Platinum corrosion products from electrode contacts of human cochlear implants induce cell death in cell culture models

Abstract

Despite the technological progress made with cochlear implants (CI), impedances and their diagnosis remain a focus of interest. Increases in impedance have been related to technical defects of the electrode as well as inflammatory and/or fibrosis along the electrode. Recent studies have demonstrated highly increased impedances as the result of corroded platinum (Pt) electrode contacts. This in vitro study examined the effects of Pt ions and compounds generated by corrosion of the electrode contacts of a human CI on cell metabolism. Since traces of solid Pt in surrounding cochlear tissues have been reported, the impact of commercially available Pt nanoparticles (Pt-NP, size 3 nm) on the cell culture model was also determined. For this purpose, the electrode contacts were electrically stimulated in a 0.5% aqueous NaCl solution for four weeks and the mass fraction of the platinum dissolute (Pt-Diss) was determined by mass spectrometry (ICP-MS). Metabolic activity of the murine fibroblasts (NIH 3T3) and the human neuroblastoma (SH-SY5Y) cells was determined using the WST-1 assay following exposure to Pt-Diss and Pt-NP. It was found that 5–50 μg/ml of the Pt-NP did not affect the viability of both cell types. In contrast, 100 μg/ml of the nanoparticles caused significant loss in metabolic activity. Furthermore, transmission electron microscopy (TEM) revealed mitochondrial swelling in both cell types indicating cytotoxicity. Additionally, TEM demonstrated internalized Pt-NP in NIH 3T3 cells in a concentration dependent manner, whereas endocytosis in SH-SY5Y cells was virtually absent. In comparison with the Pt-NP, the corrosion products (Pt-Diss) with concentrations between 1.64 μg/ml and 8.2 μg/ml induced cell death in both cell lines in a concentration dependent manner. TEM imaging revealed both mitochondrial disintegration and swelling of the endoplasmic reticulum, suggesting that Pt ions trigger cytotoxicity in both NIH 3T3 and SH-SY5Y cell lines by interacting with the respiratory chain.

Carbon Quantum Dots Codoped with Nitrogen and Lanthanides for Multimodal Imaging

“…In order to assess their potential use as probes in biomedical applications, cytotoxicity of these co-doped CQDs was evaluated in different cell types widely used as cell culture models for different physiological and pathological purposes. [20][21][22] For such purpose, MTT assays were carried out in three different and well-established cell lines: a recognized tumor cell line human, the cervical carcinoma HeLa cells, and two normal cell lines, mouse embryonic fibroblast NIH-3T3 cells and Chinese hamster ovary (CHO) cells. Cell viabilities were investigated after exposure of the three different cell lines to different concentrations of codoped CQDs (0, 0.2, 2, 20, 200 and 2000 μg mL -1 ) for 24 h and 72 h.…”

PEDOT:PSS‐Coated Stimulation Electrodes Attenuate Irreversible Electrochemical Events and Reduce Cell Electropermeabilization

“…[51] Moreover, dissolved metal particles from electrodes have been shown to be harmful to cells in a concentration dependent manner. [52] Such mechanisms indicate the complexity of these chemical changes and the effect on cells. However, PEDOT:PSS-coated electrodes enable the delivery of high voltage pulses with minimal electrochemical events at the electrode interface.…”

Current Perspectives on the Safe Electrical Stimulation of Peripheral Nerves with Platinum Electrodes

“…Several studies have been performed to determine if electrochemical reactions at a platinum electrode can affect cell viability. Biphasic electrical stimulation of a cochlear implant in 0.5% NaCl was performed for 600 hours at a duty cycle of 50%, frequency of 5 kHz, 100 µs pulse width with no interpulse delay and an amplitude of 0.3 A [53]. Strong corrosion of the electrode was found.…”