Design of Injectable Bone Tissue Engineering Scaffold Consists of ß-Tricalcium Phosphate Beads and Alginate

Abstract

Autologous bone is generally considered the gold-standard graft material. The advantage of an autograft is that it contains viable osteoblasts and osteogenic precursor cells that can contribute to the formation of new bone (Arrington et al, 1996). In addition, the autograft possesses the three essential elements of bone regeneration -osteogenesis, osteoinduction, and osteoconductionthat are required for bone regeneration. However, only a minimal amount of bone tissue can be harvested for autografts, the harvesting procedure may lead to donor site discomfort and morbidity, and it may be difficult to form this tissue into the desired shape (Goldberg & Stevenson, 1987; Damien & Parsons, 1991), a problem that is particularly important in the craniofacial region. Therefore, bone graft substitutes have been used to reconstruct bone defects. A bone graft substitute should be osteoconductive, osteoinductive, biocompatible, biodegradable, structurally similar to bone, easy to use, and cost-effective (Giannoudis et al, 2005). Hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) are both well-known ceramics that possess high tissue compatibility and osteoconductivity. However, neither HA nor βTCP has osteoinductive or osteogenic abilities, and HA usually shows minimal biodegradation (Spector, 1994; Schmitz et al, 1999). To overcome these limitations, bone tissue engineering has been promoted as a new way to regenerate bone tissue. This approach combines cells capable of osteogenic activity and osteoinductive signal molecules with an appropriate material (Livingston et al, 2005). For bone tissue engineering to succeed, osteoconductive scaffolding biomaterials must provide a suitable environment for the cells. Furthermore, it is desirable that the scaffolds can control the release of growth factors. Accordingly, functional composite scaffolds for bone tissue engineering have been developed in combination with synthetic ceramics and natural polymers. Recently, minimally invasive treatments have been developed using an injectable system for bone tissue engineering. Several injectable gels have been used to carry cells in order to engineer bone. Amongst which are collagen (Tsuchida et al, 2003), alginate (Shang et al, 14