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Abstract: In this paper, we have developed a simple and rapid method for the detection of Pb2+ based on the DNA sequence capped CdS quantum dots (QDs). We utilized the designed guanine (G)-rich DNA sequence (PS2.M) as a coating reagent to synthesize the DNA-capped CdS QDs. The designed G-rich DNA sequence PS2.M can bind with hemin to form G-quadruplex/hemin complex with K+, accompanied by the fluorescence quenching of CdS QDs via the photoinduced electron transfer. Pb2+ can induce conformational changes in the G-quadruplex/hemin complex to release the hemin molecules, so the quenched fluorescence of CdS QDs could be recovered. Therefore, the new fluorescent analysis system could be applied for the detection of Pb2+ based on the label-free DNA sequence capped CdS QDs. [Copyright &y& Elsevier]

Abstract: Water-soluble CuInS2 quantum dots (QDs) were directly synthesized in an aqueous solution with mercaptopropionic acid (MPA) as stablizers, and were functionalized using tryptophan molecules to form tryptophan-functionalized CuInS2 QDs (W-CuInS2 QDs) that had a strong fluorescence emission around 689nm. The fluorescence of W-CuInS2 QDs could be quenched by Cu2+ and then the addition of pyrophosphate (PPi) could effectively turn on the quenched fluorescence due to the strong interaction between Cu2+ and PPi. The alkaline phosphatase (ALP) could catalyze the hydrolysis of PPi that would disassemble the complex of PPi–Cu2+–PPi. Therefore, the recovered fluorescence could be quenched again by the addition of ALP. In this paper, we developed a novel near-infrared fluorescence probe for the simple and convenient assay of ALP. [Copyright &y& Elsevier]

Abstract: Water-soluble CuInS2 ternary quantum dots (QDs) capped by mercaptopropionic acid were directly synthesized in aqueous solution. Consequently, the CuInS2 QDs were covalently linked to 3-aminophenyl boronic acid molecules to form the 3-aminophenyl boronic acid-functionalized CuInS2 QDs (F-CuInS2 QDs). The F-CuInS2 QDs had a fairly symmetric fluorescence emission centered at 736nm that was in the near-infrared region (NIR). The F-CuInS2 QDs containing boronic acid functional groups were reactive toward vicinal diols to form five- or six-member cyclic esters in an alkaline aqueous solution. The reaction would cause the fluorescence quenching, which could be used as a fluorescence probe for the determination of dopamine (DA). This assay could also probe other vicinal diols such as catechol, pyrogallol, and gallate, based on the fluorescence quenching of the F-CuInS2 QDs, and this assay was nearly unaffected by other phenol compounds such as phenol, resorcinol, and hydroquinone without the vicinal diol structures. The developed F-CuInS2 QDs were applied to the detection of DA in human serum samples with satisfactory results. Therefore, this experment provided a simple and sensitve NIR fluorescence probe for the detection of DA, catechol, pyrogallol, and gallate. [Copyright &y& Elsevier]

A suspended carbon nanotube (SCNT)-based field effective transistor (SCNT-FET), which was fabricated by utilizing the surface tension of liquid silver to suspend a CNT between two Pd electrodes, was proposed for the detection of DNA hybridization. Benefits from the separation between the CNT and the substrates could be observed; namely, the conductivity of a SCNT-FET was much higher (two orders of magnitude) than that of a FET based on an unsuspended CNT and about 50% sensing surface of CNT was freed from substrate. The Slater-Koster tight-binding method was adopted for geometry optimization and transport property calculation of the SCNT bound with DNA. The result showed that the conductance (G = 1/R) of the SCNT decreased in order with the binding of single-stranded DNA (SSDNA, probe DNA) and double-stranded DNA (DSDNA) and that the ability of DSDNA to weaken the conductivity of the SCNT was several times higher than that of SSDNA. SEM and Raman spectroscopy were used to demonstrate that DNA could be bound successfully onto the SCNT using a 1-pyrenebutanoic acid succinimidyl ester (PBASE) as a linkage. Ultra-high sensitivity detection of DNA [with a limit of detection (LOD) as low as 10 aM] was obtained using such an SCNT-FET, which showed a lower value than that of a previously reported FET DNA biosensor whose sensing materials were in direct contact with the substrate. [ABSTRACT FROM AUTHOR]

Determination of iodide ions has attracted considerable interest due to the importance and urgency. In the current work, we have developed a novel fluorescent and colorimetric platform for simple and selective detection of iodide ions based on the DNA-templated gold/silver nanoclusters (DNA-Au/Ag NCs). The detection system is based on the unique interaction between iodide ions and DNA-Au/Ag NCs, which shows an obvious fluorescence quenching with the addition of iodide ions and a good linear range from 0 to 10 μmol/L for iodide ions. In the mean time, the detection system also exhibits an obvious color change from colorless transparent to purple red with the addition of iodide ions. Furthermore, the proposed system has been successfully applied for determination of iodide ions in real water samples. [ABSTRACT FROM AUTHOR]

This paper reports a novel approach for the simple assays of cell apoptosis using electrochemical technique. In this study, caspase-3 activity, which was detected with differential plus voltammetry (DPV) as an alternative to conventional spectrometry approach, was employed as an indicator of cell apoptosis and, while an acetylated peptide Ac-GGHDEVDHGGGC was used as the blocked substrate. In the presence of casepase-3, the hydrolysis of blocked peptide might release active amine groups, which could covalently conjugate with graphene oxide. Therefore, electroactive methylene blue molecules could be further attached to the electrode surface through π–π stacking and electrostatic interactions. Using this proposed new method, a very sensitive detection of caspase-3 could be achieved with a low detection limit of 0.06 pg/mL, and a new method for sensitive detection of cell apoptosis was developed. Moreover, we have successfully used this new method to detect cell apoptosis with human pulmonary carcinoma A549 cell after apoptosis inducing. [ABSTRACT FROM AUTHOR]