Studies on interaction of porphyrin and its complexes with DNA at interface on gold electrode modified by thiol-porphyrin self-assembled monolayer

The interaction of 5-p-(mercaptopropyloxy)-phenyl]-10, 15, 20-triphenylporphyrin (H₂MPTPP) and its metalloporphyrin (Co, Ni-MPTPP) with calf thymus deoxyribonucleic acid (DNA) has been studied on gold electrode modified by thiol-porphyrin self-assembled monolayer (SAM). The mode and characteristics of their interaction with DNA have been studied by cyclic voltammetry, scanning electrochemical microscope (SECM), and alternating current (AC) impedance. Some electrochemical parameters have been determined, i.e., apparent heterogeneous reaction rate constant (k _eff from SECM and k _f from AC impedance) and the hindrance (B) of electrode. K₃Fe(CN)₆] was used as probe to obtain some electrochemical information of electrode interface. SECM images obtained from interface on SAM interacted with DNA showed very good resolution with different topography. Based on a comparison with the results from experiments, a reasonable agreement between SECM and AC impedance can be obtained, which means a conjunction of them. It is proposed to be electrostatic interaction of H₂MPTPP, Co-MPTPP and Ni-MPTPP with DNA, and the attractive force between porphyrins and DNA follows the order Ni-MPTPP > Co-MPTPP > H₂MPTPP.