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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Mechanisms of the improvced Biological Response with Silicate Substitution in Hydroxy Apatite.

Author: GUTH, Katharina

Year: 2008

Supervisor(s): Karin Hing

Hydroxyapatite (HA) bioactivity has been reported to be enhanced through site specific substitution of 0.8wt% silicate for phosphate into the HA lattice (SiHA). The aim of this thesis was to explore the possible mechanisms behind this bioactivity enhancement. Two hypotheses were proposed whereby bioactivity may be enhanced by either (1) an ‘indirect effect’, where alterations in the ion concentrations in the fluid surrounding the graft materials influenced osteoblasts development or metabolism and/or (2) by a ‘direct effect’, where differences in the material physiochemistry influenced protein adsorption, which subsequently promotes osteoblasts attachment and consequently development or metabolism. In order to probe these two hypotheses a broad area of activity was undertaken, including production of morphologically matched HA and SiHA, analysis of surface physiochemistry and chemical interactions under cell culture conditions in addition to analysis of material-protein interactions, cell attachment metabolism and development.

Improved bioactivity through the ‘indirect effect’ of ionic interactions between SiHA and the surrounding medium was not established.

The work presented in this thesis supported the hypothesis that the increased bioactivity of SiHA resulted from a ‘direct effect’, where the surface physiochemistry impacted on protein adsorption, which subsequently promoted osteoblasts-like cell development.