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Title: Calcium phosphate scaffolds with controlled properties for biological applications
Author: da Costa Machado, Gil Daniel
ISNI:       0000 0004 6346 9244
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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The last few decades have seen major advances in the field of materials for healthcare applications. New approaches call for the development of biomaterials with controlled chemistry, tailored structure at different length scales and adequate degradation and dissolution profiles, all of which are crucial to the success of biomaterials for tissue regenerative therapies. Calcium phosphates are widely used to promote recovery of bone tissue due to their chemically similarity to the inorganic phase of bone. And although they have had considerable success, a discussion remains about the optimum characteristics of a bone substitute. This work aimed to develop a framework to study the combined effect of surface microroughness of calcium phosphates with varying composition - Hydroxyapatite (HA) to β-Tricalcium Phosphate (β-TCP), including biphasic materials - on human mesenchymal stem cells in vitro. Furthermore, the method used to tailor such microstructural features is translatable into 3D-printed scaffolds, i.e., it was possible to fabricated materials with complex structures, while controlling surface roughness. The thermal behaviour of calcium phosphate materials with different Ca/P ratio was studied, and adequate sintering conditions were optimised. These avoid the β to α transformation in materials with TCP. A novel processing route to control microstructure was developed: ceramic materials were functionalised with a pH-responsive polymer and used to stabilise microemulsions, where the hydrophobic phase was used as a soft porogen that evaporates. Independently of the HA/β-TCP ratio used, interconnected microporosity was obtained as a result of the emulsification process. The osteogenic potential of discs with these surface properties and three different chemical compositions (pure HA, pure β-TCP and a biphasic material HA/β-TCP) was evaluated in cultures with hMSCs from three independent donors. Finally, the behaviour of particle-stabilised emulsions was optimised to be used as inks for robocasting. Rheological characterisation and extrusion flow tests clarified the impact of different processing steps in their printability. In the end, calcium phosphate scaffolds with complex shapes and controlled chemistry and surface features (resulting from the oil templating) were fabricated.
Supervisor: Saiz, Eduardo ; Jones, Julian Sponsor: European Commission
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral