Development and Assessment of In Vitro Models of Osteogenic Microstructures

In vitro models of bone aim to use materials that encourage the fast deposition of significant amounts of mineral and collagen. Although this would be beneficial in tissue engineering applications, using this for in vitro modelling oversimplifies the organised structure that is observed in mature bone. Furthermore, cortical and trabecular bone have notably different architectures. Within this thesis, two differential scaffolds were developed and tested, for use in lamellar and trabecular bone models, to mimic structural features of the two bone-type organisations that are commonly overlooked in in vitro models. For a model of lamellar bone, aligned and non-aligned polycaprolactone fibres were explored, to test whether human cells at an early stage of osteogenic differentiation would deposit collagen exhibiting a twisted plywood deposition behaviour and provide a model system of laboratory-grown lamellae. On aligned fibres, there was an observable spacial change in collagen direction comparable to that seen within physiological human lamellae, which shows a gradual change in fibril direction between 10-60° from the initial orientation of the fibrils closest to the osteon’s centre. A method to produce a more cortical bone-like structure may be valuable for a variety of applications, including the development of more accurate models of lamellar osteogenesis, or for use in high-throughput drug testing. To produce a trabecular-like material, a novel method for producing a porous emulsion was explored. By the combination of mechanical properties of methacrylated polycaprolactone-triol (3PCL-MA) and the biocompatibility of gelMA, this work aimed to develop a tuneable and mechanically robust porous bioink for the 3D printing of trabecular bone, using a curable two-phase emulsion system. 3PCL-MA/GelMA emulsions provide a viable route for the fabrication of stiff, printable inks. The mechanical properties of the inks are significantly higher than that of pure gelMA, which may make them a more promising option for the culture of bone cells