CaTiO3-hydroxyapatite bioceramic composite: Synthesis of reactant powders from waste cockle shell, sintering, characterization and investigation of physical, mechanical and in-vitro biological properties

Calcium titanate-hydroxyapatite composites (CT-HAp) were synthesized using a conventional sintering process. The calcium source was derived from cockle shell waste. The combustion synthesis of CT (CaTiO₃) produced fine, irregular, sub-micron size particles. The precipitation synthesis of HAp (Ca₅(PO₄)₃OH) produced rod-like nanoparticles. The obtained powders were used to fabricate CT-HAp bioceramic composites sintered at 1250 °C for 2 h. The phase formation, microstructure, and physical and mechanical properties of HAp and various CT-HAp composites were investigated. A CT-HAp composite with 8%wt of CT, having a density of 3.00 ± 0.01 g/cm³ and a grain size of 0.90 ± 0.06 μm, produced the highest values for flexural strength, Vickers hardness and fracture toughness: 56.67 ± 1.122 MPa, 6.03 ± 0.02 GPa, and 7.77 MPa.m^1/2, respectively. The chemical solubility of the CT-HAp composites was very low, showing an average weight loss of 0.24% in a simulated body fluid solution. The properties of the CT-HAp composites were controlled by CT content and porosity. In-vitro biological studies demonstrated the growth and proliferation of MC3T3-E1 osteoblast cells on all composites after three days of culture. The highest cell viability was exhibited on a CT-HAp composite with a CT content of 8%wt. The expression of alkaline phosphatase (ALP) activity on the composite surface promoted cellular osteoinduction, indicating the potential of the developed composite for bone formation and repair.