This paper proposes a sensing strategy which employs an aptamer, unmodified gold nanoparticles (AuNP), and hexadecyltrimethylammonium bromide (CTAB) to detect tetracycline (TET) in raw milk. The method is based on the colorimetric assay of aggregating AuNP. In the absence of TET, the CTAB and aptamer form a complex which allows the aggregation of AuNP. In the presence of TET, the TET aptamer is exhausted first due to the formation of aptamer-TET complexes, which prevents assembly of the CTAB–aptamer supramolecule, causing a colour change and no aggregation of AuNP. This mechanism for the detection of TET proved to be sensitive and convenient. The colorimetric assay has a detection limit of 122 nM TET. This sensor has great potential for the sensitive, colorimetric detection of a wide range of molecular analytes.
A fluorescence quenching result was obtained when an FAMlabelled G-rich oligonucleotide T30695 was treated with Pb 2+ , owing to the formation of a lead(II)-stabilized G-quadruplex.Based on this phenomenon a selective fluorescent assay for lead(II) detection with a limit of detection of 0.77 ppb and a detection range from 0 to 200 ppb was constructed.
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