Biocompatibility and neurotoxicity of magnesium alloys potentially used for neural repairs.

Nerve injury, especially the large-size nerve damage, is a serious problem affecting millions of people. Entubulation of two ends of the injured nerve by using an implantable device, e.g., nerve guidance conduit (NGC), to guide the regeneration of nerve tissue is a promising approach for treating the large-size nerve defect. Magnesium (Mg) and its alloys are biodegradable, conductive, and own good mechanical properties. Mg ion, one of the main degradation products of Mg and its alloys, was reported to promote the proliferation of neural stem cells and their neurite production. Thus, Mg and its alloys are potential materials for fabricating the nerve repair implants, such as NGC or scaffold. However, the compatibility of Mg alloys to cells, especially neurons is not clear. In this work, NZ20 (Mg-2Nd-Zn), ZN20 (Mg-2Zn-Nd) and Mg-10Li magnesium alloys were selected for study, due to the improved mechanical properties of NZ20 and ZN20 alloys and bio-function of Li ions from Mg-10Li to nervous system, respectively. The degradation behavior and biocompatibility were studied by in vitro degradation test and cell adhesion assay, respectively. Specifically, the cytocompatibility to dorsal root ganglion (DRG) neurons, RF/6A choroid-retina endothelial cells, and osteoblasts in the cell culture media containing Mg alloy extracts were investigated. The results showed that Mg alloys degraded at different rates in cell culture media and artificial cerebrospinal fluid. The three alloy extracts showed negligible toxic effects on the endothelial cells and osteoblasts at short term (1 day), while NZ20 extract inhibited the proliferation of these two types of cells. The effect of Mg alloy extracts on cell proliferation was also concentration-dependent. For DRG neurons, ZN20 and Mg-10Li alloy extracts showed no neural toxicity compared with control group. The results of the present work show a potential and feasibility of Mg-10Li and ZN20 for nerve repair applications.