Design, production and biocompatibility of nanostructured porous HAp and Si-HAp ceramics as three-dimensional scaffolds for stem cell culture and differentiation

Biocompatible and biodegradable scaffolds can provide a convenient support for stem cell differentiation leading to tissue formation. Porous hydroxyapatite (HAp) scaffolds are clinically used for applications such as spinal fusions, bone tumors, fractures, and in the replacement of failed or loose joint prostheses. The incorporation of small amounts of silicon within hydroxyapatite lattice significantly improves HAp solubility and rate of bone apposition, as well as the proliferation of human osteoblasts in vitro. In the present paper we report biocompatibility data obtained on a newly designed three-dimensional nano-structured porous scaffold made of pure and silicon-substituted hydroxyapatite. A suitable amount of porosity (60 vol%) was obtained within a well densified ceramic skeleton by using polyethylene spheres. Biocompatibility was tested by using murine embryonic stem cells (ES). Cell culture analysis indicated that ES cells adhere well on both hydroxyapatite and silicon-substituted hydroxyapatite scaffolds. Si-substitution, however, improved subsequent ES cell proliferation rate. Bioresorption of hydroxyapatite scaffolds was tested by using human osteoclasts obtained from peripheral blood monocytes, made to differentiate on disks and evaluated by SEM analysis.