3D-Printed Multifunctional Ag/CeO₂/ZnO Reinforced Hydroxyapatite-Based Scaffolds with Effective Antibacterial and Mechanical Properties

Conventional three-dimensional (3D)-printed hydroxyapatite (HA)-based constructs have limited utility in bone tissue engineering due to their poor mechanical properties, elevated risk of microbial infection, and limited pore interconnectivity. 3D printing of complex multiple components to fabricate fully interconnected scaffolds is a challenging task; here, in this work, we have developed a procedure for fabrication of printable ink for complex systems containing multinanomaterials, i.e., HA(ACZ) (containing 1 wt % Ag, 4 wt % CeO2, and 6 wt % ZnO) with better shear thinning and shape retention properties. Moreover, 3D-printed HA(ACZ) scaffolds showed a modulus of 143.8 GPa, a hardness of 10.8 GPa, a porosity of 59.6%, effective antibacterial properties, and a fully interconnected pore network to be an ideal construct for bone healing. Macropores with an average size of similar to 469 and similar to 433 mu m within the scaffolds of HA and HA(ACZ) and micropores with an average size of similar to 0.6 and similar to 0.5 mu m within the strut of HA and HA(ACZ) were developed. The distribution of fully interconnected micropores was confirmed using computerized tomography, whereas the distribution of micropores within the strut was visualized using Voronoi tessellation. The water contact angle studies revealed the most suitable hydrophilic range of water contact angles of similar to 71.7 and similar to 76.6 degrees for HA and HA(ACZ), respectively. HA(ACZ) scaffolds showed comparable apatite formation and cytocompatibility as that of HA. Antibacterial studies revealed effective antibacterial properties for the HA(ACZ) scaffold as compared to HA. There was a decrease in bacterial cell density for HA(ACZ) from 1 x 10(5) to 1.2 x 10(3) cells/mm(2) against Gram-negative (Escherichia coli) and from 1.9 x 10(5) to 5.6 x 10(3) bacterial cells/mm(2) against Gram-positive (Staphylococcus aureus). Overall, the 3D-printed HA(ACZ) scaffold resulted in mechanical properties, comparable to those of the cancellous bone, interconnected macro- and microporosities, and excellent antibacterial properties, which could be utilized for bone healing.