Properties of Retinal Precursor Cells Grown on Vertically Aligned Multiwalled Carbon Nanotubes Generated for the Modification of Retinal Implant-Embedded Microelectrode Arrays.

Background. To analyze the biocompatibility of vertically aligned multiwalled carbon nanotubes (MWCNT), used as nanomodification to optimize the properties of prostheses-embedded microelectrodes that induce electrical stimulation of surviving retinal cells. Methods. MWCNT were synthesized on silicon wafers. Their growth was achieved by iron particles (Fe) or mixtures of iron-platinum (Fe-Pt) and iron-titanium (Fe-Ti) acting as catalysts. Viability, growth, adhesion, and gene expression of L-929 and retinal precursor (R28) cells were analyzed after nondirect and direct contact. Results. Nondirect contact had almost no influence on cell growth, as measured in comparison to reference materials with defined levels of cytotoxicity. Both cell types exhibited good proliferation properties on each MWCNT-coated wafer. Viability ranged from 95.9 to 99.8%, in which better survival was observed for nonfunctionalized MWCNT generated with the Fe-Pt and Fe-Ti catalyst mixtures. R28 cells grown on the MWCNT-coated wafers showed a decreased gene expression associated with neural and glial properties. Expression of the cell cycle-related genes CCNC, MYC, and TP53 was slightly downregulated. Cultivation on plasma-treated MWCNT did not lead to additional changes. Conclusions. All tested MWCNT-covered slices showed good biocompatibility profiles, confirming that this nanotechnology is a promising tool to improve prostheses bearing electrodes which connect with retinal tissue.

In situ reaction mechanism studies on ozone-based atomic layer deposition of Al(2)O(3) and HfO(2).

The mechanisms of technologically important atomic layer deposition (ALD) processes, trimethylaluminium (TMA)/ozone and tetrakis(ethylmethylamino)hafnium (TEMAH)/ozone, for the growth of Al(2)O(3) and HfO(2) thin films are studied in situ by a quadrupole mass spectrometer coupled with a 300 mm ALD reactor. In addition to released CH(4) and CO(2), water was detected as one of the reaction byproduct in the TMA/O(3) process. In the TEMAH/O(3) process, the surface after the ozone pulse consisted of chemisorpted active oxygen and -OH groups, leading to the release of H(2)O, CO(2), and HNEtMe during the metal precursor pulse.