Tue Jul 12, 2016 9:34 pm by mleipold
Hi William,
I think there are a couple topics here.
1. I haven't seen any evidence that EDTA will rip lanthanide metal ions out of a MAXPAR polymer. In fact, my antibody staining buffer contains 2mM EDTA.
It's not easy for another chelator to pull away a metal ion already chelated, without some kind of denaturant or heat. Even then, it usually takes a stronger chelator (for that metal ion) and/or substantially higher concentrations of the second chelator to ensure that the metal ion doesn't go back in. Dojindo has a nice table of chelator stability constants (attached to this post). If you look at, say, Eu (III): EDTA has a constant of 17.35 while DTPA (in the MAXPAR polymer) has a constant of 22.39. Therefore, it would be difficult for EDTA to rip Eu(III) out of DTPA.
2. Removal of metal ions affecting antibody binding. This can be due to their recognition epitopes requiring a structural metal ion.
For example: DOI: 10.1002/cyto.a.20084
"Calcium chelators caused a dose-dependent decrease in fluorescence intensity, using specific anti-human CD8α mAbs. This phenomenon was not due to CD8 internalization and could be reversed by the addition of calcium ions. In contrast, calcium depletion increased staining intensity with one anti-CD8β mAb."
So, I think ultimately, you're just going to have to test which is better for your purposes and your panel(s). The vast majority of the PBMCs we run are from heparin tubes.
Mike