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Skulason H.S.,Regroupement Quebecois sur les Materiaux de Pointe | Skulason H.S.,McGill University | Nguyen H.V.,Ecole Polytechnique de Montréal | Guermoune A.,Center Quebecois sur les Materiaux Fonctionnels | And 8 more authors.
Applied Physics Letters | Year: 2011

We report high-frequency scattering parameter measurement of large-area monolayer graphene integrated on low-loss quartz substrates. High-quality graphene was grown by chemical vapour deposition on copper, chemically hole doped, and transferred to quartz. Microwave measurements were performed from 0.01 to 110 GHz. Simple microwave models were used to extract graphene impedance parameters. We find that contact resistance is effectively shunted above 3 GHz. Atomically thin large area graphene behaves as a wideband resistor with negligible kinetic inductance and negligible skin effect. © 2011 American Institute of Physics.

Laterreur V.,Laval University | Gauvin R.,Center Quebecois sur les Materiaux Fonctionnels | Tremblay C.,Laval University | Germain L.,Laval University | And 2 more authors.
Acta Biomaterialia | Year: 2015

There is an ongoing clinical need for tissue-engineered small-diameter (<6 mm) vascular grafts since clinical applications are restricted by the limited availability of autologous living grafts or the lack of suitability of synthetic grafts. The present study uses our self-assembly approach to produce a fibroblast-derived decellularized vascular scaffold that can then be available off-the-shelf. Briefly, scaffolds were produced using human dermal fibroblasts sheets rolled around a mandrel, maintained in culture to allow for the formation of cohesive and three-dimensional tubular constructs, and then decellularized by immersion in deionized water. Constructs were then endothelialized and perfused for 1 week in an appropriate bioreactor. Mechanical testing results showed that the decellularization process did not influence the resistance of the tissue and an increase in ultimate tensile strength was observed following the perfusion of the construct in the bioreactor. These fibroblast-derived vascular scaffolds could be stored and later used to deliver readily implantable grafts within 4 weeks including an autologous endothelial cell isolation and seeding process. This technology could greatly accelerate the clinical availability of tissue-engineered blood vessels.

Massey S.,Center Quebecois sur les Materiaux Fonctionnels | Massey S.,École Nationale Supérieure de Chimie de Paris | Gallino E.,Center Quebecois sur les Materiaux Fonctionnels | Gallino E.,École Nationale Supérieure de Chimie de Paris | And 5 more authors.
Polymer Degradation and Stability | Year: 2010

Radiation used in biomedical applications causes chemical changes to biomedical materials. This work is an ex situ simulation of the influence of low-energy electron (LEE) impact and X-ray irradiation on the chemical properties of plasma-polymerized allylamine (PPA) bioactive and biocompatible stent coatings. Preliminary X-ray photoelectron spectroscopy (XPS) results show that PPA coatings oxidize in contact with ambient air by the detection of C-O and C{double bond, long}O bonds which are typical of polymer oxidation. Chemical changes after LEE and X-ray irradiation are mainly a loss of oxygen, assuming a surface deoxidizing and not a complete destruction of the surface. XPS survey analyses show that the amine groups remain stable during irradiation. LEE impact measurements by TOF mass spectrometry show that the main ionic losses are H- ions. It appears that CN groups are stable under irradiation and we observe a loss of hydrogen and oxygen as the main chemical modifications. In conclusion, these results suggest that PPA coatings are stable under biomedical radiation, and they can therefore be used for bioactive and biocompatible stent coatings. © 2009 Elsevier Ltd. All rights reserved.

Guidoin R.,Laval University | Bes T.M.,Laval University | Cianciulli T.,Dr Cosme Argerich Hospital | Klein J.,Research Center St Boniface General Hospital | And 7 more authors.
Journal of Long-Term Effects of Medical Implants | Year: 2012

A failing mitral valve prosthesis made from bovine pericardium was explanted from a 50-year-old patient. Preoperative transthoracic-echocardiography had confirmed severe mitral regurgitation due to structural failure of this HP Bio bovine pericardium heart valve prosthesis. The explanted device was examined macroscopically, by scanning electron microscopy (SEM), by light microscopy, and by transmission electron microscopy (TEM). Samples of unassembled patches of bovine pericardium were used as a pre-implantation control to better understand the changes that occurred in the structure of the pericardium following the 7 years of implantation. Examination confirmed complete dehiscence of a cusp along a valve post and the stent: This detached cusp was observed floating in the bloodstream at echocardiography. The fibrous pannus overgrowth was well developed along the stent and extended to the bottom of the cusps both on the inflow and the outflow sides. The fibrous panni were found to be poorly adhesive to the pericardium cusps and had become stiff, thus impairing the opening and closure of the valve. The structure of the pericardium cusps was severely deteriorated compared to the control bovine pericardium tissue samples. The collagen bundles were frequently broken and more stretched in the explanted device, lacking the wavy histological pattern of normal collagen fibers. However, the tissues were devoid of any calcification. In conclusion, the failure mode of this valve was the dehiscence of a cusp from a valve post and along the stent cloth in the absence calcification. © 2012 by Begell House, Inc.

Imam S.A.,Regroupement Quebecois sur les Materiaux de Pointe | Imam S.A.,McGill University | Deshpande T.,Regroupement Quebecois sur les Materiaux de Pointe | Deshpande T.,McGill University | And 6 more authors.
Applied Physics Letters | Year: 2011

We report controlled charge transfer between large-area graphene and a dual-dielectric, silicon nitride/silicon oxide substrate. Graphene was grown on copper by chemical vapour deposition, transferred to the nitride substrates, and patterned into test structures. Hysteresis in conductance with varying gate voltage is easily understood in terms of electron transfer between graphene and nitride traps. Increased hysteresis with temperature suggests thermally activated charge transfer of a Poole-Frenkel or Schottky nature. A 7.3 change in graphene sheet resistance is observed at room temperature with the nitride in a charged and discharged state. © 2011 American Institute of Physics.

Sabri S.S.,Regroupement Quebecois sur les Materiaux de Pointe | Sabri S.S.,McGill University | Guillemette J.,Regroupement Quebecois sur les Materiaux de Pointe | Guillemette J.,McGill University | And 6 more authors.
Applied Physics Letters | Year: 2012

We demonstrate that large-area, graphene field effect transistors with a passive parylene substrate and a polyethyleneimine functional layer have enhanced sensitivity to CO 2 gas exposure. The electron doping of graphene, caused by protonated amine groups within the polyethyleneimine, is modulated by the formation of negatively charged species generated by CO 2 adsorption. The charge doping mechanism is general, and quantitative doping density changes can be determined from the graphene field effect transistor characteristics. © 2012 American Institute of Physics.

Ledwosinska E.,Regroupement Quebecois sur les Materiaux de Pointe | Ledwosinska E.,McGill University | Gaskell P.,Regroupement Quebecois sur les Materiaux de Pointe | Gaskell P.,McGill University | And 6 more authors.
Applied Physics Letters | Year: 2012

We report an entirely organic-free method to suspend monolayer graphene grown by chemical vapour deposition over 10-20 μm apertures in a Cu substrate. Auger electron spectroscopy, Raman spectroscopy, scanning electron microscope, and transmission electron microscope measurements confirm high quality graphene with no measurable contamination beyond that resulting from air exposure. This method can be used to prepare graphene for fundamental studies and applications where the utmost cleanliness and structural integrity are required. © 2012 American Institute of Physics.

Beaudoin Cloutier C.,Laval University | Beaudoin Cloutier C.,University of Montréal | Guignard R.,Laval University | Bernard G.,Laval University | And 8 more authors.
Tissue Engineering - Part C: Methods | Year: 2015

Our bilayered self-assembled skin substitutes (SASS) are skin substitutes showing a structure and functionality very similar to native human skin. These constructs are used, in life-threatening burn wounds, as permanent autologous grafts for the treatment of such affected patients even though their production is exacting. We thus intended to shorten their current production time to improve their clinical applicability. A self-assembled decellularized dermal matrix (DM) was used. It allowed the production of an autologous skin substitute from patient's cells. The characterization of SASS reconstructed using a decellularized dermal matrix (SASS-DM) was performed by histology, immunofluorescence, transmission electron microscopy, and uniaxial tensile analysis. Using the SASS-DM, it was possible to reduce the standard production time from about 8 to 4 and a half weeks. The structure, cell differentiation, and mechanical properties of the new skin substitutes were shown to be similar to the SASS. The decellularization process had no influence on the final microstructure and mechanical properties of the DM. This model, by enabling the production of a skin substitute in a shorter time frame without compromising its intrinsic tissue properties, represents a promising addition to the currently available burn and wound treatments. Copyright 2015, Mary Ann Liebert, Inc.

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