Biomineralized Matrices as Intelligent Scaffolds for Bone Tissue Regeneration
Bone is an example of a biomineralized functional living tissue. The mineralized components of bone tissue endow them with unique mechanical and chemical functions. Specifically, bone tissue is composed of inorganic calcium phosphate (CaP)-rich mineralized phases built upon the organic substrate (osteoid) whose major components are type I collagen and noncollagenous proteins (NCPs), such as osteocalcin (OCN) and bone sialoprotein (BSP). 1 , 2 One of the key functions of these organic proteins is to mediate mineralization of bone tissue. Native bone contains a mixture of various minerals, such as nonstoichiometric crystalline hydroxyapatite (HAp) and amorphous calcium phosphate (ACP). 3 Bone minerals also contain 60other mineral components including carbonate, sodium, and magnesium. Native bone exhibits excellent regenerative capacity; however, critical-size bone defects often require exogenous interventions, such as bone grafts to assist tissue regeneration or implants to fix nonunion defects. While native bone tissue and its derivatives are still the best solutions to treat critical-size bone defects, emerging studies implicate that CaP-based synthetic biomaterials, which emulate a bone-specific mineral environment, could be used as an alternative to treat such bone defects. Over the past decade, a number of CaP mineral-based matrices have been examined to promote bone tissue regeneration, which include CaP-based ceramics and polymer composites containing CaP minerals. In this chapter, we describe the development of CaP-based biomaterials and their applications in bone tissue regeneration ranging from directing stem cell differentiation to supporting bone tissue formation in vitro and in vivo. We also discuss the molecular mechanism through which CaP-based biomaterials promote bone tissue regeneration and the importance of CaP mineral phase in mediating the tissue repair. We finally conclude the chapter with future perspectives toward the translational applications of synthetic CaP-bearing materials for bone tissue regeneration.