Synthesis and incorporation of rod-like nano-hydroxyapatite into type I collagen matrix: a hybrid formulation for 3D printing of bone scaffolds

Over the recent years, nanometric hydroxyapatite (HA) has gained interest as constituent of hybrid systems for bone scaffold fabrication, due to its biomimicry and biocompatibility. In this study, rod-like nano-HA particles were introduced in a type I collagen matrix to create a composite mimicking the bone composition. HA nanorods (40−60 nm ×20 nm) were synthesised by hydrothermal method involving the use of an ammonium-based dispersing agent (Darvan 821-A) and fully characterised. The homogeneous dispersion of HA nanoparticles throughout the final hybrid formulation was achieved through their suspension in a collagen solution in presence of Darvan 821-A. The resulting homogeneous collagen/nano-HA suspension proved to be suitable for extrusion printing applications, showing shear thinning and sol-gel transition upon simil-physiological conditions. Furthermore, mesh-like structures were printed in a gelatine-supporting bath by means of a commercial bioprinter further demonstrating the potential of the designed hybrid system for the fabrication of 3D bone-like scaffolds.