Abstract
In this report, we present a method for the detection of Pb2+ based on the different adsorption capacity on the surface of gold nanoparticles (AuNPs) between ssDNA (single-stranded DNA) and G-quartet. In the absence of Pb2+, the DNA oligonucleotides probe, which is guanine-rich ssDNA, can be adsorbed on the surface of AuNPs protecting them from aggregation. After adding Pb2+, the DNA oligonucleotides probe can specifically form compact G-quartet, which can induce the aggregation of unmodified AuNPs, especially after adding NaCl aqueous solution. Consequently, the color turns from red to blue. Pb2+ can be detected by colorimetric response of AuNPs; its detection limit can reach 5 μM only observed by naked eyes. Most metal ions have no interferences, and the interference of Cu2+ can be effectively eliminated by adding cysteine. It provides a simple and effective colorimetric sensor for on-site and real time detection of Pb2+.
Highlights
Lead ion, one of the most toxic heavy metal ions, can have serious effects on the environment and human health
Transmission electron microscopy (TEM) measurements were made on a Hitachi 7500 transmission electron microscope
The rigid G-quartet structure cannot adsorbed on AuNPs to prevent them from aggregation, resulting in an obviously color change from red to blue under high-salt condition
Summary
One of the most toxic heavy metal ions, can have serious effects on the environment and human health. (2015) Colorimetric Detection of Lead Ion Based on Gold Nanoparticles and Lead-Stabilized G-Quartet Formation. DNA molecules are often chosen as recognition element because of its highly stable and specific binding properties. Colorimetric sensor for Pb2+ based on AuNPs and lead-stabilized G-quartet formation [24] relatively has few studies. SsDNA expose nitrogenous base which has high affinity to gold, making themselves adsorb on AuNPs and prevents AuNPs from aggregation, but dsDNA cannot do so because the electrostatic repulsion between their phosphate backbones and negatively charges AuNPs. Interestingly, formation of rigid G-quartet structure reduces the exposure of nitrogenous base and increases surface charge density, disfavoring adsorption on AuNPs. We just make use of this property to design our assay.
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