Ferrocenyl naphthalene diimide can bind to DNA·RNA hetero duplex: potential use in an electrochemical detection of mRNA expression

The novel ferrocenyl naphthalene diimide derivative 1 was synthesized by the condensation reaction between ferroceneacetic acid and terminal amino moieties of two imide substituents of naphthalene diimide. Stopped-flow analysis of the ligand 1 and DNA interaction revealed the following results: (i) the ligand binds to double stranded DNA more strongly than to single stranded DNA; (ii) the ligand does not have a bias against DNA sequence; (iii) the ligand can bind to the DNA·RNA hetero duplex more strongly than to the DNA·DNA duplex. These properties of 1 make it a suitable ligand for analysis of not only DNA but RNA. In fact, a current due to 1 was observed at 269 mV in the differential pulse voltammetric analysis of dA20-immobilized electrode in an electrolyte containing 1. The current increased markedly upon hybridization with polyU, whereas no current increase was obtained for polyA. Since the DNA·RNA hetero duplex is formed between sample RNA and DNA on the electrode, 1 may be used for the electrochemical detection of mRNA expression.