Rapid Nuclease-Assisted Selection of High-Affinity Small-Molecule Aptamers

Aptamers are nucleic acid bioreceptors that have been widely utilized for a variety of biosensing applications, including in vivo detection methods that would not be possible with antibody-based systems. However, it remains challenging to generate high-quality aptamers for small molecule targets, particularly for use under physiological conditions. We present a highly effective aptamer selection technology for small-molecule targets that utilizes the nuclease EcoRI to remove nonspecific or weakly binding sequences in solution phase, rapidly enriching high-affinity target binders within just a few rounds of selection. As proof-of-concept, we used our nuclease-assisted SELEX (NA-SELEX) method to isolate aptamers for a synthetic cannabinoid, AB-FUBINACA. Within five rounds, we identified two highly specific aptamers that exhibit nanomolar affinity at physiological temperature. We also demonstrate the robustness and reproducibility of NA-SELEX by performing the same selection experiment with fresh reagents and libraries, obtaining the same two aptamers as well as two other high-quality aptamer candidates. Finally, we compare NA-SELEX against a conventional library-immobilized SELEX screen for AB-FUBINACA using the same screening conditions, identifying aptamers with 25-100-fold weaker affinity after 11 rounds of selection. NA-SELEX therefore could be an effective selection method for the isolation of high-quality aptamers for small-molecule targets.