Selective release of DNA from the surface of indium-tin oxide thin electrode films using thiol-disulfide exchange chemistry.

A new challenge in biointerfacial science is the development of dynamic surfaces with the ability to adjust and tune the chemical functionality at the interface between the biological and nonbiological entities. In this paper we describe fabrication of indium-tin oxide (ITO) electrodes and the design of a ligand that can be switched to enable selectively controlled interactions with DNA. Tailoring the surface composition of the ITO electrode to optimize its optical and electrical properties was also studied. The surface attachment chemistry investigated utilizes thiol-disulfide exchange chemistry. This chemistry involved the covalent attachment of a thiol-functionalized silane anchor to a hydroxyl-activated ITO electrode surface. Subsequent reaction with 2-(2-pyridinyldithio)ethanamine hydrochloride formed the disulfide bridge and provided the terminal amine group, which facilitates addition of a cross-linker. DNA was then covalently bound to the cross-linker, and hybridization with the complementary Cy3-labeled target DNA was achieved. Selective release of the attached DNA was demonstrated by both chemical and electrical reduction of the disulfide bond. The surface chemistry was then recycled, and rehybridization of the target DNA was achieved. The ability to control specific release of biomolecules has applications for the development of novel biosensor platforms and a range of medical devices.