Introduction: Nanoparticles can serve as carrier substances for drugs, proteins and even nucleic acids. They penetrate the membrane of a target cell so that their conjugates can create intracellular effects. Also DNA, coding for a growth factor or anti-inflammatory factors,, can be transfected using the nanoparticles without any further reagents. However, there has been little research to date on whether this approach could play a role in the modeling of cochlear implant electrodes.

Materials and Methods: DNA-functionalized (with fluorescent dye and the growth factor BDNF) calciumphosphate-nanoparticles (CaP-NP) were applied to a cell culture dish bottom by a layer-by-layer process in combination with the adhesion molecule poly-(L)-lysine. Spiral ganglion cell explants from rats were then cultured on these surfaces, and marked and evaluated immunohistochemically after a minimum of 3 days of growing. Furthermore, an electrophoretic method for coating cochlear implant electrodes with nanoparticles was investigated by scanning electron microscopy.

Results: Using the layer-by-layer process, relatively large amounts of CaP-NP can be bound to the surface. However, the evaluation of the cell cultures shows limited biocompatibility of the nanoparticles with the spiral ganglion explants over a longer culture period. If the Ca-NP are added as a supplement to the growth medium, better survival of the cells was shown as well as a low but stable transfection of DNA into the cells.

Discussion: The present results show that surfaces can be successfully coated with DNA-conjugated CaP-NP. The CaP-NP have limited biocompatibility with the inner ear cells in vitro, but show detectable DNA transfection.

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