Multifunctional Hydroxyapatite–Barium Titanate Coatings with Green-Synthesized Silver Nanoparticles for Orthopedic Implants: Piezodynamic, Biological, and Antibacterial Evaluation

Infection associated with orthopedic implants remains a major challenge in the development of biomimetic materials for bone tissue engineering. Surface modification strategies are widely employed to transform bioinert metallic substrates into bioactive interfaces that promote tissue integration while preventing bacterial colonization. This study investigated the effect of incorporating silver nanoparticles (nAg) into hydroxyapatite–barium titanate (HA–BT) coatings on their structural, mechanical, piezoelectric, biological, and antibacterial properties. Raw materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), whereas coatings were evaluated by XRD, scanning electron microscopy (SEM), tensile adhesion testing, electrochemical analysis, piezoresponse force microscopy (PFM), cell viability, and antibacterial assays. The coatings exhibited secondary phases, including β-tricalcium phosphate (β-TCP), tetracalcium phosphate (TTCP), and calcium oxide (CaO), generated during atmospheric plasma spraying (APS), while no silver oxide phases were detected after nAg incorporation. SEM observations revealed homogeneous phase distribution and strong coating–substrate adhesion. The addition of nAg did not significantly affect adhesive strength (44.58 ± 2.2 MPa for HA30BT and 43.28 ± 2.8 MPa for HA30BT–nAg). Protein adsorption studies indicated moderate albumin affinity (Kads = 0.45) for nAg-containing coatings. Both coatings exhibited piezodynamic activity with d33 values of approximately 13 pm/V. MTT assays confirmed non-cytotoxic behavior, with viability reductions below 2%. Osteocalcin expression demonstrated comparable osteogenic activity in coatings with and without nAg, regardless of low-intensity pulsed ultrasound stimulation. These findings highlight the potential of HA–BT–nAg coatings as multifunctional surfaces for bone regeneration and infection prevention.