The biocompatibility of commercially pure magnesium-based (cp Mg) biodegradable implants is compromised by strong hydrogen evolution due to high initial corrosion rates of cp Mg in physiological environment. To mitigate this problem, the addition of corrosion-retarding alloying elements or coating of implant surfaces has been suggested. In the present work, Magnesium (cp) was coated with a linker molecule known to reduce corrosion and immobilize proteins in order to enhance biocompatibility.
Magnesium samples were pre-treated and afterwards coated with amino-propyltriethoxysilane + vitamin C (AV). Cell tests up to 20 days were conducted with endothelial (DH1+/+) and osteosarcoma (Mg63) cells. Among others, the cell spreading area was calculated in order to elucidate short- and long-term biocompatibility of the samples. We also investigated the speed of initial cell spreading after seeding using fluorescently labeled fibroblasts (NIH/3T3). The influence of cell growth on the corrosion behaviour of magnesium was investigated by electrochemical impedance spectra (EIS).
Cell tests show that growth of DH1+/+ and Mg63 is possible on cp Mg in general, even if initial biocompatibility seems to be limited due to corrosion of Mg. The AV treatment leads to a faster increase of cell adhesion and spreading in the case of DH1+/+ and shows better long-term stability of cell growth for Mg63. These improvements are dedicated to the protein immobilizing effect of AV and the increased corrosion resistance by the coating leading to a decreased hydrogen evolution. The investigation of the speed of the initial cell spreading elucidates as well a beneficial effect of AV coatings. EIS measurements after 1 day show no effect of cell adhesion compared to the reference immersed in cell culture medium without cells. However, after 5 days an increase of Rct can be observed for both cell lines, with the one for osteosarcoma being very significant. The different influences of the two cell lines can be explained by different spreading and adhesion behaviour.