Electrical control over antibody–antigen binding

We show that the binding of an antibody to its antigen can be controlled electrically in a reversible manner. The antibody–antigen interaction is monitored by an electrochemical surface plasmon resonance (SPR) instrument. The antigen is immobilized on the working electrode while the antibody is injected in solution. After binding, application of a bias more negative than −0.5 V versus Ag/AgCl reference electrode causes rapid detachment of the antibody molecules from the antigens. Removal of the applied voltage restores the antigen ability to bind antibody molecules. The mechanism underlying the reported phenomenon is traced to deprotonation of positively charged amino acids, particularly lysine, by hydroxyl ions generated at the electrode/solution interface. Our finding facilitates exquisite control over one of the main interactions responsible for biomolecular recognition, namely, the attraction between positively and negatively charged residues. Potential applications to diagnostics and sensing are briefly discussed.