ABSTRACT
Comprehensive assessments of the cytotoxicity of nitrided iron, a promising bioabsorbable metallic material, were conducted using in vitro methods. Extracting and standing experiments were conducted to determine the factors influencing the precipitation of the extract during extraction and incubation. The MTT method, fluorescent staining, and direct contact method were used to explore the in vitro cytotoxicity of nitrided iron stent extracts, nitrided iron foils, and their bulk corrosion products. The extracting and standing experiments confirmed that the extraction medium and available oxygen are crucial for precipitation during the extraction and incubation processes. In the MTT test, the extract of nitrided iron stents with a high iron ion concentration (124.11 ± 7.55 µg/mL) was not cytotoxic to L929 fibroblasts. Thus, the in vitro cytotoxicity of nitrided iron stents was actually caused by the size effect of corrosion particles and not the material itself. Test methodology for in vitro cytotoxicity of biodegradable iron-based materials was analyzed, and the results demonstrate that multiple methods should be combined for comprehensive evaluation of the cytocompatibility of bioabsorbable iron-based materials to get an impartial conclusion.