Calcium phosphates are of prime importance in the field of hard tissue repair and orthopedic implants due to their high biocompatibility and -resorption.The aim of the present work is to develop an injectable bone filling system based on calcium phosphates possessing controlled nanoporosity and allowing controlled release of growth factors in situ. In comparison to macroporous materials, it can be expected that nanoporous calcium phosphates show better biomolecule retention combined with improved growth factor release control. Our objective is to synthesize a nanoporous material having pores size between 2-30 nm, big enough for protein immobilization.To fulfill this goal, new synthesis strategies must be proposed. Conventional procedures used to prepare hydroxyapatite (HA) lead to porous calcium phosphates with micro- (< 2 nm in diameter) or macroporosity (> 50 nm). In this work, we propose new synthesis pathways, based on templating techniques with the use of organized porous silica (SBA-15 or mesocellular foam) or ordered porous carbon as template, filled with aqueous HA or calcium metaphosphate precursors. The template elimination by oxidative heat treatment (carbon template) or by etching with NaOH (silica template) resulted in a porous calcium phosphate material with a high surface area and an interconnected porosity. A multi-scale characterization was performed on the obtained ceramics.The structural and textural characteristics of the HA obtained will be discussed in relation with the synthesis conditions and the nature of the host material used.
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