ABSTRACT
Based on target cycling amplification and 3 ,4 ,9 ,10-perylenetetracarboxylic dianhydride derivative functionalized singal probe, an ultrasensitive electrochemiluminescence ( ECL) sensor was designed for the detection of lead ions. The hairpin substrate DNA was immobilized on the electrode through molecular self-assembly. In the presence of Pb2+and DNAzyme, the substrate was cleaved with single strand DNA fragments left on the electrode surface. Meanwhile, the target and DNAzyme was released for another cleaving circularly. As a result, the single strand DNA fragments hybridized with the assist hairpin probe H1, which leaded to the fabrication of H2 labeled with the 3 , 4 , 9 , 10-perylenetetracarboxylic dianhydride derivative functionalized hollow gold nanoparticles. With the increasing concentration of Pb2+, much more signal probe was been captured and the ECL signal of the biosensor in peroxydisulfate ( S2 O2-8 ) solution would increase. An ECL assay demonstrates that the sensor has a good linear response to Pb2+ concentration in the range of 1í10-12 mol/L-1í10-6 mol/L, with a detection limit of 1í10-12 mol/L. The fabricated sensor shows good selectivity toward Pb2+against other common metal ions.
ABSTRACT
A turn on model of electrochemiluminescence ( ECL)-Pb2+ biosensor based on G-quadruplex of aptamer probe was developed by using quantum dots ( QDs) as labels. The ECL-Pb2+ biosensor was prepared by immobilizing a hairpin aptamer probe with a thiol group at 5 '-end and an amino group at 3 '-end on gold electrode via an Au-S bond. In the presence of Pb2+, the G-rich hairpin aptamer probe opened the stem-loop and formed G-quadruplex, which exposed the amino group at 3'-end and then covalently linked to the carboxyl group on the surface of CdS quantum dots. The fabrication and reaction process of the Pb2+ biosensor were characterized. The responsive ECL intensity was linearly related to the Pb2+ concentration in the range of 2. 0×10-10-5. 0×10-8 mol/L, with the detection limit of 3. 74×10-11 mol/L. In addition, the ECL biosensor exhibited high sensitivity, good selectivity, satisfying stability, and repeatability.
ABSTRACT
An electrochemical aptasensor for Pb2+ was constructed based on the layer-by-layer assembly of graphene (GR) and anthraquinone -2-sulfonic acid sodium salt (AQMS) on the surface of Pb2+ aptamer. The mercapto-modified Pb2+ aptamer was first anchored on a gold electrode. Then the highly conductive material of GR was adsorbed on apt through the unique π-π stacking interaction, which was further used for the assembly and signal amplification of the electroactive AQMS. Upon interaction with Pb2+ ions, the apt on the aptasensor undergone conformational switch from a single-stranded form to the G-quadruplex structure, causing the GR assembled with AQMS releasing from the electrode surface into solution. As a result, the electrochemical signal of AQMS on the aptasensor was substantially reduced. Base on this concept, a useful platform for detection of Pb2+ ions was constructed. Under the optimal experimental conditions, the attenuation of peak currents (△Ipa ) showed linear relationship with the logarithm of Pb2+ concentrations (lgCPb2+) over the range from 5. 0×10-10 to 5. 0×10-8 mol/ L. The detection limit was estimated to be 6. 0×10-11 mol/ L.