Reduced responses of macrophages on nanometer surface features of altered alumina crystalline phases

Extensive prolonged interactions of inflammatory cells (such as macrophages) at the host–implant interface may lead to implant failure. While previous studies have shown increased in vitro and in vivo bone cell adhesion, proliferation and mineralization on nanophase compared to currently implanted ceramics, few studies have been conducted to elucidate inflammatory cell responses on such nanophase ceramics. Controlling surface feature size and corresponding surface roughness on implants may clearly alter immune cell responses, which would be an extremely important consideration for the use of nanostructured materials as improved biomaterials. In this study, reduced macrophage density was observed on alumina (Al2O3) compacts with greater nanometer surface roughness accompanied by changes in crystallinity for up to 24 h in culture. Since alumina is a commonly used ceramic in orthopedic applications, this in vitro study continues to support the use of nanophase ceramics as improved orthopedic implants by demonstrating reduced macrophage responses.