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

Figure 6

Growth characteristics of R28 cells after cultivation on plasma-treated MWCNT structures. (a) Analysis of cell viability in cultures incubated for 24 hours with increasing serial dilutions of extractive media obtained from nonfunctionalized and plasma-treated MWCNT-Fe-Pt wafer slices and certified RM A, RM B, and RM C ( individual experiments). Extractive medium without the incubation of any material (glass) was used as internal negative control; its mean values are marked by the dotted lines. Data are represented as mean ± SD. They were compared to the glass control and analyzed using unpaired two-tailed test. , RM A (1 : 1) and RM B (1 : 1); , treated MWCNT (1 : 1); , RM A (1 : 2); , RM A (1 : 4). (b) Effects of direct contact on viability of cells grown on glass and on nonfunctionalized and plasma-treated MWCNT-Fe-Pt wafer slices ( individual experiments). Cells were stained using FDA/PI and counted 72 hours after seeding. For each substrate, 12 randomly selected microscopic fields were analyzed. Data are represented as mean ± SD. The total cell numbers were normalized and compared to the glass control and analyzed using unpaired two-tailed test (, treated MWCNT). The quantity of dead cells is shown as a percentage of the corresponding total cell number. They were compared to the treated MWCNT probe and analyzed using unpaired two-tailed test (, glass; , MWCNT). (c) qRT-PCR was used to analyze the expression of different genes representing neuronal/glial and retinal markers or involved in the cell cycle ( individual experiments). Using the comparative CT () method, the relative gene expression ratio of cells cultivated on nonfunctionalized MWCNT was set to 1. For plasma-treated MWCNT, values >1 denote an upregulated and values <1 denote a downregulated gene expression. Each column represents the median, maximum, minimum, and the 50th percentile of the data. Data were analyzed using one sample two-tailed test, showing no significant differences. (d) Scanning electron microscopy images of R28 cells plated on nonfunctionalized (scale bar: 10 μm) and plasma-treated (scale bar: 20 μm) MWCNT-Fe-Pt silicon wafers. Cultivation was terminated 72 hours after seeding. Arrows indicate cell adhesion and individual cell nuclei are marked with stars. Note that the cracks within the MWCNT structures were due to the fixation and drying processes.

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