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Title: Development of three-dimensional fibrous structures via electrospinning for applications in scaffold-based tissue engineering
Keywords: tissue engineering, biomaterials, electrospinning, angiogenesis, scaffold, periosteum
Issue Date: 26-Aug-2009
Citation: ANDREW KRISHNA EKAPUTRA (2009-08-26). Development of three-dimensional fibrous structures via electrospinning for applications in scaffold-based tissue engineering. ScholarBank@NUS Repository.
Abstract: Various reports have been published citing the suitability of electrospun fibrous meshes as tissue engineering scaffolds due to their unique physical properties. However, as promising as it may seem, this technology is still in its infancy and further development is critical before it can be used for any practical biomedical applications. Moving towards the next generation of electrospun tissue engineering scaffolds, increasing research efforts are being focused on issues such as bio-functionalization, three-dimensionality and improved biomechanical properties of the scaffolds. The research project outlined in this thesis was aimed to address the first two issues mentioned. To do so, electrospinning system was setup and optimized for the fabrication of poly (e-caprolactone)-based (PCL) fibrous meshes. First step of bio-functionalization of the PCL meshes was the incorporation of a ubiquitous natural extracellular matrix (ECM) protein component, collagen, creating a synthetic-natural electrospun composite fiber. The effects of collagen incorporation were investigated with respect to the resulting mesh?s ability to support in vitro osteogenic morphogenesis. Compared to PCL alone, its collagen composite (PCL/Col) was proven to be more osteo-conductive as judged by proliferative capacity of bone marrow progenitor cells and their development into mature bone-like tissue. Functionalization of the PCL with gelatin yielded a less optimum osteogenic response compared to collagen. Addressing the second issue of three-dimensionality of electrospun scaffolds, a novel hybrid electrospun mesh was fabricated via a modified electrospinning system. The new system enabled simultaneous electrospinning of micron-sized PCL/Col fibers with electrospraying of hyaluronic-acid derived hydrogel, HeprasilTM and their combination into a single scaffold entity. The novel hybrid PCL/Col-Hep mesh allowed cellular infiltration throughout its architecture as assayed in vitro using a model osteoblast cell line. This method proved to be significantly better than other modifications method attempted here. A second step of bio-functionalization was introduced into this mesh by the incorporation of bioactive growth factors vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF-BB) and bone morphogenetic proteins (BMP-2) within the HeprasilTM component. Sustained time-release profiles were obtained through this method highlighting the potential of the mesh as a cytokine delivery vehicle. Furthermore, bio-activities of the proteins were retained in this manner indicating minimal processing damage. Investigations into the performance of this novel hybrid mesh as a three-dimensional (3D), bio-functional tissue engineering scaffold were carried out in an in vitro neo-vascularization model. Co-culture of endothelial cells and fibroblast were utilized as a model system optimized in a 3D setting on the PCL/Col-Hep meshes. The fibrous mesh surface properties proved to be suitable for the culture of both cell types. The interplay of the co-cultured cells even recapitulated the formation of primitive endothelial capillary networks on the surface and within the mesh?s interior implying a more physiological phenotype expression of the cells. Furthermore, similar results were attained when endothelial cells and fibroblast were cultured on PCL/Col-Hep meshes impregnated with angiogenic factors VEGF and PDGF-BB and without exogenous supplementation of the cytokines in the media. This signifies the potential therapeutic benefits in cytokine delivery in the scaffold. In conclusion, the work presented in this thesis provided a method of fabricating the next generation of electrospun scaffolds capable of 3D tissue integration and bioactive factor delivery. Such a technological advancement will prove advantageous in achieving improved tissue regeneration and repair.
Appears in Collections:Ph.D Theses (Open)

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