Cyclic ferrocenylnaphthalene diimides as a probe for electrochemical telomerase assay

Novel cyclic naphthalene diimides, 8 and 12, containing ferrocene in the cyclic linker were synthesized as G-quartet (G4) specific electrochemical ligands via the reaction of 1,1'-ferrocenedipropanoic acid and the terminal amine moieties of naphthalene diimides with varying linker lengths. The redox potentials of 8 and 12 were ca. 0.2 V (vs. Ag/AgCl), and the background current in an electrolyte was successfully suppressed. Both 8 and 12 bound to TA-core, representing human telomere G4, with K = 4.4 and 38 × 10⁵ M^-1, respectively. The current response of 12 to an electrode immobilized with G4 was the highest among the acyclic derivatives, suggesting its potential application in electrochemical telomerase assays.