Selection and identification of diethylstilbestrol-specific aptamers based on magnetic-bead SELEX

Diethylstilbestrol (DES) is a synthetic estrogen with significant public health impact. Developing recognition elements of DES is of great significance for the establishment of DES detection methods. Aptamers are short and single-stranded (ss) oligonucleotides able to recognize target molecules with high affinity. Currently, a variety of estrogen specific aptamers were screened and used for the design of detection probes and the establishment of rapid detection methods. In order to obtain aptamer of DES, magnetic-bead SELEX was applied. In this work, DES was immobilized on the magnetic beads, and the nucleotide chains that bind to DES were obtained by magnetic separation. Negative and reverse screening processes were designed to enhance the specificity and affinity of the selected aptamers. After 11 rounds of screening, multiple nucleic acid chains were obtained by SELEX and the chains was sequenced. Two aptamers with better affinity were obtained and the value of the dissociation constant (Kd) were calculated to be 98.5 nM and 126.3 nM, respectively. The specificity of the aptamer candidate was initially determined by gold nanoparticle (Au-NP) colorimetric assay and the potential application of the aptamers was also investigated by this method.