Perez-Ruiz et al. (2014) Anal. Chem. 86, 3084−3091
Aptamers are emerging as powerful synthetic bioreceptors for fundamental research, diagnostics, and therapeutics. For further advances, it is important to gain a better understanding of how aptamers interact with their targets. In this work, we have used magnetic force-induced dissociation experiments to study the dissociation process of two different aptamer–protein complexes, namely for hIgE and Ara h 1. The measurements show that both complexes exhibit dissociation with two distinct regimes: the dissociation rate depends weakly on the applied force at high forces but depends stronger on force at low forces. We attribute these observations to the existence of at least one intermediate state and at least two energy barriers in the aptamer–protein interaction. The measured spontaneous dissociation rate constants were validated with SPR using both Biacore and fiber optic technology. This work demonstrates the potential of the magnetic force-induced dissociation approach for an in-depth study of the dissociation kinetics of aptamer–protein bonds, which is not possible with SPR technologies. The results will help in the development and expansion of aptamers as bioaffinity probes.