Effects of Antibacterial Co-Cr-Mo-Cu Alloys on Osteoblast Proliferation, Differentiation, and the Inhibition of Apoptosis

Abstract

Objectives: To investigate the effects of antibacterial Co-Cr-Mo-Cu alloys with different Cu contents on osteoblast proliferation, differentiation, and the inhibition of apoptosis to optimize the selection of surgical implantation.

Methods: Microstructure, phase structure, and ion release were evaluated using X-ray diffraction, scanning electron microscopy (SEM), and inductively coupled plasma (ICP) spectrometry. The effects on osteoblast proliferation, differentiation, and apoptosis were characterized by cell proliferation assay, alkaline phosphatase (ALP) activity assay, and western blotting, respectively.

Results: Compared to the original Co-Cr-Mo alloys, the released Cu ions from Co-Cu alloys promoted osteoblast proliferation and differentiation and inhibited apoptosis. It can be noted that the optical density (OD490) and the ALP activity have increased to 1.237 and 1.053, respectively, in Co-2Cu alloy (0.604 and 0.171 for original Co-Cr-Mo alloy). Meanwhile, these effects were evaluated through the upregulation of ROS levels and 4E-binding protein 1 (4E-BP1) expression and the downregulation of adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and p-AMPK. Moreover, the antibacterial properties of the Co-Cu alloys were also enhanced, as demonstrated by the strong antibacterial activity of Cu phases in Co-Cu alloys incubated with Staphylococcus aureus, in which more than 99.8% of the bacteria has been killed.

Conclusions: The addition of Cu element in the Co-Cr-Mo alloys could induce OB proliferation and differentiation and inhibited OB apoptosis. Meanwhile, it can be recognized that the Co-Cu alloys with 2wt% Cu exhibit the highest performance among all the samples, indicating that the effects of osteoblast differentiation and the inhibition of apoptosis are highly dependent on the adding of Cu elements. Co-Cr-Mo-Cu alloys with an excellent antibacterial property could be used as a tool to improve osteogenic ability and antibacterial properties in orthopaedic implant operations.

Keywords: Antibacterial property; Co-Cr-Mo alloy; Osteoblast differentiation; Osteoblast proliferation; Released Cu ion.