Resolving electrical stimulus triggered molecular binding and force modulation upon thrombin-aptamer biointerface

Abstract

Experimental and computational approaches are utilized to investigate the influence of electrostatic fields on the binding force between human coagulation protein thrombin and its DNA aptamer. The thiolated aptamer was deposited onto gold substrate located in a liquid cell filled with binding buffer, then the thrombin-functionalized atomic force microscopy (AFM) probe was repeatedly brought into contact with the aptamer-coated surface under applied electrical potentials of -100, 0, and 100 mV respectively. Force drops during the pull-off process were measured to determine the unbinding forces between thrombin and aptamer in a range of loading rates spanning from ~3 × 10² to ~1 × 10⁴ pN/s. The results from experiments showed that both of the binding strength and propensity of the complex are drastically diminished under positive electrode potential, whereas there is no influence on the molecular binding from negative electrode potential. We also used a theoretical analysis to explain the nature of electrostatic potential and field inside the aptamer-thrombin layer, which in turn could quantify the influence of the electrostatically repulsive force on a thrombin molecule that promotes dissociation from the aptamer due to positive electrode potential, and achieve good agreement with the experimental results. The study confirms the feasibility of electrostatic modulation upon the binding interaction between thrombin and aptamer, and implicates an underlying application perspective upon nanoscale manipulation of the stimuli responsive biointerface.

Keywords: Analytical modeling; Aptamer; Dynamic force spectroscopy; Electrochemical atomic force microscopy; Electrostatic actuation; Single energy barrier model; Thrombin.