A note on cookies

We use cookies to improve your experience of our website. Privacy Policy

Queen Mary University of LondonQueen Mary University of London
Research menu

School of Engineering and Materials Science
Research Student Awards

PhD Thesis: Novel synthesis routes to conventional and modified bioceramics and composite bone cements

Author: HAQUE, Saba

Year: 2007

Supervisor(s): Jawwad Darr

Hydroxyapatites (HA) and carbonated apatites (CA) have a chemical composition and crystal structure similar to the mineral phase of bone.

The work in this thesis involved the development of several novel bioceramics. For example, high-pressure CA was prepared by reacting calcium and phosphate solutions in dense-phase carbon dioxide (CO2) (a highly compressible medium that acted as a carbonating source). The CA powder was heat-treated in an atmosphere of dry CO2 and subsequent spectral analyses showed an excellent match to human bone mineral with a calculated carbonate content of 8 wt% after heat-treatment. The mild acidity of the dense-phase CO2 medium was also used to synthesise a low pH phase calcium orthophosphate (brushite).

Sodium-substituted HA and monetite syntheses were carried out using a conventional water-in-oil emulsion method. Emulsion processing is advantageous since it allows products of increased homogeneity and surface area, whilst the minimised particle agglomeration allows better sinterability. The difficulties in obtaining phase-pure bioceramics in an emulsion are discussed.

In the final parts of the work, three different bifunctional coupling agents were successfully grafted onto the surface of HA, via phosphonate [-P(O)(O)22-] or carboxylate (-COO-) groups. Their solubility in water allowed them to be used directly in a modified, wet co-precipitation reaction. These surface-grafted HAs were incorporated as fillers into poly(ethyl methacrylate)/n-butyl methacrylate (PEMA/nBMA) bone cement, using 10 and 20 wt% HA filler content. In the case of 20 wt% filler content, the flexural strength, flexural modulus, tensile strength and fatigue life of the injectable HA/PEMA/nBMA bone cements were significantly improved for grafted-HA compared to ungrafted-HA.