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The present thesis was focused on the design and development of novel porous bioactive ceramic materials and scaffolds addressed to the regeneration of large and load-bearing bone defects. This research was carried out to meet the increasing demand for bioactive scaffolds enabling bone regeneration, due to the several drawbacks affecting the use of autologous bone, especially for large bone reconstruction. Nowadays, it is well established that effective tissue regeneration requires the implantation of scaffolds exhibiting tissue-mimicking compositional, morphological and mechanical features to promote the formation and maturation of new healthy tissue. In this context, my work was organized in three research topics on the basis of specific clinical requirements, thus leading to the development of different types of bioceramic scaffolds based on calcium phosphates, particularly: i) macroporous implants for cranio-maxillofacial defects obtained by direct foaming of ceramic suspensions, ii) 3D printed macro- and microporous scaffolds based on β-tricalcium phosphate and iii) injectable self-hardening bone cement formulations based on strontium-substituted apatite. A rationale design and optimization of the different processes involved in the development of the new scaffolds allowed to obtain bioceramics exhibiting adequate bioactivity, porosity and promising mechanical performance, as assessed by robust physicochemical, morphological, mechanical and biological characterizations. On the basis of the reported results, a potential clinical application of the developed materials can be envisaged.

Titanium and its alloys have been extensively used as implantation materials due to their favorable properties such as lower modulus, good tensile strength, excellent biocompatibility, and enhanced corrosion resistance. However, their intrinsic bioinertness generally prevents a direct bond with the bone on the surface especially at an early stage of implantation. In recent years, bioactive scaffolds for bone regeneration are progressively replacing bioinert prostheses in orthopedic, maxillofacial, and neurosurgery fields. Given the need of enhanced mechanical strength, several combinations of bioactive and reinforcing phases have been studied, but still no convincing solutions have been found so far. In this context, titanium oxides are light and high-resistance bioactive materials widely employed in dental and bone application due to their capacity of forming strong bonds with bone tissue via the formation of a tightly bound apatite layer on their surface. The addition of titania particles to hydroxyapatite has attracted considerable attention based on the assumption that resulting materials can enhance osteoblast adhesion and promote cell growth while also providing high strength and fracture toughness in the final composite material, thus being adequate for load-bearing applications.

The present work describes the synthesis of novel injectable, self-setting bone cements made of strontium-substituted hydroxyapatite (Sr-HA), obtained by single-phase calcium phosphate precursors doped with different amounts of strontium and enriched with alginate. The addition of alginate improved the injectability, cohesion, and compression strength of the cements, without affecting the hardening process. A Sr-HA cement exhibiting adequate hardening times and mechanical strength for clinical applications was further tested in vivo in a rabbit model, in comparison with a commercial calcium phosphate cement, revealing the maintenance of biomimetic composition and porous microstructure even after one month in vivo, as well as enhanced ability to induce new bone formation and penetration.