Aptamer based electrostatic-stimuli responsive surfaces for on-demand binding/unbinding of a specific ligand
We report an aptamer functionalized stimuli responsive surface that can controllably switch between binding and releasing its specific ligand under application of electrical stimuli. The high affinity of the aptamer for thrombin makes the surface undergo specific binding while electrostatic field induced actuation of the aptamer is utilized to release the ligand from the surface. Atomic force microscopy (AFM) was utilized to determine the characteristic height change, associated with the specific binding of thrombin, on anti-thrombin aptamer coated surfaces. Subsequently, the thrombin/aptamer complex covered surfaces were subjected to different magnitudes of electrostatic field and height changes on the surface were measured to investigate the influence of an electrical field. Application of positive electrical potential led to the removal of thrombin from the aptamer-covered surface. While under moderate magnitude of negative electrical potential the binding complexes were maintained, increasing the magnitude led to the removal of both molecules from the surface. Molecular dynamics (MD) simulations of the thrombin/aptamer complex under electrostatic fields show that thrombin dissociates from the aptamers in the presence of a positive electric field. These results demonstrate that aptamer covered surfaces undergo specific binding to the ligand and an electrostatic field may be used to disrupt the binding and on-demand release of the ligand from the surface.