Photocontrollable DNA hybridization on reversibly photoresponsive surfaces

Abstract

Herein we have developed a new DNA sensor which displays the possibility of photocontrollable DNA hybridization by changing the orientation of azobenzene layers on the silicon wafer surface. Basically, the trans-form layers present a coordinating surface, the “on” state that can be switched “off” in the cis-form. Water contact angles of the prepared substrates have been measured after UV and visible light irradiation to understand the switchable properties of each form of the surface. The photocontrollable DNA chip was prepared using Cy3 labeled amino terminated single stranded probe-DNA (Cy3–ssDNA–NH₂) molecules which were immobilized onto a COOH-terminated photoswitchable surface. The optimum hybridization conditions were performed with Cy5 labeled complementary-DNA (Cy5–ssDNA) using fluorescence microscopy. Furthermore, the photocontrolling of DNA hybridization onto prepared surfaces was verified by confocal microscopy before and after light irradiation. The percentage hybridization ratios from confocal microscopy for on and off positions of the DNA sensor were calculated to be 61% and 5%, respectively. These results show that the prepared surfaces can be reversibly photoswitched between two states efficiently. As a result we believe that the results demonstrate the great potential to control DNA hybridization within and on the surfaces of molecular constructs using light.