## 3 Results
### Human Fibro Blast Cell's Viability and Proliferation  
Figure 7 shows the proliferation rates obtained by comparing the OD values of the cultures using the CCK-8 reagent on Days 2 and 3 of culturing on the GO-coated polystyrene film. As pure polystyrene is a hydrophobic material containing only phenyl groups, it is unsuitable for cell adhesion but can be deformed to a hydrophilic state with surface charges for cell culturing [22; 23; 24]. On the unmodified polystyrene film (negative control), the number of cells decreased between Days 2 and 3 and the cell proliferation rate was 1.0 or lower. However, the cell proliferation rate increased on the PS film coated with GO, regardless of the coating conditions. Among the GO-coated films, L3 and H3 demonstrated obviously higher ODs on Day 3 than on the positive control at Day 3. If the coating conditions of GO are appropriately adjusted, the cell culture efficiency in the CO-coated vessel can exceed that in the existing cell culture vessel, and a large-area cell culture vessel can be expected. Therefore, when developing cell culture vessels, one must select coating conditions that maximize the cell culture efficiency. For this purpose, the optimal conditions of the proposed vessel were selected by comparing the results of physical and biological analyses. Figure 6: Schematic diagram of contact angle measurement. This is the contact angle between the polystyrene cell culture plate and the GO-coated polystyrene cell culture plate (the sample showing the best cell growth). The contact angle of PS was measured to be 85.6\({}^{\circ}\), and that of H3 was measured to be 54.6\({}^{\circ}\). \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**L3**} & \multirow{2}{*}{**L5**} & \multirow{2}{*}{**L7**} & \multirow{2}{*}{**M3**} & \multirow{2}{*}{**M5**} & \multirow{2}{*}{**M7**} & \multirow{2}{*}{**H3**} & \multirow{2}{*}{**H5**} & \multirow{2}{*}{**H7**} & \multirow{2}{*}{**PS**} \\ \hline Average deviation & 40.0 & 39.0 & 39.8 & 51.0 & 36.6 & 38.4 & 54.6 & 36.2 & 36.0 & 85.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Water contact angles of the L, M, and H surfaces. (PS = polystyrene) The measurement results are expressed as average values after 5 measurements. As reported previously, the surface roughness values of the GO-coated polystyrene films tended to increase with the number of coatings. Additionally, the slower the speed, the larger the degree of change was analyzed. However, when comparing the L group and the fastest cell proliferation on the third day of the H group, it was analyzed that the OD value decreased as the number of coatings increased (Figure 8). Cell cytotoxicity was confirmed by live/dead assay using a double-staining kit. The images taken under a fluorescence microscope are shown in Figure 9. The live cells emitted green fluorescence (excitation wavelength = 514 nm) while their dead counterparts expressed red fluorescence (excitation wavelength = 561 nm). While the negative control PS film expressed green and red fluorescence at a similar ratio, all samples coated with GO demonstrated insignificant red fluorescence, affirming the non-cytotoxicity of the GO-coated film. Figure 8: Comparison of OD on the 3 rd day and roughness values in the L group (**a**) and H group (**b**). The surface roughness values of the GO-coated polystyrene films tended to increase with the number of coatings. Figure 7: OD values of cells on the control slides and the GO-coated film, analyzed by the CCK-8 assay: (**a**) OD values measured on Days 2 and 3 (n = 3). The cells significantly proliferated on the positive control and GO-coated film. The cell growths (OD values) on both days were highest in the H3 sample. Data are presented as the means \(\pm\) SDs, * \(p\) \(<\) 0.05, ** \(p\) \(<\) 0.01, *** \(p\) \(<\) 0.001, *** \(p\) \(<\) 0.0001 vs. day 2.