Abstract
Purpose:
In patients suffering from retinal degenerative diseases, e.g., retinitis pigmentosa, functionality can be regained by prostheses, where electrical stimulation of surviving retinal cells is induced by microelectrodes that interface with neuronal tissue. With regard to charge transfer capacity and signal-to-noise ratio, microelectrode properties can be optimized by nano modification, e.g., coating with nano-lawn structures. The biological compatibility of nano-lawn structures and their substrate materials was analyzed after direct and indirect cell contact with regard to proliferation, survival and gene expression profile.
Methods:
Manufacturing of the nano-lawn structures was carried out by our partner from the Fraunhofer Institute for Microelectronic Circuits and Systems. The nano-lawn structures have been realized as an array of free-standing tubes made from Ruthenium. Growth rates and survival of L-929 and retinal precursor (R28) cells were determined after indirect and direct contact. Indirect contact implies the cultivation in medium pre-incubated with the respective structures using a luminescent cell viability assay. Direct contact was evaluated using a fluorescein-diacetate/propidiumiodide-based life-dead assay. For R28 cells, gene expression was analyzed by quantitative real-time PCR.
Results:
Compared to reference materials with defined levels of cytotoxicity, the indirect contact with pre-incubated medium had no significant influence on cell growth rates. Both cell types exhibited good proliferation and morphological properties on the nano-lawn structures and their substrate materials, showing less than 2% death cells. Related to glass, cultivation on the nano-lawn structures indicated no significant differences in the gene expression profile of R28 cells.
Conclusions:
With regard to direct and indirect cell contact, the tested nano-lawn structures showed good biocompatibility profiles, demonstrating that this nanotechnology provides a promising tool to improve microelectrodes that connect with retinal tissue.