Microelectrode Array-evaluation of Neurotoxic Effects of Magnesium as an Implantable Biomaterial

Magnesium (Mg)-based biomaterials have shown great potential in clinical applications. However, the cytotoxic effects of excessive Mg²⁺ and the corrosion products from Mg-based biomaterials, particularly their effects on neurons, have been little studied. Although viability tests are most commonly used, a functional evaluation is critically needed. Here, both methyl thiazolyl tetrazolium (MTT) and lactate dehydrogenase (LDH) assays were used to test the effect of Mg²⁺ and Mg-extract solution on neuronal viability. Microelectrode arrays (MEAs), which provide long-term, real-time recording of extracellular electrophysiological signals of in vitro neuronal networks, were used to test for toxic effects. The minimum effective concentrations (EC_min) of Mg²⁺ from the MTT and LDH assays were 3 mmol/L and 100 mmol/L, respectively, while the EC_min obtained from the MEA assay was 0.1 mmol/L. MEA data revealed significant loss of neuronal network activity when the culture was exposed to 25% Mg-extract solution, a concentration that did not affect neuronal viability. For evaluating the biocompatibility of Mg-based biomaterials with neurons, MEA electrophysiological testing is a more precise method than basic cell-viability testing.