An electrochemical biosensor for the detection of Pb based on G-quadruplex DNA and gold nanoparticles.

We present a novel simple strategy for the detection of Pb based on G-quadruplex DNA and gold nanoparticles. First, gold nanoparticles were chemically adsorbed onto the surface of a thiol-modified gold electrode. Subsequently, the substrate DNA1 was adsorbed onto the surfaces of the gold nanoparticles via thiol-gold bonds, so that the complementary guanine-rich DNA2 could be hybridized to the gold electrode in sequence. [Ru(NH)] (RuHex), which can be electrostatically adsorbed onto the anionic phosphate of DNA, served as an electrochemical probe. The presence of Pb can induce DNA2 to form a stable G-quadruplex and fall off the gold electrode. The amount of RuHex remaining on the electrode surface was determined by electrochemical chronocoulometry (CC). The prepared biosensor showed high sensitivity for Pb with a linear range with respect to ln(c) from 0.01 to 200 nM and a low detection limit of 0.0042 nM under optimal conditions. Because of the high selectivity of the Pb-specific DNA2, the designed biosensor also showed low false-positive signal rates with other metal ions in real-world examples. Therefore, this strategy has the potential for practical application in environmental monitoring. Graphical abstract ᅟ.