The overall goal of this research project is to develop methods for producing a tissue engineered ligament. The envisioned tissue engineering strategy involves three steps: seeding bone marrow stromal cells (BMSCs) onto electrospun scaffolds, processing them into cords that allow cell infiltration, and conditioning them with uniaxial cyclic stretch. These steps were addressed in three complimentary studies to establish new methods to engineer a tissue with ligament-like cells depositing organized extracellular matrix (ECM). In the first study scaffold topographies were systematically varied to determine topographies that induce cells to orient and differentiate into ligament-like cells in static culture. Scaffolds — electrospun from poly (ester-urethane urea) (PEUUR) with different fiber diameters degrees of fiber alignments — were biocompatible and supported cell growth. Topographic cues guided cell alignment, and cell elongation increased with increasing fiber alignment. Finally, expression of the ligament-like markers collagen type I and decorin were enhanced on the smallest fiber diameters compared to larger diameters. In the second study BMSCs — seeded onto aligned electrospun PEUUR scaffolds — were cyclically stretched to determine the effect of dynamic mechanical stimulation on BMSC alignment and differentiation. BMSCs remained aligned parallel to the direction of fiber alignment and expressed ligament markers (e.g. collagen type I, decorin, scleraxis, and tenomodulin) on electrospun scaffolds after the application of stretch. However, the cyclic stretch regimen was not able to enhance expression of ECM components. In the third study techniques were developed to produce more clinically relevant constructs with improved cell infiltration. Specifically, a co-electrospun scaffold composed of two well integrated components was developed to create larger pores. The scaffold was also embedding in a photo-crosslinkable hydrogel to prevent the fibers from collapsing. These results demonstrate the feasibility of making a tissue engineered ligament by seeding BMSCs on an aligned, co-electrospun scaffold with submicron diameter fibers and then applying cyclic mechanical stretch. Future work will involve combining these three steps to achieve materials suitable for in vivo testing. / Ph. D.

Strong, durable terminal regions that can be easily handled by researchers and surgeons are a key factor in the successful fabrication of tissue engineered blood vessels (TEBV). The goal of this study was to fabricate and characterize electrospun cuffs made of poly-caprolactone (PCL) combined with gelatin that reinforce and strengthen each end of cell-derived vascular tissue tubes. PCL is ideal for vascular tissue engineering applications due to its mechanical properties; however, PCL alone does not support cell attachment. Therefore, we introduced gelatin, a natural matrix-derived protein, into the electrospun material to promote cell adhesion. This work compared the effects of two different methods for introducing gelatin into the PCL materials: gelatin coating and gelatin co-electrospinning. Porosity, pore size, fiber diameter, and mechanical properties of the electrospun materials were measured in order to compare the features of gelatin PCL composites that have the greatest impact on cellular infiltration. Porosity was quantified by liquid intrusion, fiber diameter and pore size were measured using scanning electron microscopy, and tensile mechanical testing was used to evaluate strength, elastic modulus, and extensibility. Attachment and outgrowth of smooth muscle cells onto cuff materials was measured to evaluate differences in cellular interactions between materials by using a metabolic attachment assay and a cellular outgrowth assay. Finally, cuffs were fused with totally cell-derived TEBV and the integration of cuffs with tissue was evaluated by longitudinal pull to failure testing and histological analysis. Overall, these cuffs were shown to be able to add length and increase strength to the ends of TEBV for tube cannulation and manipulation during in vitro culture. In particular, PCL:gelatin cospun cuffs were shown to improve cellular attachment and cuff fusion compared to pure PCL cuffs, while still increasing the strength of the TEBV terminal ends.

This thesis explored the use of sodium alginate-pectin-poly(ethylene oxide) electrospun fibers as a carrier to stabilize folic acid - an essential micronutrient that is susceptible to degradation when exposed to light and acidic conditions. In the first phase of this research, electrospinning behaviour of aqueous alginate-pectin solutions was investigated. Aqueous polysaccharide solutions could not be electrospun unless poly(ethylene oxide) (PEO) was added (≥20% w/w), resulting in electrospun alginate-pectin fibers that varied from fiber to fiber-bead, depending on the polymer blend ratio, and concentration of the polymer solutions. Polymer solutions properties (surface tension, viscosity, conductivity) were determined to study their effects on the electrospinning behaviour of the polymer solutions. In the second phase of this research, folic acid was incorporated into the polymer solutions and electrospun. The efficacy of these fibers in improving the stability of folic acid under different pH conditions was investigated. FTIR and NMR spectroscopies were employed to elucidate the nature of polymer-polymer and folic acid-polymer interaction. In phase three, the release behaviour of folic acid under simulated gastrointestinal conditions was evaluated. Overall, this research showed that electrospun fibers with different morphologies could be produced by manipulating the polymer concentration, polysaccharide/PEO blend ratio, extent of sonication treatment during sample preparation, and electrospinning process parameters. The positive effect of PEO on the electrospining of alginate-pectin fibers was attributed to its electrical conductivity and surface tension lowering effects on the polymer solutions. Electrospun fibers produced from the combination of alginate-pectin resulted in higher retention of folic acid compared to that of alginate alone. Folic acid encapsulated in crosslinked electrospun fibers achieved close to 100% retention when stored in the dark at pH 3 after 41 days of storage. Minimal release of folic acid from the electrospun fibers was observed at pH 3, although the release was significantly higher at pH 1.2. On the other hand, the release of folic acid was nearly 97% at pH 7.8, a condition that simulated the pH condition in the intestine. From NMR and FTIR data, the stabilization effect of electrospun fibers on folic acid was attributed to physical entrapment and not specific chemical interaction. The research suggests that ethanol-treated crosslinked alginate-pectin electrospun fibers can potentially be used as a folic acid carrier to protect the micronutrient in food products, especially acidic food products such as fruit juices and acidified beverages. / Natural Sciences and Engineering Research Council of Canada (NSERC) and Heinz Company of Canada

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Electrospinning is a novel technique to fabricate non-woven fibers with sizes ranging from nano to micrometers. Polymers have been electrospun into nanofibers that can be developed into desirable materials with excellent biocompatibility and biodegradability for biomedical applications in wound healing and tissue regeneration. These nanofiber materials can be further functionalized to be loaded with bioactive molecules, including antibacterial agents, functional proteins that promote tissue reconstruction while protect host tissues from contamination. This study focuses on the development of multifunctional nanofibers that are incorporated with antibacterial drug(s) and immobilized with bioactive proteins. These nanofibers are potentially useful for wound care and tissue engineering scaffolding to provide both infection control and promotion of wound healing or tissue regenerations.

Electrospinning is a novel technique to fabricate non-woven fibers with sizes ranging from nano to micrometers. Polymers have been electrospun into nanofibers that can be developed into desirable materials with excellent biocompatibility and biodegradability for biomedical applications in wound healing and tissue regeneration. These nanofiber materials can be further functionalized to be loaded with bioactive molecules, including antibacterial agents, functional proteins that promote tissue reconstruction while protect host tissues from contamination. This study focuses on the development of multifunctional nanofibers that are incorporated with antibacterial drug(s) and immobilized with bioactive proteins. These nanofibers are potentially useful for wound care and tissue engineering scaffolding to provide both infection control and promotion of wound healing or tissue regenerations.

M.Sc. (Nanoscience) / Supported bimetallic Fe/Ni nanoparticles have been used for years as catalysts for the dechlorination of organochlorine compounds in ground water remediation. However, their fate and potential harm to the environment is of concern, hence, ways of reducing these negative aspects are being explored. As a way to solve this problem, catalytic nanoparticles are immobilised on a variety of substrates ranging from membranes, clays, silica, etc. In the current effort, the immobilisation of Fe/Ni bimetallic nanoparticles on electospun cellulose-based nanofibers was examined with the ultimate view to apply the materials for dechlorination studies. Fe/Ni bimetallic nanoparticles were anchored on ligand-functionalised cellulose nanofibers by the successive reduction of Fe(II) and Ni(II) ions from their respective solutions using NaBH₄...

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