The Fabrication and Characterisation of Membranes and Scaffolds for Guided Bone Regeneration

Membranes are used in maxillofacial surgery to provide a barrier against soft tissue in-growth into a bone defect, to retain a bone filler if used, and therefore to facilitate guided bone regeneration. Although there are membranes already available on the commercial market, these do little to actively promote bone regeneration, and instead merely provide a barrier function. Issues surround the two “gold standard” materials; a natural resorbable porcine collagen membrane and a synthetic non-resorbable polytetrafluoroethylene membrane. Additionally, neither of these materials contain a bioactive component to help promote bone regeneration. Scaffolds can be used in conjunction with membranes, and provide a mechanical support for the defect site and a structure for cells to proliferate on.

The aims of this research were therefore to investigate the potentials of resorbable polymer-ceramic membranes and scaffolds with bioactive properties to be viable options for use in guided bone regeneration procedures. Heterogeneous membranes were successfully fabricated via electrospun poly(lactide-co-glycolide) and combined with a hydroxyapatite coating to promote osteoinduction. Several coating methods were tested and the most promising, a titration coating with an average particle size of 30 x 11 nm and an average coating of 7.67 μg/mm2 (15 wt%), was taken forward for in vitro testing. The average size of hydroxyapatite found within the body is 20 nm; particles close of a similar size are expected to have better bioactive properties due to their biomimetic nature. Biocompatibility experiments using human and rat mesenchymal stem cells demonstrated that the membranes were able to support cell proliferation for up to 21 days. DNA and alkaline phosphatase levels were quantified to investigate the degree of osteogenic differentiation. The coating supported an increased rate of cell proliferation in comparison to uncoated membranes.

Composite polycaprolactone-hydroxyapatite scaffolds were fabricated via 3D printing at a range of hydroxyapatite concentrations (0-40 %). The addition of a surfactant made printing of higher weight concentrations of hydroxyapatite possible at lower temperatures and pressures than previously reported. 40 wt% HA scaffolds had an average fibre width of 720 x 1320 μm and pore size of 960 x 540 μm, The bioactivity of the scaffolds was investigated using rat mesenchymal stem cells. In vitro results suggest that the pore size is critical for the attachment of cells. Pure PCL scaffolds had the best cell attachment at day 1, quantified by levels of DNA. This work demonstrated that a custom-built low cost 3D printer can be used to produce scaffolds intended for bone tissue regeneration, although they must have a higher resolution in order to print scaffolds with smaller pore sizes.