Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Mequanint, Kibret

2nd Supervisor

Rizkalla, Amin S

Joint Supervisor

Abstract

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 phases are homogenously dispersed, are the ideal choices for bone tissue engineering.

In this research, polycaprolactone/borophosphosilicate glass (PCL/BPSG) and poly(vinylpyrrolidone-co-triethoxyvinylsilane)/bioactive glass (Poly(VP-co-TEVS)/BG) class II hybrid biomaterials were successfully prepared via a sol-gel process. PCL was functionalized with 3-glycidoxypropyl trimethoxysilane at both ends prior to hybrid syntheses. Trimethoxysilane-functionalized PCL was then polycondensed with the glass precursors via non-aqueous sol gel reactions to form covalently bonded O/I network with -C-Si-O-Si- bonds. The resultant amorphous and transparent hybrid materials exhibited apatite depositions when incubated with simulated body fluid. The ultimate compressive stress, modulus and toughness of these hybrids were significantly greater compared with their conventional composites counterparts, attributed to the covalent bonding between the O/I phases. In addition, these hybrids exhibited more controlled degradation and subsequent ion release without showing any abrupt features. Pre-osteoblast cells seeded on the hybrid biomaterials displayed enhanced spreading, focal adhesion formation, and cell number, indicating cytocompatibility. PCL/BPSG hybrid scaffolds were prepared by a solvent-free casting and particulate leaching methods to obtain consistent pore size distribution, controllable porosity and pore interconnectivity. Significant number of cell infiltration and adhesion into the scaffolds were observed in cell culture conditions. Bone-associated gene expression by induced pluripotent stem cells on these scaffolds revealed that the hybrid scaffolds had an upregulating effect on gene expressions for alkaline phosphatase, osteopontin and osteocalcin.

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