DNA-binding studies of complex of Pt(bpy)(pip)]2+and [Pt(bpy) (hpip)]2+by electrochemical methods: development of an electrochemical DNA biosensor

The electrochemical properties and deoxyribonucleic acid (DNA)- binding affinities of [Pt(bpy)(pip)](2+) (1) and [Pt(bpy)(hpip)](2+) (2) in homogeneous solution were studied. These platinum(II) complexes have shown to interact with DNA via intercalation mode. For the cyclic voltammetry (CV) experiments, since 2 leads to a larger decrease in the peak current and more positive shift in the peak potential in comparison to the analogous compound of 1, it could be noted that 2 exhibits higher intercalative binding affinity against DNA. The effect of ionic strength and competitive binding studies in the presence of ethidium bromide (EB) were also investigated by CV. Electrochemical DNA biosensor based on the immobilization of double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) probe and 1 and 2 onto electrochemically activated glassy carbon (GC) electrode was also achieved. The immobilization of dsDNA and ssDNA probe and hybridization were monitored by differential pulse voltammetry using 1 and 2 as hybridization indicators. It was found that both platinum complexes show larger and more evident electrochemical signals for the hybridized probe dsDNA with respect to ssDNA immobilized on GC electrode. The developed electrochemical DNA biosensor showed good selectivity and analytical performance for the complementary target nucleotide with limit of detection of 1.23 x 10(-8) and 8.05 x 10(-9) mol L-1 and limit of quantification of 4.06 x 10(-7) and 2.66 x 10(-8) for 1 and 2, respectively.