Base-pair mapping by chemical force microscopy on nucleobase self-assembled monolayers

Self-assembled monolayers (SAMs) of double-chain disulfide derivatives of nucleobases (adenine and thymine) were formed on Au substrates in order to measure complementary hydrogen bonding by chemical force microscopy at the interfaces. Surface plasmon resonance measurements indicated that the formation of the nucleobase SAMs on Au surface was completed within 80 min. To measure adhesion force by atomic force microscopy (AFM), Au-coated AFM tips were modified with the nucleobase SAMs, too. SAM-modified Au substrates micro-patterned on quartz substrates were prepared for adhesion force mapping. The adhesion force between the complementary nucleobases is larger than that of the non-complementary combination. Electrochemical detection using a redox-intercalator was demonstrated for hybridization of single-stranded polynucleic acid with the nucleobase SAMs modified on Au electrodes.