Effect of Surface Wettability

Next, the effects of surface wettability on the cell behaviors in growth and adhesion were studied by testing neonatal rat cardiac fibroblasts on Nanopillar samples of varying structural aspect ratios in both hydrophilic and hydrophobic surface conditions. Figures 4.9, 4.10, 4.11, 4.12 show the results of microscopy.

Figure 4.9 shows the SEM images of neonatal rat cardiac fibroblasts cultured on hydrophilic samples for 2 days to 8 weeks. In 2 days, cells on Smooth

Hydrophilic

Smooth Nanopillar-Low Nanopillar-Mid Nanopillar-High

Fig. 4.9 SEM images of neonatal rat cardiac fibroblasts cultured on hydrophilic samples. Neonatal rat cardiac fibroblasts were cultured on Smooth (a, e, i, and m), Nanopillar-Low (b, f, j, and n), Nanopillar-Mid (c, g, k, and o), and Nanopillar-High (d, h, l, and p) in a hydrophilic surface condition for 2 days (a-d), 1 week (e-h), 4 weeks (i-l), and 8 weeks (m-p). In (p), an arrow (right arrow) indicates the boundary of cell sheet curled up from the surface

Fig. 4.9 SEM images of neonatal rat cardiac fibroblasts cultured on hydrophilic samples. Neonatal rat cardiac fibroblasts were cultured on Smooth (a, e, i, and m), Nanopillar-Low (b, f, j, and n), Nanopillar-Mid (c, g, k, and o), and Nanopillar-High (d, h, l, and p) in a hydrophilic surface condition for 2 days (a-d), 1 week (e-h), 4 weeks (i-l), and 8 weeks (m-p). In (p), an arrow (right arrow) indicates the boundary of cell sheet curled up from the surface

Hydrophilic

Smooth Nanopillar-Low Nartopi liar-Mid Nanopillar-High

Hydrophilic

Smooth Nanopillar-Low Nartopi liar-Mid Nanopillar-High

Fig. 4.10 Fluorescence microscope images of neonatal rat cardiac fibroblasts cultured on hydrophilic samples. Neonatal rat cardiac fibroblasts were cultured on Smooth (a, e), Nanopillar-Low (b, f), Nanopillar-Mid (c, g), and Nanopillar-High (d, h) in a hydrophilic surface condition for 2 days (a-d) and 1 week (e-h). Blue and red colors represent nuclei and actins, respectively

Fig. 4.10 Fluorescence microscope images of neonatal rat cardiac fibroblasts cultured on hydrophilic samples. Neonatal rat cardiac fibroblasts were cultured on Smooth (a, e), Nanopillar-Low (b, f), Nanopillar-Mid (c, g), and Nanopillar-High (d, h) in a hydrophilic surface condition for 2 days (a-d) and 1 week (e-h). Blue and red colors represent nuclei and actins, respectively exhibited well-spread, flattened, and rounded cell morphology (Fig. 4.9a). In contrast, cells on Nanopillar showed less-spread, spindled or elongated cell morphology (Fig. 4.9b-d). In particular, the cell shape became slenderer and the cell size smaller for taller Nanopillars. Although cell population increased on all samples in 1 week, the slender and spindle-like shape with a smaller cell size was still observed on Nanopillar (Fig. 4.9f-h). In terms of cell size, cells on Nano-pillar-High (Fig. 4.9h) were significantly smaller than those on the other samples. In 4 weeks, cells on Nanopillar exhibited better spreading with less slender morphology (Fig. 4.9j-l) than before, while cells on Smooth became confluent (Fig. 4.9i). In 8 weeks, a cell sheet was formed on all the samples (Fig. 4.9m-p). It was observed that the edges of the cell sheet formed on Nanopillar-High were curled up (Fig. 4.9p), while the edges on Smooth remained firmly attached. In a simple detachment test, the cell sheet formed on the tall and sharp-tip Nanopillar was easier to peel off than that on Smooth. This result was consistent with the case of human foreskin fibroblasts (Fig. 4.8).

Furthermore, Fig. 4.10 shows the fluorescence microscope images of actin filament (F-actin) of neonatal rat cardiac fibroblasts on hydrophilic samples after 2 days and 1 week. F-actins were less developed on Nanopillar-High (Fig. 4.10d, h), supporting the smaller cell size in cell morphology. Many radiations of F-actins at the periphery of cells were observed on Nanopillar-Mid (Fig. 4.10c, g) and Nanopillar-High (Fig. 4.10d, h), whereas the radiating length was much longer on Nanopillar-Mid than on Nanopillar-High.

In contrast to the hydrophilic samples, Fig. 4.11 shows the SEM images of neonatal rat cardiac fibroblasts cultured on hydrophobic samples from 2 days to 8 weeks. Nanopillar, compared to Smooth, tended to support cell proliferation in early periods (till 1 week), which was especially evident on Nanopillar-High (Fig. 4.11d, h). Cells on Nanopillar-High appear to be more viable than those on the other samples and showed stellate morphology (Fig. 4.11d, h, l). However, compared to the hydrophilic samples, cells did not proliferate much on the hydrophobic samples, and eventually few viable cells were left on the hydrophobic samples after 4 weeks. This result suggests that neonatal rat cardiac fibroblasts do not attain sufficient adhesion for proliferation on the hydrophobic surface. Although cells on the Nanopillar-High exhibited better cell proliferation than those on other samples, we speculate that it was because cells have less contact area to the hydrophobic surface due to the levitation by the tall and sharp-tip nanostructures.

Figure 4.12 also shows the fluorescence microscope images of actin filament (F-actin) of neonatal rat cardiac fibroblasts on hydrophobic samples in 2 days and 1 week. F-actins were seldom developed on hydrophobic samples, suggesting poor cell adhesion. Considerable development of F-actins was only observed on Nanopillar-High in 1 week (Fig. 4.12h). F-actins radiated at the cells' periphery (Fig. 4.12h), which was consistent with the cells' morphology.

Fig. 4.11 SEM images of neonatal rat cardiac fibroblasts cultured on hydrophobic samples. Neonatal rat cardiac fibroblasts were cultured on Smooth (a, e, i, and m), Nanopillar-Low (b, f, j, and n), Nanopillar-Mid (c, g, k, and o), and Nanopillar-High (d, h, l, and p) in a hydrophobic surface condition for 2 days (a-d), 1 week (e-h), 4 weeks (i-l), and 8 weeks (m-p)

Fig. 4.11 SEM images of neonatal rat cardiac fibroblasts cultured on hydrophobic samples. Neonatal rat cardiac fibroblasts were cultured on Smooth (a, e, i, and m), Nanopillar-Low (b, f, j, and n), Nanopillar-Mid (c, g, k, and o), and Nanopillar-High (d, h, l, and p) in a hydrophobic surface condition for 2 days (a-d), 1 week (e-h), 4 weeks (i-l), and 8 weeks (m-p)

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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