High-throughput in vitro assay to evaluate the cytotoxicity of liberated platinum compounds for stimulating neural electrodes

BackgroundIt is currently unclear how the platinum (Pt) species released from platinum-containing stimulating electrodes may affect the health of the surrounding tissue. This study develops an effective system to assess the cytotoxicity of any electrode-liberated Pt over a short duration, to screen systems before future in vivo testing.New methodA platinum electrode was stimulated for two hours under physiologically relevant conditions to induce the liberation of Pt species. The total concentration of liberated Pt species was quantified and the concentration found was used to develop a range of Pt species for our model system comprised of microglia and neuron-like cells.ResultsUnder our stimulation conditions (k = 2.3, charge density of 57.7 μC/cm2), Pt was liberated to a concentration of 1 ppm. Interestingly, after 24 h of Pt exposure, the dose-dependent cytotoxicity plots revealed that cell death became statistically significant at 10 ppm for microglia and 20 ppm for neuronal cells. However, in neuron-like cell cultures, concentrations above 1 ppm resulted in significant neurite loss after 24 h.Comparison with existing methodsTo our knowledge, there does not exist a simple, in vitro assay system for assessing the cytotoxicity of Pt liberated from stimulating neural electrodes.ConclusionsThis work describes a simple model assay that is designed to be applicable to almost any electrode and stimulation system where the electrode is directly juxtaposed to the neural target. Based on the application, the duration of stimulation and Pt exposure may be varied.