Abstract
Purpose:
Interfacing neuronal tissue with extracellular microelectrodes is a promising approach to regain functionality in patients suffering from photoreceptor degeneration, e.g., retinitis pigmentosa. To restore vision, prostheses that electrically stimulate surviving retinal cells have already been developed. Optimization of the microelectrode properties related to charge transfer capacity and signal to noise ratio can be achieved by nano modification, e.g., coating with aligned multiwalled carbon nanotubes (MWCNTs). Aligned MWCNTs were synthesized with different catalyst particles mixtures and investigated with regard to survival and proliferation of different cell types grown on these wafer pieces.
Methods:
Synthesis of aligned MWCNTs was carried out on 4-inch silicon wafers by chemical vapour deposition. Length and homogeneity were improved with a SiO2 and an Al2O3 layer. Aligned MWCNT growth was achieved by iron particles (3 nm in diameter) or mixtures of iron-platinum and iron-titanium acting as catalysts. Synthesis was carried out at atmospheric pressure using Argon as carrier gas. Survival of L-929 cells and retinal precursor (R28) cells was estimated after direct contact with the wafer pieces using fluorescein-diacetate/propidiumiodide life-dead assay. Cell growth was determined after indirect contact, which implies cultivation in medium pre-incubated with the respective wafer pieces, using a luminescent cell viability assay.
Results:
Both cell types, L-929 and R28, exhibited good proliferation and cluster formation properties on each tested MWCNT-coated silicon wafer, compared to non-coated pieces and a glass control. Cell viability ranged from 96.9% to 99.1%. However, cell survival on wafers generated with iron-platinum and iron-titanium catalyst mixtures was better than on wafers generated with iron catalyst. The indirect contact with pre-incubated medium had no significant influence on cell growth rates, measured in comparison with positive reference materials that show defined levels of toxicity.
Conclusions:
Different catalyst mixtures were tested to improve the synthesis of aligned MWCNTs on silicon wafer pieces. Regarding cell viability, MWCNT-coating did not show any significant decrease in cell viability and is therefore a promising technology to improve interfacing microelectrodes with retinal tissue.
Keywords: 449 cell survival •
694 retinal culture