*3.2. Determination of Cellular Viability*

Figure 4A shows qualitative results for the viability of cell spheroids at Day 3 using a Live/Dead assay kit (Figure 4A). In all cases, the cells in the spheroids produced intense green fluorescence. Red fluorescence was partly noted around the boundary of the spheroids. No significant differences

were noted at Day 7 when compared with results of Day 3 (Figure 4B). Figure 4C shows the quantitative results for cellular viability on Days 1, 3, 5, and 7. No significant differences were observed among the groups on Day 1 (*p* > 0.05). In general, there were no significant differences among the groups with longer incubation times.

**Figure 4.** *Cont*.

**Figure 4.** (**A**) Optical, live, dead, and merged images of stem cell spheroids on Day 3. The scale bar indicates 200 μm. (**B**) Results of optical, live, dead, and merged images of stem cell spheroids on Day 7. The scale bar represents 200 μm. (**C**) Cellular viability using CCK-8 assay on Days 1, 3, 5, and 7. \* Statistically significant differences were noted when compared with the 2 ng/mL group on Day 1 (*p* < 0.05).

(**C**)
