Effect of surface pre-treatments on biocompatibility of magnesium Carla Lorenz a , Johannes G. Brunner a , Philip Kollmannsberger b , Leila Jaafar b , Ben Fabry b , Sannakaisa Virtanen a, * a Institute of Surface Science and Corrosion, Department of Materials Science and Engineering (WW-4), University of Erlangen-Nuremberg, 91058 Erlangen, Germany b Center for Medical Physics and Technology, Department of Physics, University of Erlangen-Nuremberg, Erlangen, Germany Received 29 January 2009; received in revised form 13 March 2009; accepted 17 April 2009 Available online 3 May 2009 Abstract This study reports the influence of Mg surface passivation on the survival rate of human HeLa cells and mouse fibroblasts in cell culture experiments. Polished samples of commercially pure Mg show high reactivity in the cell culture medium, leading to a pH shift in the alkaline direction, and therefore cell adhesion and survival is strongly impaired. Passivation of the Mg surface in 1 M NaOH can strongly enhance cell survival. The best initial cell adhesion is observed for Mg samples incubated in simulated body fluid (M-SBF), which leads to the formation of a biomimetic, amorphous Ca/Mg-phosphate layer with high surface roughness. This surface layer, how- ever, passivates and seals the Mg surface only partially. Subsequent Mg dissolution leads to a significantly stronger pH increase com- pared to NaOH-passivated samples, which prevents long-term cell survival. These results demonstrate that surface passivation with NaOH and M-SBF together with the associated changes of surface reactivity, chemistry and roughness provide a viable strategy to facil- itate cell survival on otherwise non-biocompatible Mg surfaces. Ó 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Magnesium; Corrosion; Cell culture; Passivation 1. Introduction Magnesium and its alloys are of growing interest for biomedical applications, in particular as a biodegradable material for cardiac or orthopedic implants [1–16]. Bioab- sorbable Mg implants might provide a solution for a num- ber of problems associated with permanent metallic implants such as permanent physical/mechanical irritation, and inability to adapt to growth and other ongoing shape changes in the human body. Bioabsorbable Mg implants might also be able to prevent problems associated with long-term release of metallic ions and/or particles through corrosion or wear processes. To reliably predict the behavior of Mg implants in the human body, the in vivo corrosion behavior as well as the biological interactions with the Mg surface need to be characterized. Corrosion behavior of commercial Mg alloys has been widely studied in typical environments the alloys may encounter in different applications, e.g. in NaCl solutions. General information on the electrochemi- cal corrosion behavior of Mg and its alloys have been reviewed in Ref. [17,18]. Mg corrosion takes place under H 2 gas formation, and leads to alkalization of the sur- roundings. On the one hand, both factors could strongly impair the biocompatibility of Mg, e.g. by preventing cell adhesion on the implant surface. On the other hand, release of Mg ions by implant dissolution is not expected to lead to toxic reactions, as the concentration of Mg in the body is controlled by homeostatic mechanisms [6]. Even though the interest in Mg in medicine is increasing, only a few studies on cell behavior on Mg alloy surfaces can be found in the literature. It has been reported that osteoblasts and human bone derived cells adhere, prolifer- 1742-7061/$ - see front matter Ó 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actbio.2009.04.018 * Corresponding author. Tel.: +49 91318527577. E-mail address: virtanen@ww.uni-erlangen.de (S. Virtanen). Available online at www.sciencedirect.com Acta Biomaterialia 5 (2009) 2783–2789 www.elsevier.com/locate/actabiomat