This study demonstrates the rapid selection of RNA aptamers that can target various small molecules through a newly established automated capture-systematic evolution of ligands by exponential enrichment technique. Throughout the study, this method is applied to aptamer selection for several small molecules, resulting in aptamers that bind with high specificity. The affinity of these aptamers is assessed using fluorescence polarization assays and isothermal calorimetry.

Due to their small size, stability, and cost-effectiveness compared to antibodies, aptamers developed by systematic evolution of ligands by exponential enrichment (SELEX) are promising candidates for the detection of small molecules. In SELEX, a small target molecule is usually covalently immobilized on a surface to separate bound from unbound nucleic acid sequences. However, this immobilization alters the molecule, that is, additional chemical entities are added and the electron distribution is altered, compromising the enrichment properties. To overcome this problem, a capture SELEX method has been successfully developed in which the RNA or DNA libraries are bound to a surface via a complementary oligodeoxynucleotide, and the soluble ligand is used to capture nucleic acids that bind to it from that surface. Herein, the development of an automated version of the capture SELEX method for the identification of RNA aptamers that bind small molecules is described. This method is fully automated and performs up to 12 iterative selection cycles without manual interference in 72 h. The approach is therefore suitable as rapid route to aptamers and enables resource-efficient test selections to assess “aptamerogenicity” of a target.