Combined Target-Immobilized and Library-Immobilized SELEX for Selecting High-Affinity α-Amanitin Aptamers

Deaths from the accidental ingestion of poisonous Amanita mushrooms occur every year due to the lack of a specific antidote against α-amanitin poisoning. Intervention and treatment can be promptly carried out to avoid serious consequences when the toxin can be effectively detected in whole blood before liver toxicity develops. Aptamers are molecular recognition units similar to antibodies, capable of specifically recognizing and detecting small molecules such as α-amanitin for which monoclonal antibodies are difficult to prepare. However, α-amanitin has a small molecular size and limited binding sites, which bring difficulties to aptamer selection. Moreover, achieving highly specific detection of α-amanitin in whole blood remains challenging due to the presence of potentially interfering components, such as human serum albumin (HSA). For these problems, we propose an aptamer selection method for small-molecule target α-amanitin, combining target-immobilized and library-immobilized SELEX to select high-affinity aptamers. To exclude HSA interference, counter-selection was introduced to remove HSA-bound sequences. Through these strategies, we successfully selected a highly specific α-amanitin aptamer with nanomolar affinity.