Porous hydroxyapatite bioceramics in bone tissue engineering: current uses and perspectives

Abstract

The goals of bone tissue engineering are to apply biomaterial scaffolds with adhered cells, such as osteoblasts, bone marrow stromal stem cells, or chondrocytes, to repair, regenerate, and restore the functions of damaged bone tissue or to replace those tissues with porous engineered biomaterials. Over recent decades, a diverse class of biomaterials has been applied in bone tissue engineering field. Porous hydroxyapatite bioceramic is currently receiving significant attention as a bone tissue engineering substitute because of its biological characteristics, including biocompatibility, bioactivity, osteoconduction, and vasculogenesis. This biomaterial has a three-dimensional structure with interconnected spherical pores of uniform size, which encourages bone ingrowth and achieves good integration of the material and the host bone over time. However, the compressive strength and elastic modulus of porous hydroxyapatite scaffolds generally weaken as the porosity increases, in both in vitro and in vivo testing. Zirconia can be used to toughen hydroxyapatite materials for bone repair and replacement because of its unique biomechanical properties, including compressive strength and fracture toughness. Additionally, a zirconia chitosan hybrid containing bone morphogenetic protein-2 and mesenchymal stem cells derived from induced pluripotent stem cells has been used as a coating material adhered to surface of scaffolds to promote bone regeneration and repair. Here, we provide a succinct review of zirconia toughened hydroxyapatite biomaterial scaffolds that incorporate bone morphogenetic protein-2 and mesenchymal stem cells for bone tissue engineering and describe the biomaterials that are currently being investigated based on the recent literature and our own data.

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…Nowadays, the biomaterials' field is shifting towards biologically active systems to improve their performance and to expand their use (Kolk et al 2012;Garg and Goyal 2014;Tang and Diehl 2014). Therefore, tissue engineering is the strongest direction of current research, which, in the case of CaPO 4 , means fabrication of proper substrates and/or scaffolds to carry cells, hormones and biochemical factors to be further used in surgery and medicine (Zhou and Lee 2011;Zakaria et al 2013;Shao et al 2015). Presumably, a synthesis of various types of CaPO 4 -based biocomposites and hybrid biomaterials occupies the second important place (Dorozhkin 2015b).…”

Surface modification using the biomimetic method in alumina‐zirconia porous ceramics obtained by the replica method

“…Currently, the modification of surfaces of materials approved by the Food and Drug Administration is becoming a reality. Among these, bioceramics, used for bone replacement or repair, can be surface modified to make them bioactive . They are used to repair, regenerate and restore the functions of damaged bone tissue .…”

“…Among these, bioceramics, used for bone replacement or repair, can be surface modified to make them bioactive . They are used to repair, regenerate and restore the functions of damaged bone tissue . For this, porous bioceramics must have pores with pore sizes and morphologies (interconnectivity and rounded pores) that directly affect bone regeneration and, as a consequence, affect cell adhesion and internal growth of bone tissue …”

“…These ceramics are used as implants to promote adhesion and cell growth, acting as a carrier or model for bone cell growth . To be used in bone regeneration, these scaffolds must have interconnected pores, with sizes between 5 and 300 μm, to promote bone growth and cell adhesion …”

“…The adhesion between the formed bioactive layer and the material, as well as its morphology, depends on the surface properties. In this sense, there is the possibility of functionalization of the scaffolds using chemical treatment on the surface, seeking an ideal surface that provides active sites for the precipitation of calcium phosphates homogeneously …”