Cellular Response to Surface Voltage and Metal Ion Release In Polarized CoCr Biomedical Alloy

Metallic biomaterials implanted inside body undergo significant voltage variations at their surfaces due to breaching and repassivation of the oxide film during mechanically assisted corrosion. The effect of these voltage changes on the behavior of cells surrounding the implant surface has not been studied in detail. The goal of this abstract is to study the effect of voltage variation on the viability of cells cultured on CoCr biomedical alloy surfaces. Furthermore, metallic ions released from the surface of the implant biomaterial due to these voltage changes, may have an effect on the observed cellular response. Therefore, we also study the cellular response to conditioned culture media, which contains corrosion products released at different voltages, and compare it to culture with normal media. Fibroblasts (MC3T3) are cultured on the surface of CoCr alloy placed in an electrochemical chamber inside an incubator. The standard three electrode system is used, where Ag/AgCl is the reference, carbon rod the counter and the sample is the working electrode. The temperature and CO2 concentration are maintained at 37° C and 5% respectively. Different voltages are applied for 24 hours and cell viability is investigated using SEM and live/dead assay. Results show that after 24 hour culture at +500 mV, where release of chromium IV happens, cells are mostly dead. Cells grown at OCP, however, remain healthy within the same time period. Culturing cells for 24 hours using the conditioned media also revealed a large number of dead cells, which indicates the cytotoxicity of the corrosion products. Moreover, cellular response to cathodically polarized surfaces is believed to be mainly initiated by charge transfer through cell membrane. The results of this study will help to provide a better insight on biomaterial-cell interactions and also a method to control excessive cell proliferation and growth in conditions like neointimal hyperplasia.