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

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 ∼469 and ∼433 μm within the scaffolds of HA and HA_ACZ and micropores with an average size of ∼0.6 and ∼0.5 μm 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 ∼71.7 and ∼76.6° 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 × 10⁵ to 1.2 × 10³ cells/mm² against Gram-negative (Escherichia coli) and from 1.9 × 10⁵ to 5.6 × 10³ bacterial cells/mm² 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.