Electrochemical aptasensor based on aptamer-complimentary strand conjugate and thionine for sensitive detection of tetracycline with multi-walled carbon nanotubes and gold nanoparticles amplification

Herein, a novel aptasensor with thionine as the electroactive probe was fabricated for the sensitive detection of tetracycline (TET). Carboxyl functionalized multi-walled carbon nanotubes and gold nanoparticles composites (COOH-MWCNTs/AuNPs) with high surface area and excellent conductivity were employed as the carrier of the complementary strands (CS). In addition, thionine was added to enhance the sensitivity of the developed aptasensor. After the immobilization of the COOH-MWCNTs/AuNPs/CS on the aptamer modified gold electrode (Apt/AuE), thionine was added on the surface of the electrode to complete the construction of the aptasensor. The change of the peak currents (ΔI) of thionine, evaluated by differential pulse voltammetry before and after the incubation of TET solution, was used for TET detection. Under optimal conditions, the proposed aptasensor showed a wide linearity from 0.1 nM to 1 μM and a low detection limit of 0.06 nM. In addition, the aptasensor displayed good selectivity, reproducibility and stability.