Electrically controlled DNA adhesion.

The ability to control the interaction of polyelectrolytes, such as DNA or proteins, with charged surfaces is of pivotal importance for a multitude of biotechnological applications. Previously, we measured the desorption forces of single polymers on charged surfaces using an atomic force microscope. Here, we show that the adhesion of DNA on gold electrodes modified with self-assembled monolayers can be biased by the composition of the monolayer and externally controlled by means of the electrode potential. Positive potentials induced DNA adsorption onto OH-terminated electrodes with adhesion forces up to 25 pN (at +0.5 V versus Ag/AgCl), whereas negative potentials suppressed DNA adsorption. The measured contributions of the DNA backbone phosphate charges and the doubly charged terminal phosphate on adsorption agreed with a model based on the Gouy-Chapman theory. Experiments on an NH(2)-terminated electrode revealed a similar force modulation range of the coulomb component of the desorption force. These findings are important for the development of new DNA-based biochips or supramolecular structures.