Personne :
Laroche, Gaétan

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Université Laval. Département de génie des mines, de la métallurgie et des matériaux
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Voici les éléments 1 - 10 sur 37
  • Publication
    Accès libre
    Rapid nucleation of iron oxide nanoclusters in aqueous solution by plasma electrochemistry
    (ACS Publications, 2015-06-18) Turgeon, Stéphane; Fortin, Marc-André; Laroche, Gaétan; Sarra-Bournet, Christian; Lagueux, Jean; Létourneau, Mathieu; Chevallier, Pascale; Laprise-Pelletier, Myriam; Bouchard, Mathieu
    Progresses in cold atmospheric plasma technologies have made possible the synthesis of nanoparticles in aqueous solutions using plasma electrochemistry principles. In this contribution, a reactor based on microhollow cathodes and operating at atmospheric pressure was developed to synthesize iron-based nanoclusters (nanoparticles). Argon plasma discharges are generated at the tip of the microhollow cathodes, which are placed near the surface of an aqueous solution containing iron salts (FeCl₂ and FeCl₃) and surfactants (biocompatible dextran). Upon reaction at the plasma−liquid interface, reduction processes occur and lead to the nucleation of ultrasmall iron-based nanoclusters (IONCs). The purified IONCs were investigated by XPS and FTIR, which confirmed that the nucleated clusters contain a highly hydrated form of iron oxide, close to the stoichiometric constituents of α-FeOOH (goethite) or Fe₅O₃(OH)₉ (ferrihydrite). Relaxivity values of r₁ = 0.40 mM−¹ s−¹ and r₂/r₁ = 1.35 were measured (at 1.41 T); these are intermediate values between the relaxometric properties of superparamagnetic iron oxide nanoparticles used in medicine (USPIO) and those of ferritin, an endogenous contrast agent. Plasma-synthesized IONCs were injected into the mouse model and provided positive vascular signal enhancement in T₁-w. MRI for a period of 10−20 min. Indications of rapid and strong elimination through the urinary and gastrointestinal tracts were also found. This study is the first to report on the development of a compact reactor suitable for the synthesis of MRI iron-based contrast media solutions, on site and upon demand.
  • Publication
    Accès libre
    Synthesis, characterization, and functionalization of ZnO nanoparticles by N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (TMSEDTA) : investigation of the interactions between Phloroglucinol and ZnO@TMSEDTA
    (King Saud University, 2016-05-14) Barrak, Haythem; Laroche, Gaétan; Saied, Taieb; Chevallier, Pascale; M’nif, Adel; Hamzaoui, Ahmed Hichem
    The use of semiconductor oxides, such as chemical or biological sensors, requires their functionalization with appropriate molecules displaying specific interaction with the substance to be detected. Generally, the support materials used are TiO₂ or SiO₂. In the present work, zinc oxide nanoparticles (ZnO NPs), known for its reactivity and high specific area, were used. The synthesis of nanoscale ZnO was advantageously performed by precipitation at low temperature (60 °C). To our knowledge, it was the first time that this material was synthesized at such a low temperature, therefore lowering production cost. Moreover, the surface functionalization of ZnO was performed with N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (TMSEDTA) in ethanol. This allowed shortening the functionalization reaction duration as compared to previously published literaturein the field. The samples obtained were analyzed by XRD, TEM, DLS, FTIR, TGA and XPS, which all concur with the successful synthesis of ZnO nanoparticles as well as the efficiency of TMSEDTA grafting on ZnO. Then, the interactions of this functionalized material, ZnO@TMSEDTA, with the Phloroglucinol (drug) were evaluated by using cyclic voltammetry measurements in solution. The cyclic voltammograms showed an intense cathodic peak which was correlated to the initial concentration of free Phloroglucinol. This cathodic peak was degraded upon addition of ZnO@TMSEDTA particles due to the drug interactions with free available carboxylic groups on the functionalized NPs. Based on a calibration curve, the drug concentration uptake can be therefore quantified. Thus, these results establish a big step to develop a Phloroglucinol sensor.
  • Publication
    Accès libre
    Characterization of argon dielectric barrier discharges applied to ethyl lactate plasma polymerization
    (Institute of Physics Publishing Ltd, 2017-11-03) Laroche, Gaétan; Desjardins, Edouard; Naudé, Nicolas; Meichelboeck, Maximilian; Laurent, Morgane; Stafford, Luc; Gherardi, Nicolas
    The influence of the input voltage frequency (35 and 150 kHz), interelectrode gap (1 and 2 mm) and precursor concentration (250, 350, and 450 ppm) on the electron temperature (Te), number density of metastable Ar atoms (n(Arm)), and discharge current density (proportional to the electron density ne) is studied in an argon-ethyl lactate dielectric barrier discharge (DBD). An argon-ammonia Penning mixture is also considered as reference. These results are correlated to the chemistry (XPS, IR) and topography (AFM) of the ethyl-lactate-based plasma polymer coatings. Low Te values from 0.3 to 0.5 eV were obtained for all discharges. This observation, in addition to resemblances with the Ar–NH3 mixture, suggested that the ionization kinetics of ethyl lactate-based discharges is driven by Penning reactions. Among the investigated parameters, the dissipated power obtained through changes of the excitation frequency had the largest impact on both the coatings properties and the discharge behavior.
  • Publication
    Accès libre
    Water drop-surface interactions as the basis for the design of anti-fogging surfaces : theory, practice, and applications trends
    (Elsevier Science, 2018-11-24) Laroche, Gaétan; Rodríguez Durán, Iván
    Glass- and polymer-based materials have become essential in the fabrication of a multitude of elements, including eyeglasses, automobile windshields, bathroom mirrors, greenhouses, and food packages, which unfortunately mist up under typical operating conditions. Far from being an innocuous phenomenon, the formation of minute water drops on the surface is detrimental to their optical properties (e.g., light-transmitting capability) and, in many cases, results in esthetical, hygienic, and safety concerns. In this context, it is therefore not surprising that research in the field of fog-resistant surfaces is gaining in popularity, particularly in recent years, in view of the growing number of studies focusing on this topic. This review addresses the most relevant advances released thus far on anti-fogging surfaces, with a particular focus on coating deposition, surface micro/nanostructuring, and surface functionalization. A brief explanation of how surfaces fog up and the main issues of interest linked to fogging phenomenon, including common problems, anti-fogging strategies, and wetting states are first presented. Anti-fogging mechanisms are then discussed in terms of the morphology of water drops, continuing with a description of the main fabrication techniques toward anti-fogging property. This review concludes with the current and the future perspectives on the utility of anti-fogging surfaces for several applications and some remaining challenges in this field.
  • Publication
    Accès libre
    Optical emission spectroscopy as a process-monitoring tool in plasma enhanced chemical vapor deposition of amorphous carbon coatings - multivariate statistical modelling
    (Elsevier Science, 2018-03-01) Turgeon, Stéphane; Anooshehpour, Farid; Laroche, Gaétan; Mantovani, D.; Cloutier, Maxime
    Production of Diamond-Like Carbon (DLC) nanocoatings using plasma enhanced chemical vapor deposition is studied by Optical Emission Spectroscopy (OES) as a plasma diagnostic technique. The objective of the current research is to establish a predictive model of DLC properties using a multivariate analysis method. This model is based on OES data instead of process parameters, which are reactor dependent and accordingly, their effect on the plasma deposition process may vary from one reactor to another. The predictive potential of OES is evaluated using partial least square regression (PLSR) analysis. The results show that OES derived data are capable of replacing some process parameters to predict the DLC properties. The perspective of PLSR modelling and OES application for the development and monitoring of a structurally graded DLC coating is also discussed.
  • Publication
    Accès libre
    Effect of linking arm hydrophilic/hydrophobic nature, length and end-group on the conformation and the RGD accessibility of surface-immobilized fibronectin
    (Elsevier, 2019-10-30) Laroche, Gaétan; Vanslambrouck, Stéphanie; Guay-Bégin, Andrée-Anne; Chevallier, Pascale
    In order to stimulate the cellular response to implant materials, extracellular matrix (ECM) proteins, such as collagen and fibronectin (FN), are immobilized on the implant surface. Amongst all ECM proteins used for biomimetic materials for medical applications, FN is one of the most investigated proteins thanks to its ability to promote cell adhesion and its contribution to important physiological processes. However, its conformation and hence its bioactivity strongly depend on the hydrophilic/hydrophobic nature of the surface as well as on immobilization strategies. This work investigates the effect of these two parameters, as well as the effect of the crosslinker length. FN was grafted onto silicon wafers using eights different linking arms presenting different lengths, hydrophilic/hydrophobic characters and binding sites. The protein was linked through either its amino groups (lysine amino acids) or sulfhydryl functionalities (cysteine amino acids). The grafting of each crosslinker and subsequent FN conjugation onto the surfaces was evidenced by X-ray photoelectron spectroscopy, while the surface hydrophilicity was determined by contact angle measurements. Moreover, atomic force microscopy images revealed that the conformation of surface conjugated FN only depends on the hydrophilicity of the linking arm. The FN conformation was also probed by enzyme-linked immunosorbent assays (ELISA). ELISA data demonstrated that all of the three investigated parameters linking arm parameter (length, hydrophobic/hydrophilic character, and terminal end-group) somewhat influence the RGD accessibility.
  • Publication
    Accès libre
    Current trends, challenges, and perspectives of anti-fogging technology : surface and material design, fabrication strategies, and beyond
    (Pergamon Press, 2018-09-07) Laroche, Gaétan; Rodríguez Durán, Iván
    Transparent materials such as glasses and some polymers play an essential role in our daily life. Indeed, it is well known that their application in mirrors, windows, automobile windshields, and eyewear make our day-to-day activities more comfortable. These examples aside, many more can also be found in several spheres of human activity, including such sectors as diverse and distinct as the medical, photovoltaic and food industry fields. Unfortunately, due to the unavoidable condensation of water vapor on solid surfaces, these materials undergo fogging under normal operating conditions. More than a mere nuisance, this naturally occurring phenomenon adversely affects their optical performance as it lowers the light-transmitting capability and often gives rise to esthetical, hygienic, and safety concerns. In this context, research in the field of anti-fogging technology has attracted growing interest, particularly in recent years, for numerous potential applications. In this review, recent developments in the design and manufacturing of anti-fogging surfaces are described in detail, beginning with the fogging mechanism in terms of nucleation and growth of water drops. Anti-fogging strategies explored thus far and mainly focusing on hydrophilic and hydrophobic surfaces are then extensively described. Finally, based on current research in this promising field, future trends and prospects for their effective implementation are presented.
  • Publication
    Atmospheric pressure plasma polymer of ethyl lactate: In vitro degradation and cell viability studies
    (Wiley, 2016-03-29) Laroche, Gaétan; Koehler, Julia; Hoesli, Corinne A.; Laurent, Morgane; Sabbatier, Gad; Ghérardi, Nicolas
    Ethyl lactate is injected into a dielectric barrier discharge (DBD) to build up a degradable plasma polymer (PP) to be used as a drug delivery system. Plasma power, deposition time, and type of carrier gas (Ar, N2) are correlated to the coating in vitro degradation rate. PPs are characterized by AFM, SEM, IR spectroscopy, XPS, and SEC, while surface profilometry is used to monitor the degradation kinetics. PPs deposited under N2 are mainly composed of hydrophilic functionalities, which explain their fast degradation upon exposure to an aqueous environment. In contrast, PPs synthesized under Ar lead to a slower degradation rate due to their hydrocarbon structure containing some hydrolyzable moieties. The potential of the PPs for vascular applications is verified
  • Publication
    Accès libre
    Interplay of geometric cues and RGD/BMP-2 crosstalk in directing stem cell fate
    (American Chemical Society, 2017-08-21) Bilem, Ibrahim; Laroche, Gaétan; Plawinski, Laurent; Chevallier, Pascale; Sone, E. (Eli); Durrieu, Marie-Christine
    Within the native microenvironment, extracellular matrix (ECM) components are thought to display a complex and heterogeneous distribution, spanning several length scales. Herein, the objective is to mimic, in vitro, the hierarchical organization of proteins and growth factors as well as their crosstalk. Photolithography technique was used to adjacently pattern geometrically defined regions of RGD and BMP-2 mimetic peptides onto glass substrates. These ECM-derived ligands are known to jointly regulate mesenchymal stem cells (MSCs) osteogenic differentiation. By manipulating the spatial distribution of dually grafted peptides, the extent of human MSCs osteogenic differentiation was significantly affected, depending on the shape of peptide micropatterns. Our data highlight the existence of a strong interplay between geometric cues and biochemical signals. Such in vitro systems provide a valuable tool to investigate mechanisms by which multiple ECM cues overlap to regulate stem cell fate, thereby contributing to the design of bioinspired biomaterials for bone tissue engineering applications.
  • Publication
    Accès libre
    Evaluation of an air spinning process to produce tailored biosynthetic nanofiber scaffolds
    (Elsevier Science, 2013-11-14) Abadie, Pierre; Laroche, Gaétan; Dieval, Florence; Sabbatier, Gad; Durand, Bernard
    We optimised the working parameters of an innovative air spinning device to produce nanofibrous polymer scaffolds for tissue engineering applications. Scanning electron microscopy was performed on the fibre scaffolds which were then used to identify various scaffold morphologies based on the ratio of surface occupied by the polymer fibres on that covered by the entire polymer scaffold assembly. Scaffolds were then produced with the spinning experimental parameters, resulting in 90% of fibres in the overall polymer construct, and were subsequently used to perform a multiple linear regression analysis to highlight the relationship between nanofibre diameter and the air spinning parameters. Polymer solution concentration was deemed as the most significant parameter to control fibre diameter during the spinning process, despite interactions between experimental parameters. Based on these findings, viscosity measurements were performed to clarify the effect of the polymer solution property on scaffold morphology.