Actually, in a feeder-based culture, dispase (2 mg/mL) should take about 15-25 min to work at 37 degrees C. Two to three minutes' dissociation time would apply to feeder-free cultures. Dispase is a more aggressive enzyme, so it works faster, but that also means that when the PSC clumps are harvested, they are more sensitive to being broken apart by trituration. Once the clumps are harvested, they should be pipetted up and down a few times to break up the clumps to the appropriate size. If the cells are harvested with collagenase type IV, they have to be pipetted more times because the clumps are harder to break up, but this means that there is less likelihood to break up the clumps into pieces that are too small. If the cells are harvested with dispase, they have to be pipetted fewer times, and care has to be taken to ensure that the clumps are not broken too much. Either enzyme is fine to use, and if you have enough experience, you may prefer to use dispase to save time. But for a less experienced user, we recommend using collagenase type IV as it is safer and you are less likely to ruin your culture by over-triturating.
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