[en] The authors report on a one-pot approach for synthesizing highly fluorescent protamine-stabilized gold nanoclusters. These are shown to be a viable nanoprobe for selective and sensitive fluorometric determination of lead(II) via quenching of fluorescence via Pb(II)-Au(I) interaction. Under optimized conditions, fluorescence measured at excitation/emission peaks of 300/599 nm drops in the 80 nM–15 μM lead(II) concentration range. The detection limit is 24 nM, and relative standard deviations (for n = 11) at concentrations of 0.10, 4.0 and 15 μM are 1.6, 2.5 and 1.9%, respectively. The relative recoveries of added lead(II) in the water samples ranged from 97.9 ± 2.29% to 101.2 ± 1.83%. .

[en] Various methods have been developed in recent years for the determination of uranyl ion by making use of uranyl-specific DNAzymes. However, many of them suffer from hydrolysis by nucleases present in samples such as body fluids. We report here on an uranyl-specific nuclease-resistant DNA aptamer (UApt) as the recognition element, and how gold nanoparticles (AuNPs) can be used as signal reporters in the respective assay. The presence of uranyl ion leads to a conformational change of UApt, and this results in the dispersion of AuNPs and a decrease in the intensity of resonance light scattering (RLS) at around 573.0 nm. The conformational changes were also studied by polyacrylamide gel electrophoresis, circular dichroism, and UV–vis spectroscopy. The RLS signals are linearly related to the concentration of uranyl ion in the 22 to 550 nM range, with a detection limit of 6.7 nM. This method is more simple and robust than others owing to use of a UApt without a ribonucleotide adenosine. It has been successfully applied to the determination of uranyl ion in real samples. We presume that this method may be extended to the determination of other analytes by making use of the corresponding aptamer for the target. (author)

[en] This work describes a method for the determination of 1-hydroxypyrene (OH-Py) via aggregation-induced quenching of the emission of protamine-coated gold nanoclusters using 9-hydroxyphenanthrene (OH-Phe) as a sensitizer to boost the emission efficiency of nanoprobe. Under optimum conditions, the drop in fluorescence intensity at excitation/emission wavelengths of 300/596 nm is proportional to the concentrations of OH-Py in the range from 1.0 to 65 nM. The relative standard deviations are 4.2, 2.4 and 1.9% (for n = 11) at concentration levels of 8.0, 32 and 48 nM of OH-Py, respectively. The detection limit is 0.3 nM which is much lower than that of some previously reported methods. The recoveries from urine samples spiked with OH-Py ranged between 94.4 and 98.8%.

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[en] The authors describe a strategy for fluorometric determination of lead(II) that is based on the suppression of the surface energy transfer that occurs between acridine orange and gold nanoparticles (AuNPs). As a result, the fluorescence of the system is recovered. Under optimized conditions, the enhancement of fluorescence intensity is related to the concentration of lead(II) in the 44 nM to 4.8 μM range, with a detection limit of 13 nM. The relative standard deviations for 11 determinations at concentrations of 0.386 μM, 1.93 μM and 2.89 μM are 1.02 %, 1.06 % and 1.75 %, respectively. This result suggests that the method can potentially be used to monitor the level of lead(II) in environmental samples. (author)

[en] We report on a sensitive and specific method for the visual and colorimetric detection of 8-hydroxy-2′-deoxyguanosine (8-OHdG) in human urine by using the 8-OHdG-aptamer (Apt) as the recognition element. The aptamer was adsorbed on the surface of gold nanoparticles which enhances their stability. On addition of 8-OHdG, the conformation of the aptamer changes to form a G-quadruplex structure, thereby losing the ability to protect the nanoparticles and causing a color change from red to blue. The conformational changes were also studied by circular dichroism. The response is linearly dependent on the concentration of 8-OHdG in the range from 5.6 to 282 nM, the limit of detection is 1.7 nM, the relative standard deviation ranges from 1.1 to 4.2 % (for n = 6), and the recoveries range from 95.9 to 104.9 %. The method paves the way for visual analysis of samples without the use of costly instruments. (author)

[en] Based on ciprofloxacin (CIP)–Cu(II) system, the novel methods for the detection of metallothioneins (MTs) have been developed by fluorescence (FL) and resonance light scattering (RLS) strategies. The FL strategy avoids the label and derivatization steps in common methods, while the RLS strategy can be applied for determining bio-macromolecules and small molecules without native fluorescence. The response signals linearly correlated with the concentration of MTs over the ranges of 1.03×10⁻⁸–1.23×10⁻⁶ mol L⁻¹ for FL, and of 2.56×10⁻⁷–1.54×10⁻⁶ mol L⁻¹ for RLS. The limits of detection (LOD) are 3.1×10⁻⁹ mol L⁻¹ for FL and 7.68×10⁻⁸ mol L⁻¹ for RLS. This study represents the comparison of these two methods using the same CIP–Cu²⁺–MTs system. They not only allow practical application for MTs detection but also serve as a potential choice for the operators according to their concrete needs. In addition, the mechanisms for FL and RLS enhancement of the system were also discussed. -- Highlights: ► Determination of MTs was developed based on CIP–Cu(II) system by FL and RLS strategies. ► FL strategy provides lower limit of detection and wider linear range, and avoids the label and derivatization steps. ► RLS strategy can be applied for determining bio-macromolecules and small molecules. ► The mechanism of interaction of MTs with CIP–Cu(II) chelate was discussed