Engineering therapeutic approaches to wound healing can be divided into two major categories of fibrous and non-fibrous approaches. There has been significant progress in designing artificial skin products to replace autografting. For patients with non-healing/hard-to-heal wounds, there is an unmet clinical need for inexpensive skin substitutes to be transplanted. In skin regeneration area of research, electrospinning is a very commonly used method of production of grafts for wound healing applications, owing its popularity to the fibrous nature of the resultant product, which mimics the extracellular matrix of the native skin. Despite the high degree of porosity in conventional electrospun scaffolds, the small pore size effectively limits the penetration of cells into the scaffold. Transplantation of such scaffolds with poor cell infiltration abilities may lead to a range of negative consequences, from prolongation of the first/destructive phase of inflammation to rejection of the scaffolds. Several experimental approaches have been developed to generate interfibrillar space in the electrospun scaffolds, including but not limited to modifications of the electrospinning set-up and inclusion of sacrificial components. It has been reported that scaffolds with larger pore diameters in the range of ~ 40-100 μm can modulate, moderate and reduce acute inflammatory responses of the body, by influencing macrophages biological behavior, and direct the course of the wound healing process to the tissue remodeling phase. Macrophages are the major cell component of innate immune system and play critical roles in clearance of pathogens, resolution of inflammation and wound healing following an injury. Macrophages are characterized by their diversity and plasticity. In response to environmental stimuli, they acquire different functional phenotypes of pro-inflammatory (M1) or anti-inflammatory (M2). In this thesis, we developed a novel unique gradient porous structure from a plant-based “green” soy protein isolate (SPI) with improved pore size for macrophages to infiltrate. We further showed the ability of the scaffold to modulate phenotype switch in macrophages in vitro and in vivo. The proposed scaffold, moreover, appeared to support transition of the inflammation process from the destructive to the constructive phase in vivo. Based on the promising results of this thesis, we propose our newly developed scaffold has the ability to be used as a new therapeutic modality for treatment of non-healing chronic wounds. / Bioengineering

Ces travaux ont pour objet l’élaboration de nouvelles structures poreuses non tissées antibactériennes. Différentes stratégies ont été développées : l’une a consisté à élaborer des mats poreux par electrospinning en utilisant un polymère biosourcé et biocompatible et l’autre voie consistait à modifier un support fibreux provenant d’un masque de protection respiratoire commercial. La méthode des assemblages par interactions ioniques en superposant de façon alternative les couches de polymères cationiques et les polymères anioniques à la surface du filtre médian en polypropylène (PP) a permis d’élaborer de nouvelles structures ayant de bonnes propriétés antioxydantes et antibactériennes. Le polymère anionique, dérivé du polymère de cyclodextrine présente l’avantage de pouvoir encapsuler un agent antimicrobien biosourcé, le carvacrol. Une autre approche a consisté à modifier des supports en PP avec de l'acide tannique, un polyphénol d'origine naturelle. Dans cette étude, deux stratégies ont été mises en place afin de fonctionnaliser le PP avec de l’acide tannique (AT). La première est l’extrusion réactive du PP avec l’AT en présence (ou non) de peroxyde de dicumyle (DCP) pour greffer directement l’acide tannique sur le PP. La deuxième stratégie consiste à polymériser l’AT au travers d’une couche poreuse de PP extraite d’un masque de protection commercial, afin de permettre l’immobilisation physique de l’AT à la surface du mat fibreux en PP. Le greffage en surface via un procédé “grafting from” a également été étudié. Ces matériaux ont montré de bonnes propriétés antiradicalaires. / The purpose of this work is to develop new antibacterial non-woven porous structures. Different strategies were developed: one was to develop porous structures by electrospinning using a biosourced and biocompatible polymer, the other was to modify a fibrous support from a commercial respiratory protection mask. Assembling materials using ionic interactions by alternatively superposing cationic polymer layers and anionic polymers on the surface of the polypropylene (PP) median filter allowed to develop new structures with good antioxidant and antibacterial properties. The anionic polymer, derived from the cyclodextrin polymer, has the advantage of being able to encapsulate a bio-based antimicrobial agent, carvacrol. Another approach was to modify PP filters with tannic acid, a naturally occurring polyphenol. In this study, two strategies were implemented to functionalize PP with tannic acid (TA). The first is the reactive extrusion of PP with TA in the presence (or not) of dicumyl peroxide (DCP) to directly graft tannic acid onto PP. The second strategy consists in polymerizing the TA through a porous layer of PP extracted from a commercial mask, in order to allow the physical immobilization of the TA on the surface of the PP fibrous mat. Surface grafting using a "grafting from" process was also studied. These materials have shown good anti-free radical properties.

In this work, a new polyurethane (PU) chain extender was developed to incorporate a Glycine-Leucine (Gly-Leu) dipeptide, the cleavage site of several matrix metalloproteinases. PUs were synthesized with either the Gly-Leu-based chain extender (Gly-Leu PU) or a phenylalanine-based chain extender (Phe PU). Both PUs had high molecular weight averages (Mw > 125,000 g/mol) and were phase segregated, semi-crystalline polymers (Tm ~ 42°C) with a low soft segment glass transition temperature (Tg < -50°C). Uniaxial tensile testing of PU films revealed that the polymers could withstand high ultimate tensile strengths (~ 8-13 MPa) and were flexible with breaking strains of ~ 870-910% but the two PUs exhibited a significant difference in mechanical properties. The Phe and Gly-Leu PUs were electrospun into porous scaffolds for degradation and cell-based studies. Fibrous Phe and Gly-Leu PU scaffolds were formed with randomly organized fibers and an average fiber diameter of approximately 3.6 µm. In addition, the Phe PU was electrospun into scaffolds of varying architecture to investigate how fiber alignment affects the orientation response of cardiac cells. To achieve this, the Phe PU was electrospun into aligned and unaligned scaffolds and the physical, thermal, and mechanical properties of the scaffolds were investigated. The degradation of the Phe and Gly-Leu PU scaffolds was investigated in the presence of active MMP-1, active MMP-9, and a buffer solution over 28 days to test MMP-mediated and passive hydrolysis of the PUs. Mass loss and structural assessment suggested that neither PU experienced significant hydrolysis to observe degradation over the course of the experiment. In cell-based studies, Phe and Gly-Leu PU scaffolds successfully supported a high density of viable and adherent mouse embryonic fibroblasts (MEFs) out to at least 28 days. Culturing murine embryonic stem cell-derived cardiomyocytes (mESCDCs) alone and with MEFs on aligned and unaligned Phe PU scaffolds revealed both architectures supported adherent and functionally contractile cells. Importantly, fiber alignment and coculture with MEFs improved the organization and differentiation of mESCDCs suggesting these two parameters are important for developing engineered myocardial constructs using mESCDCs and PU scaffolds.

In this work, a new polyurethane (PU) chain extender was developed to incorporate a Glycine-Leucine (Gly-Leu) dipeptide, the cleavage site of several matrix metalloproteinases. PUs were synthesized with either the Gly-Leu-based chain extender (Gly-Leu PU) or a phenylalanine-based chain extender (Phe PU). Both PUs had high molecular weight averages (Mw > 125,000 g/mol) and were phase segregated, semi-crystalline polymers (Tm ~ 42°C) with a low soft segment glass transition temperature (Tg < -50°C). Uniaxial tensile testing of PU films revealed that the polymers could withstand high ultimate tensile strengths (~ 8-13 MPa) and were flexible with breaking strains of ~ 870-910% but the two PUs exhibited a significant difference in mechanical properties. The Phe and Gly-Leu PUs were electrospun into porous scaffolds for degradation and cell-based studies. Fibrous Phe and Gly-Leu PU scaffolds were formed with randomly organized fibers and an average fiber diameter of approximately 3.6 µm. In addition, the Phe PU was electrospun into scaffolds of varying architecture to investigate how fiber alignment affects the orientation response of cardiac cells. To achieve this, the Phe PU was electrospun into aligned and unaligned scaffolds and the physical, thermal, and mechanical properties of the scaffolds were investigated. The degradation of the Phe and Gly-Leu PU scaffolds was investigated in the presence of active MMP-1, active MMP-9, and a buffer solution over 28 days to test MMP-mediated and passive hydrolysis of the PUs. Mass loss and structural assessment suggested that neither PU experienced significant hydrolysis to observe degradation over the course of the experiment. In cell-based studies, Phe and Gly-Leu PU scaffolds successfully supported a high density of viable and adherent mouse embryonic fibroblasts (MEFs) out to at least 28 days. Culturing murine embryonic stem cell-derived cardiomyocytes (mESCDCs) alone and with MEFs on aligned and unaligned Phe PU scaffolds revealed both architectures supported adherent and functionally contractile cells. Importantly, fiber alignment and coculture with MEFs improved the organization and differentiation of mESCDCs suggesting these two parameters are important for developing engineered myocardial constructs using mESCDCs and PU scaffolds.