Electrochemical Biosensor Assay of the Interaction between [PtCln(NH3)4-n](2-n) (n=0-4) Complexes and ds-DNA

We report on the results of electrochemical DNA biosensor assay of the interaction between double-stranded DNA (dsDNA) and a series of six neutral, anionic or cationic Pt complexes of the general formula [PtCln(NH3)(4-n)]((2-n)) [n = 4, 1; n = 3, 2; n = 2, isomers cisplatin (3) and transplatin (4); n = 1, 5; n = 0, 6]. The ability of the electrophilic Pt-II agents generated in solution to interact with DNA, and hence to form Pt-DNA adducts, was measured as a function of the decrease in the guanine oxidation signal recorded on a screen-printed electrode by using square wave voltammetry. Hydrolysis of the platinum complexes was studied by using time-resolved RP-HPLC and conductivity measurements to determine the aquation rate, which modulates the formation of the electrophilic agent prone to quickly interact with DNA. Our findings indicate that, if time is allowed for sufficient hydrolysis to occur, the interaction of these PtII complexes with ds-DNA follows the order 2 > 1 > 3 approximate to 4 > 5 >> 6.