Screening of Aptamer for Human IgG Fc Fragment by Capillary Electrophoresis-Systematic Evolution of Ligands by Exponential Enrichment

Abstract

A DNA aptamer screening method for human immunoglobulin G (IgG) Fc fragments was established based on capillary electrophoresis- systematic evolution of ligands by exponential enrichment (CE-SELEX). The purity, charged properties and non-adsorptivity of the samples of IgG, Fc and Fab were analyzed by capillary zone electrophoresis (CZE), and their affinity with ssDNA libraries was compared. The results showed that IgG formed significant complex with the ssDNA libraries, while Fc and Fab fragments exhibited weak affinity with the ssDNA libraries. Therefore, the use of the Fab fragment as the reverse screening target had no significant effect on the sequence except for the specific binding of Fc. The aptamer screening strategy for Fc fragments was designed. Aptamers (Seq Fc1–3) were obtained under optimized incubation conditions (10 mmol/L Na2HPO4-KH2PO4 (pH 7.17), 0.05 mmol/L Mg2+, incubated at 37 °C for 25 min) by three rounds of CE-SELEX, with KD values of 0.071–0.321 μmol/L, and their affinity and specificity were verified by AuNPs colorimetry assay.