of unoccupied MCs of 0.365, 0.135, and 0.05, respectively. Con-

sequently, from a theoretical perspective, cell densities for inocula-

tion are in the range of 3–5 cells per MC. Following the cell

attachment phase, which is performed statically or with periodic

stirring, each MC should have at least one cell on its surface. In

reality, this is not always the case. Studies have shown that uneven

distribution of cells on MCs led to increased MC aggregation,

reducing the efficiency of the expansion process [33, 34]. However,

the success of MC-based cultivations is not only dependent on

suitable MC choice but also on the cell culture medium formula-

tion (discussed in further detail in Subheading 1.2).

Various authors have shown that the stirred, single-use bio-

reactors of the Eppendorf BioBLU^® series are suitable for

MC-based cultivation of hMSCs on a benchtop scale, with maxi-

mum cell densities of up to 0.4  10⁶ described in literature for the

BioBLU® 0.3c (Fig. 1a) and BioBLU® 5c [35, 36]. The Bio-

BLU® 0.3c, which was also used in the present study, is well suited

for the suspension of MCs due to its geometric dimensions

(Fig. 1b). These dimensions, namely the stirrer diameter (d), liquid

height (HL), vessel diameter (D), and vessel height (H), may be

used to calculate specific ratios which facilitate the comparison

Fig. 1 BioBLU^® 0.3c bioreactor. (a) Picture of the BioBLU^® 0.3c vessel. (b) Technical drawing with the main

geometrical dimensions. D ¼ 65 mm, d ¼ 33 mm, HL ¼ 78 mm, H ¼ 117 mm

86

Misha Teale et al.