Synthesis and physicochemical,in vitroandin vivoevaluation of an anisotropic, nanocrystalline hydroxyapatite bisque scaffold with parallel-aligned pores mimicking the microstructure of cortical bone

Abstract

Scaffolds for bone regeneration are mostly prepared with an isotropic, sponge-like structure mimicking the architecture of trabecular bone. We have developed an anisotropic bioceramic with parallel aligned pores resembling the honeycomb arrangement of Haversian canals of cortical bone and investigated its potential as a scaffold for tissue engineering. Parallel channel-like pores were generated by ionotropic gelation of an alginate-hydroxyapatite (HA) slurry, followed by ceramic processing. Organic components were thermally removed at 650 °C, whereas the pore system was preserved in the obtained HA bioceramic in the processing stage of a bisque. Even without further sintering at higher temperatures, the anisotropic HA bisque (AHAB) became mechanically stable with a compressive strength (4.3 MPa) comparable to that of native trabecular bone. Owing to the low-temperature treatment, a nanocrystalline microstructure with high porosity (82%) and surface area (24.9 m(2)/g) was achieved that kept the material dissolvable in acidic conditions, similar to osteoclastic degradation of bone. Human mesenchymal stem cells (hMSCs) adhered, proliferated and differentiated into osteoblasts when osteogenically induced, indicating the cytocompatibility of the bisque scaffold. Furthermore, we demonstrated fusion of human monocytes to osteoclast-like cells in vitro on this substrate, similar to the natural pathway. Biocompatibility was demonstrated in vivo by implantation of the bisque ceramic into cortical rabbit femur defects, followed by histological analysis, where new bone formation inside the channel-like pores and generation of an osteon-like tissue morphology was observed.

In vitro degradation of calcium phosphates: Effect of multiscale porosity, textural properties and composition

“…the sealing zone) that delimits the resorbing area onto which osteoclasts generate an acid milieu that can reach values below pH 3, resulting in the dissolution of the underlying mineral [36]. In this regards, studies performed at low pH can be used as predictors of osteoclastic degradation [37][38][39][40].…”

Cell-laden biphasic scaffolds with anisotropic structure for the regeneration of osteochondral tissue

“…The present study demonstrated the feasibility of directed ionotropic gelation of alginate to fabricate cellladen biphasic constructs with an anisotropic pore structure mimicking osteochondral tissue. This method was previously applied to fabricate constructs for bone tissue engineering (Dittrich et al, 2007;Bernhardt et al, 2009;Despang et al, 2013). The first steps to adapt this process to osteochondral tissue engineering were already taken in 2007 (Gelinsky et al, 2007) and are being continued with regard to the embedding of living cells during alginate gelation and are being investigated in more detail.…”

Hierarchical microchannel architecture in chitosan/bioactive glass scaffolds via electrophoretic deposition positive‐replica

“…Although other processing methods are also being explored—parallel channel‐like pores, for example, were generated by directed ionotropic gelation of alginate–hydroxyapatite (HA) slurry, followed by thermal removal of alginate—additive manufacturing techniques are drawing the majority of research efforts, mainly due to the increased availability of equipment and their improved resolution.…”