Highly Sensitive Electrochemical Sensor for Mercury(II) Ions by Using a Mercury-Specific Oligonucleotide Probe and Gold Nanoparticle-Based Amplification

Abstract

We report a highly sensitive electrochemical sensor for the detection of Hg(2+) ions in aqueous solution by using a thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe and gold nanoparticles (Au NPs)-based signal amplification. The MSO probe contains seven thymine bases at both ends and a "mute" spacer in the middle, which, in the presence of Hg(2+), forms a hairpin structure via the Hg(2+)-mediated coordination of T-Hg(2+)-T base pairs. The thiolated MSO probe is immobilized on Au electrodes to capture free Hg(2+) in aqueous media, and the MSO-bound Hg(2+) can be electrochemically reduced to Hg(+), which provides a readout signal for quantitative detection of Hg(2+). This direct immobilization strategy leads to a detection limit of 1 microM. In order to improve the sensitivity, MSO probe-modified Au NPs are employed to amplify the electrochemical signals. Au NPs are comodified with the MSO probe and a linking probe that is complementary to a capture DNA probe immobilized on gold electrodes. We demonstrated that this Au NPs-based sensing strategy brings about an amplification factor of more than 3 orders of magnitude, leading to a limit of detection of 0.5 nM (100 ppt), which satisfactorily meets the sensitivity requirement of U.S. Environmental Protection Agency (EPA). This Au NPs-based Hg(2+) sensor also exhibits excellent selectivity over a spectrum of interference metal ions. Considering the high sensitivity and selectivity of this sensor, as well as the cost-effective and portable features of electrochemical techniques, we expect this Au NPs amplified electrochemical sensor will be a promising candidate for field detection of environmentally toxic mercury.

Application of Starch-Stabilized Silver Nanoparticles as a Colorimetric Sensor for Mercury(II) in 0.005 mol/L Nitric Acid

“…In spite of being very sensitive and precise for Hg determination, these methods often require a time-consuming sample preparation step as well as expensive instrumentation. Various colorimetric assays (based on the use of sensitive chromophores or fluorophores [8][9][10][11], polymers [12,13], oligonucleotides [14,15], DNA [16,17], and metal nanoparticles [18][19][20]) have been developed and reported in the literature as convenient and simple alternative methods for the detection of target analytes without the requirement of sophisticated apparatus.…”

An Ultrasensitive and Selective Probe for Ratiometric Determination and Removal of Hg2+

“…4b). The detection limit was achieved down to 0.12 nM, which is much lower than the standard values required by WHO and EPA, and those previously reported (Table S1, ESM) [33][34][35][36]. The sensitivity was improved to be 1.27 A cm -2 M -1 , *5.3-fold greater than that obtained at the electrode without modification of small AuNSs (Fig.…”

Highly sensitive potentiometric sensor for detection of mercury in Cl−-rich samples

“…Currently available detection methods for mercury include cold vapor atomic absorption spectrometry [2,3], atomic fluorescence spectrometry [4,5], and inductively coupled plasma mass spectrometry [6]. Although these approaches are well established, they require expensive apparatus and complicated sample pretreatment [7,8].…”