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In this study, we report the dual detection of kanamycin (KMY) and oxytetracycline (OTC) using metal polydopamine frameworks (MPDA) for the first time. This sensing system employed metal polydopamine frameworks (MPDA), which acted as a fluorescence quencher in the interaction between MPDA and dye-labeled DNA molecules; the metal polydopamine frameworks exhibited an excellent fluorescence quenching behaviour and good analytical response towards the detection of the biomolecules KMY and OTC. The accumulated kanamycin and oxytetracycline in the sensing system were recovered, and changes in their fluorescence intensity were monitored at 525 and 583 nm. Under the optimal conditions, the proposed sensing system remarkably achieved highly sensitive and selective detection of KMY and OTC with the limit of detection of 304 pM and 481 pM, respectively. In addition, the selectivity of the developed sensor was explored in the presence of competitive biomolecules. Moreover, this sensing system demonstrated great potential and versatility for the rapid detection of molecules. In addition, this biosensor was successfully evaluated for the dual detection of KMY and OTC in different real samples. [ABSTRACT FROM AUTHOR]

We describe a highly sensitive fluorescence biosensor incorporating polydopamine nanotubes (PDNTs) based on the mechanism of exonuclease III (Exo III) assisted signal amplification for the determination of Hg2+ in aqueous solution. Fluorescent probes of FAM labeled ssDNA (FAM-ssDNA) adsorbed on the PDNTs act as an efficient quencher. In the presence of Hg2+, the FAM-ssDNA can bind to Hg2+ to form double stranded DNA (dsDNA) via the formation of T–Hg2+–T base pairs. Then, the dsDNA was removed from the surface of the PDNTs to restore the fluorescence. The release of the dsDNA was triggered by Exo III digestion. At the same time, the liberated Hg2+ mediates a new cycle of digestion. This assay is ultrasensitive for the selective recognition of Hg2+, and a detection limit as low as 10 pM was achieved. In addition, the fluorescent biosensing system also displays remarkable specificity to Hg2+ in the presence of other possible competing ions. This approach was applied to the determination of Hg2+ in real water samples with good recovery and high efficiency for practical analysis. [ABSTRACT FROM AUTHOR]