Scaffolds for tissue engineering must meet certain requirements to make it suitable for use as a bone graft substitute, including a three-dimensional and highly porous structure, with an interconnected pore network to facilitate cell growth and transport of nutrients and metabolic waste products. In addition, the construct must be biocompatible and bioresorbable with controllable degradation and resorption rates to match cell/tissue growth in vitro and/or in vivo. Finally, a suitable surface chemistry for cell attachment, proliferation, and differentiation is required, along with sufficient mechanical properties to provide a support for the formation of new bone tissue.
Collagen based scaffolds are known to be highly biocompatible, with porosity, pore size and permeability suitable for bone tissue engineering. From a clinical perspective however, collagen scaffolds are limited by their mechanical properties, and therefore the primary objective of this thesis was to develop a technique to reinforce a highly porous collagen scaffold by the introduction of the bioactive ceramic, nano-hydroxyapatite (nHA). In Chapter 2 of the thesis, a technique to produce non-aggregating nano-sized particles (<100 nm) of HA was developed using a novel, dispersant-aided synthesis procedure.
In Chapter 3, the incorporation of the synthesised nHA into the collagen scaffolds was investigated. The optimised technique involved the addition of a nHA particle suspension (0 - 500 wt % nHA) to a collagen fibre slurry prior to freeze-drying, and resulted in a highly porous (>99 %), resorbable composite material with significantly improved mechanical stiffness (18 fold increase) vs. a collagen only control. The homogeneous distribution of the osteoinductive nHA particles also influenced the behaviour of cells cultured on the composite constructs, and in vitro analysis (Chapter 4) demonstrated their excellent biocompatibility and capacity to support bone tissue formation. Superior cell attachment was achieved on the collagen-nHA constructs in comparison to the collagen control, in addition to promoting the earlier onset of mineralisation.
Recently in bone tissue engineering, the use of gene therapy has shown much promise for osteogenic applications, with therapeutic genes demonstrating enhanced bone regeneration and healing. However, the efficiency of current delivery systems must be improved to attain controlled and sustained localised gene delivery. The ability of the materials developed in this thesis to transfect cells with plasmid DNA was established in Chapter 5. The nHA particles served as a non-viral delivery method, and were combined with the collagen-nHA composite scaffolds to produce a gene activated matrix. These composite scaffolds facilitated sustained gene expression compared to the collagen only control scaffold, validating their potential for use in bone tissue regeneration.
|Date of Award||Dec 2009|
- Queen's University Belfast
|Supervisor||Glenn Dickson (Supervisor) & Fergal O'Brien (Supervisor)|