Fluorescein-labeled “arch-like” DNA probes for electrochemical detection of DNA on gold nanoparticle-modified gold electrodes

In the present study, a gold nanoparticle-modified gold electrode (nanogold electrode) was used to develop a novel fluorescein electrochemical DNA biosensor based on a target-induced conformational change. The nanogold electrode was obtained by electrodepositing gold nanoparticles onto a bare gold electrode. This modification not only immobilized probe oligonucleotides, but also adsorbed fluorescein onto the surface of the gold nanoparticles to form an “arch-like” structure. This article compares the electrochemical signal changes caused by the hybridization of “arch-like” DNA on nanogold electrode and linear DNA on bare gold electrode. The results showed that the adsorption effect of nanogold can enhance the sensitivity of the sensor. The linear range of target ssDNA is from 2.0 × 10⁻⁹ M to 2.0 × 10⁻⁸ M with a correlation coefficient of 0.9956 and detection limit (3σ) of 7.10 × 10⁻¹⁰ M. Additionally, the specificity and hybridization response of this simple sensor were investigated.