Apatite-wollastonite glass ceramic scaffolds for bone tissue engineering applications

Abstract

In bone tissue engineering, one of the main challenges is to fabricate scaffolds that promote and support osseous reconstruction. The research reported in this thesis considers the use of apatite-wollastonite (A-W) as a bone scaffold. A variety of scaffold fabrication techniques, all based on initially processing powder to create a pre-form for subsequent sintering, have been developed and characterised for their ability to create microporous; and interconnected macroporous scaffolds. A range of powder processing techniques were used: pelleting, dry powder and slurry moulding, and different powder particle size ranges were assessed for the preparation of microporous scaffolds to influence their surface roughness without significantly varying the porosity. To introduce macroporosity within the ceramic scaffolds that would be comparable in terms of scale and organisation to trabecular bone, a variety of methods were employed. Burning off negative templates such as polymeric particles, filaments and fused deposition modelling 3D constructs was investigated, together with a novel method based on thermally induced phase separation (TIPS), freeze-drying and sintering. Selected microporous scaffolds with different surface topography and pore size; and highly interconnected scaffolds with porosity >80% were fabricated with height 2± 0.1 mm and diameter 8- 10 mm depending on the fabrication method and the particle range that was used. The parameters that were evaluated in vitro were the effect of variable topographies on microporous constructs and the influence of high porosity on cell adhesion, proliferation and cell differentiation. It is concluded that the surface area of A-W scaffolds affects their bioactivity, degradation and mechanical properties. Microporous scaffolds with smaller pores allow cell-cell interaction and promote osteogenesis. Further investigation is required to clarify the observed chondrogenesis that occurred when MSCs were cultured on microporous scaffolds with larger pores. Highly porous A-W scaffolds allow cell infiltration, migration and demonstrate signs of osteochondral lineage differentiation.