Application of the Reduced Graphene Oxide–Multiwalled Carbon Nanotubes Composite for Development of the Electrochemical Aptasensor for Oxytetracycline Detection

Excessive use of oxytetracycline (OTC) in veterinary medicine has increased the presence of antibiotics in food, which accelerates the development of antimicrobial resistance. We report the development of a highly sensitive electrochemical aptasensor for OTC detection, based on a glassy carbon electrode (GCE) modified with reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNTs) nanocomposite. DNA aptamers specific to OTC were covalently attached to the nanocomposite surface via carbodiimide chemistry. Differential pulse voltammetry (DPV) showed a decrease in peak current due to the binding of OTC to the aptamers. The sensor exhibited a limit of detection (LOD) of 1.72 ng/mL, which is below the maximum residue limit (MRL) for OTC (100 ng/mL) established by European Union. The sensor has been tested on a spiked milk sample.