Fabrication of polymer composites as potential bone replacement materials

In the field of bone replacement therapy, biomaterials capable of acting in a scaffolding capacity are under constant review and improvement. To operate as a scaffold material, several requirements must be met. Initially, materials must exhibit mechanical properties similar to natural bone. Degradability is another key requirement; the material must degrade at a rate compatible with ongoing bone regeneration at the site of implantation. Finally, the implanted product must induce a biological response to promote bone formation. In this regard, calcium phosphate ceramics are commonly used in clinical applications to promote bone regeneration, whilst composite materials containing several different components satisfying the above criteria have also been developed. The aim of the research described herein was to investigate the potential of combining polylactic acid (PLA) and calcium phosphate (CaP) compounds together to develop composite materials with good mechanical properties, degradability adjustability, and an increased potential for promoting bone regeneration. CaP materials focused on β-tricalcium phosphate (β-TCP) and magnesium substituted β-tricalcium phosphate (Mg-TCP), whilst an industrial collaboration provided a protein (casein) alternative to investigate. β-TCP samples were synthesised using a surfactant templated process, which allowed for control over the size, morphology and surface area of samples. Cationic substitutions of magnesium for calcium, at a range of levels, were carried out to study the mechanism of substitution into the crystal structure of β-TCP. All films were synthesised via the solvent casting method, and the composition and surface morphology was characterised. The degradation of non-filled PLA and composite films was analysed in deionised water, and the bioactive potential of the films was determined in simulated body fluid (SBF). Tensile strength measurements of the films were noted at several time points throughout the degradative process to evaluate maintenance of mechanical stability. In vitro assessment of the films was investigated with immunofluorescence and real time polymerase chain reaction (q-PCR) evaluations. This project addresses the various steps necessary to successfully synthesise a scaffold biomaterial for acceptable bone replacement, from the initial synthesis of the filler materials, through to the various mechanical and biological assessments which must be conducted to the suitability of said materials for use in clinical applications