Designing tissue engineering scaffolds with the required mechanical properties and
favourable microstructure to promote cell attachment, growth and new tissue
formation is one of the key challenges in the tissue engineering field. An important
class of scaffolds for bone tissue engineering is based on bioceramics and bioactive
glasses. The primary disadvantage of these materials is their low fracture resistance
under load and their high brittleness. These drawbacks are exacerbated by the fact that
optimal scaffolds must be highly porous (>90% porosity). As a main focus of this
thesis, a novel approach was investigated to enhance the structural integrity, fracture
strength and toughness of partially sintered 45S5 Bioglass® based glass-ceramic
scaffolds by polymer infiltration and to develop an understanding of the interaction of
these two phases in the final composite structure. Commercially available synthetic
poly(D,L-Lactic acid) (PDLLA) was incorporated as a coating onto the partially
sintered Bioglass® based scaffolds by dipping technique. Two natural polymers
synthesised from bacteria, which exhibit different properties to those of PDLLA, were
also investigated: i.e. poly(3-hydroxybutryate) (P(3HB)) and poly(3-
hydroxyoctanoate) (P(3HO)). The work of fracture of partially sintered 45S5
Bioglass® scaffolds was significantly improved by forming interpenetrating polymerbioceramic
microstructures which mimic the composite structure of bone. It was
demonstrated that coating with polymers such as PDLLA, P(3HB) and P(3HO) does
not impede the bioactivity of the scaffolds but the extent of bioactivity, given by the
kinetic of HA formation, was seen to depend on polymer type and on scaffold
sintering conditions. Polymer coated 45S5 Bioglass® pellets sintered at the same
condition as the scaffolds and immersed in SBF were investigated to better evaluate
the bioactivity mechanism and interfacial properties of the materials. It was
demonstrated that polymer coated 45S5 Bioglass® based glass-ceramic scaffolds can
have higher bioactivity and improved fracture toughness when the basic scaffold
structure is sintered at relative lower sintering temperatures leaving residual open
porosity which can be efficiently infiltrated by the polymer.
A bilayered scaffold structure was also designed and fabricated to develop for the first
time a porous bioactive glass-ceramic scaffold coated with PDLLA nanofibers.
Electrospinning was used to deposit a PDLLA fibrous layer on top of the bioactive glass scaffold. These scaffolds were developed for osteochondral tissue engineering
applications. SBF studies showed that the extent of mineralisation of the PDLLA
fibres depended on the fibrous mesh thickness. PDLLA fibres deposited for 2 hours
did not mineralise when immersed for 7, 14 and 28 days in SBF making the structure
suitable for osteochondral defect applications. Initial in vitro cell response studies
showed that the bilayered scaffolds were non toxic and chondrocyte cells were able to
proliferate on the PDLLA fibre layers, demonstrating the potential of the novel
scaffolds for osteochondral tissue engineering.