Abstract
A novel dual-signal amplificatory electrochemiluminescence (ECL) deoxyribonucleic acid (DNA) biosensor was designed for the determination of Hg2+. One amplification unit was gold nanoparticles (AuNPs) modified on a glassy carbon electrode, and the other was single-stranded DNA (ssDNA) (with amino at the 3’ terminal and thiol at the 5’ terminal) labeled with a carboxyl-functionalized Ru@SiO2 nanoparticles (Ru1@SiO2) as a nanoprobe. The ECL biosensor was obtained through a strong gold-sulfur bond between Au on AuNPs modified electrode and thiol in the nanoprobe. In the presence of Hg2+, the ECL signal reduced because the T-Hg2+-T existed between the ECL nanoprobe and the complementary DNA (c-DNA), which exhibited a sensing platform for the detection of Hg2+. The results revealed that the reduced ECL intensity was linearly proportional to the logarithm of the Hg2+ concentration in the range of 1.0 pmol L-1-100 nmol L-1 with limit of detection 0.02 pmol L-1. The proposed method was applied for the analysis of Hg2+ in the river water and the results were in good agreement with that obtained by atomic fluorescence spectroscopy.
Highlights
Mercury is one of the most toxic metal pollutants in our environment
A characteristic absorption peak at 260 nm was observed in the spectrum of single-stranded DNA (ssDNA)
This indicates that the T-Hg2+-T reaction were complete when the concentration is 0.8 μmol L-1, so this concentration was chosen in the test
Summary
Mercury is one of the most toxic metal pollutants in our environment. It can accumulate in ecosystems through biological cycles[1] and pose serious problems to the immune system, nervous system, cardiovascular system and reproductive system.[2]. The Ru1@SiO2 nanoparticles were prepared according to the literature reported before.[37] Firstly, cyclohexane, Triton x-100 and 1-hexanol were mixed at a volume ratio of 4.2:1:1, together with 500 μL of ultrapure water, stirred for 30 min. Ru1@SiO2-ssDNA as an ECL probe was synthesized in accordance with a previously described method with some modifications.[38] Firstly, a newly prepared mixed solution containing 5 mg mL-1 NHS and 2 mg mL-1 EDC was added to the Ru1@SiO2 nanoparticles to activate the carboxyl groups in Ru1@SiO2 for 30 min. The amino and thiol-binding ssDNA solution, which was prepared by dissolving 2.0 OD (optical density, about 66 μg) of ssDNA in 1.0 mL of 0.1 mol L-1 PBS (pH 7.0), was added and shaken at low speed for 24 h at room temperature. All experiments were conducted at room temperature (25 ± 1 °C)
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