Abstract
We herein report a label-free and non-enzymatic electrochemical sensor for the highly sensitive detection of hydrogen peroxide (H2O2) based on a novel “on-off-on” switch system. In our design, MB was used as an electron mediator to accelerate the electron transfer while AuNPs was used to amplify the electrochemical signal due to its excellent biocompatibility and good conductivity. The “switch-off” state was achieved by introducing the guanine-rich capture probe (CP) and an iridium complex onto the electrode surface to form a hydrophobic layer, which then hinders electron transfer. Upon addition of H2O2, fenton reaction occurs and produces OH• in the presence of Fe2+. The OH• cleaves the CP into DNA fragments, thus resulting in the release of CP and iridium complex from the sensing interface, recovering the electrochemical signal to generate a “switch-on” state. Based on this novel switch system, a detection limit as low as 3.2 pM can be achieved for H2O2 detection. Moreover, satisfactory results were obtained by using this method for the detection of H2O2 in sterilized milk. To the best of our knowledge, this is the first G-quadruplex-based electrochemical sensor using an iridium(III) complex.
Highlights
We report a label-free and non-enzymatic electrochemical sensor for the highly sensitive detection of hydrogen peroxide (H2O2) based on a novel “on-off-on” switch system
Linn and co-workers reported that the antibacterial property of H2O2 is due to DNA damage resulting from Fenton-like reactions in the presence of metal ions such as Fe2+ 17, it was reported that H2O2 could react with certain transition metal ions in low oxidation states and produce HO, which may cleave single-stranded DNA to DNA fragments[18]
To investigate the conductivity of the iridium(III) complex, several modified electrodes were characterized by cyclic voltammetry experiments (CVs) in the presence of 5 mM Fe(CN)63−/4−
Summary
To investigate the conductivity of the iridium(III) complex, several modified electrodes were characterized by cyclic voltammetry experiments (CVs) in the presence of 5 mM Fe(CN)63−/4−. Upon incubation of the sensor with 1.5 nM of H2O2 and Fe2+, a dramatic increase of the peak current was observed (curve e) This increase could be ascribed to the release of iridium(III) complex and CP fragments from the electrode surface after the cleavage of CP by Fenton reaction in the presence of Fe2+ and H2O2. The ΔIof the sensor after the incubation of it with a solution containing both H2O2 and the interferences was almost the same with that of H2O2 (1.5 nM) only Such high selectivity could be attributed to the highly specific cleavage of DNA based on the Fenton reaction in the presence of H2O2 and Fe2+. The sensitive and rapid detection of H2O2 in milk samples is of Figure 4. (A) DPV experiments for H2O2 detection in 10 mM of tris-buffer solution (pH 7.4); (B) Calibration curve for the sensor
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