[Show abstract][Hide abstract] ABSTRACT: A dual-signal amplification method based on two molecular beacons was designed for human hemochromatosis (HFE) gene detection. The two probes, P1 and P2, could resist the exonuclease III (Exo III) digestion due to the 3'-termini protrusion, and could coexist stably with Exo III. In the presence of HFE targets, P1 hybridized with a HFE target to form a duplex DNA with a recessed 3'-hydroxyl termini and then partially digested by Exo III, releasing the HFE target and a residual sequence (X). This X sequence could trigger the digestion of P2 probes with 6-carboxy-fluoresceins and Black Hole Quenchers and then result in the increase of fluorescence intensity. The X sequences were more stable than HFE targets and could cyclically trigger the P2 digestion for a long time even though the HFE targets were digested by Exo III. This method improved the sensitivity and reached 4 orders of magnitude in detection limit, and showed excellent selectivity to discriminate single base mismatched targets well.
[Show abstract][Hide abstract] ABSTRACT: We report two novel electrochemical sensors (E-sensors) for the detection of target DNA and miRNA. The E-sensors were fabricated using label-free functional allosteric molecular beacons (aMBs), which can form streptavidin aptamers to bind to streptavidin peroxidase polymer and so generate catalytic currents in the presence of the targets. These E-sensors eliminate the antigen antibody interactions which require sophisticated DNA modification. During the experiment, we found a pair of CV peaks located at around 0.17V. These peaks contributed to the redox reaction between TMB and TMB(+), and the adsorption-desorption process of TMB(+) to the negative aMB backbone. When the E-sensor was hybridized with the complement of the aMB sequence, a pair of CV peaks were found at around 0.47V which were related to the redox reaction between TMB(+) and TMB(2+), and the process of intercalation of the planar structure of TMB(2+) to dsDNA. The RSV-aMB E-sensor could detect 44amol RSV DNA in the 4μL sample and performed well in complicated biological environments. The let-7a-aMB E-sensor reached a detection limit of 13.6amol let-7a miRNA in the 4μL sample and showed good selectivity for one base mismatched miRNA.
[Show abstract][Hide abstract] ABSTRACT: A facile approach was developed to prepare positively charged and red-emitting lysozyme-stabilized Ag nanoclusters (Lys-AgNCs) using NaBH₄ as a reducing agent at room temperature. The Lys-AgNCs can be applied in the highly selective detection of Hg²⁺.
[Show abstract][Hide abstract] ABSTRACT: A facile one-pot sonochemical approach is presented to prepare highly blue-emitting Ag nanoclusters (AgNCs) using glutathione as a stabilizing agent in aqueous solution. The as-prepared AgNCs can be applied in the selective detection of S(2-) with a limit of detection of 2 nM based on fluorescence quenching.
[Show abstract][Hide abstract] ABSTRACT: An electrochemiluminescence (ECL) approach for methamphetamine determination was developed based on a glassy carbon electrode modified with a Ru(bpy)₃ (2+)-doped silica nanoparticles/Nafion composite film. The monodispersed nanoparticles, which were about 50 nm in size, were synthesized using the water-in-oil microemulsion method. The ECL results revealed that Ru(bpy)₃ (2+) doped in silica nanoparticles retained its original photo- and electrochemical properties. The ECL intensity was found to be proportional to methamphetamine concentration over the range from 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1), and the detection limit was found to be 2.6 × 10(-8) mol L(-1). The proposed ECL approach was used to analyze the methamphetamine content in drugs.
[Show abstract][Hide abstract] ABSTRACT: Amino acids with different chemical structures have different abilities in terms of increasing the intensity of chemiluminescence (CL) of tris(2,2'-bipyridine)ruthenium(II) [Ru(bpy)3(2+)]. In a flow system, CL caused by the reaction between Ru(bpy)3(3+) and 15 amino acids was observed, but only tryptophan (Trp) and histidine (His) enhanced the intensity obviously, and so the CL of Trp and His and their molecular groups was studied. A calculation of the ionization potentials (IPs) of their N atom indicated that the CL intensities of these compounds depended on their IPs. In addition, the flow system was used for the determination of Trp and His, and the detection limits were 3 x 10(-8) mol L(-1) for His and 2.5 x 10(-9) mol L(-1) for Trp. The calibration curves for the two amino acids were 1.0 x 10(-7) to 5.0 x 10(-3) mol L(-1) for His and 1.0 x 10(-8) to 1.0 x 10(-4) mol L(-1) for Trp. The proposed approach was applied to the determination of His in Ganoderma.