Fabrication of doped ?-tricalcium phosphate bioceramics by Direct Ink Writing for bone repair applications

beta-tricalcium phosphate (beta-TCP, beta-Ca3(PO4)2) is one of the most attractive biomaterials for bone regeneration and beta-TCP macroporous scaffolds are very promising for both cell proliferation and mechanical support. The Additive Manufacturing (AM) process called Direct Ink Writing (DIW), based on the extrusion of a concentrated ceramic slurry, is particularly adapted to resolve the main drawbacks associated with conventional shaping of ceramic scaffolds. In this work, co-doped beta-TCP powders were synthetized and used to print macroporous scaffolds by DIW. Doped beta-TCP powders have been proved to exhibit higher thermal stability, densification and mechanical properties compared to undoped beta-TCP. Two co-doped compositions were produced via the aqueous precipitation technique combining magnesium, strontium, silver and copper cations: Mg-Sr (2.0-2.0 mol%) and Mg-Sr-AgCu (2.0-2.0-0.1-0.1 mol%). DIW slurries were optimized with undoped and co-doped beta-TCP with the use of a dispersant and a carboxymethylcellulose and polyethyleneimine mixture to obtain aqueous slurries filled with 42 vol% of powder. Complete rheological characterizations were realized to assess the suitability of the beta-TCP slurries for the DIW process (shear-thinning and thixotropic behaviour). The whole processing chain including printing, osmotic drying (PEG 10000) and sintering (1100 degrees C, 3 h) was optimized to successfully print co-doped beta-TCP macroporous scaffolds. Characterizations after sintering showed a reduction of macropores and microcracks using co-doped beta-TCP powders as well as improved compressive strengths and densities compared to undoped beta-TCP. A significant enhancement of compressive strength values was obtained compared to literature data.

Automated summary

Beta-tricalcium phosphate (beta-TCP) is a promising biomaterial for bone regeneration. In this study, macroporous scaffolds were printed using co-doped beta-TCP powders and the Direct Ink Writing process. The co-doped samples exhibited higher thermal stability, densification, and mechanical properties compared to undoped beta-TCP. The printed scaffolds showed reduced macropores and microcracks, improved compressive strengths and densities, and significantly higher values compared to literature data.