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Nickel-free, high-nitrogen austenitic steels (AHNS) have been introduced for biomedical applications, with encouraging results in terms of mechanical and corrosion properties. Here, we tested the corrosion resistance of a nickel-free high nitrogen steel (FeCrMnMoN0.9) in bovine serum solutions containing 0 or 3 g/L hyaluronic acid (HA), and 0, 3, or 30 mM hydrogen peroxide (H2 O2 ) simulating no, moderate, or strong inflammatory conditions, respectively. Nondestructive electrochemical measurements (open circuit potential [OCP], linear polarization resistance "RP ", and electrochemical impedance spectroscopy) were run in triplicate over 10 hr. The presence of HA had no significant effect either on the stabilized OCP values, or on the corrosion resistance of FeCrMnMoN0.9. Increasing H2 O2 concentrations shifted the OCP to more electropositive values; the corrosion resistance decreased only at a 30 mM H2 O2 . Final RP values at 0, 3, and 30 mM H2 O2 resulted in 1598 ± 276, 1746 ± 308, and 439 ± 47 kΩ cm2 , respectively. These values were 4-14 times higher, than the RP values measured on LC-CoCrMo in our previous study, conducted under identical conditions. While these findings are encouraging, future studies need to focus on tribocorrosive properties of the AHNS to evaluate its applicability in joint replacement.

The long-term durability of joint replacements is based on their corrosion resistance and wear behavior. Whatever the materials used, degradation products (metal ions and wear debris) are formed due to the aggressiveness of body fluids and the biomechanics of the joints. Generally, these products are associated with post-operative complications and, as a result, their effects are critical clinical concerns. In this respect, tribocorrosion is a serious consideration in the performance of joint replacements. This work aims to contribute to the improvement of the understanding of the degradation mechanisms of a CoCrMo alloy, used as a joint prosthesis, by understanding the coupling of mechanical loads and cellular activity. This thesis has been structured according to a progressive approach, which begins with the study of the electrochemical behavior of a simulated physiological environment conducive to cell culture (RPMI-1640). Metal alloys and cells were successively added to the study system. The tests revealed that the oxidation of CoCrMo is accelerated in the presence of carbonaceous species and organic compounds, and that the cells are involved in the release of metal ions. A biotribocorrosion device has been developed to evaluate the influence of degradation products on cellular metabolism. This comprehensive multidisciplinary study combined experimental techniques from electrochemistry, biology and tribology to highlight the importance of biomaterial surface chemistry on tribocorrosion resistance and cytotoxicity. Finally, an experimental methodology was proposed in this work, in order to better understand the interaction between simulated physiological fluids and biomaterials.; La durabilité à long terme des prothèses articulaires repose sur leur résistance vis-à-vis de la corrosion et leur comportement à l'usure. Quels que soient les matériaux utilisés, des produits de dégradation (ions métalliques et débris d’usure) se forment, du fait de la corrosivité des fluides corporels et de la biomécanique des articulations. Généralement, ces produits sont associés aux complications post-opératoires et en conséquence, leurs effets constituent des préoccupations cliniques critiques. A cet égard, la tribocorrosion est une considération sérieuse dans la performance des prothèses articulaires. Ce travail vise à contribuer à l'amélioration de la compréhension des mécanismes de dégradation d’un alliage de CoCrMo, utilisé en tant que prothèse articulaire, en appréhendant le couplage de charges mécaniques et l’activité cellulaire. Cette thèse a été entreprise selon une approche itérative, qui débute par l’étude du comportement électrochimique du milieu physiologique simulé, propice à la culture cellulaire (le RPMI-1640). L’alliage métallique et les cellules ont successivement été ajoutés au système d’étude. Les essais ont révélé que l'oxydation du CoCrMo est accélérée en présence d'espèces carbonées et de composés organiques, et que les cellules interviennent sur la libération d’ions métalliques. Un dispositif de biotribocorrosion a été développé dans le but d’évaluer l’influence des produits de dégradation sur le métabolisme cellulaire. Cette étude multidisciplinaire exhaustive a combiné des techniques expérimentales d’électrochimie, de biologie et de tribologie, afin de souligner l'importance de la chimie de surface du biomatériau sur sa résistance à la tribocorrosion et son caractère cytotoxique. Finalement, une méthodologie expérimentale a été proposée dans ce travail, en vue de mieux comprendre l’interaction entre les fluides physiologiques simulés et les biomatériaux.

The long-term durability of joint replacements is based on their corrosion resistance and wear behavior. Whatever the materials used, degradation products (metal ions and wear debris) are formed due to the aggressiveness of body fluids and the biomechanics of the joints. Generally, these products are associated with post-operative complications and, as a result, their effects are critical clinical concerns. In this respect, tribocorrosion is a serious consideration in the performance of joint replacements. This work aims to contribute to the improvement of the understanding of the degradation mechanisms of a CoCrMo alloy, used as a joint prosthesis, by understanding the coupling of mechanical loads and cellular activity. This thesis has been structured according to a progressive approach, which begins with the study of the electrochemical behavior of a simulated physiological environment conducive to cell culture (RPMI-1640). Metal alloys and cells were successively added to the study system. The tests revealed that the oxidation of CoCrMo is accelerated in the presence of carbonaceous species and organic compounds, and that the cells are involved in the release of metal ions. A biotribocorrosion device has been developed to evaluate the influence of degradation products on cellular metabolism. This comprehensive multidisciplinary study combined experimental techniques from electrochemistry, biology and tribology to highlight the importance of biomaterial surface chemistry on tribocorrosion resistance and cytotoxicity. Finally, an experimental methodology was proposed in this work, in order to better understand the interaction between simulated physiological fluids and biomaterials., La durabilité à long terme des prothèses articulaires repose sur leur résistance vis-à-vis de la corrosion et leur comportement à l'usure. Quels que soient les matériaux utilisés, des produits de dégradation (ions métalliques et débris d’usure) se forment, du fait de la corrosivité des fluides corporels et de la biomécanique des articulations. Généralement, ces produits sont associés aux complications post-opératoires et en conséquence, leurs effets constituent des préoccupations cliniques critiques. A cet égard, la tribocorrosion est une considération sérieuse dans la performance des prothèses articulaires. Ce travail vise à contribuer à l'amélioration de la compréhension des mécanismes de dégradation d’un alliage de CoCrMo, utilisé en tant que prothèse articulaire, en appréhendant le couplage de charges mécaniques et l’activité cellulaire. Cette thèse a été entreprise selon une approche itérative, qui débute par l’étude du comportement électrochimique du milieu physiologique simulé, propice à la culture cellulaire (le RPMI-1640). L’alliage métallique et les cellules ont successivement été ajoutés au système d’étude. Les essais ont révélé que l'oxydation du CoCrMo est accélérée en présence d'espèces carbonées et de composés organiques, et que les cellules interviennent sur la libération d’ions métalliques. Un dispositif de biotribocorrosion a été développé dans le but d’évaluer l’influence des produits de dégradation sur le métabolisme cellulaire. Cette étude multidisciplinaire exhaustive a combiné des techniques expérimentales d’électrochimie, de biologie et de tribologie, afin de souligner l'importance de la chimie de surface du biomatériau sur sa résistance à la tribocorrosion et son caractère cytotoxique. Finalement, une méthodologie expérimentale a été proposée dans ce travail, en vue de mieux comprendre l’interaction entre les fluides physiologiques simulés et les biomatériaux.

International audience; he test conditions currently used in biotribocorrosion devices often differ greatly from the physiological conditions of joint replacements, contributing to discrepancies between the simulated and actual life span of joint replacements. In this study, a multidisciplinary biotribocorrosion device was developed based on the limitations of existing tribocorrosimeters. The set-up enables corrosion measurements to be simultaneously performed with real-time visualization of living cells using fluorescence microscopy under dynamic loads and movements. The device was configured to simulate the joint contact of ankle prostheses, and the wear of ultra-high-molecular-weight polyethylene/cobalt alloy (CoCrMo) implants surrounded by murine macrophages was tested. Various characterization techniques (non-contact optical profilometry, scanning and fluorescence electron microscopy and quantitative analyses of metal ions and pro-inflammatory cytokines) were combined in-depth multidisciplinary study. Two experimental conditions were used to promote the production of either polyethylene wear particles or metal ions. The first results indicated two distinct tribocorrosion mechanisms: 1) adhesive wear coupled with slow ionic depassivation of the cobalt alloy. The main degradation products were micrometric spherical polyethylene particles that seem to have little impact effect on the metabolic activity of the macrophages. 2) Ionic wear with the production of small, fibrillar polyethylene particles was observed. The production of metal ions, mainly chromium, was the predominant degradation process. The cytotoxicity of the chromium ions was evaluated based on the secretion of pro-inflammatory cytokines (prostaglandin E2). Our findings indicate that simulated conditions that result in low mechanical wear but high ions release appear to be more harmful to cells.

International audience

cited By 0; International audience; Corrosion tests of metallic materials for biomedical applications are generally carried out in highly simplified solutions and are often disapproved by direct or indirect cytotoxicity tests. Cell culture medium is then the better alternative to get robust biocompatibility assessments. The specific intrinsic reactivity of a Roswell Park Institute Medium cell culture medium (RPMI-1640) was studied here using a platinum electrode inside and outside a dedicated CO2 incubator. Electrochemical tests and surface analyses revealed that organic compounds of the RPMI-1610 are forming an organic adsorbed layer on the surface which is electrochemically active in a wide potential range. Precipitations of inorganic salts (calcium phosphate) are also promoted by organic species. The effect of the 5% content of CO2 in the incubator was also discussed, relative to the fact that carbonate and bicarbonate ions are involved in the charge transfer and mass transport processes. All these features were taken into account when performing biocompatibility tests for material design and selection. © 2018 Elsevier Ltd