I have several blood samples in EDTA tubes. However, I now require serum from these samples for ELISA.
The protocol I know of involves allowing the blood to clot, and then spinning it down in a centrifuge. Since our blood is in EDTA tubes (I will transfer them to another non-EDTA tube for this), will it still clot sufficiently for us to obtain serum?
The samples can be centrifuged and the separation occurs, but is the resulting serum suitable for ELISA?
I am still learning about this aspect, and so any input would be greatly appreciated.
Hello Leah Maharaj
You will obtain plasma from blood treated with anticoagulant.
EDTA tube is coated with spray dried K2EDTA on its inner wall. EDTA acts as an anticoagulant, binding the calcium ions and interrupting the clotting of the blood sample. If you transfer the blood to another non-EDTA tube the blood will not clot.
Plasma is produced when whole blood is collected in tubes that are treated with EDTA. Blood collected in EDTA tubes is centrifuged (2000 rpm) at 4 degrees C for 20 minutes. After centrifugation using clean pipette technique place 1.0ml of plasma into 1.5ml eppendorf tube and label the eppendorf tube. Freeze immediately in –80-degree freezer. You can use this collected plasma for ELISA.
If you need serum for analysis by ELISA whole blood should be collected into plain red top tube containing a clot activator but no anticoagulants. After collection, the tube is allowed to sit in an upright position at room temperature for 30-45 minutes. After the clot has formed, the tube is centrifuged for 10 minutes at 3400 rpm and the serum is collected.
So, you can use plasma from the collected samples for ELISA.
Best.
Thank you Malcolm Nobre
Unfortunately our samples were initially collected with the intention of DNA isolation from them and so are already stored in anticoagulant. I was hoping for a way to induce coagulation in these samples.
I have seen some threads about the use of CaCl2, but nothing certain as yet
As other said For most Elisa, you can do with plasma also. However to make sure, you can use a random sample with serum and plasma and see there is a difference or not in the results.
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