Immunomagnetic beads-based isolation of erythropoietins from urine and blood for sports anti-doping control.

According to the World Anti-Doping Agency (WADA) technical document for erythropoiesis stimulating agents (ESA) analysis (TD2014EPO), double-blotting of serum/plasma samples is mandatory for all analysis by isoelectric focusing (IEF) and for the confirmation procedures (CP) performed by SDS-PAGE or SAR-PAGE. The goal is to prevent potential cross-reactions of the secondary antibody with remaining proteins in the purified samples. To this end, we have developed an immunopurification method of ESA in serum/plasma samples using a combination of streptavidin-coated immunomagnetic beads and biotinylated anti-EPO polyclonal antibodies. Here we report that this immunomagnetic bead-based purification allows the analysis of serum/plasma samples by single-blotting. Serum and plasma samples, either intact or spiked with different ESAs, were immunopurified and analyzed by single-blotting, after SAR-PAGE or IEF using a cross-reaction minimized secondary antibody coupled to HRP. The results show that when samples are immunopurified according to this strategy, there is no non-specific binding when single-blotting is performed after SAR-PAGE. With IEF, we observe a faint smearing, however, in the pH gradient outside the ESA detection region. These interferences did not alter ESA profiles of spiked urinary samples or of samples received for routine testing. This approach was compared to the MAIIA monoliths purification or to the isolation of ESAs with other combinations of immunomagnetic reagents (ie, anti-Mouse IgG-coated magnetic beads and anti-EPO mAb). The recovery of ESAs was shown to be significant for serum/plasma samples. Our results suggest that single-blotting could be performed on serum/plasma samples without non-specific interferences. Copyright © 2017 John Wiley & Sons, Ltd.