I know that plasma is 'low' in platelets, but there are still some in there, as I see clots in the plasma sometimes when I thaw them. Is there any way of removing them completely? Or at least close?

Dear Jocelyn,

The best way to reduce the content of platelets in plasma would be either to collect plasma by apheresis (if you have IRB and contacts with a blood establishment) or to centrifuge the plasma from whole blood at about 1000 x g for 10 min at room temperature to pellet the platelets before freezing the plasma. You could also consider to have a step of leucoreduction that can also contribute to some removal of the platelets before plasma freezing. If you freeze the plasma without good removal of the platelets, platelets will be broken and will activate at the time of thawing, while also releasing their content (growth factors, cytokines, coagulation factors, etc.) into the plasma. The clot you see may be associated to the presence of residual platelets but may also be linked to unappropriate anticoagulation of blood or plasma prior to freezing. Another thing you can due to ensure removal of the platelets is to try a filtration on a 1um filter. As platelets are 2-3 um, they would be removed. Again, I recommend doing this before freezing, to get a clean plasma. I hope this helps! Kind regards, Thierry

Thank you Thierry. Do you know which company makes a 1um filter that would remove them passively? Most of the ones I have seen online require centrifugation, and I'm not certain that that wouldn't destroy the platelets, and cause them to release their contents (which is what I'm trying to avoid). Thanks again!

You may look at filters from Pall, Millipore, Cuno/3M or Sartorius for instance. It may be a good idea to use a filter that has a graduation in the pore size to facilitate the filtration. It depends of the total volume of plasma you want to filter and recover. Best, Thierry