9H-Thioxanthen-9-one S,S-dioxide based redox active labels for electrochemical detection of DNA duplexes immobilized on Au electrodes

The reaction of 2-bromomethyl-9H-thioxanthen-9-one with 2-/4-mercaptobenzoic acids led to 2-/4-[(9-oxo-9H-thioxanthen-2-yl)methylthio]benzoic acids. Their further oxidation by H₂O₂ gave the corresponding S,S-dioxides, which were used as redox active modifiers for a model oligonucleotide. Hybridization of the modified oligonucleotide with a complementary oligoprobe immobilized on Au electrode led to formation of the corresponding redox active DNA duplex, which was reliably detected by cyclic voltammetry.