A "signal-on'' aptasensor was developed for simultaneous detection of chloramphenicols (CAP) and polychlorinated biphenyl-72 (PCB72) with a novel multi-metal ions encoded nanospherical brushes as nanotracers. To construct the assay, the respective aptamer of CAP and PCB72 labeled magnetic gold nanoparticles as capture probes (aptamer-MGPs), and their complementary single strand DNA (s-DNA) encoded metal ions (Cd(2+) and Pb(2+)) on nanospherical branched polyethylene imine brushes as tracers (s-DNA-MSPEIs), were simultaneously synthesized. After that, the capture probe and tracers were connected through a hybridization reaction between s-DNA and aptamers. In the presence of CAP and PCB72, the analytes could react with the aptamers on capture probes and release the tracers into supernatant after magnetic separation. The released tracers with metal ions (Cd(2+) and Pb(2+)) could be simultaneously detected through the square wave voltammetry (SWV) without acid dissolution, which can switch the signals of the biosensor to "on'' state. Under optimal conditions, the assay could detect CAP and PCB72 as low as 0.3 pg mL(-1) with the dynamitic range from 0.001 to 100 ng mL(-1) and exhibited excellent selectivity. More importantly, the strategy can be extended easily to other targets after changing the corresponding aptamers and other metal ions tracers, which provides a promising and facile approach in multiplex detection of ultra-trace level of pollutants in food safety without more complex separation and washing steps.
Keywords: Chloramphenicols; Competitive-type displacement reaction; Metal ion tracer; Multiplex determination; Polychlorinated biphenyls.
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