Development of a collagen calcium-phosphate scaffold as a novel bone graft substitute

Previous investigations have shown that collagen shows excellent biological performance as a scaffold for tissue engineering. As a primary constituent of bone and cartilage, it demonstrates excellent cell adhesion and proliferation. However, in bone tissue engineering, it has insufficient mechanical properties for implantation in a load-bearing defect. The objective of this preliminary study was to investigate the possibility of developing a collagen/calcium-phosphate composite scaffold which would combine the biological performance and the high porosity of a collagen scaffold with the high mechanical stiffness of a calcium-phosphate scaffold. Collagen scaffolds were produced by a lyophilisation process from a collagen slurry. The scaffolds were soaked for different exposure times in solutions of 0.1 M, 0.5 M or 1.0 M NaNH4HPO4 followed by 0.1 M, 0.5 M or 1.0 M CaCl2. Mechanical tests of each scaffold were performed on a uniaxial testing system. Young's moduli were determined from stress-strain curves. The pore structure and porosity of the scaffolds were investigated using micro-computed tomography. A pure collagen scaffold served as a control. All scaffolds showed a significantly increased compressive stiffness relative to the pure collagen scaffolds. The exposure to the 0.5 M solutions showed significantly superior results compared to the other groups. Analysis of the pore structure indicated a decrease in the overall porosity of the composite scaffolds relative to the controls. Regarding mechanical stiffness and porosity, scaffolds after 1 hour exposure to the 0.5 M solutions showed the best properties for bone tissue engineering. Further work will involve producing a scaffold with a more homogeneous calcium phosphate distribution.