Cytocompatibility evaluation of Ni-free stainless steel manufactured by nitrogen adsorption treatment

Cytocompatibility of nickel-free austenitic stainless steel manufactured by nitrogen adsorption treatment, Fe–Cr–Mo–N, was evaluated and compared with a conventional austenitic stainless steel, 316L, and nickel-free ferrite stainless steel, Fe–Cr–Mo, before nitrogen adsorption treatment. Two types of cytotoxicity tests were performed; static and dynamic conditions. In static conditions, human normal diploid fibroblast HEL299 was cultured on the disks of the three materials and cell growth was examined. In dynamic conditions, the disks were rotated in extracting medium with zirconia balls at 37 °C for 14 days, and the collected extracting medium was added into HEL299 culture to examine its inhibitive effect on cell growth. Quantification of metallic elements in collected extracting medium was also performed. As a result, Fe–Cr–Mo–N had higher cell growth than 316L in static and dynamic conditions. Nickel was detected in the extracting media of 316L and Fe–Cr–Mo, whereas no nickel was detected in that of Fe–Cr–Mo–N. These facts indicate that Fe–Cr–Mo–N has higher cytocompatibility than 316L and that the nitrogen adsorption treatment contributes to the higher corrosion resistance of Fe–Cr–Mo–N in the presence of wear.