Antibacterial and antifungal effects of silver-doped multilayered yttria-stabilized zirconia and hydroxyapatite Coatings: Potential application in biomedical implants and orthopaedics

Background Implant-associated infections remain a major clinical challenge in orthopedic surgery, often caused by microbial biofilms that resist conventional antibiotic treatments. Developing multifunctional coatings that combine bioactivity and antimicrobial properties is critical to improving the long-term performance of orthopedic implants. Objective To design and evaluate multilayered coatings that inhibit both bacterial and fungal colonization on orthopedic implant materials, while maintaining structural and chemical properties suitable for osseointegration. Methods Multilayer [YSZ/HAp-Ag] n coatings—composed of alternating layers of yttria-stabilized zirconia (YSZ) and silver-doped hydroxyapatite (HAp-Ag)—were deposited on titanium substrates via RF magnetron sputtering. Samples with varying bilayer numbers (n = 1, 10, 30, 50, 70) were characterized using transmission electron microscopy (TEM), Auger electron spectroscopy (AES), energy-dispersive X-ray spectroscopy (EDS), and profilometry. Antimicrobial performance was tested against Paenibacillus sp. (bacteria) and Penicillium sp. (fungus) using a colony-counting method over 136 hours. Results The coatings exhibited well-defined multilayer structures with homogeneously distributed Ag nanoparticles (∼100 nm) embedded in the HAp matrix. All multilayered coatings achieved complete inhibition of Paenibacillus sp. . Inhibition of Penicillium sp. was complete in samples n1, n10, and n70, while partial inhibition (61–93%) was observed in n30 and n50, attributed to differences in surface roughness and hydrophobicity. No microbial growth was detected on any coated surface, in contrast to uncoated titanium and polystyrene controls. Conclusions [YSZ/HAp-Ag] n multilayer coatings offer dual antimicrobial activity against bacterial and fungal pathogens, making them highly promising candidates for orthopedic implant applications. Their tunable architecture, biocompatible composition, and effective prevention of microbial colonization support their use in bone-contact devices, including joint prostheses and spinal implants.