Changes in biphasic electrode impedance with protein adsorption and cell growth

Carrie Newbold*, Rachael Richardson, Rodney Millard, Christie Huang, Dusan Milojevic, Robert Shepherd, Robert Cowan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Citations (Scopus)


This study was undertaken to assess the contribution of protein adsorption and cell growth to increases in electrode impedance that occur immediately following implantation of cochlear implant electrodes and other neural stimulation devices. An in vitro model of the electrode-tissue interface was used. Radiolabelled albumin in phosphate buffered saline was added to planar gold electrodes and electrode impedance measured using a charge-balanced biphasic current pulse. The polarization impedance component increased with protein adsorption, while no change to access resistance was observed. The maximum level of protein adsorbed was measured at 0.5 μg cm-2, indicating a tightly packed monolayer of albumin molecules on the gold electrode and resin substrate. Three cell types were grown over the electrodes, macrophage cell line J774, dissociated fibroblasts and epithelial cell line MDCK, all of which created a significant increase in electrode impedance. As cell cover over electrodes increased, there was a corresponding increase in the initial rise in voltage, suggesting that cell cover mainly contributes to the access resistance of the electrodes. Only a small increase in the polarization component of impedance was seen with cell cover.

Original languageEnglish
Article number056011
Pages (from-to)1-11
Number of pages11
JournalJournal of Neural Engineering
Issue number5
Publication statusPublished - Oct 2010
Externally publishedYes


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