FIG. 6.

(a) Comparison of oxygen values measured in static and dynamic cultures. During the first 3 days, oxygen concentration was significantly higher in the bioreactor cultures (gray) compared to the static cultures (black). (b) Low oxygen concentrations as found in long-term static cultures (black) were accompanied by a slow steady increase in the DNA amount implicating cell proliferation. Oxygen concentration measured in static and dynamic cultures was plotted together with percentages of DNA content normalized to initially seeded cell numbers against the time. Black bars indicate the oxygen concentration measured in static cultures, which was in the range between 2% and 7% oxygen content, whereas gray bars stand for the values obtained in dynamic cultures (here, restricted to the first 8 days of culture, where scaffold integrity was fully preserved as discussed above), which were found between 6% and 12% oxygen content. The percentage scale on the right side of the plot shows the percentage of cell survival in the whole scaffold at different time points, which were calculated from DNA content obtained at the individual time point, cell numbers used for seeding the scaffold, and average seeding efficiency of the experimental setup. At day 4, cell counts calculated from DNA concentration were about 30% of the initially seeded cell numbers (black filled circle), which rose up to 76% of the initially seeded cell numbers during a 4-week time course in static culture. Values for bioreactor cultures (gray circles) showed comparable numbers at 1 week of culture with about 37% (b, in gray).