Synthesis and Direct Ink Writing of doped β-tricalcium phosphate bioceramics for bone repair applications
Résumé
Introduction β-tricalcium phosphate (β-TCP, β-Ca3(PO4)2) is one of the most attractive biomaterials for bone regeneration and β-TCP macroporous scaffolds are highly promising for bone tissue engineering. Direct Ink Writing (DIW), an additive manufacturing process based on the extrusion of a concentrated ceramic slurry, is particularly adapted to resolve the main drawbacks associated with conventional shaping of ceramic scaffolds. Methods In this work, undoped and co-doped β-TCP powders were synthetized by aqueous precipitation and used to print macroporous scaffolds by DIW. The doped compositions were produced combining magnesium, strontium, silver and copper cations: Mg-Sr (2.0–2.0 mol%) and Mg-Sr-Ag-Cu (2.0–2.0–0.1–0.1 mol%). DIW slurries were optimized with undoped and co-doped β-TCP with the use of a dispersant and a carboxymethylcellulose and polyethyleneimine mixture to obtain aqueous slurries filled with 42 vol% of powder. Undoped and co-doped β-TCP macroporous scaffolds were successfully printed by DIW and characterized. Results Doped β-TCP powders have been proved to exhibit higher thermal stability and densification compared to undoped β-TCP. The β-TCP slurries exhibited a shear-thinning and thixotropic behaviour suitable for the DIW process. The whole processing chain including printing, osmotic drying and sintering was optimized. Characterizations of the printed parts after sintering showed a reduction of macropores and microcracks using co-doped β-TCP powders as well as improved compressive strengths and densities compared to undoped β-TCP. Conclusion Improved compressive strength and densities were observed for co-doped β-TCP scaffolds with a significant enhancement by comparison with literature data. These results are encouraging for the development of on-demand customized bone substitutes applied to load-bearing areas. It was demonstrated that the developed process was successively applied to produce complex shapes, opening new possibilities for the fabrication of synthetic bone substitutes or other applications.