Orthopedic implant surface modification with nanoengineered [YSZ/HAp-Ag]_n multilayer coatings to promote osteoblast adhesion and early differentiation.

Abstract

Metallic implants frequently face three critical challenges that compromise long-term clinical performance: (i) limited biofunctionality that delays osteointegration, (ii) corrosion processes that deteriorate the implant surface and release harmful ions, and (iii) bacterial biofilm formation, which increases the risk of persistent infection. This study explores multilayer [YSZ/HAp-Ag]n coatings engineered to overcome these issues by enhancing osteoblastic response, improving surface stability, and providing antimicrobial potential. Multilayer coatings with different bilayer numbers (n = 1, 10, 30, 50, 70) were deposited on titanium substrates using magnetron sputtering. Structural and surface characterization included morphology, roughness, wettability, and stiffness. MC3T3-E1 osteoblastic cells were cultured on the coatings to evaluate adhesion, viability (MTT), and differentiation through alkaline phosphatase (ALP) activity at 7 and 14 days. Crater-like surface textures, roughness above 220 nm, and higher hydrophilicity promoted enhanced cell spreading, greater confluence, and decreased circularity, indicative of strong anchorage. All coatings exhibited >70 % cell viability, confirming non-cytotoxic behavior. Rougher and more hydrophilic surfaces outperformed uncoated titanium. Stiffer coatings produced a significant increase in ALP activity at day 7, suggesting accelerated early osteogenic differentiation, followed by a decrease at day 14 consistent with cellular maturation. Among all configurations, the 30-bilayer coating (n30) offered the most balanced structural and mechanical properties, resulting in the highest biological performance. Multilayer [YSZ/HAp-Ag]n coatings effectively stimulate osteoblastic adhesion, viability, and early differentiation while addressing key limitations of metallic implants. Their tunable architecture-especially the n30 configuration-represents a promising strategy to enhance implant integration and long-term functional performance.