Cytocompatibility of nitrogen plasma ion immersed medical cobalt–chromium alloys

Abstract

Wear particles and ion release from medical CoCr contribute to the risk for aseptic loosening. Nitrogen plasma immersion ion implantation (PIII) has been shown to reduce wear of CoCr but is associated with increased Co ion release. This work investigated the cytocompatibility of CoCr modified by nitrogen PIII at different temperatures (mCoCr). The osteosarcoma cell line Saos-2, mesenchymal stem cells (MSCs), and mononuclear cells (MNCs) were grown directly on CoCr/mCoCr discs or treated with CoCl2. Proliferation and metabolic activity of Saos-2 and MSC were decreased on mCoCr in correlation with increasing implantation temperature. The elevated Co ion release seemed to play a decisive role since analog effects were observed by treatment of cells with CoCl2. Proliferation of phytohemagglutinin-stimulated MNC was reduced in the presence of CoCr discs or CoCl2. For MNC-alloy cultures we observed an increase in interleukin 2 (IL-2) and a decrease in interferon γ (IFN-γ) and IL-10 secretion compared to cultures without alloys. The results of this study demonstrate that PIII process temperature and corresponding Co ion release correlate with material cytocompatibility. Therefore, the two competing parameters, reduction of wear and increase in Co ions, have to be taken into consideration for the evaluation of the clinical applicability of nitrogen-implanted CoCr.

Cell death affected by dental alloys: Modes and mechanisms

“…Two theories are available regarding the possible causes of the Caspase-9 and Caspase-3 activations. The first is the DNA damage induced by the Co and Cr 22,23) . The second is the reduction reactions in the alloy leach liquors as reported by Haeri et al 24) .…”

Osseointegration Enhancement by Zr doping of Co-Cr-Mo Implants Fabricated by Electron Beam Melting

“…The mechanism underlying the difference in bone strength and quality is unknown, but it could be hypothesized that it may be due to the difference in ion-release pattern for the two materials [15] and/or the presence of Zr oxide at the surface. The ion release has been shown to affect the cells in the vicinity of the surface using different in vitro systems [33,34]. In a recent study evaluating the osseointegration of zirconium and titanium implants in rat, a high degree of mature bone was observed around both materials, showing the potential of zirconium as an implant material per se.…”

Co(II)‐mediated effects of plain and plasma immersion ion implanted cobalt‐chromium alloys on the osteogenic differentiation of human mesenchymal stem cells

“…Discs of CoCr alloy SY21med were treated with nitrogen PIII at 375 ± 5°C as described previously . These samples are identified as mCoCr in the following text.…”

“…Medium was changed at analysis time points after 1 and 3 days. Analysis was performed using inductively coupled plasma optical emission spectrometry (ICP‐OES) as described previously …”

“…To shed more light of those effects on osteoblasts and their progenitor cells such as the multipotential mesenchymal stem cells (MSC) and thus the formation of new bone at the implantation site, we investigated the influence of nitrogen PIII modified CoCr discs as well as the isolated effects of soluble Co(II) ions on the osteogenic differentiation of MSC for up to 5 weeks. Cells were permanently exposed to Co(II) ion concentrations that were based on the levels found in patients with MoM prosthesis and higher concentrations that were found to increase metabolic activity of MSC in vitro . The typical osteogenic markers such as the activity of alkaline phosphatase (ALP), the expression of the osteogenic genes Runt‐related transcription factor 2 (Runx2), osteopontin (OPN) as well as integrin‐binding sialoprotein (IBSP) and the production of osteocalcin (OCN) and hydroxyapatite were determined.…”