LAUSR

Enthalpy-driven ligands are ideal probes for biomedical applications because of the formation of more bonds between the ligand and target, compared to entropy-driven ligands with similar Gibbs free energy changes. However, there has been a lack of direct strategy for identifying enthalpy-driven ligands. Here, a Molecular Crowding SELEX strategy for discovering enthalpy-driven aptamers was developed to identify aptamers with high affinity and selectivity. Three aptamers were successfully evolved against a tumor biomarker and all proved to be enthalpy-driven, establishing the feasibility of Molecular Crowding SELEX. Further comparison of aptamers evolved from conventional SELEX and Molecular Crowding SELEX (SYL-H2C) revealed much higher affinity of SYL-H2C. With its improved thermodynamic properties, the enthalpy-driven SYL-H2C ap-tamer was able to detect circulating tumor cells in cancer samples with excellent detection accuracy (10/10). The proposed molecular crowding screening strategy offers a promising direction for discovering robust binding ligands for a great variety of biomedical applications.