Search

In this work we use a water-soluble cationic perylene derivative (compound 1) as the G-quadruplex (G4) structure fluorescence indicator to construct a fluorescent biosensor for simple, rapid and label-free detection of Pb 2+ . In the absence of Pb 2+ , strong electrostatic interactions between compound 1 and the G-rich DNA probe (PW17) induced the aggregation of compound 1 and resulted in the fluorescence quenching. In the presence of Pb 2+ , the PW17 formed Pb 2+ -stabilized G4 structure, which reduced the aggregation of compound 1 and gave rise to high fluorescence. This allowed us to use convenient “mix-and-detect” protocol for quantitative analysis of Pb 2+ . Since Pb 2+ can specially induce PW17 to form compact DNA fold, our proposed biosensor displayed high selectivity for Pb 2+ . It also exhibited a high sensitivity to Pb 2+ , with a limit of detection of 5.0 nM observed. Furthermore, the biosensor was applied for the detection of Pb 2+ in urine and paint samples, and both showed satisfactory results. [ABSTRACT FROM AUTHOR]

DNAzyme-based catalytic beacons have been widely studied for both in vivo and in vitro molecular detection. However, only a few label-free catalytic beacons with excellent analytical performance have been reported so far. In this work, by combining a catalytic DNAzyme for amplified sensing through enzymatic turnover with cleavage-induced G-quadruplex formation, a label-free DNAzyme biosensor was developed for amplified “turn-on” fluorescence detection of Pb 2+ with a detection limit of 3 nM. The method is very competitive compared to many other labeled or label-free methods with or without signal amplification. Due to the inherent specificity of the GR-5 DNAzyme, the method also exhibits excellent selectivity. This biosensor successfully detected Pb 2+ in river water samples with high sensitivity and selectivity. Such a method might provide a universal DNAzyme-based sensing platform for sensitive detection of various targets both in environmental and biomedical fields. [ABSTRACT FROM AUTHOR]

Abstract: A new and facile strategy using double-stranded DNA-copper nanoparticles (dsDNA-Cu NPs) as fluorescence reporters for the highly sensitive and selective detection of l-histidine was demonstrated. In the dsDNA-Cu NPs-based sensing system, the fluorescence was quenched considerably upon the addition of l-histidine. Under the optimized experimental conditions, the probe exhibits excellent performance (e.g., a satisfactory detection limit of 5μM and high specificity). Our in situ method requires no covalent attachment of DNA to a fluorophore, which could significantly reduce the cost and simplify the procedure for l-histidine detection. Moreover, the proposed sensing system could be applicable for the detection of target biomolecule in complex biological samples. These striking properties make it an attractive platform for the direct detection of l-histidine. [Copyright &y& Elsevier]