Figure 2.

(A–C) Determination of impedance parameters after chemical osteogenic induction. Normalized real-time and label-free impedance (frequencies at 4 (2A), 16 (2B), 64 (2C) kHz) curves of human adipose-derived stem cells (ASC, red line), bone-marrow-derived stem cells (BMSC, orange line), and primary osteoblasts (POB, yellow line), (mean ± SD, n = 3). All cells were seeded (t = 0 h) in multi-well electrode arrays. Chemical osteogenic induction was started (t = 48 h) by supplementation with an osteogenic differentiation medium. At t = 96 h, the last medium change was carried out. The total measurement time was seven days. Note that only the stem cells responded with a substantial impedance increase. At the same time, most of the already fully differentiated osteoblasts showed no significant impedance alteration after supplementation with the osteogenic differentiation medium. Further, medium changes caused short-term impedance alterations due to the small temperature fluctuations.