gms | German Medical Science

The increase of the impedance at the intracochlear electrode contacts after implantation is typically explained by the formation of fibrous tissue around the electrode array. Silver ions are known to have anti-proliferative and biostatic effects. In the current project these effects shall be transferred to cochlear implants by incorporation of metallic nanoparticles into the silicone of the electrode array in order to reduce the formation of fibrous tissue around the electrode.

Metallic nanoparticles are generated by using short pulses of a fs-laser. The particles are then incorporated into the polymer component of the electrode array during the mixing process of the silicone components. To determine biologically active concentrations of ions released from these nanoparticles, concentrations of metal ions between 0.1 µM and 1 mM were tested on cultured fibroblasts (NIH-3T3), PC-12 cells and freshly isolated spiral ganglion cells (SGC; rats p3-5). Viability of cells was evaluated after 24 and 72 hours by using neutral red assay (NIH-3T3 and PC-12). SGC were fixed, stained (neurofilament) and counted. Furthermore, very first silicone samples containing silver nanoparticles were also investigated in cell culture experiments.

Results showed reduced viability of PC-12 cells as well as fibroblasts at high concentrations of silver nitrate (30 µM) and copper sulphate (300 µM). However, silver nanoparticles immersed in silicone at the concentrations used in our preliminary experiments did not have any effect on PC-12 cells.

Based on our results, size and concentration of nanoparticles in the silicone have to be adjusted to the required concentration in the surrounding medium to reduce the formation of fibrous tissue.

Unterstützt durch: SFB/Transregio 37 TP C4 and FWO Belgium