Anwar, A; (2014) Continuous plastic flow synthesis and characterization of nanoscale bioceramics. Doctoral thesis , UCL (University College London).

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Abstract

The development and use of nanoscale biomaterials offer tremendous potential for future medical diagnosis and analysis. Various types of ceramic biomaterials (bioceramics) have been studied intensively for their potential in numerous biomedical applications. Among others, advances in the synthesis and characterisation of calcium phosphate (CaP) bioceramics have contributed much to this field. The growing demand for CaP bioceramics has stimulated research and production of materials suitable for biomedical applications such as implants. Among all the materials presented by the recent technology, only a very small fraction overcome biological and mechanical limitations rendering them suitable for use as a biomaterial. There is, therefore, a need to develop a clean synthesis methodology which could work under mild conditions to allow the synthesis of high purity, nanoscale bioceramic materials with a fine particle size and controlled surface area. The work in this thesis involves the use of a continuous plastic flow synthesis (CPFS) technology to synthesise various nano-scale bioceramics. Novel CPFS is a single step, continuous synthesis method for a stable, high purity phase-pure nanosized hydroxyapatite and other calcium phosphates at near ambient conditions (20°C to 80°C). The phase-pure HA nanoparticles obtained from this method possess a substantially superior high-temperature stability (1200°C), with remarkably high surface area (up to 264 m2/g) and the smallest particle size (20 nm) ever reported. These high surface area nanoparticles have a great range of applications for use in replacement of living hard tissues such as bone and teeth, as bone graft substitutes, injectable, coatings on metallic implants, as fillers or additives in commercial products, such as toothpastes; materials for the controlled release of drugs, or other controlled release therapies; reinforcements in biomedical composites, and in bone and dental cements. Other calcium phosphate phases (Brushite, β-TCP, CDHA and biphasic HA / β-TCP) were also obtained by changing the Ca:P ratio and pH of the precursor solutions. A variety of ion substituted calcium phosphates (Mg, Sr, Ba, Zn, Fe, Mn, Si, CO32-), nanocomposite materials (Fe3O4-HA, TiO2-HA) and surface modified organopolymer nano-dental composites have also been developed successfully by using CPFS. Furthermore, the process has the potential to offer high purity calcium phosphates because the reactor components are made of plastic and therefore will not cause contamination of the product with metals. The in vitro biocompatibility analysis indicate that these high surface area nano-sized bioceramics have better performance than commercial products and may have the potential to be used for biomedical applications where bone regeneration / replacement is required.

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