An aptamer embedded in a molecularly imprinted polymer for impedimetric determination of tetracycline

The authors introduce a new kind of aptameric imprinted polymer for sensing tetracycline (TET), thereby combining the unique features of aptamer-based and molecularly imprinted polymer based recognition. The dual recognition scheme results in sensing capabilities that are superior to those of the aptamer alone, or of a conventional molecularly imprinted polymer alone. In the first step, the aptamer-TET complex was immobilized on the surface of a glassy carbon electrode (GCE) decorated with gold nanoparticles. Dopamine was then electropolymerized on the surface of the modified GCE to entrap the aptamer-TET complex. TET was then extracted with an ethanol-acetic acid mixture (95:5) in order to create void cavities. On exposure to TET, the cavities are filled with TET again, and this leads to a retardment of the interfacial charge transfer of the redox probe hexacyanoferrate, typically measured at a peak voltage of 0.22 V vs. Ag/AgCl. The assay detects TET in the concentration ranges from 0.5-100 pM and from 1-1000 nM with a very low limit of detection of 144 fM. Its superior selectivity and affinity make this assay a viable tool as demonstrated for the successful analysis of TET in spiked milk samples. Graphical abstract Schematic representation of a glassy carbon electrode (GCE) modified with gold nanoparticles (AuNPs) and coated with an aptamer-imprinted polymer (MIP).