To remove cell debris from the FluidFM probe, a cleaning step is necessary between measurements of adherent mammalian cells. We highly recommend to wash the FluidFM probe after each (single) mammalian cell, as in this sequence: measure cell 1 - wash - measure cell 2 - wash - ...
No washing is needed for non- and lightly-adherent microorganisms such as yeast, protozoa and certain bacteria.
The following cleaning solutions are recommended for mammalian cell measurements:
Bleach (5% Sodium Hypochlorite): Bleach cleans the probe very fast and thoroughly. It has to be handled with care as it can corrode your equipment.
Terg-a-zyme: Enzyme-based cleaning solution. Slower than bleach, but gentle to the equipment.
The cleaning can be performed as follows: Cleaning solution - water - water - medium - back to sample
Leave the probe on the system: Simply exchange the sample dish with a washing dish and dip the probe while mounted to the system. This leads to significantly higher throughput than if the probe is unmounted and washed separately.
Cleaning dip: 5 sec to 60 sec in bleach, or at least 30 sec in Terg-a-zyme. Avoid bleach contact with the FluidFM pneumatic connector, as it can degrade the O-Ring, causing leaks.
If you suspect the probe has cell debris inside, you can intake some bleach with -50 mbar for 10s, then push out with +100 mbar for 10s.
Water dip 2x: Dip the probe twice in filtered ddH20 water. In two different dishes to remove any bleach.
Medium dip: Dip the probe in medium before going back to the sample with the cells. This avoids an osmotic shock.
We do not advise to clean when a coating has been applied to the probe. Either use a coating protocol or a washing protocol - not both.
While bleach cleaning will also work on coated probes, it will degrade the coating which can result in an unsuitable surface chemistry. E.g. the degraded coating will be sticky or clog up the probe, hence be harmful rather than helpful for the experiment.