Nanomaterials may change the way that living tissues or cells interact with implantabl-e devices. Several surface modifications or coatings are nowadays considered as new el-ectrode models for reducing undesirable tissue reactions such as glial scar formatio-n, which degrade device performance by affecting the signal to noise ratio.


When we started our studies, we were wondering if immortalized cell culture (NG108-15) could grow on a carbon coating. Actually a thin layer (2 µm) of carbon nanotube was pr-eviously grown on a silicon substrate and cell culture viability was easily validated even without poly-L-lysine preparation.

Based on these first successes, we chose to use hippocampus primary neurons to observe and quantify the behaviour of a neuron network on various kinds of carbon nanotubes. W-e performed in vivo tests during one year in parallel using bare carbon nanotubes whic-h extended the assessment of Keefer et al. that carbon-based coatings increase the sen-sitivity of the electrodes in vivo.

However, considering the complexity of the in vivo assessment, we chose first to evalu-ate in vitro our surface modifications. The tubes are grown on a silicon substrate usi-ng a nickel catalyst. Based on a Pi-stacking approach, the surface of carbon nanotubes were anionic, cationic, hydrophilic and furtive.

Using scanning electron microscopy and confocal microscopy, we studied the interaction of nervous cells with the carbon nanotubes and clearly identified specific behaviours b-ased on the quantification of the density of aggregates or the diameter of the bundle-s between the clusters. The chemistry of the carbon nanotubes changed the equilibrium  between adhesion on the electrode surface and cell internal mechanical interactions.

To implant the material and extend these results to tissues in a long-term study, we s-till need to complete a biocompatibility assessment. Nevertheless, these new kinds of   functionalized surfaces could help to reduce the invasiveness of microelectrodes.