Scanning electrochemical microscopy of DNA monolayers

Scanning Electrochemical Microscopy (SECM), employing electrocatalytic reduction of ferricyanide mediated by the redox intercalators, Methylene Blue or Nile Blue, affixed at specific locations within DNA films self-assembled on gold electrodes, is used for detection of abasic sites within ds-DNA and for sequence-specific detection of TATA-binding protein. The inherent differences in catalytic tip currents involving ferricyanide and Methylene Blue are used to distinguish monolayer domains containing native ds-DNA versus ds-DNA containing abasic sites within the micron-level lateral spatial resolution of SECM. The catalytic cycle involving ferricyanide and Nile Blue covalently affixed at discrete sites within DNA films allows sequence-specific and localized detection of TATA-binding protein, a eukaryotic transcription factor which severely distorts DNA upon binding. These experimental results underline the utility of DNA-modified electrodes as convenient platforms for SECM detection schemes that take advantage of efficient, intercalator-mediated, charge transfer through DNA