A key challenge in tissue engineering is overcoming cell death in the scaffold interior due to the limited diffusion of oxygen and nutrients therein. We hypothesized here that immobilizing a gradient of vascular endothelial growth factor (VEGF-165) would guide endothelial cells into the interior of the scaffold thereby enhancing angiogenesis. The protein was immobilized onto a collagen scaffold through carbodiimide chemistry by one of the three methods experimented: placing 5 µl of the solution at the center of the scaffold to create a ~2 ng/ml/mm gradient in a radial direction. D4T endothelial cells were observed to be guided by this VEGF-165 gradient deep into the center of the scaffold compared to both uniformly immobilized VEGF-165 and VEGF-free controls. We concluded that the VEGF-165 gradient scaffolds promoted the migration, and not proliferation, of cells deep into the scaffold. These gradient scaffolds provide the foundation for future in vivo tissue engineering studies.

The time when it will be possible to grow complex organs in a lab environment comes closerdue to the rapid progress taking place in the area of biotechnology and tissue engineering.Various tissue engineering methods of creating artificial scaffolds has evolved, one of thosebeing electrospinning. Electrospun scaffolds are beneficial in tissue engineering applicationsforemost in regard to their body-mimicking structure. Small pore sizes and low porosities mayhowever limit cell infiltration and thereby creation of 3D functional tissues. The issue of cellinfiltration in electrospun constructs such as nonwoven polymer scaffolds for use in tissueengineering may be solved by a method of simultaneous integration i.e. integrating particlesduring the phase of production in the electrospinning process. In this thesis investigation of aproof-of-concept to the idea of in the future distributing living cells within the threedimensionalstructure during the process of electrospinning of a polymeric biomaterial weremade. To be able to conduct simple experiments glass particles with proper sizes are used tosubstitute living cells. During this thesis a novel method called spray electrospinning tookshape enabling a fine distribution of particles in an electrospun material.The work in this thesis shows that there are methods to simultaneously integrate particles inproduction of scaffold materials, one of these composed of spraying particles whileelectrospinning on a rotating collector. The experiments were done in order to compare thedifferent methods; Double, Coaxial and Spray electrospinning pointing out similarities anddifferences between the three. The methods used to characterize the materials include scalemeasurements and SEM image analysis to determine morphology, fibre diameter, layerthickness and distance between particles. Glass particles were used as substitutes for livingcells for the sake of proof of concept which showed that these can successfully be integratedsimultaneously in an electrospun material. However porosity and the number of particles haveto be further optimized for the material to be ready for use in tissue engineering.The time when it will be possible to grow complex organs in a lab environment comes closerdue to the rapid progress taking place in the area of biotechnology and tissue engineering.Various tissue engineering methods of creating artificial scaffolds has evolved, one of thosebeing electrospinning. Electrospun scaffolds are beneficial in tissue engineering applicationsforemost in regard to their body-mimicking structure. Small pore sizes and low porosities mayhowever limit cell infiltration and thereby creation of 3D functional tissues. The issue of cellinfiltration in electrospun constructs such as nonwoven polymer scaffolds for use in tissueengineering may be solved by a method of simultaneous integration i.e. integrating particlesduring the phase of production in the electrospinning process. In this thesis investigation of aproof-of-concept to the idea of in the future distributing living cells within the threedimensionalstructure during the process of electrospinning of a polymeric biomaterial weremade. To be able to conduct simple experiments glass particles with proper sizes are used tosubstitute living cells. During this thesis a novel method called spray electrospinning tookshape enabling a fine distribution of particles in an electrospun material.The work in this thesis shows that there are methods to simultaneously integrate particles inproduction of scaffold materials, one of these composed of spraying particles whileelectrospinning on a rotating collector. The experiments were done in order to compare thedifferent methods; Double, Coaxial and Spray electrospinning pointing out similarities anddifferences between the three. The methods used to characterize the materials include scalemeasurements and SEM image analysis to determine morphology, fibre diameter, layerthickness and distance between particles. Glass particles were used as substitutes for livingcells for the sake of proof of concept which showed that these can successfully be integratedsimultaneously in an electrospun material. However porosity and the number of particles haveto be further optimized for the material to be ready for use in tissue engineering.

The incidence and long-term effects of traumatic brain injury (TBI) make it a major healthcare and socioeconomic concern. Cell transplantation may be an alternative therapy option to target prolonged neurological deficits; however, safety and efficacy of the cells must be determined. Bone marrow-derived mesenchymal stem cells (MSCs) are an accessible and expandable cell source which circumvent the many of the accessibility and ethical concerns associated with fetal tissues. A major impediment to recent clinical trials for cell therapies in the central nervous system has been the lack of consistency in functional recovery where some patients receive great benefits while others experience little, if any, effect (Watts and Dunnett 2000; Lindvall and Bjorklund 2004). There are many possible explanations for this patient-to-patient variability including genetic and environmental factors, surgical techniques, and donor cell variability. Of these, the most easily addressable is to increase the reproducibility of donor cells by standardizing the isolation and pre-transplantation protocols, which is the central goal of this dissertation. First, we present an animal study in which transplants of MSCs and neural stem cells (NSCs) were given to brain-injured mice, however, the efficacy of the treatment had high variability between individual subjects. Second, we designed a method to produce MSC-spheres and characterize them in vitro. Last, we employed an in vitro 3-D culture testbed as a pre-transplant injury model to assess the effects of the MSC-spheres on neural cells. The electrophysiological function of the uninjured testbed was assessed, and then MSC-spheres were injected into the testbed and apoptosis of the host cells were measured. The results of this study contribute to our understanding of how extracellular context may influence MSC-spheres and develop MSCs as a donor cell source for transplantation.

An estimated 200,000 injuries to the anterior cruciate ligament (ACL) occur annually in the United States, with approximately 100,000 total ACL reconstructions performed each year. Due to inherent limitations with existing ACL reconstruction strategies, the development of tissue engineered ligaments is a key area of musculoskeletal research. Although great strides have been made in the scaffold design, current strategies are limited by the inability to replicate the mechanical behavior of native ligament tissue with synthetic polyesters or natural polymers. Poly(ester urethane)s have recently been investigated as possible scaffold materials because of their established biocompatibility, excellent mechanical properties, and exceptionally tunable structure. However, non-specific degradation makes it difficult to tailor polyurethane structure to complement ligament regeneration. In contrast, a biomaterial that features system-responsive degradation would integrate with native ligament remodeling and thus provide effective load transfer to newly formed tissue that is necessary to restore mechanical integrity. In this study, enzyme-labile peptide sequences were conjugated to ether-based polyols to form collagen-mimetic soft segments that feature cell-responsive degradation. Synthetic routes were first developed to functionalize these polyols with favorable end groups for peptide coupling. Upon successful conjugation, biodegradable soft segments were then incorporated into the structure of linear polyurea elastomers. By varying soft segment chemistry, soft segment molecular weight, and the hard to soft segment ratio, a library of cell-responsive, biodegradable polyureas was developed. This library can then be used to elucidate key structure-property relationships necessary to complement neotissue formation. Overall, synthesis of a novel biomaterial that combines the strength and tunability of synthetic elastomers with cell-responsive degradation will assist in the development of an improved tissue engineered graft for ACL reconstruction.

Zugl.: Giessen, Universiẗat, Diss., 2009.

Thesis (M.S.)--University of Akron, Dept. of Chemical and Biomolecular Engineering, 2008. / "August, 2008." Title from electronic thesis title page (viewed 01/13/2010) Advisor, Stephanie T. Lopina; Committee members, Daniel B. Sheffer, Glen O. Njus; Department Chair, Daniel Sheffer; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Thesis (Ph.D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Biomedical Engineering. Title from resource description page. Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed January 5, 2010). PDF text: xiv, 328 p. : ill. (some col.) ; 7.48 Mb. UMI publication number: AAT 3373081. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 206-224).

Thesis (D.Eng.)--Cleveland State University, 2009. / Abstract. Title from PDF t.p. (viewed on Jan. 13, 2010). Includes bibliographical references (p. 139-151). Available online via the OhioLINK ETD Center and also available in print.