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Personne :
Laroche, Gaétan

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Laroche

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Gaétan

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Université Laval. Département de génie des mines, de la métallurgie et des matériaux

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ncf10316941

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Evaluating poly(Acrylamide-co-Acrylic Acid) hydrogels stress relaxation to direct the osteogenic differentiation of mesenchymal stem cells

2021-04-19, Prouvé, Émilie, Drouin, Bernard, Laroche, Gaétan, Rémy-Zolghadri, Murielle, Chevallier, Pascale, Durrieu, Marie-Christine

The aim of this study is to investigate polyacrylamide-based hydrogels stress relaxation and the subsequent impact on the osteogenic differentiation of human mesenchymal stem cells (hMSCs). Different hydrogels are synthesized by varying the amount of cross-linker and the ratio between the monomers (acrylamide and acrylic acid), and characterized by compression tests. It has been found that hydrogels containing 18% of acrylic acid exhibit an average relaxation of 70%, while pure polyacrylamide gels show an average relaxation of 15%. Subsequently, hMSCs are cultured on two different hydrogels functionalized with a mimetic peptide of the bone morphogenetic protein-2 to enable cell adhesion and favor their osteogenic differentiation. Phalloidin staining shows that for a constant stiffness of 55 kPa, a hydrogel with a low relaxation (15%) leads to star-shaped cells, which is typical of osteocytes, while a hydrogel with a high relaxation (70%) presents cells with a polygonal shape characteristic of osteoblasts. Immunofluorescence labeling of E11, strongly expressed in early osteocytes, also shows a dramatically higher expression for cells cultured on the hydrogel with low relaxation (15%). These results clearly demonstrate that, by fine-tuning hydrogels stress relaxation, hMSCs differentiation can be directed toward osteoblasts, and even osteocytes, which is particularly rare in vitro.

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Fibronectin grafting to enhance skin sealing around transcutaneous titanium implant

2021-04-30, Bilem, Ibrahim, Ghadhab, Souhaila, Ruel, Jean, Laroche, Gaétan, Auger, François A., Guay-Bégin, Andrée-Anne, Pauthe, Emmanuel, Chevallier, Pascale

Intraosseous transcutaneous amputation prosthesis is a new approach in orthopedic implants that overcomes socket prosthesis problems. Its long-term performance requires a tight skin-implant seal to prevent infections. In this study, fibronectin (Fn), a widely used adhesion protein, was adsorbed or grafted onto titanium alloy. Fn grafting was performed using two different linking arms, dopamine/glutaric anhydride or phosphonate. The characterization of Fn-modified surfaces showed that Fn grating via phosphonate has led to the highest amount of Fn cell-binding site (RGD, arginine, glycine, and aspartate) available on the surface. Interestingly, cell culture studies revealed a strong correlation between the amount of available RGD ligands and cellular behavior, since enhanced proliferation and spreading of fibroblasts were noticed on Fn-grafted surfaces via phosphonate. In addition, an original in vitro mechanical test, inspired from the real situation, to better predict clinical outcomes after implant insertion, has been developed. Tensile test data showed that the adhesion strength of a bio-engineered dermal tissue was significantly higher around Fn-grafted surfaces via phosphonate, as compared to untreated surfaces. This study sheds light on the importance of an appropriate selection of the linking arm to tightly control the spatial conformation of biomolecules on the material surface, and consequently cell interactions at the interface tissue/implant.

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PublicationRestreint

Atmospheric-pressure plasma-enhanced chemical vapor deposition of nanocomposite thin films from ethyl lactate and silica nanoparticles

2020-10-09, Milaniak, Natalia, Laroche, Gaétan, Massines, Françoise

Nanocomposite coatings are made by atmospheric-pressure plasma-enhanced chemical vapor deposition from ethyl lactate (EL) and silica nanoparticles (NPs) in a dielectric barrier discharge (DBD) using frequency-shift keying (FSK) to alternate between 1- and 15-kHz voltages. In situ plasma Fourier-transform infrared spectroscopy (FTIR) and thin film FTIR, scanning electron microscopy, atomic force microscopy, and profilometry show that (i) 1 kHz DBD mainly deposits NPs, 15 kHz only polymerizes EL; (ii) the EL polymerization rate is the same in FSK and continuous modes; (iii) despite the 50/50 contribution of both frequencies, the NP deposit is three times faster in FSK mode than in 1 kHz DBD and compared with 1 and 15 kHz coatings, in the nanocomposite, NP Si–O–Si and EL C═O bonds per unit length are equal to 68% and 34%, respectively. In situ FTIR detects SiO2 NPs, their functionalization, and the formation of CO2.

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PublicationAccès libre

Response surface methodology as a predictive tool for the fabrication of coatings with optimal anti-fogging performance

2020-12-15, Laroche, Gaétan, Profili, Jacopo, Rodríguez Durán, Iván, Stafford, Luc

In this study, response surface methodology was applied to optimize the anti-fogging performance of coatings deposited on commercial glass samples from 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS)/N2O mixtures by atmospheric pressure plasma enhanced chemical vapor deposition. The effect of the dissipated power (DP), [N2O]/[TMCTS] ratio, and sample scroll speed on the anti-fogging performance was investigated by means of a Box-Behnken experimental design. The regression model relating transmittance of the coated glasses to these deposition parameters revealed that the anti-fogging performance strongly depends on the second-order interaction of the dissipated power and [N2O]/[TMCTS] ratio (i.e., DP × [N2O]/[TMCTS]). Contour plots showed that the dissipated power required to prepare optimal anti-fogging coatings should be of at least 0,7, 0,5 or 0,4 W cm−2, if the [N2O]/[TMCTS] ratio in the plasma is 20, 30, or 40, respectively. When placed over water at 50°C, the coated glass samples allowed 80% (or more) of 590-nm light to pass through, thus meeting the minimal anti-fogging requirement for alpine skier goggles and faceshields. Despite not having a significant impact on the anti-fogging performance, the sample scroll speed is key to fabricating coatings with the desired thickness during in-line manufacturing.

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Fourier-Transform infrared spectroscopy of ethyl lactate decomposition and thin-film coating in a filamentary and a glow dielectric barrier discharge

2021-07-05, Milaniak, Natalia, Laroche, Gaétan, Massines, Françoise

Glow and filamentary regimes of atmospheric pressure plasma-enhanced chemical vapor deposition in a planar dielectric barrier discharge configuration were compared for thin-film deposition from ethyl lactate (EL). EL decomposition in the plasma phase and thin-film composition were both characterized by Fourier- transform infrared spectroscopy. EL chemical bonds' concentration along the gas flow decreases progressively in the glow dielectric barrier discharge (GDBD), whereas it drastically oscillates in the filamentary dielectric barrier discharge (FDBD), with values higher than that of the initial mixture. EL decomposition route depends on the discharge regime, as the decrease of the concentration of the different investigated bonds is different for an identical amount of energy provided to EL molecules. CO2 is systematically formed reaching concentrations of 25 and 40 ppm, respectively, in FDBD and GDBD.

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Atmospheric pressure townsend discharges as a promising tool for the one‐step deposition of antifogging coatings from N2O/TMCTS mixtures

2020-02-13, Laroche, Gaétan, Durocher-Jean, Antoine, Rodríguez Durán, Iván, Profili, Jacopo, Stafford, Luc

The need to ensuring the “see‐through” property of transparent materials when exposed to sudden temperature changes or very humid conditions has encouraged the development of antifogging strategies, such as the deposition of (super)hydrophilic coatings. However, despite the effectiveness of these coatings in combating the effects of fogging, most of the coating techniques explored to date are typically time‐consuming and environment‐unfriendly. Bearing this in mind, we demonstrate that the application of dielectric barrier discharges operated at atmospheric pressure proves to be successful in preparing antifogging coatings on glass samples from 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCTS) and nitrous oxide (N2O). The antifogging performance of the coatings was found to be governed by the [N2O]/[TMCTS] ratio and not by the [N2O] + [TMCTS] sum. Coatings prepared under a [N2O]/[TMCTS] = 30 were superhydrophilic (water contact angles ≈ 5°–10°) due to surface silanol groups and endowed glass samples with a superior antifogging property, as revealed by the ASTM F 659‐06 test. In contrast, because of the lesser hydrophilicity (water contact angles ≈ 60°), coatings prepared under a [N2O]/[TMCTS] = 10 did not endow glass samples with antifogging property. Regardless of the deposition conditions, the plasma‐deposited coatings displayed crack‐free smooth surfaces (Rrms = 2−4 nm).

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Surface grafting of Fc-binding peptides as a simple platformto immobilize and identify antibodies that selectively capture circulating endothelial progenitor cells

2020-09-09, Bashth, Omar S., Laroche, Gaétan, Elkhodirya, Mohamed A., Hoesli, Corinne A.

Antibody surface immobilization is a promising strategy to capture cells of interest from circulating fluids in vitro and in vivo. An application of particular interest in vascular interventions is to capture endothelial progenitor cells (EPCs) on the surface of stents to accelerate endothelialization. The clinical impact of EPC capture stents has been limited by the lack of efficient selective cell capture. Here, we describe a simple method to immobilize a variety of immunoglobulin G antibodies through their fragment crystallizable (Fc) regions via surface-conjugated RRGW peptides for cell capture applications. As an EPC capture model, peripheral blood endothelial colony-forming cells suspended in cell culture medium with up to 70% serum were captured by immobilized anti-CD144, anti-CD34 or anti-CD309 antibodies under laminar flow. The endothelial colony-forming cells were successfully enriched from a mixture with peripheral blood mononuclear cells using surfaces with anti-CD309 but not anti-CD45. This antibody immobilization approach holds great promise to engineer vascular biomaterials with improved EPC capture potential. The ease of immobilizing different antibodies using the same Fc-binding peptide surface grafting chemistry renders this platform suitable to screen antibodies that maximize cell capture efficiency and selectivity.

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Deposition of anti-fog coatings on glass substrates using the jet of an open-to-air microwave argon plasma at atmospheric pressure

2020-04-22, Durocher-Jean, Antoine, Rodríguez Durán, Iván, Asadollahi, Siavash, Laroche, Gaétan, Stafford, Luc

This study reports a one-step process for the formation of anti-fog coatings on commercial glass substrates using the jet of an open-to-air microwave argon plasma at atmospheric pressure with hexamethyldisiloxane (HMDSO) as the precursor for plasma-enhanced chemical vapor deposition. Optical microscopy and broadband light transmittance measurements revealed significant precursor fragmentation and gas phase association reactions when HMDSO was injected close to the tube outlet, resulting in powder-like, hydrophobic, and semiopaque glass surfaces. On the contrary, injection of HMDSO close to the substrate led to smoother, homogeneous, hydrophilic, and transparent glass surfaces. In addition, transmittance measurements at 590 nm in humid air according to American Society for Testing and Materials standard tests revealed superior antifogging properties to plasma-treated glass substrates. On the basis of the optical emission and absorption spectroscopy measurements, electrons, metastable argon atoms, and hot neutral argon atoms were mostly responsible for the significant precursor fragmentation close to the tube outlet, whereas the contribution of hot neutrals and ultraviolet photons became important close to the substrate.

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Polycaprolactone (PCL) chains grafting on the surface of cellulose nanocrystals (CNCs) during in situ polymerization of ε-caprolactone at room temperature

2020-11-13, Astruc, jérémy, Cousin, Patrice, Laroche, Gaétan, Robert, Mathieu, Elkoun, S. (Saïd)

This work aimed at investigating the feasibility of surface modification of cellulose nanocrystals (CNCs) using in situ ring opening polymerization of ε-caprolactone (ε-CL) at room temperature. Residues of flax and milkweed (Asclepias syriaca) stem fibers were used as a source of cellulose to obtain and isolate CNCs. The cationic ring opening polymerization (CROP) of the monomer ε-CL was used to covalently graft polycaprolactone (PCL) chains at the CNCs surface. Silver hexafluoroantimonate (AgSbF6) was used in combination with the extracted CNCs to initiate, at room temperature, the polymerization and the grafting reactions with no other stimulus. Fourier-Transform InfraRed (FTIR), X-ray Photoelectron Spectrometry (XPS), UV/visible absorption and Gel Permeation Chromatography (GPC) analyses evidenced the presence of PCL chains covalently grafted at CNCs surface, the formation of Ag(0) particles as well as low or moderate molecular weight free PCL chains.

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Atmospheric pressure cold plasma versus wet-chemical surface treatments for carboxyl functionalization of polylactic acid : a first step toward the immobilization of bioactive molecules

2020-02-08, Laroche, Gaétan, Rodríguez Durán, Iván, Vanslambrouck, Stéphanie, Chevallier, Pascale

The use of polylactic acid (PLA) has attracted growing interest, particularly in recent years, for biomedical applications because of its mechanical properties, biocompatibility, and biodegradability. Despite this, features such as surface hydrophobicity and the absence of suitable functional groups for covalent immobilization of bioactive molecules, make it challenging to endow PLA-based medical devices with additional features and thus broaden their range of applicability. In the present study, we demonstrate the suitability of atmospheric pressure dielectric barrier discharges operating in the Townsend regime as a promising alternative to other surface treatments, such as diazonium and alkali hydrolytic treatments, for carboxyl functionalization of PLA. Chemical changes in PLA surfaces are evaluated by contact angle measurements and by X-ray photoelectron spectroscopy while physical changes are investigated by scanning electron microscopy and atomic force microscopy. The amount of carboxyl groups generated on PLA surfaces is assessed by toluidine blue O assay and substantiated by grafting, through carboxyl groups, a fluorescent probe containing amino functionalities. All of the surface treatments have proven to be very effective in generating carboxylic groups on the PLA surface. Nevertheless, plasma treatment is shown to not degrade the PLA surface, in sharp contrast with diazonium and alkali hydrolytic treatments.