Influence of Cu doping on the biocompatibility of zirconia-toughened alumina ceramics for artificial joints

Abstract

Zirconia-toughened alumina (ZTA) is considered the gold standard material for total hip arthroplasty (THA). However, it still lacks sufficient lubrication and fracture toughness, and it has the risk of wearing, squeaking, and fracturing. Cu doping is considered to address these issues. To further promote the application of Cu doping, its effect on biocompatibility needs to be studied. In this study, Cu-doped ZTA (Cu-ZTA) ceramics with different Cu contents were prepared using a fast hot pressed sintering (FHPS) equipment and their biocompatibility was systematically studied. The results demonstrate that, depending on the Cu content, Cu doping reduces the stability of the tetragonal zirconia, resulting in a tetragonal-to-monoclinic phase transition of zirconia, thereby creating pores on the surface of the ZTA. The biocompatibility of the Cu-ZTA with different Cu contents was analyzed based on osteoblasts and macrophages. The results suggested that Cu doping increased the adhesion of osteoblasts and slightly improved their viability. In contrast, Cu doping influenced the morphology of macrophages, causing the shrinkage and extension of their pseudopodia. Cu doping also induced the pro-inflammatory polarization of macrophages and stimulated the secretion of pro-inflammatory cytokines (TNF-α and IL-6). Therefore, Cu doping can improve the cytocompatibility of osteoblasts with ZTA ceramic surfaces, however, the enhanced effect of Cu-doped ZTA ceramics on the early inflammatory response requires special attention and further study.