Direct electrochemical sensor for label-free DNA detection based on zero current potentiometry

A direct electrochemical DNA biosensor based on zero current potentiometry was fabricated by immobilization of ssDNA onto gold nanoparticles (AuNPs) coated pencil graphite electrode (PGE). One ssDNA/AuNPs/PGE was connected in series between clips of working and counter electrodes of a potentiostat , and then immersed into the solution together with a reference electrode , establishing a novel DNA biosensor for specific DNA detection. The variation of zero current potential difference (Δ E zcp ) before and after hybridization of the self-assembled probe DNA with the target DNA was used as a signal to characterize and quantify the target DNA sequence . The whole DNA biosensor fabrication process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy with the use of ferricyanide as an electrochemical redox indicator . Under the optimized conditions, Δ E zcp was linear with the concentrations of the complementary target DNA in the range from 10   nM to 1   μM, with a detection limit of 6.9   nM. The DNA biosensor showed a good reproducibility and selectivity . Prepared DNA biosensor is facile and sensitive, and it eliminates the need of using exogenous reagents to monitor the oligonucleotides hybridization.