Electrochemical Stability of Thin-Film Platinum as Suitable Material for Neural Stimulation Electrodes.

Only thin-film technology can satisfy the requirements of high spatial selectivity at high-channel-count electrode array designs by simultaneously good conformability to the targeted tissue through mechanical flexibility enriching future applications of functional neural stimulation. However, caused by the high impact of the microstructure on the mechanical and electrochemical film properties, varying fabrication processes of the same thin-film makes the difference between acute and chronic long-term stable electrodes. The influence of standard clinical electrical pulsing on flexible polyimide-based thin-film platinum electrodes for neuroprostheses, either sputter deposited or evaporated, and different diameters was assessed and compared. The electrochemical and morphological analysis showed a higher corrosion susceptibility and electrochemical degradation for the sputter deposited platinum electrodes with even total failures of smaller diameters. In contrast, the evaporated thin-films provided itself as more stable and reliable metallization with also smaller electrodes keeping their film integrity intact over the experimental period, -appearing to be the preferable material for improving thin-film electrodes' longevity.

Association of histone acetylation at the ACTA2 promoter region with epithelial mesenchymal transition of lens epithelial cells.

PURPOSE: Epithelial mesenchymal transition (EMT) plays a central role in the development of fibrotic complications of the lens. The current study is designed to check whether EMT of lens epithelial cells (LECs) is regulated by epigenetic modifications and to evaluate the effect of Trichostatin-A (TSA) on the transforming growth factor-ß (TGF-ß)-induced EMT. METHODS: Fetal human LECs (FHL124) were treated with TGF-ß2 in the presence or absence of TSA. Levels of mRNA, protein, as well as localization of α-smooth muscle actin (αSMA) were studied along with migration of LECs. Acetylation of histone H4 was analyzed and chromatin immunoprecipitation (ChIP) was carried out to study the level of acetylated histone H4 at the promoter of αSMA gene (ACTA2). Student's t-test was used for statistical analysis. RESULTS: TGF-ß2 treatment resulted in myofibroblast-like changes and increased migratory capacity of FHL124. Protein and mRNA expression of αSMA increased, and immunofluorescence revealed presence of extensive stress fibers. TSA treatment preserved epithelial morphology, retarded cell migration, and abrogated an increase in αSMA levels. TSA led to the accumulation of acetylated histone H4 that was reduced on TGF-ß2 treatment. However, increased level of histone H4 acetylation was found at the ACTA2 promoter region during TGF-ß treatment. CONCLUSIONS: The increased level of αSMA, a hallmark of EMT in LECs, is associated with increased level of histone H4 acetylation at its promoter region, and TSA helps in suppressing EMT by epigenetically reducing this level. TSA thus shows promising potential in management of fibrotic conditions of the lens.