Enhanced biocompatibility of robotic microplasma sprayed Zr–2.5Nb coatings for orthopaedic implants

The surface bioactivity of orthopaedic implants plays a critical role in osseointegration and long-term clinical performance. In this study, zirconium-niobium (Zr-2.5Nb) coatings were deposited onto gas-abrasively treated Ti6Al4V alloy substrates using robot-assisted microplasma spraying (MPS) to enhance implant bioactivity. The MPS parameters were selected to produce uniform coatings with controlled porosity (∼20%), rough surface, and satisfactory adhesion to the substrate. Surface topography and microstructure of coated specimens were characterised using confocal laser scanning microscopy and scanning electron microscopy, and compared with the uncoated Ti6Al4V alloy. Zr-2.5Nb coatings exhibited significantly increased surface roughness and a developed microrelief. In vitro angiogenesis assays using human umbilical vein endothelial cells demonstrated enhanced microvascular network formation on Zr-2.5Nb-coated surfaces. Biocompatibility assessment with rat bone marrow-derived mesenchymal stromal cells revealed improved cell adhesion, spreading, and cytoskeletal organisation. These findings demonstrate that robot-assisted MPS of Zr-2.5Nb coatings on titanium implants with precise maintenance of selected spraying parameters can provide a biologically favourable surface that promotes angiogenic responses and represents a promising approach to enhancing the implant biocompatibility. LAY DESCRIPTION: Robotic microplasma spraying of Zr-2.5Nb onto Ti6Al4V implants produced porous coatings that supported endothelial network formation and mesenchymal stromal cell adhesion - two processes central to implant survival. The porous microarchitecture and zirconium surface chemistry work together to create conditions that the surrounding tissue actually responds to. These findings point to a practical coating strategy that could meaningfully improve the integration of orthopaedic implants with bone and vasculature.