Page 300 - IJB-10-3

International Journal of Bioprinting Design and optimization of 3DP bioscaffolds

Figure 9. Impact of the bioreactor’s inlet flow rate on (a) average oxygen concentration within the scaffold, (b) average cell density, and (c) wall shear stress
at the outer edge of the scaffold.

is parallel to the direction of nutrient flow. Although the over time due to cell consumption, and the reduction rate
oxygen concentration and cell density were the highest was significantly augmented when the initial cell density
for the 0.3 mm scaffold, its cell loading on day 7 was only (ρ ) was increased. The oxygen concentration was lowered
0
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one-eighth of the 3.0 mm scaffold. The cell population is by ~50% for an initial cell density of 3 × 10 cells/mL after
vital for intercellular signaling that is of great importance a 7-day culturing, while it was utterly hypoxic when the
to viability and proliferation. A balance between oxygen initial density tripled, leading to a discrepancy in the cell
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permeability and cell loading should be thus considered density on day 7 as high as ~13 times (see Figure 11e). On
during the design of scaffolds. the 7th day of culture, the cells had proliferated by ~31
times from an initial density of 3 × 10 cells/mL, while
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4.2.3. Material and cell parameters extremely low cell proliferation was observed for the
Figure 11 presents the effects of initial material porosity, scaffold with 9 × 10 cells/mL density. In cell culturing, a
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initial cell density, maximum oxygen uptake rate, and low initial density will weaken cell-to-cell interaction and
maximum cell growth rate on oxygen transportation communication, leading to slow cell growth and eventually
and cell growth, where the normalized average oxygen death. Conversely, excessive initial density brings about
concentration and cell density were presented with a factor overcrowding and insufficient nutrients, resulting in
of 222.5 and 3 × 10 cells/mL, respectively. As shown in local metabolic waste accumulation. Therefore, optimal
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Figure 11a, the average oxygen concentration decreased initial cell density is required to maximize cell growth.

Volume 10 Issue 3 (2024) 292 doi: 10.36922/ijb.1838