Bone tissue engineering via nanostructured calcium phosphate biomaterials and stem cells

Tissue engineering is promising to meet the increasing need for bone regeneration. Nanostructured calcium phosphate (CaP) biomaterials/scaffolds are of special interest as they share chemical/crystallographic similarities to inorganic components of bone. Three applications of nano-CaP are discussed in this review: nanostructured calcium phosphate cement (CPC); nano-CaP composites; and nano-CaP coatings. The interactions between stem cells and nano-CaP are highlighted, including cell attachment, orientation/morphology, differentiation and in vivo bone regeneration. Several trends can be seen: (i) nano-CaP biomaterials support stem cell attachment/proliferation and induce osteogenic differentiation, in some cases even without osteogenic supplements; (ii) the influence of nano-CaP surface patterns on cell alignment is not prominent due to non-uniform distribution of nano-crystals; (iii) nano-CaP can achieve better bone regeneration than conventional CaP biomaterials; (iv) combining stem cells with nano-CaP accelerates bone regeneration, the effect of which can be further enhanced by growth factors; and (v) cell microencapsulation in nano-CaP scaffolds is promising for bone tissue engineering. These understandings would help researchers to further uncover the underlying mechanisms and interactions in nano-CaP stem cell constructs in vitro and in vivo, tailor nano-CaP composite construct design and stem cell type selection to enhance cell function and bone regeneration, and translate laboratory findings to clinical treatments.