Three-Dimensional Extrusion Printing of Porous Scaffolds Using Storable Ceramic Inks

Impact statement In this study, we developed a novel ceramic ink for the preparation of porous ceramic scaffolds useful in bone tissue engineering. The ready-to-use ink can be stored for at least 14 days and printed using printing parameters compatible with any commercially available bioprinter. The composition of the ink can be adapted to incorporate the most relevant ceramics for bone tissue engineering, including hydroxyapatite and beta-tricalcium phosphate, without affecting the printability or storability properties. The high ceramic content of the ink and the low shrinkage after sintering enable the custom fabrication of patient-specific tissue-engineered scaffolds. In this study, we describe the additive manufacturing of porous three-dimensionally (3D) printed ceramic scaffolds prepared with hydroxyapatite (HA), beta-tricalcium phosphate (beta-TCP), or the combination of both with an extrusion-based process. The scaffolds were printed using a novel ceramic-based ink with reproducible printability and storability properties. After sintering at 1200 degrees C, the scaffolds were characterized in terms of structure, mechanical properties, and dissolution in aqueous medium. Microcomputed tomography and scanning electron microscopy analyses revealed that the structure of the scaffolds, and more specifically, pore size, porosity, and isotropic dimensions were not significantly affected by the sintering process, resulting in scaffolds that closely replicate the original dimensions of the 3D model design. The mechanical properties of the sintered scaffolds were in the range of human trabecular bone for all compositions. All ceramic bioinks showed consistent printability over a span of 14 days, demonstrating the short-term storability of the formulations. Finally, the mass loss did not vary among the evaluated compositions over a period of 28 days except in the case of beta-TCP scaffolds, in which the structural integrity was significantly affected after 28 days of incubation in phosphate-buffered saline. In conclusion, this study demonstrates the development of storable ceramic inks for the 3D printing of scaffolds of HA, beta-TCP, and mixtures thereof with high fidelity and low shrinkage following sintering that could potentially be used for bone tissue engineering in load-bearing applications.