Fabrication of doped b-tricalcium phosphate bioceramics by robocasting for bone repair applications
Résumé
b-tricalcium phosphate (b-TCP, b-Ca 3 (PO 4 ) 2 ) is one of the most attractive biomaterials for bone repair since it shows an
excellent biological compatibility, osteoconductivity, and resorbability. It is already commercialized under granules or
preforms for bone filling but there are still some issues for b-TCP porous scaffolds fabrication. Indeed, b-TCP cannot
be used as scaffolds in large bone defects or in load-bearing areas due to its weak mechanical properties related to
insufficient densification level. Indeed, the sintering temperature is limited because of the occurrence of a phase
transition b to a-TCP at 1150°C with a large lattice expansion causing microcracks and reducing shrinkage during
sintering. The thermal stability can be increased by the incorporation of dopants inside the b-TCP lattice. Indeed, such
dopants like cations can replace the calcium inside the structure and stabilize the b phase reaching higher densities.
Moreover, dopants can also improve biological properties of b-TCP as bone implant like the osteoconductivity or the
antibacterial behaviour.
In this work, doped b-TCP powders are synthetized by coprecipitation of Ca(NO 3 ) 2 and (NH 4 ) 2 HPO 4 solutions in presence
of magnesium, strontium, silver and copper cations in order to prevent the phase transformation, increase the sintering
temperature as well as the mechanical properties and bring an antibacterial behaviour. Rapid microwave sintering can
then be successfully applied with a limited grain growth and compared with conventional sintering. Cytotoxicity and
antibacterial evaluation are conducted to assess the potential of the doped b-TCP.
Finally, 3D-printable suspensions are prepared from optimized doped powder to manufacture porous scaffolds by
robocasting using water-based inks.