Gang Liang

Impedimetric DNA sensor for detection of Hg2+ and Pb2+

An electrochemical DNA sensor based on DNA conformational changes for simultaneous detection of Hg2+ and Pb2+ was reported. The sensor was consisted of a probe strand (DNA), a Pb2+-specific DNAzyme, and a substrate strand contains mercury-specific oligonucleotide (MSO). When Hg2+ and Pb2+ interacted with DNA, the induced conformational changes were tracked by electrochemical impedance spectroscopy (EIS), which led to a decreased RCT. The RCT difference (ΔRCT) was applied to selectively detect Hg2+ and Pb2+ with detection limit of 1 pM and 0.1 pM, respectively. Through using masking agents, such as cysteine (masking Hg2+) and G-DNA (CTG-GGA-GGG-AGG-GAG-GGA) (masking Pb2+), Hg2+ and Pb2+ were simultaneously detected in buffer solution, human serum and river water, respectively.

Highly sensitive detection of α-naphthol based on G-DNA modified gold electrode by electrochemical impedance spectroscopy

A highly sensitive, reusable G-rich DNA sensor was reported for the detection of α-naphthol by electrochemical impedance spectroscopy (EIS). Specifically, a single-stranded G-rich DNA was self-assembled on the electrode and transformed into K(+)-stabilized G-quadruplex, which could catalyze H2O2-mediated oxidation of α-naphthol (with hemin as a cofactor) to 1, 4-naphthoquinone precipitated on the DNA films. Due to the insolubility of 1, 4-naphthoquinone, the charge transfer resistance (RCT) was increased to maximum within 15 min. Depending on the difference in charge transfer resistance change (ΔRCT), the α-naphthol could be detected with the detection limit of 0.1 nM in Tris-ClO4 buffer solution (20mM, pH=7.4). Moreover, the sensor demonstrated a high selectivity over other selected phenolic compounds. The performance of the sensor in the real lake water was also explored with the detection limit of 0.8 nM. Finally, the regeneration of the sensor was investigated, which allowed for reuse more than 4 cycles with a mean recovery of 94% of the original signal.