Correlation of osteoblast activity and metallic ions released from an implantable and biodegradable metallic material

Abstract

INTRODUCTION: Current implantable metallic materials consist of stainless steel, titanium and cobalt-chromium based alloys. To avoid stress shielding effect, degradable metallic materials such as magnesium based alloy are an alternative. However, its rapid degradation after implantation is a major obstacle in clinical use. In addition to hydrogen gas release, large amount of magnesium ions will release to the human body upon degradation. Mg ions may affect bone healing if the physiological balance is suddenly altered. Hence, this study aims to investigate the correlation of magnesium ion concentration and osteoblast activity in vitro. METHODOLOGY: With the use of cell culturing, different concentrations of magnesium ions ranging from 50 to 10,000ppm were tested against to the SaOs-2 human osteoblast activity. MTT assay (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) was used to determine the cell viability and cell enzymatic activity. RESULTS AND DISCUSSION: The results suggest that the higher the magnesium ions concentration, the lower the osteoblast activity will be. The osteoblasts become inactivated at 200ppm and the cells cannot survive when the ion concentration reaches to 1,500ppm or above. However, the osteoblast activity is maintained at 150ppm or below. This study demonstrates the magnesium ions can inactivate human osteoblast activity as the concentration rises to 200ppm. In conclusion the use of magnesium based alloy as degradable orthopaedic implants is feasible if the degradation rate is controlled carefully.