Biomedical Engineering and Bioengineering Commons^™

Development Of A Cell-Based Regenerative Strategy To Modulate Angiogenesis And Inflammation In Ischemic Muscle, Fiona E. Serack

Electronic Thesis and Dissertation Repository

The delivery of human adipose-derived stromal cells (hASCs) to ischemic tissues represents a promising strategy to promote vascular regeneration for patients with critical limb ischemia (CLI). This thesis focused on the evaluation of hydrogels to enhance the retention and pro-angiogenic capacity of hASCs following delivery in vivo. Additionally, priming strategies to augment the paracrine function of hASCs were developed and assessed.

Recognizing the importance of endogenous macrophages in the pro-regenerative function of hASCs, delivery using a previously-developed hydrogel system, composed of peptide-functionalized methacrylated glycol chitosan (MGC-RGD) and a copolymer of poly(ethylene glycol) and poly(trimethylene carbonate) (PEG(PTMC-A)₂), was …

Investigation Of Dynamic Culture On Matrix-Derived Microcarriers As A Strategy To Modulate The Pro-Regenerative Phenotype Of Human Adipose-Derived Stromal Cells, Mckenna R. Tosh

Electronic Thesis and Dissertation Repository

Pre-conditioning of adipose-derived stromal cells (ASCs) by tuning the cellular microenvironment during expansion has the potential to modulate their pro-regenerative functionality. The current study investigated the effects of microcarrier composition (decellularized adipose tissue versus collagen), oxygen tension (2% versus ~20% O₂) and stirring rate (static, 20, 40 rpm) on human ASCs cultured within spinner flask bioreactors. Dynamic culturing under 20% O₂ resulted in more consistent cell growth on both microcarrier substrates, leading to increases in microcarrier contraction and stiffness. Culturing on the microcarriers modulated the hASC immunophenotype, with varying CD90 and CD26 expression levels observed under the …

Conducting Polypyrrole Hydrogel Biomaterials For Drug Delivery And Cartilage Tissue Regeneration, Iryna Liubchak

Electronic Thesis and Dissertation Repository

Articular cartilage tissue has limited capacity for self-regeneration leading to challenges in the treatment of joint injuries and diseases such as osteoarthritis. The tissue engineering approach combines biomaterials, cells and bioactive molecules to provide a long-term and stable cartilage repair. In the following work, electroactive polymer polypyrrole~(PPy) was incorporated into the synthetic hydrogel to enhance the mechanical properties of the material for cartilage applications. PPy was loaded with drug compound and the \emph{on demand} drug release was demonstrated. The composite PPy hydrogel was 3D printed using stereolithography to create a porous tissue engineering scaffold. Biocompatibility and cell adhesion to the …

Characterization Of Tissue-Specific Matrix-Derived Bioscaffolds For Nucleus Pulposus Cell Culture, Marco A. Herrera Quijano

Electronic Thesis and Dissertation Repository

Bioscaffolds derived from the extracellular matrix (ECM) have shown the capacity to promote regeneration by providing tissue-specific biological instructive cues that can enhance cell survival and direct lineage-specific differentiation. This study focused on the development and characterization of two-dimensional (2-D) and three-dimensional (3-D) cell culture platforms incorporating decellularized nucleus pulposus (DNP). First, a novel detergent-free protocol was developed for decellularizing bovine NP tissues that was effective at removing cellular content while preserving key ECM constituents including collagens and glycosaminoglycans. Culture studies showed that 2-D coatings derived from the DNP could support cell attachment but did not maintain or rescue the …

Fibrin-Based Engineered Vascular Tissues As Platforms For Cellular Studies And Disease Modeling, Khalil Dayekh

Electronic Thesis and Dissertation Repository

Vascular tissue engineering (VTE) is an emerging alternative therapeutic intervention strategy to treat diseases such as atherosclerosis. While the ultimate goal of VTE is designing tissues to serve as graft substitutes, they can also serve as powerful tools to study tissue and disease development and drug discovery.

In this work, engineered vascular tissues from fibrin gel, mouse embryonic multipotent progenitor cell line (10T1/2 cells), and rat embryonic thoracic artery smooth muscle cells (A-10 cells) were used as models to study the Notch signaling pathway and vascular calcification. The 10T1/2 cells were successfully differentiated into vascular smooth muscle cells with TGFβ1 …

Immobilized Jagged1 For Notch3-Specific Differentiation And Phenotype Control Of Vascular Smooth Muscle Cells, Kathleen E. Zohorsky

Electronic Thesis and Dissertation Repository

Notch signaling plays a critical role in regulating vascular morphogenesis. In vascular interventions, the endothelial cells (ECs) are often damaged, and EC-SMC contact is compromised. The objective of this study was to investigate if immobilized Jagged1 can act as an EC-surrogate material to direct and control vascular smooth muscle cell (VSMC) behavior via Notch signaling. It was shown that immobilized Jagged1 induced vascular differentiation of iPSC-derived mesenchymal stem cells and mouse embryonic multipotent cells. Immobilized Jagged1 was insufficient to induce mature contractile markers in coronary artery SMCs; therefore, serum starvation and TGFβ1 treatment were investigated. Although Notch signaling is mechanosensitive …

Cardiac Modelling Techniques To Predict Future Heart Function And New Biomarkers In Acute Myocardial Infarction, Sergio C. H. Dempsey

Electronic Thesis and Dissertation Repository

Fundamental to treatment planning for patients that have suffered myocardial infarction are predictive biomarkers and risk factors. Important among these in terms of a patient’s treatment plan or prognosis are the contractility of the damaged myofibers, final infarct volume, and poor infarct healing rate. Proposed and developed in this thesis are techniques to predict these biomarkers and risk factors using cardiac biomechanical modelling. One of the developed techniques was a CT compatible shape optimization technique which can predict the contraction force of healthy, and stunned myofibers within 6.3% and the distribution of potentially necrotic myofibers within 10% accuracy. The second …

Extracellular Matrix-Derived Modular Bioscaffolds For Soft Connective Tissue Regeneration, Pascal Morissette Martin

Electronic Thesis and Dissertation Repository

Human decellularized adipose tissue (DAT) represents a promising extracellular matrix (ECM) source for the development of biomaterials, with its properties conductive of angiogenesis, adipogenesis, and scaffold remodelling. This thesis sought to provide new fundamental insight into the design of ECM-derived bioscaffolds by developing novel modular biomaterials for soft connective tissue regeneration and by studying the effects of ECM composition on cell function and fate.

Initial studies explored the effects of ECM composition of pre-assembled bead foams derived from DAT or commercially-sourced bovine collagen (COL) on human wound edge dermal fibroblasts (weDFs) sourced from chronic wounds. In vitro testing under conditions …

The Co-Delivery Of Syngeneic Adipose-Derived Stromal Cells And Macrophages On Decellularized Adipose Tissue Bioscaffolds For In Vivo Soft Tissue Regeneration, Hisham A. Kamoun

Electronic Thesis and Dissertation Repository

Decellularized adipose tissue (DAT) bioscaffolds are a promising platform for the delivery of pro-regenerative cell populations with the goal of promoting adipose tissue regeneration. The current study investigated the effects of seeding DAT bioscaffolds with syngeneic bone marrow-derived macrophages and/or adipose-derived stromal cells (ASCs) on in vivo soft tissue regeneration. Methods were established to derive the macrophages from MacGreen mice, which were dynamically seeded onto the DAT scaffolds alone or in combination with ASCs. Seeded and unseeded scaffolds were implanted subcutaneously into C57Bl/6 mice. At 2 and 4 weeks, cell infiltration, angiogenesis, and adipogenesis were analyzed through histology and immunohistochemistry. …

Design Of Cell-Instructive Biomaterial Scaffolds For Intervertebral Disc Regeneration, Nadia Sharma

Electronic Thesis and Dissertation Repository

Biomaterials-based therapies targeting the nucleus pulposus (NP) have the potential to promote regeneration and restore mechanical function to the intervertebral disc. This study developed composite hydrogels incorporating decellularized NP (DNP) and assessed its effects on viability, retention and differentiation of U-CH1 cells, an NP progenitor-like cell line. A minimal protocol was developed to decellularize bovine NP that reduced nuclear content while preserving key extracellular matrix components predicted to be favourable for bioactivity. The resulting DNP demonstrated cell-instructive effects, supporting U-CH1 viability and retention within the hydrogels, and promoted the differentiation of the progenitor-like cells towards an NP-like phenotype. These studies …

Formation Of A Vascular Regenerative Microenvironment Within Implantable Human Decellularized Adipose Tissue Bioscaffolds, Christopher Leclerc

Electronic Thesis and Dissertation Repository

Cellular therapies targeted at stimulating therapeutic angiogenesis in individuals with critical limb ischemia (CLI) have been under intense investigation. Hematopoietic progenitor cells (HPC) derived from umbilical cord blood have been previously shown to support limb revascularization in animal models of CLI, despite limited cell survival at the site of ischemia. This study attempted to improve HPC survival after transplantation and prolong pro-angiogenic function using human decellularized adipose tissue (hDAT) as a novel cell delivery platform. Compared to HPC conventionally grown on tissue-cultured plastic, hDAT scaffolds were shown to promote viability and proliferation of seeded HPC, and had cell- instructive effects …

Fabrication And Characterization Of Collagen-Polypyrrole Constructs Using Direct-Ink Write Additive Manufacturing, Rooshan Arshad

Electronic Thesis and Dissertation Repository

Current efforts in the tissue engineering field are being directed towards the creation of platforms which will facilitate in instructing cells towards biologically relevant outcomes such as stem cell differentiation and disease pathophysiology. Traditional fabrication methods serve as a limiting factor for the production of such platforms as they lack feature and geometric complexity. Additive Manufacturing (AM) offers advantage over said methods by affording designers creative freedom and great control over printed constructs. Such constructs can then be used to create appropriate models for study- ing a plethora of tissues and structures. An AM methodology for Direct-Ink Write (DIW) printing …

Development Of In Situ Forming Hydrogels For Intra-Articular Drug Delivery, Andy Prince

Electronic Thesis and Dissertation Repository

Hydrogels are 3-dimensional crosslinked polymer networks that can absorb significant amounts of water. The physical properties associated with hydrogels affords them resemblance to biological tissues making them good candidates for biomedical applications. Many pharmaceuticals, specifically non-steroidal anti-inflammatory drugs (NSAIDs), have poor aqueous solubility, which limits their bioavailability and efficacy. People suffering from chronic osteoarthritis (OA) are required to frequently take large doses to mitigate pain, which can lead to serious side effects. Hydrogels are good strategies to deliver NSAIDs via articular injection because they can form solid gels in situ. This thesis describes the synthesis, formulation, mechanical testing, in …

Development Of Granulation Tissue Mimetic Scaffolds For Skin Healing, Adam Hopfgartner

Electronic Thesis and Dissertation Repository

Impaired skin healing is a significant and growing clinical concern, particularly in relation to diabetes, venous insufficiency and immobility. Previously, we developed electrospun scaffolds for the delivery of periostin (POSTN) and connective tissue growth factor 2 (CCN2), matricellular proteins involved in the proliferative phase of healing. This study aimed to design and validate a novel electrosprayed coaxial microsphere for the encapsulation of fibroblast growth factor 9 (FGF9), as a component of the POSTN/CCN2 scaffold, to promote angiogenic stability during wound healing. For the first time, we observed a pro-proliferative effect of FGF9 on human dermal fibroblasts (HDF) in vitro, indicating …

Covalently Crosslinked Organic/Inorganic Hybrid Biomaterials For Bone Tissue Engineering Applications, Dibakar Mondal

Electronic Thesis and Dissertation Repository

Scaffolds are key components for bone tissue engineering and regeneration. They guide new bone formation by mimicking bone extracellular matrix for cell recruitment and proliferation. Ideally, scaffolds for bone tissue engineering need to be osteoconductive, osteoinductive, porous, degradable and mechanically competent. As a single material can not provide all these requirements, composites of several biomaterials are viable solutions to combine various properties. However, conventional composites fail to fulfil these requirements due to their distinct phases at the microscopic level. Organic/inorganic (O/I) class II hybrid biomaterials, where the organic and inorganic phases are chemically crosslinked on a molecular scale, hence the …

Syngenic Adipose-Derived Stem/Stromal Cells Delivered In Decellularized Adipose Tissue Scaffolds Enhance In Vivo Tissue Regeneration Through Host Cell Recruitment, Kevin P. Robb

Electronic Thesis and Dissertation Repository

Decellularized adipose tissue (DAT) represents a promising adipogenic bioscaffold for applications in soft tissue augmentation or reconstruction. With the goal of investigating the role of syngeneic donor adipose-derived stem/stromal cells (ASCs) and host myeloid cells during in vivo adipose tissue regeneration, transgenic reporter mouse strains were used to track these cell populations within ASC-seeded and unseeded DAT scaffolds. Donor ASCs were obtained from dsRed transgenic mice. These cells were shown to express characteristic cell surface markers, and multilineage differentiation capacity was confirmed. To facilitate cell tracking, DAT scaffolds were subcutaneously implanted into MacGreen mice in which myeloid cells express enhanced …

Electrospinning Of Poly (Ester Amide) Fibres For Mesenchymal Progenitor Cell Differentiation, Sarah Kiros

Electronic Thesis and Dissertation Repository

The in vitro vascular tissue engineering paradigm seeks to produce biologically responsive vascular substitutes using cells, biodegradable scaffolds, and bioreactors to mature the tissue for the potential treatment of vascular occlusions and to create 3D tissue models for pre-clinical testing. In this work, a poly (ester amide) (PEA) derived from from L-phenylalanine, sebacoyl chloride and 1,4 butanediol was synthesized and electrospun to form both 3D fibrous mats and tubular constructs. Both the polymer solution concentration and mandrel rotation speed were optimized to fabricate bead-free fibres. Cytocompatibility and proliferation studies using mesenchymal progenitor 10T1/2 cells showed PEA fibres were not cytotoxic …

Adipose-Derived Stem Cell Differentiation In Cell Aggregates Supplemented With Micronized, Decellularized Extracellular Matrix, Danielle Heinbuch

Electronic Thesis and Dissertation Repository

In the human body there are tissues with limited regenerative potential, raising the need for cell-based regenerative therapies. The main objective of this thesis was to examine how tissue-specific extracellular matrix (ECM) affects the differentiation of human adipose-derived stem/stromal cells (ASCs). The effects of incorporating milled, decellularized adipose (DAT) or cartilage (DCT) ECM particles on ASC lineage-specific differentiation in 3-D cell aggregate cultures were explored. The results demonstrated that the addition of ECM improved differentiation for both adipogenesis and chondrogenesis. Analysis of adipogenic gene and protein expression indicated enhanced differentiation in the DAT+ASC aggregates relative to the DCT+ASC and ASC-alone …

The Role Of Bone Sialoprotein In Periodontal Tissue Development And Bone Repair, Yohannes Soenjaya

Electronic Thesis and Dissertation Repository

Bone development and repair involve complex processes that include interaction between cells and their surrounding matrix. In the body, bone sialoprotein (BSP) expression is up-regulated at the onset of mineralization. BSP is a multifunctional acidic phosphoprotein with collagen-binding, hydroxyapatite nucleating, and integrin recognition (RGD sequence, which is important for cell-attachment and signaling) regions. Mice lacking BSP expression (Bsp^-/-), exhibit a bone phenotype with reductions in bone mineral density, bone length, osteoclast activation, and impaired bone healing. This thesis examined the role of BSP in tooth development and also its potential use as a therapeutic reagent for bone …

Engineering Periodontal Tissue Regeneration With The Use Of A Novel Periostin Electrospun Scaffold, Kendal I. Creber

Electronic Thesis and Dissertation Repository

Clinical therapies for the treatment of periodontitis are unable to reproducibly stimulate regeneration of the periodontium. We assessed the use of a novel electrospun type I collagen scaffold containing recombinant periostin to stimulate regeneration of the periodontal ligament (PDL) and bone. Human PDL cells demonstrated the ability to form a mineralized matrix in vitro and reduced osteogenic potential with increased donor age. In vitro analysis indicated scaffolds were biocompatible, however, periostin did not significantly influence adhesion or growth. In the healing of fenestration defects in rats, type I collagen scaffolds (with and without periostin) initially delayed cell infiltration and increased …

Humidity Effect On The Structure Of Electrospun Core-Shell Pcl-Peg Fibers For Tissue Regeneration Applications, Adam P. Golin

Electronic Thesis and Dissertation Repository

With the aim of creating a biodegradable scaffold for tympanic membrane (TM) tissue regeneration, core-shell nanofibers composed of a poly(caprolactone) shell and a poly(ethylene glycol) core were created using a coaxial electrospinning technique. In order to create fibers with an optimal core-shell morphology, the effect of relative humidity (RH) on the core-shell nanofibers was systematically studied, with a FITC-BSA complex encapsulated in the core to act as a model protein. The core-shell nanofibers were electrospun at relative humidity values of 20, 25, 30, and 40% RH within a glove box outfitted for humidity control. The core-shell morphology of the fibers …

Sol-Gel Derived Biodegradable And Bioactive Organic-Inorganic Hybrid Biomaterials For Bone Tissue Engineering, Bedilu A. Allo

Electronic Thesis and Dissertation Repository

Treatments of bone injuries and defects have been largely centered on replacing the lost bone with tissues of allogeneic or xenogeneic sources as well as synthetic bone substitutes, which in all lead to limited degree of structural and functional recovery. As a result, tissue engineering has emerged as a viable technology to regenerate the structures and therefore recover the functions of bone tissue rather than replacement alone. Hence, the current strategies of bone tissue engineering and regeneration rely on bioactive scaffolds to mimic the natural extracellular matrix (ECM) as templates onto which cells attach, multiply, migrate and function.

In this …

Calcium Phosphate-Based Resorbable Biomaterials For Bone Regeneration, Daniel O. Costa

Electronic Thesis and Dissertation Repository

Bone defects are a prevalent problem in orthopedics and dentistry. Calcium phosphate-based coatings and nanocomposites offer unique solutions towards producing scaffolds with suitable physical, mechanical and biological properties for bone regeneration.

We developed a novel method to synthesize hydroxyapatite (HA) particles with high aspect ratio using sol-gel chemistry and hydrothermal treatment. We obtained tunable pure-phase carbonated-HA in the form of micro/nanorods and nanowires (diameters 25-800 nm). To mimic the structure of bone, HA nanowires were homogenously mixed within poly(ε-caprolactone) (PCL) to produce nanocomposites with improved mechanical properties as determined by uniaxial tensile testing.

Surface chemistry and topography of biomaterials play …

Co-Culture Of Smooth Muscle Cells And Endothelial Cells On Porous 3d Polyurethane Scaffolds For Vascular Tissue Engineering, Aparna Bhattacharyya

Electronic Thesis and Dissertation Repository

One of the challenges in the designing of clinically-relevant vascular substitutes is our lack of understanding on how vascular smooth muscle cells (VSMCs) and vascular endothelial cells (VECs) interact in the graft. The aim of this study was to examine the factors that play a role in VSMC and VEC interaction in 3D co-culture. Highly porous 3D poly(carbonate urethane) scaffolds were fabricated using a solvent casting and particulate leaching method. VSMCs and VECs were co-cultured for 48 hours. Immunofluorescence staining showed that VSMCs readily attached to the scaffold and formed dense confluent layers which facilitated the organization of VECs of …