Nanostructured fumarate copolymer-chitosan crosslinked scaffold: an in vitro osteochondrogenesis regeneration study

In the tissue engineering field, the design of the scaffold inspired on the natural occurring tissue is of vital importance. Ideally, the scaffold surface must promote cell growth and differentiation, while promote angiogenesis in the in vivo implant of the scaffold. On the other hand, the material selection must be biocompatible and the degradation times should meet tissue reparation times. In the present work, we developed a nanofibrous scaffold based on chitosan crosslinked with diisopropylfumarate-vinyl acetate copolymer using anodized aluminum oxide (AAO) templates. We have previously demonstrated its biocompatibility properties with low cytotoxicity and proper degradation times. Now, we extended our studies to demonstrate that it can be successfully nanostructured using the AAO templates methodology, obtaining a nanorod-like scaffold with a diameter comparable to those of collagen fibers of the bone matrix (170 and 300 nm). The nanorods obtained presented a very homogeneous pattern in diameter and length, and supports cell attachment and growth. We also found that both osteoblastic and chondroblastic matrix production were promoted on bone marrow progenitor cells and primary condrocytes growing on the scaffolds, respectively. In addition, the nanostructured scaffold presented no cytotoxicity as it was evaluated using a model of macrophages on culture

Tautomerizable β-ketonitrile copolymers for bone tissue engineering: Studies of biocompatibility and cytotoxicity

β-Ketonitrile tautomeric copolymers have demonstrated tunable hydrophilicity/hydrophobicity properties according to surrounding environment, and mechanical properties similar to those of human bone tissue. Both characteristic properties make them promising candidates as biomaterials for bone tissue engineering. Based on this knowledge we have designed two scaffolds based on β-ketonitrile tautomeric copolymers which differ in chemical composition and surface morphology. Two of them were nanostructured, using an anodized aluminum oxide (AAO) template, and the other two obtained by solvent casting methodology. They were used to evaluate the effect of the composition and their structural modifications on the biocompatibility, cytotoxicity and degradation properties. Our results showed that the nanostructured scaffolds exhibited higher degradation rate by macrophages than casted scaffolds (6 and 2.5% of degradation for nanostructured and casted scaffolds, respectively), a degradation rate compatible with bone regeneration times. We also demonstrated that the β-ketonitrile tautomeric based scaffolds supported osteoblastic cell proliferation and differentiation without cytotoxic effects, suggesting that these biomaterials could be useful in the bone tissue engineering field.Facultad de Ciencias ExactasLaboratorio de Investigación en Osteopatías y Metabolismo MineralInstituto de Investigaciones Fisicoquímicas Teóricas y AplicadasLaboratorio de Estudio de Compuestos Orgánico

Nanostructured fumarate copolymer-chitosan crosslinked scaffold: An in vitro osteochondrogenesis regeneration study

In the tissue engineering field, the design of the scaffold inspired on the natural occurring tissue is of vital importance. Ideally, the scaffold surface must promote cell growth and differentiation, while promote angiogenesis in the in vivo implant of the scaffold. On the other hand, the material selection must be biocompatible and the degradation times should meet tissue reparation times. In the present work, we developed a nanofibrous scaffold based on chitosan crosslinked with diisopropylfumarate-vinyl acetate copolymer using anodized aluminum oxide (AAO) templates. We have previously demonstrated its biocompatibility properties with low cytotoxicity and proper degradation times. Now, we extended our studies to demonstrate that it can be successfully nanostructured using the AAO templates methodology, obtaining a nanorod-like scaffold with a diameter comparable to those of collagen fibers of the bone matrix (170 and 300 nm). The nanorods obtained presented a very homogeneous pattern in diameter and length, and supports cell attachment and growth. We also found that both osteoblastic and chondroblastic matrix production were promoted on bone marrow progenitor cells and primary condrocytes growing on the scaffolds, respectively. In addition, the nanostructured scaffold presented no cytotoxicity as it was evaluated using a model of macrophages on culture.Fil: Lastra, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Ciencias Biológicas. Laboratorio de Investigación en Osteospatías y Metabolismo Mineral; ArgentinaFil: Molinuevo, María Silvina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Ciencias Biológicas. Laboratorio de Investigación en Osteospatías y Metabolismo Mineral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Blaszczyk Lezak, Iwona. Consejo Superior de Investigaciones Científicas; España. Instituto en Ciencia y Tecnología de Polímeros; EspañaFil: Mijangos, Carmen. Consejo Superior de Investigaciones Científicas; España. Instituto en Ciencia y Tecnología de Polímeros; EspañaFil: Cortizo, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Electrically conducting polymer nanostructures confined in anodized aluminum oxide templates (AAO)

Intrinsically or extrinsically conducting polymers are considered good candidates for replacement of metals in specific applications. In order to further expand their applications, it seems necessary to examine the influence of confinement effects on the electric properties of nanostructured conducting polymers in comparison to the bulk. The present study reports a novel way to fabricate and characterize high quality and controllable one-dimensional (1D) polymer nanostructures with promising electrical properties, with the aid of two examples polyaniline (PANI) and poly(vinylidene fluoride) with multiwall carbon nanotubes (PVDF-MWCNT) as representative of intrinsically and extrinsically conducting polymers, respectively. In this work, porous anodic aluminum oxide (AAO) templates have been used both as a nanoreactor to synthesize 1D PANI nanostructures by polymerization of the ANI monomer and as a nanomold to prepare 1D PVDFMWCNT nanorods by melt infiltration of the precursor PVDF-MWCNT film. The obtained polymer nanostructures were morphologically and chemically characterized by SEM and Confocal Raman Spectroscopy, respectively, and the electrical properties determined by Broadband Dielectric Spectroscopy (BDS) in a non-destructive way. SEM study allowed to establish the final nanostructure of PANI and PVDF-MWCNT and confirmed, in both cases, the well-aligned and uniform rodlike polymer nanostructures. Confocal Raman Microscopy has been performed to study the formation of the conducting emeraldine salt of PANI through all the length of AAO nanocavities. Finally, the electrical conductivity of both types of polymer nanostructures was easily evaluated by means of Dielectric Spectroscopy.Financial support from the Spanish ‘Ministerio de Economia y Competitividad’ under projects MAT2011-24797 and MAT2014-53437-C2-1 is acknowledged. The authors thank D. Gómez for SEM experiments and I. Muñoz for Raman spectra. Authors thank Miguel Ángel López Manchado por providing MWCNTsPeer Reviewe

Gecko-like branched polymeric nanostructures from nanoporous templates

Here, we report a simple method to produce hierarchically shaped polymeric one-dimensional nanostructures. More specifically, dual-sized polymer nanowires are fabricated employing multibranched anodic aluminum oxide templates. By fine selection of the anodization conditions, we achieve branched nanopores having a first segment of 400 nm in diameter from which seven further 55 nm in diameter pores arise. Wetting of such nanopores with polymer melts - for example, poly(μ-caprolactone) and polystyrene - allows for the nanomolding of their respective inverse nanostructures, that is, dual-sized multibranched polymer nanowires that, when supported on a flat surface, strongly resemble the spatulae of geckos' toes. The structural features of the dual-sized polymer nanostructures, namely, crystalline phase, crystallinity, texture, and so on, are furthermore characterized and interpreted within the context of polymer phase transitions in confined media. Our work presents a readily applicable approach to produce soft nanomaterials of high morphological complexity, thereby with promising implications in the nanotechnology area, for example, in biomimetic solid adhesion.Financial support from the Spanish Ministerio de Ciencia, Innovación e Universidades under projects MAT2014-53437- C2 and MAT2017-83014-C2-2-P is acknowledged. J.M. thanks MEC for the Ramón y Cajal contract and Fundación Iberdrola (Ayudas a la Investigación en Energía y Medio Ambiente 2017) for the financial support.Peer Reviewe

One Dimensional PMMA Nanofibers from AAO Templates. Evidence of Confinement Effects by Dielectric and Raman Analysis

The aim of this work is to examine the influence of confinement effects on the chemical and dielectric properties of nanostructured polymethylmetacrylate (PMMA) in comparison to the bulk. In general, authors have focused their research on isotactic PMMA and only a few have studied PMMA with other tacticity so, in consequence, we have chosen a PMMA with main content of syndiotactic form. One-dimensional polymer nanostructures of PMMA have been prepared by infiltration into AAO templates with different dimensions of pores: 28, 35, and 65 nm. Laboratory-made, electrochemically fabricated porous materials have been used as confining systems with very well-defined geometry. Scanning electron microscopy micrographs present the regularity of the obtained nanofibers and show the appropriate, homogeneous filling of the nanocavities. As methods of physical and chemical characterization we have chosen broadband dielectric and Raman spectroscopy. By dielectric spectroscopy experiments we observe that the relaxation behavior of confined PMMA within templates of cylindrical nanopores differs from that of the bulk polymer. By Raman spectroscopy, we are able to visualize changes in the chemical structure of PMMA. Results obtained by using both spectroscopic methods are compatible

Confinement induced first order crystallization kinetics for the poly(ethylene oxide) block within A PEO-b-PB diblock copolymer infiltrated within alumina nano-porous template

We report homogeneous nucleation and first order crystallization kinetics for the PEO block within a PEO-b-PB diblock copolymer infiltrated within alumina nanopores. For the highly confined heterogeneity free PEO block nano-domains, the overall crystallization kinetics is dominated by nucleation and therefore becomes first order. The nucleation mechanism changes from heterogeneous nucleation for the PEO block within the uninfiltrated copolymer (since it has a composition with 79% PEO that conforms a percolated matrix) to homogeneous nucleation for confined and isolated heterogeneity free nanodomains. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Peer Reviewe

Confined crystallization of polymers within anodic aluminum oxide templates

In this article, a review of recent literature on confined crystallization within nanoporous anodic aluminum oxide (AAO) templates is presented. For almost all infiltrated polymeric materials, crystal orientation within the nanopores is a function of pore diameter. Tc and Tm usually decrease and are a function of pore size. When no pore interconnection remains, the crystallization occur at large supercoolings in heterogeneity free environments. Hence, the nucleation mechanism changes from heterogeneous to surface or homogeneous nucleation. The crystallization kinetics of infiltrated polymers should be close to first order, since in confined environments nucleation is the determining step of the overall crystallization and Avrami indexes (n) of ∼1 (or lower in some cases) should be obtained. Examples are provided where these conditions have been met and first order kinetics (n = 1) were measured as opposed to higher orders (n = 3-4) for the same polymer in the bulk.Peer Reviewe

In-situ polymerization of styrene in AAO nanocavities

One of the most promising aspects of the alumina oxide (AAO) template is the ability to generate a variety of different hierarchical one-dimensional (1D) polymer morphologies with structural definition on the nanometric scale. In-situ polymerization of monomers in reduced spaces of porous aluminum oxide (AAO) nanocavities can give rise to the direct production of versatile polymer nanostructures. In this work, porous anodic aluminum oxide (AAO) devices of 35 nm of diameter have been obtained by a two-step electrochemical anodization process and used as a nanoreactor to study the radical polymerization kinetics of styrene (St) in confinement and the results compared to those of polymerization in bulk. SEM morphological study has been conducted to establish the final structure of obtained polymer nanostructures. Confocal Raman microscopy has been performed to study the formation of the polymer through the AAO cavities as a function of time and with this methodology it has been possible to establish the monomer conversion for styrenic polymerization in AAO devices. Polystyrene obtained in the nanoreactor was characterized by SEC, NMR, TGA and DSC and the properties compared with those of bulk polymer. It was found that both the average molecular weights and polydispersity index of nanostructured polymer are lower than those obtained for bulk polymer. NMR studies have shown that the use of a reactor with nanometric size dimensions gave the obtained polystyrene greater stereospecificity than that obtained in bulk. Thermal stability and Tg values are higher for nanostructured than bulk polymers. Moreover, the methodology proposed in this work, using AAO nanocavities as nanoreactors for polymerization reaction, can be generalized and applied to obtain polymer nanostructures of very different chemical nature and morphology by choosing the appropriate monomer or monomer reactants and by tailoring the dimension of AAO cylindrical nanocavities, that is, diameter from 20 to 400 nm and length from a few to hundreds of microns.Fil: Giussi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Instituto en Ciencia y Tecnologia de Polimeros; España. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Departamento de Quimica. Laboratorio de Estudio de Compuestos Organicos; ArgentinaFil: Blaszczyk Lezak, Iwona. Instituto en Ciencia y Tecnologia de Polimeros; EspañaFil: Cortizo, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Departamento de Quimica. Laboratorio de Estudio de Compuestos Organicos; ArgentinaFil: Mijangos, Carmen . Instituto en Ciencia y Tecnologia de Polimeros; Españ

Confinement effects on polymer crystallization: From droplets to alumina nanopores

We review previous works on polymer confined crystallization employing strategies that allow confinement to go from the micron to the nanometer scale: droplets, blends, block copolymers and infiltration into alumina nanopores. We also present novel results, reporting homogeneous nucleation and first order crystallization kinetics, for the first time, in a homopolymer and a diblock copolymer infiltrated within alumina nanopores. Confinement can produce fractionated crystallization or exclusive crystallization at much higher supercoolings as compared to bulk polymers, as the degree of confinement increases. For highly confined heterogeneity free micro or nano-domains, the overall crystallization kinetics is dominated by nucleation and therefore becomes first order. The nucleation mechanism changes from heterogeneous nucleation for the bulk polymer to surface or homogeneous nucleation for ensembles of confined and isolated heterogeneity free micro or nanodomains. Surface nucleation is more commonly found than homogenous nucleation, although this fact is not frequently recognized in the literature.Peer Reviewe