Three-dimensional printable nanocomposite biomaterials as bone scaffolds and grafts

Geometrically complex bone grafts are needed to repair of large bone defects in which bone has been lost or damaged beyond its capacity to heal itself. Designing materials with microstructure, sufficient strength, and sufficient porosity that can facilitate new bone formation is a major challenge for bone repair. Compared with other classes of materials, multifunctional nanocomposites can provide better mechanical properties and cell–material interactions owing to the large surface-to-volume ratio of particles, providing nanoscale reinforcement and enhanced surface chemistry. The nature of the polymer matrices and nanoscale interactions between phases greatly affect the mechanical properties of nanocomposites. Additive manufacturing or three-dimensional (3D) printing is an inexpensive, high-speed, and versatile technique that involves multiaxis motion and a layer-by-layer scheme to fabricate complex objects with design-specific features. Thus, 3D printable nanocomposite inks are promising options for the production of by-design nanocomposites structures with complex hierarchical microstructure. This technique has been used to prepare nanocomposite grafts and scaffolds for bone tissue engineering with micron-scale resolution and excellent pore morphologies. Various 3D printing techniques can be applied to achieve dense or porous grafts with design-specific geometries and features. Multifunctional nanocomposites with tailorable interfaces and suitable rheologic properties are 3D printed into objects with excellent mechanical strength and a controlled biodegradation rate. In this chapter, we review 3D printable nanocomposite inks in view of their mechanical, rheologic, and biodegradation properties required for bone reconstruction applications.