Cobalt complex plays a dual role in the construction of E-DNA sensor

► An electrochemical DNA sensor was constructed base on a new design concept. ► [Co(phen)2(L-Cys)] were immobilized on the gold electrode surface by two steps. ► [Co(phen)2(L-Cys)] act as anchors for probe DNA immobilization and also as redox indicators. ► The designed DNA sensor can be used for one-base mismatch discrimination and detection of the specific oligonucleotide sequence of Hepatitis C virus subtype 1b from 1 pM to 1 μM.