To work quickly
during kinetics experiments and to avoid procedural artifacts, e.g.
caused by cell detachment, which could lead to damage or permeabilization
of the cells, it is advisable to grow cells in suspension.
Importantly, the ability of the adherent cells to grow in
suspension should be tested beforehand. The cells are seeded at
1–5 105 cells/ml per well the day before analysis in 24-well
suspension plates (Sarstedt). The next day cell death is induced.
Cell samples from suspension cultures are analyzed at regular
intervals on the flow cytometer. For this, 270 ll of cell suspension
from the 24-well suspension plate is transferred to a 5-ml polypropylene
round bottom tube, and 30 ll of cell impermeant
probe (e.g. PI) is added from a 10 solution (30 lM) prepared
from a 3-mM stock). The laser and detector need to be adapted
according to the excitation and emission properties of the probe.
The flow cytometer is set up for a dot plot with forward and sideward
scatters, both on a linear scale, to determine cell size and
granularity (Fig. 2). PI uptake is detected at 610 nm. To clearly
see the dead cells on the dot plot, PI-positive cells are gated,
e.g. in red. The region of analysis is gated (R1), and gating must
be large enough for measurement of both living and dying cell
populations.