depends heavily on the resulting circulation and residence times of the MCs. In both
cases, the mean volume-weighted values for the highest tested impeller speeds were
much closer to the detrimental theoretical value of 141 μm. Even though such eddies
occurred at the suspension criteria, the frequency with which the MCs were exposed
to such eddies was much lower due to the lower circulation times and residence
times.
3.2.4 Linking of CFD-Derived Data with Cultivation Studies
In order to link the CFD-derived engineering data with cell biological aspects,
cultivation studies in the two spinner flask types at different impeller speeds were
performed. The results of the cultivation studies with hMSCs from the adipose tissue
are summarized in Table 8. It is obvious that the different hydrodynamic stress levels
have a significant effect on the cell growth in both spinner flask types. Highest living
cell densities were achieved, of up to 1.68 Æ 0.36 Â 10
5 cells/cm
2 (¼ 6.25 Æ
0.35 Â 10
5 cells/mL, EF 56) and 2.46 Æ 0.16 Â 10
5 cells/cm
2 (¼ 8.77 Æ 0.66 Â 10
5
cells/mL, EF 81), in the SP100 and SP300 when working at N s1u N N s1 (SP100
¼ 49–63 rpm, SP300 ¼ 41–52 rpm). The peak living cell densities in the SP300
were on average up to 40% higher than those in the SP100. Although the two spinner
Table 7 Overview of the main biochemical engineering parameters derived from the CFD
simulations
N
[rpm]
u tip
[m/s]
Re
P/V
[W/m
3
]
t cir.
[s]
t res.
[s]
l λ
(a)
[μm]
τ nt
(b)
[10
À3 Pa]
τ nn
(b)
[10
À3 Pa]
F
(c) [10
-
5 N]
Corning 125 mL spinner (SP100)
25
0.05
715
0.07
11.5 4.9
130/
530
2.72/79
0.79/43
0.75
49
N s1u
0.11
1,402 0.63
6.5
2.4
66/
228
5.39/169
1.15/108
0.85
60
N s1
0.13
1,717 1.12
6.0
1.9
60/
191
6.62/211
1.32/138
0.91
120
0.26
3,434 7.56
4.0
0.9
30/
111
12.91/437 2.24/301
1.82
Corning 500 mL spinner (SP300)
20
0.05
841
0.05
10.0 4.2
136/
546
2.04/214
0.30/138
0.83
41
N s1u
0.11
1,724 0.33
6.2
2.6
76/
295
4.00/481
0.69/362
0.89
52
N s1
0.14
2,186 0.61
5.9
1.6
66/
282
5.00/679
0.87/473
1.04
100
0.26
4,204 3.70
2.7
0.7
47/
181
9.26/
1,350
1.70/872
2.10
a Volume -weighted minimum/mean values of turbulent Kolmogorov length scale
b
Local shear (τ nt ) and normal (τ nn ) stress for volume-weighted mean/maximum values
c Mean values of acting particle force weighted by number
Numerical Methods for the Design and Description of In Vitro Expansion. . .
213
cases, the mean volume-weighted values for the highest tested impeller speeds were
much closer to the detrimental theoretical value of 141 μm. Even though such eddies
occurred at the suspension criteria, the frequency with which the MCs were exposed
to such eddies was much lower due to the lower circulation times and residence
times.
3.2.4 Linking of CFD-Derived Data with Cultivation Studies
In order to link the CFD-derived engineering data with cell biological aspects,
cultivation studies in the two spinner flask types at different impeller speeds were
performed. The results of the cultivation studies with hMSCs from the adipose tissue
are summarized in Table 8. It is obvious that the different hydrodynamic stress levels
have a significant effect on the cell growth in both spinner flask types. Highest living
cell densities were achieved, of up to 1.68 Æ 0.36 Â 10
5 cells/cm
2 (¼ 6.25 Æ
0.35 Â 10
5 cells/mL, EF 56) and 2.46 Æ 0.16 Â 10
5 cells/cm
2 (¼ 8.77 Æ 0.66 Â 10
5
cells/mL, EF 81), in the SP100 and SP300 when working at N s1u N N s1 (SP100
¼ 49–63 rpm, SP300 ¼ 41–52 rpm). The peak living cell densities in the SP300
were on average up to 40% higher than those in the SP100. Although the two spinner
Table 7 Overview of the main biochemical engineering parameters derived from the CFD
simulations
N
[rpm]
u tip
[m/s]
Re
P/V
[W/m
3
]
t cir.
[s]
t res.
[s]
l λ
(a)
[μm]
τ nt
(b)
[10
À3 Pa]
τ nn
(b)
[10
À3 Pa]
F
(c) [10
-
5 N]
Corning 125 mL spinner (SP100)
25
0.05
715
0.07
11.5 4.9
130/
530
2.72/79
0.79/43
0.75
49
N s1u
0.11
1,402 0.63
6.5
2.4
66/
228
5.39/169
1.15/108
0.85
60
N s1
0.13
1,717 1.12
6.0
1.9
60/
191
6.62/211
1.32/138
0.91
120
0.26
3,434 7.56
4.0
0.9
30/
111
12.91/437 2.24/301
1.82
Corning 500 mL spinner (SP300)
20
0.05
841
0.05
10.0 4.2
136/
546
2.04/214
0.30/138
0.83
41
N s1u
0.11
1,724 0.33
6.2
2.6
76/
295
4.00/481
0.69/362
0.89
52
N s1
0.14
2,186 0.61
5.9
1.6
66/
282
5.00/679
0.87/473
1.04
100
0.26
4,204 3.70
2.7
0.7
47/
181
9.26/
1,350
1.70/872
2.10
a Volume -weighted minimum/mean values of turbulent Kolmogorov length scale
b
Local shear (τ nt ) and normal (τ nn ) stress for volume-weighted mean/maximum values
c Mean values of acting particle force weighted by number
Numerical Methods for the Design and Description of In Vitro Expansion. . .
213