In bone engineering, the adhesion, proliferation and differentiation of mesenchymal stromal cells... more In bone engineering, the adhesion, proliferation and differentiation of mesenchymal stromal cells rely on signaling from chemico-physical structure of the substrate, therefore prompting the design of mimetic "extracellular matrix"-like scaffolds. In this study, three-dimensional porous poly-L-lactic acid (PLLA)-based scaffolds have been mixed with different components, including single walled carbon nanotubes (CNT), micro-hydroxyapatite particles (HA), and BMP2, and treated with plasma (PT), to obtain four different nanocomposites: PLLA + CNT, PLLA + CNTHA, PLLA + CNT + HA + BMP2 and PLLA + CNT + HA + PT. Adult bone marrow mesenchymal stromal cells (MSCs) were derived from the femur of orthopaedic patients, seeded on the scaffolds and cultured under osteogenic induction up to differentiation and mineralization. The release of specific metabolites and temporal gene expression profiles of marrow-derived osteoprogenitors were analyzed at definite time points, relevant to in vitro culture as well as in vivo differentiation. As a result, the role of the different biomimetic components added to the PLLA matrix was deciphered, with BMP2-added scaffolds showing the highest biomimetic activity on cells differentiating to mature osteoblasts. The modification of a polymeric scaffold with reinforcing components which also work as biomimetic cues for cells can effectively direct osteoprogenitor cells differentiation, so as to shorten the time required for mineralization.
A deposition process on a conducting surface, in which water acted as the dispersed phase and a m... more A deposition process on a conducting surface, in which water acted as the dispersed phase and a mixture of poly(methyl methacrylate) and chloroform as the continuous phase, was applied to prepare poly(methyl methacrylate) films. The influence of relative humidity during the film preparation on the surface morphology was investigated by field emission scanning microscopy. High-humidity preparation conditions lead to porous poly(methyl methacrylate) films. These films were then used as templates to perform the selective deposition into the pores of single-walled carbon nanotubes by an electrophoretic method. The attractive properties of carbon nanotubes combined with the versatile properties of poly(methyl methacrylate) open up new opportunities for these nanocomposites to achieve novel architectures in nanodevices and microdevices.
ABSTRACT Smectite clays (e.g. montmorillonite), belonging to the structural family called 2:1 phy... more ABSTRACT Smectite clays (e.g. montmorillonite), belonging to the structural family called 2:1 phyllosilicates, are the main choice for designing polymer nanocomposites due to their low cost and rich intercalation chemistry allowing them to be chemically modified (organoclays) and to improve the compatibility with the polymer matrix. These hybrid materials, normally called polymeric nanocomposites (PNC), represent a radical alternative to conventional polymer composites and have focused the attention of both academia and industry because of their unexpected properties, and their straightforward synthesis and processing. Such materials on the nanoscale level show significant improvements in mechanical properties, heat distortion temperatures, thermal stability, flame retardancy and enhanced barrier properties. The combination of enhanced properties, weight reduction, and low cost has led to interesting commercial applications such as automotive and packaging, among others. All this justifies the growing interest of both academia and industry in the development of these hybrid materials. In this paper we describe the most significant findings in the clay/polymer nanocomposites field considering three polymer families: elastomers, thermosets and polymers from natural resources or biopolymers.
This article fabricates and characterizes the combination of single walled carbon nanotubes (SWCN... more This article fabricates and characterizes the combination of single walled carbon nanotubes (SWCNTs) and silver nanoparticles (Ag) with a biodegradable polymer matrix. Different SWCNT amount were mixed with Ag nanoparticles and introduced in the poly(ε-caprolactone) (PCL) polymer matrix by solvent cast process. Nanostructure synergistic effects were evaluated in terms of morphological, electrical, dielectrical, mechanical and biological properties of binary PCL/Ag, PCL/SWCNTs and ternary PCL/Ag/SWCNTs composites. Results showed a good dispersion of nanostructures in the PCL and an increase of Young modulus with silver content in the binary systems. The PCL/Ag composites exhibited poor electrical properties, while in PCL/Ag/SWCNTs ternary films higher values of conductivity were measured compared to both binary composites. Results obtained in this research indicate that Ag particles facilitate the formation of conductive pathways in the presence of SWCNTs, they act as conductive bridges among nanotube bundles and facilitate the electron transfer. The addition of a small percentage of SWCNTs promoted significantly the electrical properties of PCL/Ag nanohybrid films. Biocompatibility of binary and ternary composites, evaluated by human mesenchymal stem cells-bone marrow derived (hBM-MSCs), suggests that the combination of Ag nanoparticles and SWCNTs with a biodegradable polymer opens new perspectives for biomedical applications.
The growth behavior of carbon nanotubes (CNTs), produced by radio frequency plasma enhanced chemi... more The growth behavior of carbon nanotubes (CNTs), produced by radio frequency plasma enhanced chemical vapor deposition, is studied here as a function of the CH4/N2 ratio and Ni catalyst layer thickness. Scanning electron microscopy shows that by employing a suitable deposition (methane) to etching (nitrogen) gas ratio, it is possible to obtain the growth of nanotubes with a limited presence of amorphous carbon on the substrate surface. In particular a progressive transition from random to aligned CNTs is observed when nitrogen is added to the plasma atmosphere. The electronic structure was then investigated by C 1s and valence band photoemission spectroscopy. The results show a shift of the overall spectral to a higher-binding-energy side and a larger density of the states at the Fermi level indicating the formation of metallic aligned tubes with increasing nitrogen fraction in the plasma atmosphere. The electronic structure indicates the insertion of odd-member rings in the graphene network leading to an improvement of the mechanical properties. The thickness of the Ni layer has a strong influence on the CNTs growth showing maximum value for nanotube formation at 20 nm.
Supramolecular structures consisting of dendritic porphyrins and single-walled carbon nanotubes (... more Supramolecular structures consisting of dendritic porphyrins and single-walled carbon nanotubes (SWNTs) have been prepared and characterized as an efficient donor/acceptor system. Non-covalent interactions enable the pair system to produce suitable electron transfer through a process occurring from the dendritic porphyrin core to the graphenic wall of carbon nanotubes. The role of structure/architecture of our dendritic molecules on SWNT photoelectrical behaviour has been also investigated.
This work focuses on the combination of the complementary properties of carbon nanotube (CNT) thi... more This work focuses on the combination of the complementary properties of carbon nanotube (CNT) thin film and poly3-octylthiophene (P3OT), following a dielectric route to the characterization of a novel composite material. The structural and electrical characterization of a P3OT/CNTs hybrid system performed by X-ray diffraction, differential scanning calorimetry and a.c. impedance spectroscopy show interesting effects, including the tendency of the nanotube structure to nucleate crystal growth and substantial changes in the dielectric behavior of the polymer, due to the effect of the polymer on the nanotube conformation. Dielectric relaxation spectroscopy demonstrates that the crystallization of the polymer onto the nanotubes results into a different relaxation of the composite's electronic structure. The changes in the dielectric properties can be explained in terms of a reduced vibrational freedom of the polymer chains as a consequence of the intercalation of the polymer matrix into the nanotubes’ lattice.
In bone engineering, the adhesion, proliferation and differentiation of mesenchymal stromal cells... more In bone engineering, the adhesion, proliferation and differentiation of mesenchymal stromal cells rely on signaling from chemico-physical structure of the substrate, therefore prompting the design of mimetic "extracellular matrix"-like scaffolds. In this study, three-dimensional porous poly-L-lactic acid (PLLA)-based scaffolds have been mixed with different components, including single walled carbon nanotubes (CNT), micro-hydroxyapatite particles (HA), and BMP2, and treated with plasma (PT), to obtain four different nanocomposites: PLLA + CNT, PLLA + CNTHA, PLLA + CNT + HA + BMP2 and PLLA + CNT + HA + PT. Adult bone marrow mesenchymal stromal cells (MSCs) were derived from the femur of orthopaedic patients, seeded on the scaffolds and cultured under osteogenic induction up to differentiation and mineralization. The release of specific metabolites and temporal gene expression profiles of marrow-derived osteoprogenitors were analyzed at definite time points, relevant to in vitro culture as well as in vivo differentiation. As a result, the role of the different biomimetic components added to the PLLA matrix was deciphered, with BMP2-added scaffolds showing the highest biomimetic activity on cells differentiating to mature osteoblasts. The modification of a polymeric scaffold with reinforcing components which also work as biomimetic cues for cells can effectively direct osteoprogenitor cells differentiation, so as to shorten the time required for mineralization.
A deposition process on a conducting surface, in which water acted as the dispersed phase and a m... more A deposition process on a conducting surface, in which water acted as the dispersed phase and a mixture of poly(methyl methacrylate) and chloroform as the continuous phase, was applied to prepare poly(methyl methacrylate) films. The influence of relative humidity during the film preparation on the surface morphology was investigated by field emission scanning microscopy. High-humidity preparation conditions lead to porous poly(methyl methacrylate) films. These films were then used as templates to perform the selective deposition into the pores of single-walled carbon nanotubes by an electrophoretic method. The attractive properties of carbon nanotubes combined with the versatile properties of poly(methyl methacrylate) open up new opportunities for these nanocomposites to achieve novel architectures in nanodevices and microdevices.
ABSTRACT Smectite clays (e.g. montmorillonite), belonging to the structural family called 2:1 phy... more ABSTRACT Smectite clays (e.g. montmorillonite), belonging to the structural family called 2:1 phyllosilicates, are the main choice for designing polymer nanocomposites due to their low cost and rich intercalation chemistry allowing them to be chemically modified (organoclays) and to improve the compatibility with the polymer matrix. These hybrid materials, normally called polymeric nanocomposites (PNC), represent a radical alternative to conventional polymer composites and have focused the attention of both academia and industry because of their unexpected properties, and their straightforward synthesis and processing. Such materials on the nanoscale level show significant improvements in mechanical properties, heat distortion temperatures, thermal stability, flame retardancy and enhanced barrier properties. The combination of enhanced properties, weight reduction, and low cost has led to interesting commercial applications such as automotive and packaging, among others. All this justifies the growing interest of both academia and industry in the development of these hybrid materials. In this paper we describe the most significant findings in the clay/polymer nanocomposites field considering three polymer families: elastomers, thermosets and polymers from natural resources or biopolymers.
This article fabricates and characterizes the combination of single walled carbon nanotubes (SWCN... more This article fabricates and characterizes the combination of single walled carbon nanotubes (SWCNTs) and silver nanoparticles (Ag) with a biodegradable polymer matrix. Different SWCNT amount were mixed with Ag nanoparticles and introduced in the poly(ε-caprolactone) (PCL) polymer matrix by solvent cast process. Nanostructure synergistic effects were evaluated in terms of morphological, electrical, dielectrical, mechanical and biological properties of binary PCL/Ag, PCL/SWCNTs and ternary PCL/Ag/SWCNTs composites. Results showed a good dispersion of nanostructures in the PCL and an increase of Young modulus with silver content in the binary systems. The PCL/Ag composites exhibited poor electrical properties, while in PCL/Ag/SWCNTs ternary films higher values of conductivity were measured compared to both binary composites. Results obtained in this research indicate that Ag particles facilitate the formation of conductive pathways in the presence of SWCNTs, they act as conductive bridges among nanotube bundles and facilitate the electron transfer. The addition of a small percentage of SWCNTs promoted significantly the electrical properties of PCL/Ag nanohybrid films. Biocompatibility of binary and ternary composites, evaluated by human mesenchymal stem cells-bone marrow derived (hBM-MSCs), suggests that the combination of Ag nanoparticles and SWCNTs with a biodegradable polymer opens new perspectives for biomedical applications.
The growth behavior of carbon nanotubes (CNTs), produced by radio frequency plasma enhanced chemi... more The growth behavior of carbon nanotubes (CNTs), produced by radio frequency plasma enhanced chemical vapor deposition, is studied here as a function of the CH4/N2 ratio and Ni catalyst layer thickness. Scanning electron microscopy shows that by employing a suitable deposition (methane) to etching (nitrogen) gas ratio, it is possible to obtain the growth of nanotubes with a limited presence of amorphous carbon on the substrate surface. In particular a progressive transition from random to aligned CNTs is observed when nitrogen is added to the plasma atmosphere. The electronic structure was then investigated by C 1s and valence band photoemission spectroscopy. The results show a shift of the overall spectral to a higher-binding-energy side and a larger density of the states at the Fermi level indicating the formation of metallic aligned tubes with increasing nitrogen fraction in the plasma atmosphere. The electronic structure indicates the insertion of odd-member rings in the graphene network leading to an improvement of the mechanical properties. The thickness of the Ni layer has a strong influence on the CNTs growth showing maximum value for nanotube formation at 20 nm.
Supramolecular structures consisting of dendritic porphyrins and single-walled carbon nanotubes (... more Supramolecular structures consisting of dendritic porphyrins and single-walled carbon nanotubes (SWNTs) have been prepared and characterized as an efficient donor/acceptor system. Non-covalent interactions enable the pair system to produce suitable electron transfer through a process occurring from the dendritic porphyrin core to the graphenic wall of carbon nanotubes. The role of structure/architecture of our dendritic molecules on SWNT photoelectrical behaviour has been also investigated.
This work focuses on the combination of the complementary properties of carbon nanotube (CNT) thi... more This work focuses on the combination of the complementary properties of carbon nanotube (CNT) thin film and poly3-octylthiophene (P3OT), following a dielectric route to the characterization of a novel composite material. The structural and electrical characterization of a P3OT/CNTs hybrid system performed by X-ray diffraction, differential scanning calorimetry and a.c. impedance spectroscopy show interesting effects, including the tendency of the nanotube structure to nucleate crystal growth and substantial changes in the dielectric behavior of the polymer, due to the effect of the polymer on the nanotube conformation. Dielectric relaxation spectroscopy demonstrates that the crystallization of the polymer onto the nanotubes results into a different relaxation of the composite's electronic structure. The changes in the dielectric properties can be explained in terms of a reduced vibrational freedom of the polymer chains as a consequence of the intercalation of the polymer matrix into the nanotubes’ lattice.
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Papers by Jose Kenny