Electrostatic actuation based modulation of polar molecules and associated force interaction studies

Seamless integration of artificial components with biological systems to form an elegant biotic-abiotic interface or smart surface has promising application potential in biomedical engineering. The specific aim of this study is to implement the actuation and modulation of binding behavior between biomolecules under electrostatic stimuli, and investigate the corresponding force interaction between the complementary pairs. The nanofabrication technology was utilized to establish the patterned binding pair of thrombin and DNA aptamer on gold substrate, and different electrical fields were applied on the system to evaluate electrostatic influence. The atomic force microscopy (AFM) surface imaging was then used to explicate the surface height change after the removal of the electrical fields. The height change of the surface showed that positive electrical fields can successfully break the bonds between thrombin and aptamer, while moderate negative electrical fields kept the integral structure. The experimental studies implement the idea of electrostatic actuation and modulation of the complementary pair. The force interaction between the pair was then investigated through AFM based dynamic force spectroscopy (DFS). The open circuit DFS experiment was conducted first to clarify the magnitude of single molecule level force interaction between thrombin and aptamer, and the linear dependence of rupture force on logarithmic loading rate was observed. A single energy barrier model was used to understand the binding physics and kinetics. By fitting the model with experiment data, we could acquire important kinetic parameters toff and xβ. Then in-situ electrochemical atomic force microscopy (ECAFM) based DFS experiment was conducted to investigate the electrostatic influence upon molecular force interaction between thrombin and aptamer. The force interaction difference showed that positive