Trends in Biotechnology
ReviewRecent advances in bone tissue engineering scaffolds
Section snippets
Bone scaffolds
Bone tissue engineering is a complex and dynamic process that initiates with migration and recruitment of osteoprogenitor cells followed by their proliferation, differentiation, matrix formation along with remodeling of the bone. Major advances in bone tissue engineering with scaffolds are achieved through growth factors, drugs and gene deliveries. Bone scaffolds are typically made of porous degradable materials that provide the mechanical support during repair and regeneration of damaged or
Design and fabrication of scaffolds
Bone is a natural composite of collagen and hydroxycarbonate apatite with 10–30% porous hard outer layer, i.e., cortical bone; and 30–90% porous interior, i.e., cancellous bone. Mechanical properties of bone vary widely from cancellous to cortical bone which along with complex geometry makes it difficult to design an “ideal bone scaffold” (Box 1). The key factors for an ideal scaffold for bone tissue engineering are: (i) macro- (pore size >100 μm) and micro-porosity (pore size < 20 μm); (ii)
In vitro and in vivo evaluation of bone scaffolds
The following summary highlights scaffolds made with different materials that have been tested under in vitro and in vivo conditions.
Third generation scaffolds
Although CaP scaffolds allow new bone formation and biomineralization, next generation scaffolds are predicted to be osteoinductive. Different approaches have been investigated to make CaP scaffold osteoinductive, which includes but is not limited to modifying scaffold chemistry, seeding bone marrow stem cells, and incorporation of different growth factors such as TGF-β, BMP, and VEGF in the scaffold. Osteoinduction is associated with both material composition and porosity. Si-TCP/HA with 60%
Critical issues in bone tissue engineering scaffolds
Several in vitro and in vivo studies have demonstrated excellent biocompatibility and new bone formation for a variety of bone scaffolds, however, some key challenges still remain: (i) biocompatibility and biomechanical strength in polymeric scaffolds, (ii) metal ion release, limited bioactivity and biodegradation for metallic scaffolds, and (iii) toughness as well as reliable and reproducible manufacturing techniques for ceramic scaffolds. Moreover, controlling the degradation rate of any
Concluding remarks and future directions
Research on bone tissue engineering over the past decades have inspired innovation in new materials, processing techniques, performance evaluation, and applications. Significant progress has been made towards scaffold materials for structural support with desired osteogenesis and angiogenesis abilities. Bioresorbable scaffolds with controlled porosity and tailored properties are possible today due to innovation in scaffold fabrication using advanced technologies, e.g., SFF. One of the drawbacks
Acknowledgments
The authors like to acknowledge the support from the National Institute of Health, specifically NIBIB (Grant no. R01A1EB 007351).
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