Electrochemical determination of calf thymus DNA on Zr(IV) immobilized on gold–mercaptopropionic-acid self-assembled monolayer

An electrochemical biosensor, constructed by immobilization of Zr(IV) on the topside of gold–mercaptopropionic acid self-assembled monolayer (Au–MPA–Zr SAM), is developed for the sensitive quantification of calf thymus DNA (ct-DNA). The sensor is based on ionic adsorption of ct-DNA from its phosphate backbone onto the Au–MPA–Zr(IV) SAM electrode. Preparation, characterization, and application of the sensor for determination of ct-DNA are described by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Osteryoung square wave voltammetry (OSWV) in the presence of an appropriate redox reaction probe. Parameters influencing the method have been tested. A linear range calibration curve from 1.0 × 10− 4 to 5.0 × 10− 7 g mL− 1 ct-DNA with a detection limit of 9.5 × 10− 8 g mL− 1 and mean of relative standard deviations (R.S.D) of 2.5% for n = 4 at each point was observed in the best conditions by EIS. Regeneration of the surface was carried out successfully by 5 min sonication in 0.1 M KOH solution and then 1 min incubation in 1.0 × 10− 3 M Zr(IV) with a good reproducibility, R.S.D = 1.5% for n = 4 as detected by EIS. The long-term storage stability of the electrode was also studied.