Colorimetric multiplexed analysis of mercury and silver ions by using a unimolecular DNA probe and unmodified gold nanoparticles

Abstract

In this paper, a colorimetric assay for multiplexed analysis of mercury and silver ions was demonstrated by using a rationally designed unimolecular multifunctional DNA probe (UMDP) as sensing element, and unmodified gold nanoparticles (AuNPs) as color-reporting probes. The UMDP had a random coil structure that changed into two different hairpin-like structures with a T-Hg 2+ -T or C-Ag + -C basepairing built-in the stem upon binding Hg 2+ or Ag + ions, respectively. As a result, the conformation changes facilitated the salt-induced AuNPs aggregation, leading red-to-blue color change with a red shift of the plasmon band in the UV-visible absorption spectrum. Thus, the change in absorption intensity allowed the multiplexed detection of Hg 2+ and Ag + ions. The sensing system could detect as low as 2.5 Â 10 À7 M Hg 2+ ions and 5 Â 10 À7 M Ag + ions. Both the color and absorption changes of the system were selective for Hg 2+ and Ag + ions, which met the selective requirements for biomedical and environmental application. Moreover, the two target ions were simply distinguished by using EDTA, Hg 2+ ions could not cause AuNPs aggregation while Ag + ions still could in the presence of EDTA. Then, the colorimetric response of the two target ions in spiked lake water and tap water were tested, respectively. We expect this simple and cost-effective method to have wide-ranging applications for monitoring water quality in the developing region.

Colorimetric detection of mercury ion based on unmodified gold nanoparticles and target-triggered hybridization chain reaction amplification

“…According to the 3d rule [30], the detection limit of this method was estimated to be 30 nM. It was about 1-2 orders of magnitudes lower than that of previous unmodified AuNPs-based colorimetric methods [15][16][17][18][19].…”

“…Up to now, several conventional methods have been developed, such as cold vapor atomic fluorescence spectrometry [3], inductively coupled plasma mass spectrometry [4,5], surface enhanced Raman scattering [1,6], electrochemical methods [7,8], fluorescent methods [9][10][11] and colorimetric methods [12][13][14][15][16][17][18][19][20][21]. Among these methods, gold nanoparticles (AuNPs)-based colorimetric assay has drawn great attention [12][13][14][15][16][17][18][19][20][21][22][23], since it is a simple, fast and efficient method for determining targets with the aid of obvious color change. Since Ono and co-workers described the stabilization of DNA duplexes via the formation of thymineHg 2+ -thymine (T-Hg 2+ -T) [24], a variety of colorimetric assays based on DNA and AuNPs for the determination of Hg 2+ have been developed [12][13][14][15][16][17][18][19].…”

“…Among these methods, gold nanoparticles (AuNPs)-based colorimetric assay has drawn great attention [12][13][14][15][16][17][18][19][20][21][22][23], since it is a simple, fast and efficient method for determining targets with the aid of obvious color change. Since Ono and co-workers described the stabilization of DNA duplexes via the formation of thymineHg 2+ -thymine (T-Hg 2+ -T) [24], a variety of colorimetric assays based on DNA and AuNPs for the determination of Hg 2+ have been developed [12][13][14][15][16][17][18][19]. For colorimetric detection of Hg 2+ , there are two major classes of AuNP-based assays.…”

“…In this strategy, DNAfunctionalized AuNPs were linked by the formation of T-Hg 2+ -T complex, and the linked AuNPs would aggregate with a red-to-blue color variation. The other one relied on the difference in binding properties of single-stranded DNA and double-stranded DNA toward unmodified AuNPs [15][16][17][18][19]. Single-stranded DNA could stabilize AuNPs, and salt-induced AuNPs aggregation could be effectively prevented.…”

“…The strategy based on unmodified AuNPs suffers from the constraint of limited sensitivity. For example, the detection limit of most unmodified AuNPs-based colorimetric assays for Hg 2+ is above 200 nM [15][16][17][18][19]. Thus, constructing a simple colorimetric method based on unmodified AuNPs for high sensitive analysis of Hg 2+ is particularly intriguing.…”