferation of both fibroblast and epithelial cell lines. (C) 2015 Elsevier B.V. All rights reserved.
En las últimas décadas, los biopolímeros sintéticos han atraído gran atención en el campo biomédico. Las poliesteramidas son una familia de polímeros biodegradables que pueden ser modificados en multitud de variables para aplicaciones específicas gracias a la presencia de los enlaces ester, susceptibles a rotura; y a las unidades amida, que establecen uniones de puentes de hidrógeno dando lugar a un aumento en propiedades térmicas y mecánicas. Gracias a la gran variabilidad de las propiedades descritas, las poliesteramidas se presentan como materiales muy prometedores en aplicaciones de diferentes campos de la medicina y constituyen el eje central de estudio en esta Tesis Doctoral. El ácido poliglicólico ha demostrado ser un material biodegradable y biorreabsorbible, por ello, en la primera parte se han preparado diversas poliesteramidas que contienen la unidad de ácido glicólico mediante el método de policondensación en estado sólido. Para explotar el potencial de variabilidad en las propiedades resultantes, las unidades que constituyen al polímero constan de proporciones variables de unidades de ácido glicólico y láctico, y en la sección amida, se incluyen el ácido aminohexanoico o unidades ramificadas de diamina (con 5 o 6 carbonos). Al tratarse de nuevos materiales, su cinética de polimerización in situ y la caracterización de los monómeros y copolímeros se ha estudiado exhaustivamente. Además, se ha sintetizado la poliamida nylon 6 9 para evaluar los cambios morfológicos y los característicos cambios estructurales presentes en los nylons par-impar mediante ensayos a tiempo real SAXS y WAXD en una instalación de radiación sincrotrón y también mediante microscopía óptica. En el capítulo siguiente, se diseña una poliesteramida basada en amino ácidos esenciales, como un ejemplo de biopolímero de última generación. En este caso, se ha planteado un proceso alternativo para obtener un polímero híbrido basado en las unidades de ácido L-láctico y L-fenilalanina que consiste en el uso de un péptido como iniciador de una reacción de apertura de anillo aniónica de la unidad de ácido láctico. Los diferentes copolímeros resultantes se han caracterizado mediante diversas técnicas y también se han respaldado con estudios de simulación. El trabajo de la Tesis Doctoral se ha completado preparando diversos dispositivos biomédicos como pueden ser andamios temporales y nanopartículas mediante un dispositivo de electrospinning. También se ha examinado la técnica de preparación de mini emulsiones. Además, se han usado poliesteramidas que incluyen grupos de ácido glicólico y diaminas pares o impares, fenilalanina o Bionolle®. Se cargan fármacos antiinflamatorios (i.e. ketoprofeno), antibacterianos (i.e. clorhexidina, PHMB) o anticancerígenos (i.e. derivados del indol) y se evalúa su liberación para determinar la posible utilización de estos dispositivos poliméricos como sistemas de liberación controlada. Asimismo, también se han realizado ensayos de biocompatibilidad y tests bacterianos para determinar su comportamiento en aplicaciones biomédicas. Finalmente, otro aspecto fundamental a determinar ha sido el comportamiento frente a degradación enzimática de los diversos materiales.
Synthetic biopolymers have attracted considerable attention in the last decades in the biomedical field. Poly(ester amide)s are a family of biodegradable polymers that can be tailored for specific applications due to the presence of cleavable ester locations and amide units, which establish hydrogen bond interactions and result in good thermal and mechanical properties. Thanks to these adaptable properties, they are promising materials for applications in different medical fields and constitute the core of this Thesis.
Poly(glycolic acid) has proven to be a successful biodegradable and bioresorbable material, so in the first part, diverse poly(ester amide)s containing the glycolic acid unit are prepared using a solid-state polycondensation. To exploit the potential variability of the resulting properties, the constituting units include a variable ratio of glycolic acid and lactic acid, and the amide part comprises aminohexanoic acid or branched diamine units (with 5 and 6 carbons). As new materials, in situ polymerization kinetics and characterization of monomers and copolymers were extensively studied. In addition, the preparation of a polyamide, NY 6 9, was performed to evaluate the morphological changes and peculiar structure present in even-odd nylons by means of time-resolved SAXS and WAXD experiments in a synchrotron radiation facility and optical microscope.
In the next chapter a new amino acid-based poly(ester amide) was designed as a new example of last generation biopolymer. In this case, an alternative approach was aimed to obtain a polymer hybrid based in the L-lactic acid and L-phenylalanine units: the use of a peptide as initiator of an anionic ROP of the L-lactide unit. The different resulting polymers have been characterized by diverse techniques and also are supported by simulation studies.
The work in this Thesis is completed by the preparation of diverse biomedical devices as scaffolds and nanoparticles with an electrospinning setup. The mini-emulsion technique was also explored. Poly(ester amide)s that include glycolic acid and odd or even diamines, phenylalanine or Bionolle® were used. As prospective drug delivery systems anti-inflammatory (i.e. ketoprofen), antibacterial (i.e. chlorhexidine, PHMB) or anti-carcinogenic (i.e. indole derivatives) drugs were loaded and their release was evaluated. Also, biocompatibility and bacterial tests were essential assays to determine their behaviour as biomedical applications. Finally, another fundamental aspect that was reviewed is the enzymatic degradation behaviour of the prepared samples.
Llorens, E.; Ibañez, H.; del Valle, LJ.; Puiggali, J. Materials science and engineering C. Biomimetic and supramolecular systems Vol. 49, p. 472-484 DOI: 10.1016/j.msec.2015.01.039 Data de publicació: 2015-04-01 Article en revista
Scaffolds constituted by electrospun microfibers of poly(ethylene glycol) (PEG) and poly(butylene succinate) (PBS) were studied. Specifically, coaxial microfibers having different core-shell distributions and compositions were considered as well as uniaxial micro/nanofibers prepared from mixtures of both polymers. Processing conditions were optimized for all geometries and compositions and resulting morphologies (i.e. diameter and surface texture) characterized by scanning electron microscopy. Chemical composition, molecular interactions and thermal properties were evaluated by FTIR, NMR, XPS and differential scanning calorimetry. The PEG component of electrospun fibers could be solubilized by immersion of scaffolds in aqueous medium, giving rise to high porosity and hydrophobic samples. Nevertheless, a small amount of PEG was retained in the PBS matrix, suggesting some degree of mixing. Solubilization was slightly dependent on fiber structure: specifically, the distribution of PEG in the core or shell of coaxial fibers led to higher or lower retention levels, respectively. Scaffolds could be effectively loaded with hydrophobic drugs having antibacterial and anticarcinogenic activities like triclosan and curcumin, respectively. Their release was highly dependent on their chemical structure and medium composition. Thus, low and high release rates were observed in phosphate buffer saline (SS) and SS/ethanol (30:70 v/v), respectively. Slight differences in the release of triclosan were found depending on fiber distribution and composition. Antibacterial activity and biocompatibility were evaluated for both loaded and unloaded scaffolds. (C) 2015 Elsevier B.V. All rights reserved.
Pérez-Madrigal, M.M.; Armelin, E.; Giannotti, M.I.; del Valle, LJ.; Sanz, Fausto; Aleman, C. International Conference on Multifunctional, Hybrid and Nanomateri Data de presentació: 2015-03-09 Presentació treball a congrés
Maione, S.; Fabregat, G.; del Valle, LJ.; Bendrea, A.; Cianga, L.; Cianga, Ioan; Estrany, F.; Aleman, C. Journal of polymer science. Part B, polymer physics Vol. 53, num. 4, p. 239-252 DOI: 10.1002/polb.23617 Data de publicació: 2015-02-15 Article en revista
Graft copolymers formed by anchoring poly(ethylene glycol) (PEG) chains to conjugated polythiophene have been prepared by copolymerizing two compounds: unsubstituted -terthiophene (Th-3) and a thiophene-derived macromonomer having an -terthiophene conjugated sequence and one Th-3 bearing a PEG chain with molecular weight of 2000 as substitute at the 3-position of the central heterocycle (Th-3-PEG(2000)). The grafting ratio of the resulting copolymers (PTh3*-g-PEG), which were obtained using 75:25 and 50:50 Th-3-PEG(2000):Th-3 weight ratios, is significantly smaller than that of copolymers derived from polymerization of macromonomers consisting of a -pentathiophene sequence in which the central ring bears a PEG chain of M-w = 2000 (PTh5-g-PEG). The electroactivity and electrochemical stability of PTh3*-g-PEG is not only higher than that of PTh5-g-PEG but also higher than that of PTh3, the latter presenting a very compact structure that makes difficult the access and escape of dopant ions into the polymeric matrix during the redox processes. Furthermore, the optical -(*) lowest transition energy of PTh3*-g-PEG is lower than that of both PTh5-g-PEG and PTh3. These properties, combined with suitable wettability and roughness, result in an excellent behavior as bioactive platform of PTh3*-g-PEG copolymers, which are more biocompatible, in terms of cellular adhesion and proliferation, and electro-compatible than PTh5-g-PEG. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 239-252
Bertran, O.; del Valle, LJ.; Revilla-López, G.; Rivas, M.; Chaves, G.; Casas, M.; Casanovas Salas, Jordi; Turon, P.; Puiggali, J.; Aleman, C. Chemistry: a european journal Vol. 21, num. 6, p. 2537-2546 DOI: 10.1002/chem.201405428 Data de publicació: 2015-02-02 Article en revista
Although the content of Mg2+ in hard tissues is very low (typically 1.5wt%), its incorporation into synthetic hydroxyapatite (HAp) particles and its role in the mineral's properties are still subject of intensive debate. A combined experimental-computational approach is used to answer many of the open questions. Mg2+-enriched HAp particles are prepared using different synthetic approaches and considering different concentrations of Mg2+ in the reaction medium. The composition, morphology and structure of the resulting particles are investigated using X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, scanning and transmission electron microscopies, FTIR, and wide-angle X-ray diffraction. After this scrutiny, the role of the Mg2+ in the first nucleation stages, before HAp formation, is investigated using atomistic molecular dynamics simulations. Saturated solutions are simulated with and without the presence of DNA, which has been recently used as a soft template in the biomineralization process. This synergistic investigation provides a complete picture of how Mg2+ ions affect the mineralization from the first stages onwards
Pérez-Madrigal, M.M.; del Valle, LJ.; Armelin, E.; Michaux, C.; Roussel, G.; Perpete, E.; Aleman, C. ACS applied materials and interfaces Vol. 7, num. 3, p. 1632-1643 DOI: 10.1021/am507142f Data de publicació: 2015-01-28 Article en revista
Biomedical platforms constructed by immobilizing membrane proteins in matrixes made of synthetic organic polymers is a challenge because the structure and function of these proteins are affected by environmental conditions. In this work, an operative composite that regulates the diffusion of alkali ions has been prepared by functionalizing a supporting matrix made of poly(N-methylpyrrole) (PNMPy) with a beta-barrel membrane protein (Omp2a) that forms channels and pores. The protein has been unequivocally identified in the composite, and its structure has been shown to remain unaltered. The PNMPy-Omp2a platform fulfills properties typically associated with functional bio-interfaces with biomedical applications (e.g., biocompatibility, biodegrabadility, and hydrophilicity). The functionality of the immobilized protein has been examined by studying the passive ion transport response in the presence of electrolytic solutions with Na+ and K+ concentrations close to those found in blood. Although the behavior of PNMPy and PNMPy-Omp2a is very similar for solutions with very low concentration, the resistance of the latter decreases drastically when the concentration of ions increases to similar to 100 mM. This reduction reflects an enhanced ion exchange between the biocomposite and the electrolytic medium, which is not observed in PNMPy, evidencing that PNMPy-Omp2a is particularly well suited to prepare bioinspired channels and smart biosensors.
A new bis-thienyl type monomer with preformed azomethine linkages (AzbT) was chemically synthesized and, subsequently, electro-copolymerized with 2,2' : 5', 2 ''-terthiophene (Th-3). AzbT : Th-3 mixtures with different molar ratios (i.e. 50 : 50, 60 : 40 and 80 : 20) were considered, the resulting thin films being made of random insoluble copolymers, P(AzbT-co-Th-3)s. The content of AzbT in P(AzbT-co-Th-3) s was found to increase with the AzbT : Th-3 molar ratio in the electropolymerization medium. Furthermore, characterization of the different copolymers suggests the existence of several concomitant processes in the reaction medium. Thus, depending on the composition of the reaction medium, AzbT worked as a co-monomer and/or as a dopant for the growing polymer chains. The morphology of the films evolved from a porous multi-level surface to a more compact and flat globular structure with increasing AzbT content. On the other hand, the electrochemical and optical properties were also influenced by the AzbT : Th-3 ratio. Cytotoxicity and cell adhesion and proliferation tests, which were performed using human osteosarcoma and monkey kidney epithelial cell lines (MG-63 and Vero, respectively), revealed that P(AzbT-co-Th-3) matrices can be potentially applied as bioactive substrates. This behaviour was especially relevant for the 80 : 20 copolymer, which exhibits optical and electrochemical properties in the range of polythiophene derivatives, suggesting that it is a promising functional biomaterial.
Murase, S. K.; Kaltbeitzel, A.; Landfester, K.; del Valle, LJ.; Katsarava, R.; Puiggali, J.; Crespy, D. RSC advances Vol. 5, num. 68, p. 55006-55014 DOI: 10.1039/c5ra06267e Data de publicació: 2015-01-01 Article en revista
Novel enzyme loaded scaffolds with enzyme-responsive degradable properties for drug delivery are prepared by an original inverse-miniemulsion electrospinning method. Miniemulsions with aqueous nanodroplets containing different enzymes, i.e. lipase or alpha-chymotrypsin, and a fluorophore are electrospun with a solution of poly(ester amide) and polycaprolactone to fabricate multicompartment nanofibers. The poly(ester amide) contains the two essential amino acids phenylalanine and leucine that promote low cytotoxicity degradation products and makes them suitable for the preparation of drug delivery devices for the biomedical field. The activity of the loaded enzymes in different conditions and a sustained degradation of fibers mechanism with an approximate 20% weight loss within one month are observed. Locating enzymes in degradation medium accelerated the degradation until complete scaffold destruction in less than 5 days. In all cases, a nearly complete release of the loaded fluorophore (from 80% and upwards) was achieved before the complete degradation of fibers occurred, suggesting that the nanofibers are suitable as self-triggered drug release systems with sustained mechanical integrity and a flexible range of degradation rates.
Planellas, M.; Pérez-Madrigal, M.M.; del Valle, LJ.; Kobauri, S.; Katsarava, R.; Aleman, C.; Puiggali, J. Polymer chemistry Vol. 6, num. 6, p. 925-937 DOI: 10.1039/c4py01243g Data de publicació: 2015-01-01 Article en revista
Hybrid scaffolds constituted of a mixture of conducting and biodegradable polymers are obtained by the electrospinning technique. Specifically, poly(3-thiophene methyl acetate) (P3TMA) and a copolymer derived from L-leucine, which bears ester, urea and amide groups (PEU-co-PEA), have been employed. Both polymers were selected because of their intrinsic properties and their high solubility in organic solvents. The biodegradable polymer renders continuous and homogeneous microfibers under most of the electrospinning conditions tested, appearing to be an ideal carrier for the polythiophene derivative. A spontaneous phase separation has been observed for concentrated solutions of PEU-co-PEA and P3TMA in chloroform-methanol mixtures. An enriched dense phase results on the conducting polymer and can be successfully electrospun, giving rise to scaffolds with up to 90 wt% of P3TMA. Morphological observations have indicated that continuous and regular microfibers are attained despite the high conducting polymer content. P3TMA presents a high doping level and leads to stable electrospun scaffolds by the simple addition of a low percentage of a high molecular weight carrier. The resulting scaffolds are practically amorphous and thermally stable, also presenting a pronounced electrochemical response and being electrochemically active. Thus, the formation of polarons and bipolarons at specific positions, the ability to exchange charge reversibly and the electrical stability of hybrid PEU-co-PEA/P3TMA electrospun scaffolds and P3TMA alone are practically the same. biodegradability for their use as scaffolds. Different strategies
Fundamental characteristics of bioactive platforms based on biocomposites of poly(3,4-ethylenedioxythiophene) (PEDOT) and collagen, named P(EDOT:CLG), have been examined using an experimental–computational approach. The protein affects both the morphology and electrochemical activity of PEDOT. Specifically, P(EDOT:CLG) shows spherical-like nodules that have been attributed to the collagen rod aggregates organized in phases separated from that of PEDOT. This phase separation results in a reduction of the ability to exchange charge reversibly, even though collagen stabilizes the PEDOT matrix from electrochemical degradation. On the other hand, viability assays indicate that the bioactivity of P(EDOT:CLG) is significantly higher than that of PEDOT in terms of cellular adhesion and proliferation. Thus, the biocomposite promotes the formation of 3D biostructures formed by the superposition of cellular monolayers, mimicking the growth of biological tissues. In order to gain microscopic information about the formation of specific interactions between PEDOT and collagen molecules in the biocomposite, quantum mechanical calculations on complexes formed by their building blocks have been performed in different environments (i.e. vacuum, chloroform and aqueous solution). Results evidence the important role played by non-conventional C–HO hydrogen bonds, which is consistent with previous findings on complexes involving DNA and dopamine. The environment affects considerably the binding energy, which decreases with increasing polarity of the environment. However, in all environments the repeating units of PEDOT form stronger interactions with L-hydroxyproline than with L-proline. On the other hand, intermolecular interaction patterns predicted using implicit and explicit solvation models present a remarkable agreement and have been identified by visualizing the reduced electron density gradient.
Rivas, M.; Casanovas Salas, Jordi; del Valle, LJ.; Bertran, O.; Revilla-López, G.; Turon, P.; Puiggali, J.; Aleman, C. Dalton transactions Vol. 44, num. 21, p. 9980-9991 DOI: 10.1039/c5dt00209e Data de publicació: 2015-01-01 Article en revista
The adsorption of orthophosphate, pyrophosphate, triphosphate and a trisphosphonate onto hydroxyapatite has been examined using experiments and quantum mechanical calculations. Adsorption studies with FTIR and X-ray photoelectron spectroscopies have been performed considering both crystalline hydroxyapatite (HAp) and amorphous calcium phosphate particles, which were specifically prepared and characterized for this purpose. Density functional theory (DFT) calculations have been carried out considering the (100) and (001) surfaces of HAp, which were represented using 1 x 2 x 2 and 3 x 3 x 1 slab models, respectively. The adsorption of phosphate onto the two crystallographic surfaces is very much favored from an energetic point of view, which is fully consistent with current interpretations of the HAp growing process. The structures calculated for the adsorption of pyrophosphate and triphosphate evidence that this process is easier for the latter than for the former. Thus, the adsorption of pyrophosphate is severely limited by the surface geometry while the flexibility of triphosphate allows transforming repulsive electrostatic interactions into molecular strain. On the other hand, calculations predict that the trisphosphonate only adsorbs onto the (001) surface of HAp. Theoretical predictions are fully consistent with experimental data. Thus, comparison of DFT results and spectroscopic data suggests that the experimental conditions used to prepare HAp particles promote the predominance of the (100) surface. Accordingly, experimental identification of the adsorption of trisphosphonate onto such crystalline particles is unclear while the adsorption of pyrophosphate and triphosphate is clearly observed.
Diaz, A.; del Valle, LJ.; Tugushi, D.; Katsarava, R.; Puiggali, J. Materials science and engineering C. Biomimetic and supramolecular systems Vol. 46, p. 450-462 DOI: 10.1016/j.msec.2014.10.055 Data de publicació: 2015-01-01 Article en revista
Electrospun scaffolds from an amino acid containing poly(ester urea) (PEU) were developed as promising materials in the biomedical field and specifically in tissue engineering applications. The selected poly(ester urea) was obtained with a high yield and molecular weight by reaction of phosgene with a bis(alpha-aminoacy1)-alpha,omega-dioldiester monomer. The polymer having L-Ieucine, 1,6-hexanediol and carbonic acid units had a semicrystalline character and relatively high glass transition and melting temperatures. Furthermore it was highly soluble in most organic solvents, an interesting feature that facilitated the electrospinning process and the effective incorporation of drugs with bactericidal activity (e.g. biguanide derivatives such as clorhexidine and polyhexamethylenebiguanide) and enzymes (e.g. alpha-chymotrypsin) that accelerated the degradation process. Continuous micro/nanofibers were obtained under a wide range of processing conditions, being diameters of electrospun fibers dependent on the drug and solvent used.; Poly(ester urea) samples were degradable in media containing lipases and proteinases but the degradation rate was highly dependent on the surface area, being specifically greater for scaffolds with respect to films. The high hydrophobicity of new scaffolds had repercussions on enzymatic degradability since different weight loss rates were found depending on how samples were exposed to the medium (e.g. forced or non-forced immersion). New scaffolds were biocompatible, as demonstrated by adhesion and proliferation assays performed with fibroblast and epithelial cells. (C) 2014 Elsevier B.V. All rights reserved.
Electroactive polymer-peptide conjugates have been synthesized by combining poly(3,4-ethylenedioxythiophene), a polythiophene derivative with outstanding properties, and an Arg-Gly-Asp (RGD)-based peptide in which Gly has been replaced by an exotic amino acid bearing a 3,4-ethylenedioxythiophene ring in the side chain. The incorporation of the peptide at the ends of preformed PEDOT chains has been corroborated by both FTIR and X-ray photoelectron spectroscopy. Although the morphology and topology are not influenced by the incorporation of the peptide at the ends of PEDOT chains, this process largely affects other surface properties. Thus, the wettability of the conjugates is considerably higher than that of PEDOT, independently of the synthetic strategy, whereas the surface roughness only increases when the conjugate is obtained using a competing strategy (i.e. growth of the polymer chains against termination by end capping). The electrochemical activity of the conjugates has been found to be higher than that of PEDOT, evidencing the success of the polymer-peptide links designed by chemical similarity. Density functional theory calculations have been used not only to ascertain the conformational preferences of the peptide but also to interpret the electronic transitions detected by UV-vis spectroscopy. Electroactive surfaces prepared using the conjugates displayed the higher bioactivities in terms of cell adhesion, with the relative viabilities being dependent on the roughness, wettability and electrochemical activity of the conjugate. In addition to the influence of the peptide fragment in the initial cell attachment and subsequent cell spreading and survival, the results indicate that PEDOT promotes the exchange of ions at the conjugate-cell interface.
La técnica de 'electrospinning' o electrohilado es un proceso de fabricación que utiliza un campo eléctrico para producir fibras a partir de disoluciones de polímeros. La acumulación de estas fibras conforma una matriz tri-dimensional o 'scaffold', y las fibras pueden ser preparadas en escala micro y nanométrica. Además, estas matrices o 'scaffold' se caracterizan por su gran superficie por unidad de masa, estructura porosa y propiedades mecánicas influenciadas por la orientación de las fibras. El 'electrospinning' es muy versátil y un gran número de polímeros con diferentes propiedades pueden ser procesados. Sin embargo, un gran número de variables pueden influir en las características de las fibras obtenidas, siendo variables propias del polímero (p.e., solubilidad, peso molecular, etc.) o relacionadas a los parámetros del proceso (voltaje, flujo, distancia colector-aguja). Estas matrices de fibras son atractivas para aplicaciones biomédicas como la ingeniería de tejidos y sistemas de liberación controlada de fármacos. En el último caso, es importante la carga de diferentes fármacos o drogas para su administración directa y localizada en el cuerpo humano. El objetivo de esta Tesis es el estudio de diferentes matrices constituidas por nano o microfibras electrohiladas. El desarrollo de este estudio se divide en cuatro bloques. En el primer bloque, matrices de fibras de poliláctico (PLA) fueron cargadas con diferentes moléculas con actividad antioxidante (vitamina B6 en sus formas de piridoxina y piridoxal, ácido p-cumárico y ácido cafeico). Se determinó la influencia de estas moléculas sobre las propiedades físicas, morfología, liberación in vitro y biocompatibilidad de dichas matrices. Además, se demostró la aplicación de estos nuevos materiales en la inhibición del daño oxidativo del ADN causado por iniciadores de radicales libres, y en consecuencia, estas matrices serían útiles para la purificación de ADN plasmídico o genómico. En el segundo bloque, las matrices de PLA fueron cargadas con dos o tres fármacos para obtener matrices multifuncionales en base a sus actividades. Con esta finalidad, moléculas con actividad antioxidante, anti-inflamatoria, y antimicrobiana fueron cargadas en las matrices para evitar los procesos de oxidación de diferentes biomoléculas (proteínas, ADN, etc.), evitar la inflamación local, y reducir el riesgo potencial de infección microbiana de las heridas, respectivamente. Estas matrices son especialmente interesantes debido a las sinergias y antagonismos que pueden ocurrir durante su liberación simultánea. En el tercer bloque, se prepararon matrices biodegradables a partir de polímeros no-electrohilables. Estos polímeros pueden presentar características particulares, como actividad bactericida, o actividad conductora/electroactividad. Matrices hibridas conformadas con diferentes ratios de PLA usado como polímero biodegradable y el poli(3-tiofeno metil acetato) como polímero electroactivo fueron preparadas y evaluadas. También se prepararon matrices de nanofibras de PLA cargadas con clorhidrato de polihexametilenbiguanida (PHMB) obteniéndose matrices biodegradables con actividad antibacteriana, y la liberación del PHMB fue altamente dependiente de la hidrófilicidad del medio.Finalmente, en el cuarto bloque, se prepararon matrices electrohiladas usando un polímero de sacrificio (polietilenglicol o PEG) que puede ser eliminado fácilmente por solubilización en medios acuosos. Tres preparaciones diferentes fueron evaluadas: a) Matrices constituidas por diferentes proporciones de PLA y PEG en las fibras, b) Matrices constituidas por fibras de PLA y fibras de PEG y, c) Matrices constituidas por fibras coaxiales con diferentes distribuciones de polímeros en el núcleo y la corteza de la fibra. La colonización celular en todas estas matrices fue mejorada. Estos tres procedimientos permitieron obtener matrices con diferentes comportamientos para la liberación de fármacos.
Electrospinning is a manufacturing process that uses an electric field to produce fibers from a polymer solution. The accumulation of these fibers conform a three-dimensional fiber matrix or scaffold. Fibers can be prepared in a wide diameter range, namely from a micrometer to nanometer size. Furthermore, the fiber matrix or scaffold has a large surface per mass unit, a porous structure and mechanical properties influenced by the orientation of the fibers.
The electrospinning technique is highly versatile and therefore a large number of polymers with different properties can be processed. However, a large number of variables can influence the characteristics of the resulting fibers, either because they are related to the polymer properties (e.g., solubility, molecular weight, etc.) or with the specific processing parameters (voltage, flow rate or distance tip-collector). Electrospun fiber matrices are attractive for biomedical applications as for example tissue engineering and drug delivery systems. In the last case, it is important the possibility to load the fibers with different drugs for their direct and localized administration into the human body.
The goal of this Thesis is the study of different matrices constituted by electrospun micro- nanofibers and specifically four points have been considered. In the first one, polylactide electrospun scaffolds have been loaded with different molecules with antioxidant activity (i.e., vitamin B6 in pyridoxine and pyridoxal forms, p-coumaric acid and caffeic acid). The influence of these molecules on physical properties, morphology, in vitro release profiles and biocompatibility was determined. Furthermore, the application of these new materials for the inhibition of oxidative DNA damage caused by free radical initiators was demonstrated, and consequently, they appear appropriate candidates for purification of plasmidic or genomic DNA.
In the second point, PLLA matrices loaded with two or three drugs were prepared in order to get a multifunctional activity. Thus, antioxidant, anti-inflammatory and antimicrobial molecules were considered in order to prevent chain oxidation processes in different biomolecules (proteins, DNA, etc.), avoid the subsequent local inflammation, and reduce the potential risk of microbial infection of wounds, respectively. These matrices are especially interesting due to the synergies and antagonisms that may occur during their simultaneous release.
In the third point, the possibility of preparing biodegradable scaffolds from non electrospinable polymers has been considered. These polymers may have advantages like conductivity/electroactivity or bactericide activity. Hybrid scaffolds constituted by different ratios of polylactide as a biodegradable polymer and (poly(3-thiophene methyl acetate)) as electroactive polymer were evaluated. PLA nanofibers were also successfully loaded with polyhexamethylenebiguanide hydrochloride giving rise to 3D biodegradable scaffolds with a well proven antibacterial activity and a release that was highly dependent on the hydrophilicity of the medium.
Finally electrospun scaffolds were obtained using a sacrificial polymer (e.g. poly(ethylene glycol) (PEG)) that could easily be subsequently removed by solubilization in aqueous media. Three approaches were evaluated: a) Preparation of scaffolds constituted by different ratios of PLA and PEG electrospun fibers, b) Preparation of scaffolds constituted by electrospun fibers with different PLA and PEG content; c) Preparation of scaffolds constituted by coaxial electrospun fibers with different core-shell polymer distributions. Cell colonization was in all cases favoured. The three procedures allowed preparing scaffolds with a differentiated drug release behavior.
La técnica de 'electrospinning' o electrohilado es un proceso de fabricación que utiliza un campo eléctrico para producir fibras a partir de disoluciones de polímeros. La acumulación de estas fibras conforma una matriz tri-dimensional o 'scaffold', y las fibras pueden ser preparadas en escala micro y nanométrica. Además, estas matrices o 'scaffold' se caracterizan por su gran superficie por unidad de masa, estructura porosa y propiedades mecánicas influenciadas por la orientación de las fibras. El 'electrospinning' es muy versátil y un gran número de polímeros con diferentes propiedades pueden ser procesados. Sin embargo, un gran número de variables pueden influir en las características de las fibras obtenidas, siendo variables propias del polímero (p.e., solubilidad, peso molecular, etc.) o relacionadas a los parámetros del proceso (voltaje, flujo, distancia colector-aguja). Estas matrices de fibras son atractivas para aplicaciones biomédicas como la ingeniería de tejidos y sistemas de liberación controlada de fármacos. En el último caso, es importante la carga de diferentes fármacos o drogas para su administración directa y localizada en el cuerpo humano. El objetivo de esta Tesis es el estudio de diferentes matrices constituidas por nano o microfibras electrohiladas. El desarrollo de este estudio se divide en cuatro bloques. En el primer bloque, matrices de fibras de poliláctico (PLA) fueron cargadas con diferentes moléculas con actividad antioxidante (vitamina B6 en sus formas de piridoxina y piridoxal, ácido p-cumárico y ácido cafeico). Se determinó la influencia de estas moléculas sobre las propiedades físicas, morfología, liberación in vitro y biocompatibilidad de dichas matrices. Además, se demostró la aplicación de estos nuevos materiales en la inhibición del daño oxidativo del ADN causado por iniciadores de radicales libres, y en consecuencia, estas matrices serían útiles para la purificación de ADN plasmídico o genómico. En el segundo bloque, las matrices de PLA fueron cargadas con dos o tres fármacos para obtener matrices multifuncionales en base a sus actividades. Con esta finalidad, moléculas con actividad antioxidante, anti-inflamatoria, y antimicrobiana fueron cargadas en las matrices para evitar los procesos de oxidación de diferentes biomoléculas (proteínas, ADN, etc.), evitar la inflamación local, y reducir el riesgo potencial de infección microbiana de las heridas, respectivamente. Estas matrices son especialmente interesantes debido a las sinergias y antagonismos que pueden ocurrir durante su liberación simultánea. En el tercer bloque, se prepararon matrices biodegradables a partir de polímeros no-electrohilables. Estos polímeros pueden presentar características particulares, como actividad bactericida, o actividad conductora/electroactividad. Matrices hibridas conformadas con diferentes ratios de PLA usado como polímero biodegradable y el poli(3-tiofeno metil acetato) como polímero electroactivo fueron preparadas y evaluadas. También se prepararon matrices de nanofibras de PLA cargadas con clorhidrato de polihexametilenbiguanida (PHMB) obteniéndose matrices biodegradables con actividad antibacteriana, y la liberación del PHMB fue altamente dependiente de la hidrófilicidad del medio. Finalmente, en el cuarto bloque, se prepararon matrices electrohiladas usando un polímero de sacrificio (polietilenglicol o PEG) que puede ser eliminado fácilmente por solubilización en medios acuosos. Tres preparaciones diferentes fueron evaluadas: a) Matrices constituidas por diferentes proporciones de PLA y PEG en las fibras, b) Matrices constituidas por fibras de PLA y fibras de PEG y, c) Matrices constituidas por fibras coaxiales con diferentes distribuciones de polímeros en el núcleo y la corteza de la fibra. La colonización celular en todas estas matrices fue mejorada. Estos tres procedimientos permitieron obtener matrices con diferentes comportamientos para la liberación de fármacos.
Scaffolds comprising different ratios of poly(ethylene glycol) (PEG) and polylactide (PLA) electrospun fibers were prepared by using a single rotary collector. Electrospinning parameters and solution conditions were optimized to obtain continuous fibers and a homogeneous distribution of both polymers in the final scaffold. Short needle-collector distances allowed good overlapping of the two incident and independent jets. The composition of the scaffold was effectively tuned by varying the flow rate of the PLA solution. PEG and PLA fibers could be well distinguished in the scaffold because of their smooth and rough texture, respectively, and diameters in the nanometer and micrometer range. Greater sizes corresponded to polylactide and clearly depended on the flow rate. Drugs such as triclosan and polyhexamethylene biguanide hydrochloride, which have different hydrophilic/hydrophobic character and molecular size, were loaded into PLA microfibers by electrospinning. The high water solubility of PEG justified its use as a sacrificial polymer. Thus, it was possible to prepare scaffolds with tuned porosity (from 40 to 80 %) by water immersion of dual samples having different PEG content. Porosity greatly affected the release rate; specifically, a practically instantaneous or a sustained release was determined for triclosan in an appropriate medium. Drug loaded scaffolds had a clear bactericidal effect that was more effective for Gram-positive bacteria. Cell proliferation studies indicate that fibroblast colonization increased by 20-25 % in PLA/PEG scaffolds with high PEG contents compared to the control, whereas this effect was not observed for epithelial cells.
Diaz, A.; Franco, M.; Casas, M.; del Valle, LJ.; Aymami, J.; Olmo, C.; Puiggali, J. Journal of polymer research Vol. 21, num. 11 DOI: 10.1007/s10965-014-0584-3 Data de publicació: 2014-10-15 Article en revista
Ultrasound micro-molding technology has been tested as a new method to get polymer/clay nanocomposites. Biodegradable polylactide (PLA) and poly (nona-methylene azelate) (PE99) have been used as polymer matrices, whereas different silicate clays have been assayed. The new technology is able to get specimens without evidences of degradation during processing. Only the use of organo-modified clays could give rise to a slight molecular weight decrease when the poly (alkylene dicarboxylate) sample was considered. Ultrasonic micro-molding has revealed effective to get directly nanocomposites with the final form required for a selected application, a homogeneous clay distribution up to a load of 6 wt-% and more interestingly exfoliated structures without being necessary the use of a compatibilizer agent between the organic polymer and the inorganic silicate clay. Transmission electron micrographs and X-ray diffraction profiles revealed exfoliated structure when N757, C20A, C25A, and N848 clays were employed.; Crystallization behavior of exfoliated PLA nanocomposites was highly peculiar since clay particles had an antinucleating effect that decreased the overall crystallization rate respect to the neat polymer. In addition, the incorporation of layers into growing spherulites increased the crystal growth rate. A typical crystallization effect was on the contrary observed for nanocomposites derived from the poly (alkylene dicarboxylate) sample.
Cordova, E.; Poater, J.; Teixeira-Dias, Bruno; Bertran, O.; Estrany, F.; del Valle, LJ.; Solà, M.; Aleman, C. Journal of polymer research Vol. 21, num. 10, p. 1-13 DOI: 10.1007/s10965-014-0565-6 Data de publicació: 2014-09-03 Article en revista
The interaction between morphine (MO), a very potent analgesic psychoactive drug, and five electroactive polymers, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-methylthiophene) (P3MT), polypyrrole (PPy), poly(N-methylpyrrole (PNMPy) and poly[N-(2-cyanoethyl)pyrrole] (PNCPy), has been examined using theoretical calculations on model complexes and voltammetric measures considering different pHs and incubation times. Quantum mechanical calculations in model polymers predict that the strength of the binding between the different polymers and morphine increases as follows: PEDOT < PNMPy < Py < < P3MT a parts per thousand PNCPy. The most relevant characteristic of P3MT is its ability to interact with morphine exclusively through non-directional interactions. On the other hand, the variations of the electroactivity and the anodic current at the reversal potential evidence that the voltammetric response towards the presence of MO is considerably higher for P3MT and PNCPy than that for the other polymers at both acid (P3MT > PNMPy) and neutral (P3MT a parts per thousand PNCPy) pHs. Energy decomposition analyses of the interaction of MO with different model polymers indicate that the stronger affinity of MO for P3MT and PNCPy as compared to PEDOT, PNMPy, and PPy is due to more favorable orbital interactions. These more stabilizing orbital interactions are the result of the larger charge transfer from MO to P3MT and PNCPy model polymers that takes place because of the higher stability of the single occupied molecular orbital (SOMO) of these model polymers. Therefore, to design polymers with a large capacity to detect MO we suggest looking at polymers with high electron affinity.
Diaz, A.; del Valle, LJ.; Franco, M.; Sarasua, J.; Estrany, F.; Puiggali, J. Materials science and engineering C. Biomimetic and supramolecular systems Vol. 42, p. 517-528 DOI: 10.1016/j.msec.2014.05.069 Data de publicació: 2014-09-01 Article en revista
Fabregat, G.; Teixeira-Dias, Bruno; del Valle, LJ.; Armelin, E.; Estrany, F.; Aleman, C. ACS applied materials and interfaces Vol. 6, num. 15, p. 11940-11954 DOI: 10.1021/am503904h Data de publicació: 2014-08-13 Article en revista
Biocomposites formed by a pentapeptide (CREKA), which recognizes clotted plasma proteins, entrapped into the poly(3,4-ethylenedioxythiophene) (PEDOT) matrix have been prepared using three very different procedures. X-ray photoelectron spectroscopy analyses indicate that PEDOT-CREKA films, prepared by chronoamperometry in basic aqueous solution (pH = 10.3) and deposited onto a PEDOT internal layer, present the higher concentration of peptide: one CREKA molecule per six polymer repeat units. The surface of this bilayered system shows numerous folds homogeneously distributed, which have been exhaustively characterized by scanning electron microscopy and atomic force microscopy. Indeed, the morphology and topography of such bilayered films is completely different from those of biocomposite-prepared acid aqueous and organic solutions as polymerization media. The impact of the entrapped peptide molecules in the electrochemical properties of the conducting polymer has been found to be practically negligible. In contrast, biocompatibility assays with two different cellular lines indicate that PEDOT-CREKA favors cellular proliferation, which has been attributed to the binding of the peptide to the fibrin molecules from the serum used as a supplement in the culture medium. The latter assumption has been corroborated examining the ability of PEDOT-CREKA to bind fibrin. The latter ability has been also used to explore an alternative strategy based on the treatment of PEDOT-CREKA with fibrin to promote cell attachment and growth. Overall, the results suggest that PEDOT-CREKA is appropriated for multiple biomedical applications combining the electrochemical properties of conducting polymer and the ability of the peptide to recognize and bind proteins.
Maione, S.; Fabregat, G.; del Valle, LJ.; Ballano, G.; Cativiela, C.; Aleman, C. Journal of peptide science Vol. 20, num. 7, p. 537-546 DOI: 10.1002/psc.2660 Data de publicació: 2014-07-01 Article en revista
The roughness and thickness of films formed by hybrid conjugates prepared by coupling poly(3,4-ethylenedioxythiophene) and synthetic amino acids bearing a 3,4-ethylenedioxythiophene group in the side chain have been significantly increased using a new synthetic approach. This procedure also provoked a more effective incorporation of the amino acid at the end of the polymer chains, as has been reflected by the electronic and electrochemical properties. Although the surface polarity of all these materials is similar to that of formamide, the hydrophilicity of the conjugates is higher than that of the conducting polymer. The surface energy of all the investigated systems is dominated by the dispersive component, even though the role played by the polar contribution is more important for the conjugates than for the conducting polymer. On the other hand, all the prepared materials behave as bioactive matrices. The electrochemical response of the conjugates coated with cells reflects the electro-compatibility of these two-component substrates. Thus, the ability to exchange charge reversibly of all conjugates increases considerably when they are coated with cellular monolayers, which has attributed to favorable interactions at the interface formed by the conjugate surface and the cellular monolayer. Copyright (c) 2014 European Peptide Society and John Wiley & Sons, Ltd.
Espejo, P.; Peralta, F.; Cornejo, H.; del Valle, LJ.; Tapia, A.; Bazan, J.; Ruiz, J.; Del Valle, J. Transactions of the Royal Society of Tropical Medicine and Hygiene Vol. 108, num. 7, p. 425-430 DOI: 10.1093/trstmh/tru059 Data de publicació: 2014-07 Article en revista
Planellas, M.; Sacristan, M.; Rey, L.; Olmo, C.; Aymami, J.; Casas, M.; del Valle, LJ.; Franco, M.; Puiggali, J. Ultrasonics sonochemistry Vol. 21, num. 4, p. 1557-1569 DOI: 10.1016/j.ultsonch.2013.12.027 Data de publicació: 2014-07-01 Article en revista
Ultrasound technology was proved as an efficient processing technique to obtain micro-molded specimens of polylactide (PLA) and polybutylene succinate (PBS), which were selected as examples of biodegradable polyesters widely employed in commodity and specialty applications. Operational parameters such as amplitude, molding force and processing time were successfully optimized to prepare samples with a decrease in the number average molecular weight lower than 6%. Ultrasonic waves also seemed an ideal energy source to provide effective disaggregation of clay silicate layers, and therefore exfoliated nanocomposites. X-ray diffraction patterns of nanocomposites prepared by direct micro-molding of PLA or PBS powder mixtures with natural montmorillonite or different organo-modified clays showed the disappearance of the 001 silicate reflection for specimens having up to 6 wt.% clay content. All electron micrographs revealed relatively homogeneous dispersion and sheet nanostructures oriented in the direction of the melt flow. Incorporation of clay particles during processing had practically no influence on PLA characteristics but enhanced PBS degradation when an organo-modifier was employed. This was in agreement with thermal stability data deduced from thermogravimetric analysis. Cold crystallization experiments directly performed on micro-molded PLA specimens pointed to a complex influence of clay particles reflected by the increase or decrease of the overall non-isothermal crystallization rate when compared to the neat polymer. In all cases, the addition of clay led to a clear decrease in the Avrami exponent. (C) 2014 Elsevier B.V. All rights reserved.
Ultrasound technology was proved as an efficient processing technique to obtain micro-molded specimens of polylactide (PLA) and polybutylene succinate (PBS), which were selected as examples of biodegradable polyesters widely employed in commodity and specialty applications. Operational parameters such as amplitude, molding force and processing time were successfully optimized to prepare samples with a decrease in the number average molecular weight lower than 6%. Ultrasonic waves also seemed an ideal energy source to provide effective disaggregation of clay silicate layers, and therefore exfoliated nanocomposites. X-ray diffraction patterns of nanocomposites prepared by direct micro-molding of PLA or PBS powder mixtures with natural montmorillonite or different organo-modified clays showed the disappearance of the 0 0 1 silicate reflection for specimens having up to 6 wt.% clay content. All electron micrographs revealed relatively homogeneous dispersion and sheet nanostructures oriented in the direction of the melt flow. Incorporation of clay particles during processing had practically no influence on PLA characteristics but enhanced PBS degradation when an organo-modifier was employed. This was in agreement with thermal stability data deduced from thermogravimetric analysis. Cold crystallization experiments directly performed on micro-molded PLA specimens pointed to a complex influence of clay particles reflected by the increase or decrease of the overall non-isothermal crystallization rate when compared to the neat polymer. In all cases, the addition of clay led to a clear decrease in the Avrami exponent.
Pérez-Madrigal, Maria M.; Giannotti, M.I.; del Valle, LJ.; Franco, M.; Armelin, E.; Puiggali, A.; Sanz, Fausto; Aleman, C. ACS applied materials and interfaces Vol. 6, num. 12, p. 9719-9732 DOI: 10.1021/am502150q Data de publicació: 2014-06-25 Article en revista
Nanomembranes have been prepared by spin-coating mixtures of a polythiophene (P3TMA) derivative and thermoplastic polyurethane (TPU) using 20:80, 40:60, and 60:40 TPU:P3TMA weight ratios. After structural, topographical, electrochemical, and thermal characterization, properties typically related with biomedical applications have been investigated: swelling, resistance to both hydrolytic and enzymatic degradation, biocompatibility, and adsorption of type I collagen, which is an extra cellular matrix protein that binds fibronectin favoring cell adhesion processes. The swelling ability and the hydrolytic and enzymatic degradability of TPU:P3TMA membranes increases with the concentration of P3TMA. Moreover, the degradation of the blends is considerably promoted by the presence of enzymes in the hydrolytic medium, TPU:P3TMA blends behaving as biodegradable materials. On the other hand, TPU:P3TMA nanomembranes behave as bioactive platforms stimulating cell adhesion and, especially, cell viability. Type I collagen adsorption largely depends on the substrate employed to support the nanomembrane, whereas it is practically independent of the chemical nature of the polymeric material used to fabricate the nanomembrane. However, detailed microscopy study of the morphology and topography of adsorbed collagen evidence the formation of different organizations, which range from fibrils to pseudoregular honeycomb networks depending on the composition of the nanomembrane that is in contact with the protein. Scaffolds made of electroactive TPU:P3TMA nanomembranes are potential candidates for tissue engineering biomedical applications.
Casanovas Salas, Jordi; Revilla-López, G.; Bertran, O.; del Valle, LJ.; Turon, P.; Puiggali, J.; Aleman, C. Journal of physical chemistry B Vol. 118, num. 19, p. 5075-5081 DOI: 10.1021/jp501714q Data de publicació: 2014-05-15 Article en revista
The pseudorotational motions of highly hydroxylated pentafuranose sugars in the free state and tethered to hydroxyapatite have been compared. The conformation pentafuranose ring remains restricted at the North region of the pseudorotational wheel, which is the one typically observed for nucleosides and nucleotides in the double helix A-RNA, when the phosphate-bearing sugar is anchored to the mineral surface. Results indicate that the severe restrictions imposed by the mineral are responsible of the double helix preservation when DNA and RNA are encapsulated in crystalline nanorods.