Personne :
Auger, Michèle

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Structures organisationnelles
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Département de chimie, Faculté des sciences et de génie, Université Laval
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Voici les éléments 1 - 8 sur 8
  • Publication
    Accès libre
    Magnetic resonance imaging of human tissue-engineered adipose substitutes
    (Mary Ann Liebert, Inc, 2015-02-23) Audet, Pierre; Proulx, Maryse; Auger, Michèle; Fortin, Marc-André; Aubin, Kim; Lagueux, Jean; Fradette, Julie
    Adipose tissue (AT) substitutes are being developed to answer the strong demand in reconstructive surgery. To facilitate the validation of their functional performance in vivo, and to avoid resorting to excessive number of animals, it is crucial at this stage to develop biomedical imaging methodologies, enabling the follow-up of reconstructed AT substitutes. Until now, biomedical imaging of AT substitutes has scarcely been reported in the literature. Therefore, the optimal parameters enabling good resolution, appropriate contrast, and graft delineation, as well as blood perfusion validation, must be studied and reported. In this study, human adipose substitutes produced from adipose-derived stem/stromal cells using the self-assembly approach of tissue engineering were implanted into athymic mice. The fate of the reconstructed AT substitutes implanted in vivo was successfully followed by magnetic resonance imaging (MRI), which is the imaging modality of choice for visualizing soft ATs. T1-weighted images allowed clear delineation of the grafts, followed by volume integration. The magnetic resonance (MR) signal of reconstructed AT was studied in vitro by proton nuclear magnetic resonance (1H-NMR). This confirmed the presence of a strong triglyceride peak of short longitudinal proton relaxation time (T1) values (200±53 ms) in reconstructed AT substitutes (total T1=813±76 ms), which establishes a clear signal difference between adjacent muscle, connective tissue, and native fat (total T1 ∼300 ms). Graft volume retention was followed up to 6 weeks after implantation, revealing a gradual resorption rate averaging at 44% of initial substitute's volume. In addition, vascular perfusion measured by dynamic contrast-enhanced-MRI confirmed the graft's vascularization postimplantation (14 and 21 days after grafting). Histological analysis of the grafted tissues revealed the persistence of numerous adipocytes without evidence of cysts or tissue necrosis. This study describes the in vivo grafting of human adipose substitutes devoid of exogenous matrix components, and for the first time, the optimal parameters necessary to achieve efficient MRI visualization of grafted tissue-engineered adipose substitutes.
  • Publication
    Accès libre
    Membrane assembly and ion transport ability of a fluorinated nanopore
    (Public Library of Science, 2016-11-11) Godbout, Raphaël; Auger, Michèle; Lagüe, Patrick; Auger, Maud; Otis, François; Légaré, Sébastien; Carpentier, Claudia; Voyer, Normand
    A novel 21-residue peptide incorporating six fluorinated amino acids was prepared. It was designed to fold into an amphiphilic alpha helical structure of nanoscale length with one hydrophobic face and one fluorinated face. The formation of a fluorous interface serves as the main vector for the formation of a superstructure in a bilayer membrane. Fluorescence assays showed this ion channel's ability to facilitate the translocation of alkali metal ions through a phospholipid membrane, with selectivity for sodium ions. Computational studies showed that a tetramer structure is the most probable and stable supramolecular assembly for the active ion channel structure. The results illustrate the possibility of exploiting multiple Fd-:M+ interactions for ion transport and using fluorous interfaces to create functional nanostructures.
  • Publication
    Accès libre
    Spider silk as a blueprint for greener materials : a review
    (Taylor & Francis, 2016-03-16) Auger, Michèle; Lefèvre, Thierry
    Spider silk exhibits remarkable properties, especially its well-known tensile performances. They rely on a complex nanostructured hierarchical organisation that studies progressively elucidate. Spider silk encompasses a vast range of fibres that exhibit diverse and captivating physical and biological characteristics. The full understanding of the relation between structure and properties may lead in the future to the design of a variety of high-performance, tailored materials and devices. Reknown for being produced in mild and benign conditions, this outstanding biological material constitutes one of the more representative example of biomimetism. In addition, silk's structure is produced with limited means, i.e. low energy and relatively simple renewable constituents (silk proteins). Then, if successfully controlled and adequately transposed in biomaterials, some properties of natural silk could lead to innovative green materials that may contribute to reduce the ecological footprint of societies. In fact, striking recent advanced applications made with B. mori silk suggest that spider silk-based materials may lead to advanced resistant and functional materials, then becoming among the most promising subject of study in material science. However, several challenges have to be overcome, especially our ability to produce native-like silk, to control biomaterials’ structure and properties and to minimise their ecological footprint. This paper reviews the characteristics of spider silk that make it so attractive and that may (or may not) contribute to reduce ecological footprint of materials and the challenges in producing innovative spider silk-based materials. First, from a biomimetic perspective, the structure and models that explain the tensile resistance of natural silk are presented, followed by the state of knowledge regarding natural silk spinning process and synthetic production methods. Biocompatibility (biosafety and biofunctionality) as well as biodegradability issues are then addressed. Finally, examples of applications are reviewed. Features that may lead to the design of green materials are emphasised throughout.
  • Publication
    Accès libre
    Characterization of the structure of human skin substitutes by infrared microspectroscopy
    (Springer Link, 2013-06-21) Auger, Michèle; Laroche, Gaétan; Lafleur, Michel.; Leroy, Marie; Pouliot, Roxane
    The skin acts mainly as a protective barrier from the external environment, thanks to the stratum corneum which is the outermost layer of the skin. As in vitro tests on skin are essential to elaborate new drugs, the development of skin models closer to reality becomes essential. It is now possible to produce in vitro human skin substitutes through tissue engineering by using the self-assembly method developed by the Laboratoire d’Organogénèse Expérimentale. In the present work, infrared microspectroscopy imaging analyses were performed to get in-depth morpho-spectral characterization of the three characteristic layers of human skin substitutes and normal human skin, namely the stratum corneum, living epidermis, and dermis. An infrared spectral analysis of the skin is a powerful tool to gain information on the order and conformation of the lipid chains and the secondary structure of proteins. On one hand, the symmetric stretching mode of the lipid methylene groups (2,850 cm−1) is sensitive to the acyl chain conformational order. The evolution profile of the frequency of this vibrational mode throughout the epidermis suggests that lipids in the stratum corneum are more ordered than those in the living epidermis. On the other hand, the frequencies of the infrared components underneath the envelop of the amide I band provide information about the overall protein conformation. The analysis of this mode establishes that the proteins essentially adopt an α-helix conformation in the epidermis, probably associated with the presence of keratin, while modifications of the protein content are observed in the dermis (extracellular matrix made of collagen). Finally, the lipid organization, as well as the protein composition in the different layers, is similar for human skin substitutes and normal human skin, confirming that the substitutes reproduce essential features of real skin and are appropriate biomimetics.
  • Publication
    Accès libre
    Crown ether modified peptide interactions with model membranes
    (2019-02-17) Bacon, Anne; Provencher, Marie-Ève; Auger, Michèle; Cardinal, Sébastien; Lagüe, Patrick; Collignon, Barbara; Fillion, Matthieu; Bürck, Jochen; Otis, François; Voyer, Normand; Dionne, Justine; Paquet-Côté, Pierre-Alexandre
    A simple model of an uncharged antimicrobial peptide, carrying four crown ether side chains, is modified further by the selective incorporation of arginine side chains to control its secondary structure and its interaction with model membranes and living cells. Conformational studies show that shifting the position of a cationic residue in the peptide sequence allows to control its secondary structure and supramolecular self-assembly in solution. Results also demonstrate that the secondary structure influences the interaction with model membranes and cells. An α-helical peptide with greater amphiphilicity forms assemblies that interact with both prokaryotic and eukaryotic model membranes and cells. However, a β-stranded peptide with evenly distributed charges generates assemblies that interact more selectively with prokaryotic model membranes and cells. In addition, we observed differences in peptide orientation between uncharged and cationic α-helical peptides with different phospholipid bilayers. In general, the studied peptides have a higher affinity for thinner membranes, and cationic peptides interacted better with anionic membranes.
  • Publication
    Accès libre
    Transdermal diffusion, spatial distribution and physical state of a potential anticancer drug in mouse skin as studied by diffusion and spectroscopic techniques
    (IOS Press, 2018-05-07) Lefèvre, Thierry; Le, Quoc-Chon; Auger, Michèle; Laroche, Gaétan; C. Gaudreault, René.
    Background:Understanding the efficiency of a transdermal medical drug requires the characterization of its diffusion process, including its diffusion rate, pathways and physical state. Objective:The aim of this work is to develop a strategy to achieve this goal. Methods:FTIR spectroscopic imaging in conjunction with a Franz cell and HPLC measurements were used to examine the transdermal penetration of deuterated tert-butyl phenylchloroethylurea (tBCEU), a molecule with a potential anticancer action. tBCEU has been solubilized in an expedient solvent mixture and its diffusion in hairless mouse skin has been studied. Results:The results indicate that tBCEU diffuses across the skin for more than 10 hours with a rate comparable to selegiline, an officially-approved transdermal drug. IR image analyses reveal that after 10 hours, tBCEU penetrates skin and that its spatial distribution does not correlate with neither the distribution of lipids nor proteins. tBCEU accumulates in cluster domains but overall low concentrations are found in skin. FTIR spectroscopic imaging additionally reveals that tBCEU is in a crystalline form. Conclusions:The results suggest that tBCEU is conveyed through the skin without preferential pathway. FTIR spectroscopic imaging and transdermal diffusion measurements appear as complementary techniques to investigate drug diffusion in skin.
  • Publication
    Accès libre
    A comparative study between human skin substitutes and normal human skin using Raman microspectroscopy
    (Minerals, Metals and Materials Society, 2014-02-12) Labbé, Jean-François; Jean, Jessica; Auger, Michèle; Ouellet, Marise; Laroche, Gaétan; Leroy, Marie; Pouliot, Roxane; Lefèvre, Thierry
    Research in the field of bioengineered skin substitutes is motivated by the need to find new dressings for people affected by skin injuries (burns, diabetic ulcers), and to develop adequate skin models to test new formulations developed in vitro. Thanks to advances in tissue engineering, it is now possible to produce human skin substitutes without any exogenous material, using the self-assembly method developed by the Laboratoire d’Organogénèse Expérimentale. These human skin substitutes consist of a dermis and a stratified epidermis (stratum corneum and living epidermis). Raman microspectroscopy has been used to characterize and compare the molecular organization of skin substitutes with normal human skin. Our results confirm that the stratum corneum is a layer rich in lipids which are well ordered (trans conformers) in both substitutes and normal human skin. The amount of lipids decreases and more gauche conformers appear in the living epidermis in both cases. However, the results also show that there are fewer lipids in the substitutes and that the lipids are more organized in the normal human skin. Concerning the secondary structure of proteins and protein content, the data show that they are similar in the substitutes and in the normal human skin. In fact, the epidermis is rich in α-keratin, whereas the dermis contains mainly type I collagen.
  • Publication
    Accès libre
    Using infrared and raman microspectroscopies to compare ex vivo involved psoriatic skin with normal human skin
    (SPIE, 2015-06-17) Lefèvre, Thierry; Auger, Michèle; Laroche, Gaétan; Leroy, Marie; Pouliot, Roxane
    Psoriasis is a chronic dermatosis that affects around 3% of the world’s population. The etiology of this autoimmune pathology is not completely understood. The barrier function of psoriatic skin is known to be strongly altered, but the structural modifications at the origin of this dysfunction are not clear. To develop strategies to reduce symptoms of psoriasis or adequate substitutes for modeling, a deep understanding of the organization of psoriatic skin at a molecular level is required. Infrared and Raman microspectroscopies have been used to obtain direct molecular-level information on psoriatic and healthy human skin biopsies. From the intensities and positions of specific vibrational bands, the lipid and protein distribution and the lipid order have been mapped in the different layers of the skin. Results showed a similar distribution of lipids and collagen for normal and psoriatic human skin. However, psoriatic skin is characterized by heterogeneity in lipid/protein composition at the micrometer scale, a reduction in the definition of skin layer boundaries and a decrease in lipid chain order in the stratum corneum as compared to normal skin. A global decrease of the structural organization is exhibited in psoriatic skin that is compatible with an alteration of its barrier properties.