Abstract
CoCrMo alloys exhibit good mechanical properties, excellent biocompatibility and are widely utilised in orthopaedic joint replacements. Metal-on-metal hip implant degradation leads to the release of metal ions and nanoparticles, which persist through the implant's life and could be a possible cause of health complications. This study correlates preferential binding between proteins and metal alloy nanoparticles to the alloy's corrosion behaviour and the release of metal ions. TEM images show the formation of a protein corona in all particles immersed in albumin containing solutions. Only molybdenum release was significant in these tests, suggesting high dissolution of this element when CoCrMo alloy nanoparticles are produced as wear debris in the presence of serum albumin. The same trend was observed during extended exposure of molybdenum reference nanoparticles to albumin.
Highlights
Metal-on-Metal hip implants were intended to offer improved durability, releasing a lower volume of wear debris than traditional implant designs
Wear debris from hip implants was synthetically produced by milling CoCrMo ASTM75 gas atomized powder in Bovine Albumin Serum (BSA)
Transmission Electron Microscopy (TEM) analysis suggests the formation of a protein corona on synthetic CoCrMo wear debris particles incubated with Bovine Serum Albumin (BSA) and the particles were found to be deficient in Molybdenum by Energy-Dispersive X-ray spectroscopy (EDX)
Summary
Metal-on-Metal hip implants were intended to offer improved durability, releasing a lower volume of wear debris than traditional implant designs. The implants may release particles and soluble wear debris that, once in the bloodstream, are surrounded by a diversity of chemical species and hostile environments. B a group of particles surrounded by a thick amorphous layer; (B) and (C) TEM/EDX of a representative particle, showing a composition consisting of cobalt and chromium with the presence of nitrogen and oxygen, note the deficiency in molybdenum signal (Mo K is at 17.4 keV). Initial TEM examination shows most of the CoCrMo milled particles were surrounded by a thick amorphous layer (note darker contrast surrounding the group of particles) that could potentially be a protein corona (Figure 1). EDX spectra show that particles were mainly composed of cobalt and chromium with a deficiency in molybdenum (relative to the alloy composition), and reveal the presence of nitrogen and oxygen. The results show the clear formation of a protein biofilm (generally less than 5 nm in thickness) on the surface of all the particles (see Figure 2)
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