## 3 Results
### Effect of Different Size of Alginate Spheres on DPCs Proliferation  
To elucidate the effect of sphere size on the cell proliferation, we generated different sizes of spheres with the same cellular density. We could successfully produce 4 different sizes of alginate spheres homogenously. We classified them into 4 groups (small, middle, moderate and large). The average diameter of the spheres in the small group (100-200 \(\upmu\)m) was 151.85 \(\upmu\)m (Figure 2A), the middle size (300-500 \(\upmu\)m) was 394.85 \(\upmu\)m (Figure 2B), the moderate size (500-1000 \(\upmu\)m) was 733.90 \(\upmu\)m (Figure 2C) and large size group was more than 1000 \(\upmu\)m (Figure 2D). There were 84.5 (77-93, n = 25) cells in the small spheres, including 76.7 (68-87) live cells (90.8%) and 7.8 (4-10) dead cells (9.2%) after electrospinning. Though we could control the size and density up to 1500 \(\upmu\)m, the spherical formation tended to become irregular when the size reached more than 1000 \(\upmu\)m (large size group) and the variation in shape increased with increasing size (Figure 2H). We occasionally found entrapped air in the large spheres right after electrospinning; however, it had disappeared within 24 hours, which meant that there were diffusive communications between the inside of the alginate sphere and outside surface (Figure 2D). To investigate the short-term effects of the spherical formation, we studied the proliferation rate of the different sizes of spheres. Intriguingly, the DPCs did not seem to proliferate in any size of spherical formation (Figure 2E). Compared to 2D cultivation, in the spherical formation of alginate, DPCs did not tend to grow as quickly. Rather, in the middle-sized (300-500 \(\upmu\)m) and moderate-sized (500-1000 \(\upmu\)m) spheres, the number of live cells decreased slowly after the sphere formation. The total number of cells (live and dead cells both) did not significantly change in any size of spherical formation (Figure 2F). Considering that creating an alginate sphere as a method of entrapping DPCs inside a sphere, the dead cells would be caught in the sphere; but not washed out. Interestingly, the ratio of live to dead cells gradually decreased in the spheres of every size (Figure 2G). Though these were unexpected results, the tendency of the live cell number was decreasing. From this result, we concluded that the cells were non-proliferative and slowly dying. The larger the size of the sphere was, the more dramatic the rate of decrease was, which meant that the size dependent nutrition diffusion from the media might have been involved in the maintenance of cellular proliferation within alginate sphere. Unexpected results of DPCs in alginate sphere led us to further investigate the cellular dynamics of the long-term cultivation. To characterize the long-term properties of the alginate spheres of human DPCs, we cultivated and traced them for 90 days. The cells inside the alginate sphere seemed not to proliferate but to remain and eventually died as time passed in alginate spheres of every size (Figure 2I-K). The total number of live cells decreased until 70 days after cultivation. Intriguingly, the live cell number remained steady after 70 days and was maintained until the last day of speculation, day 90. There was a convergence phenomenon in the number of live cells in every size after 70 days (Figure 2I-K). We found that every situation of alginate long-term cultivation can diminish the total live DPCs in alginate but after 70 days, the number of DPCs in alginate sphere were maintained. In the small size alginate sphere, the number of average live cells are 8.8 (4-12) cells at day 70, 7.8 (4-13) cells at day 80 and 7.1 (3-10) cells at day 90. In case of middle size, there are 97.1 (63-131) cells at day 70, 85.8 (50-111) cells at day 80 and 80.8 (49-111) cells. In moderate size of alginate sphere, we found that their live cellsare convergent to 598.6 (483-728) cells at day 70, 529 (440-591) cells at day 80 and 462.6 (375-592) cells at day 90.