Synthesis of a naphthalene diimide derivative having four ferrocene moieties as an electrochemical DNA hybridization indicator.

A new naphthalene diimide derivative carrying four ferrocene moieties, F(4)ND, was synthesized by the reaction of trimethylammoniummethylferrocene with the terminal amino moieties of two imide substituents of naphthalene diimide. Spectrophotometric binding studies of F(4)ND with calf thymus DNA showed its high affinity of 2 x 10(5) M(-1) in 10 mM MES buffer and 1 mM EDTA (pH 6.25) containing 0.10 M NaCl. The Osteryoung square wave voltammetry (SWV) of a DNA probe-immobilized electrode before and after hybridization with target DNA gave a larger peak current in an electrolyte containing F(4)ND than that containing FND carrying two ferrocene moieties. The current peak difference between mismatched and fully matched DNA was also greater with F(4)ND than that with FND.