Integrity and redox properties of homogeneous and heterogeneous DNA films on gold surface probed by cyclic voltammetry

Abstract

5′-thiol-labeled single-stranded DNA (22 mer ssDNA) adsorbed onto the gold surface by both non-specific binding and Au–S linkage, whereas 5′-thiol-labeled double-stranded DNA (22-bp dsDNA) formed a packed layer mainly through the Au–S linkage. The coating of homogeneous ssDNA or dsDNA films or heterogeneous DNA films mixed with n-hexadecyl mercaptan (HDM) on gold surface facilitated the redox reaction of methylene blue (MB). MB binds with ssDNA through electrostatic interaction with the charged backbone and adsorbed through the ssDNA film. MB binds with dsDNA through both electrostatic interaction and intercalation into the dsDNA base pairs and undergoes redox reaction by diffusing through the dsDNA film to the gold surface and/or electron transfer through the DNA helix. The addition of HDM enhanced the integrity and stability upon NaOH treatment for both ssDNA and dsDNA films.