Surface nano-modification by ion beam–assisted deposition alters the expression of osteogenic genes in osteoblasts

Abstract

Biomaterials with enhanced biocompatibility are favored in implant studies to improve the outcomes of total joint replacement surgeries. This study tested the hypothesis that nano-structured surfaces for orthopedic applications, produced by the ion beam–assisted deposition method, would enhance osteointegration by altering the expression of bone-associated genes in osteoblasts. The ion beam–assisted deposition technique was employed to deposit nano-films on glass or titanium substrates. The effects of the ion beam–assisted deposition produced surfaces on the human osteosarcoma cell line SAOS-2 at the molecular level were investigated by assays of adhesion, proliferation, differentiation, and apoptosis on coated surfaces versus uncoated cobalt–chrome, as the control. Ion beam–assisted deposition nano-coatings enhanced bone-associated gene expression at initial cell adhesion, proliferation, and differentiation compared to cobalt–chrome surfaces as assessed by polymerase chain reaction techniques. Increased cell proliferation was observed using a nuclear cell proliferation–associated antigen. Moreover, enhanced cell differentiation was determined by alkaline phosphatase activity, an indicator of bone formation. In addition, programmed cell death assessed by annexin V staining and flow cytometry was lower on nano-surfaces compared to cobalt–chrome surfaces. Overall, the results indicate that nano-coated surfaces produced by the ion beam–assisted deposition technique for use on implants were superior to orthopedic grade cobalt–chrome in supporting bone cell adhesion, proliferation, and differentiation and reducing apoptosis. Thus, surface properties altered by the ion beam–assisted deposition technique should enhance bone formation and increase the biocompatibility of bone cell–associated surfaces.