Wang Ren,Ying Zhang,Yu Zhu Fan,Jiang Xue Dong,Nian Bing Li,Hong Qun Luo
A resonance Rayleigh scattering (RRS) aptasensor was fabricated for detection of Pb 2+ via hairpin-like label-free substrate and G-wire for signal amplification. A hairpin-like DNA substrate contains a sequence in the loop labeled with ribonucleobase A and c-myc sequence in the stem. When hybridized with 8–17 DNAzyme in the presence of Pb 2+ , the sequence in the loop was activated and cleaved. Hundreds of c-myc sequences departing from the 8–17 DNAzyme yield nanowires superstructure called G-wire in the presence of Mg 2+ . The polymer G-wire was demonstrated by the RRS spectrum, polyacrylamide gel electrophoresis, and AFM. The RRS intensity was enhanced by the product G-wires, and the RRS signal at 370 nm was linear with the logarithm of Pb 2+ concentration in the range of 2.0 nM to 5.0 μM. This method was selective for Pb 2+ even coexisting with other metal ions at high concentrations and was successfully applied to the determination of Pb 2+ in real samples. The aptasensor holds a great promise for universal RRS sensing platform for sensitive detection of various metal ions just by changing the sequence of the probe in the loop and DNAzyme.
Mei Li,Qingyou Cai,Yue Meng,Weihong Zheng,Guojiang Mao,Hua Wang
We reported a novel assembled G-wire-induced pyrene excimer switching probe for microRNA (miRNA) amplified detection on the basis of exonuclease III (Exo III)-assisted target recycling and Fe 3 O 4 @PDA nanoparticles. The multifunctional hairpin (HP) probe recognized and effectively bound to target miRNA, which formed a 3′-blunt terminal for Exo-III digestion and miRNA regeneration to initiate another Exo III-mediated cycling cleavage. After digestion, numerous HP-caged c-myc sequences were released, which were positively related to target miRNA and folded to the parallel G-quadruplex with K + . Additionally, Fe 3 O 4 polydopamine nanoparticles (Fe 3 O 4 @PDA NPs)-based magnet separation was conducted to reduce background fluorescence signal, and parallel G-quadruplexes self-asembled into filamentous G-wires with Mg 2+ . G-wires generated from 5′-terminal pyrene-labeled c-myc sequences made close distance between two labeled pyrene molecules, and induced the “turn-on” fluorescence signal of pyrene excimer switching. Moreover, gamma-cyclodextrin (γ-CD) was added, which promoted pyrene moiety, causing signal amplification in pyrene excimer fluorescence. Therefore, miRNA was efficiently measured within the homogeneous solution. This method detected miRNA within the dynamic range of 1 pM to 5 nM, with the miR-141 limit of detection (LOD) being 99 fM. It distinguished perfect-matched and mismatched target miRNAs, and showed an accurate detection of miRNA levels in different cell lines and favorable reproducibility when analyzing miRNAs within spiked serum samples. We propose a promising method for G-wire-based biosensing in disease-related biomarkers detection.
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