Selection, characterization and the application of the RNA aptamer in the capture assay of Erythropoietin (EPO)

Erythropoietin (EPO) is an erythropoietic growth factor that induces the production of red blood cells. However, this protein is also extensively manipulated by athletes to illegally enhance their performance, a phenomenon known as doping. Generating a feasible molecular recognition element against EPO would be beneficial for doping detection. In this study, we have successfully isolated an RNA aptamer against EPO using SELEX. Termed REPORA-6, this RNA aptamer has an estimated binding affinity of 25 ± 1 nM. REPORA-6 RNA aptamer also retains its binding against degylosylated EPO and interacts with both Epoetin Beta and Mircera, suggesting that this aptamer binds to the protein domain of the recombinant EPO despite the variation in the glycosylation side chains. Ethylnitrosourea mapping, in-line probing assay and docking revealed important nucleotides for interaction with EPO. Capitalizing these findings, a truncated RNA aptamer was derived, REPORA-6b RNA. This aptamer has an improved binding affinity of 22 ± 2 nM. We have incorporated this aptamer into a capture assay and found out that the limit of detection achieved was 19.6 pM. REPORA-6b RNA has an immense potential in applications involving doping detection of EPO.