A label-free Electrochemical Aptasensor Based on Electrodeposited Gold Nanoparticles and Methylene Blue for Tetracycline Detection

A label-free electrochemical aptasensor modified with electrodeposited gold nanoparticles and methylene blue was fabricated for convenient and sensitive determination of tetracycline. Firstly, gold nanoparticles were modified onto a glassy carbon electrode (GCE) by one-step electrodeposition method. Then the anti-tetracycline aptamer was immobilized onto gold nanoparticles modified gold electrode surface by Au-S bond. Finally, methylene blue was dripped onto immobilized aptamer GE surface to fabricate a sensitive aptasensor for tetracycline detection in milk. During the above process, gold nanoparticles can facilitate electron transfer, and methylene blue can provide much more adsorption sites for tetracycline. The electrochemical properties of the modified processes were characterized by cyclic voltammetry (CV). The morphologies of the nanocomposites were characterized by scanning electron microscopy (SEM). The experimental conditions such as the concentration of the aptamer, the time, temperature and the pH were optimized. Based on the above optimum conditions, this aptasensor showed a favorable analytical performance for tetracycline detection with a detection limit of 0.42 × 10-11 M.