Electrochemical determination of sulfamethazine using a gold electrode modified with multi-walled carbon nanotubes, graphene oxide nanoribbons and branched aptamers.

An aptasensor assay for sulfamethazine is introduced based on a gold electrode modified with multi-walled carbon nanotubes@graphene oxide nanoribbons (MWCNTs@GONRs) nanocomposites. The MWCNTs@GONRs nanocomposites were synthesized by a chemical longitudinal partially unzipping method. Its properties are characterized by scanning electron microscope (SEM), energy dispersive spectrometric analysis (EDS), transmission electron microscope (TEM) and X-ray diffraction (XRD). In the presence of sulfamethazine, the conformation of the aptamer changes and a G-quadruplex structure is formed. It inhibits the electron transfer of the redox probe [Fe(CN)6]3-/4- on the electrode surface, causing weakening of the peak current response at the peak potential of 0.17 V (vs. Ag/AgCl). Using differential pulse voltammetry, a linear response was obtained for sulfamethazine concentrations in the range 0.01 ~ 50 ng mL-1 with a detection limit of 5.2 pg mL-1. Graphical abstract Schematic representation of an electrochemical aptasensor for sulfamethazine determination. A gold electrode is modified with multi-walled carbon nanotubes@graphene oxide nanoribbons to improve the electrode performance. When the aptamer binds to sulfamethazine to form G-quadruplex, the peak current response decreases.