Electrochemical aptasensor for the determination of cocaine incorporating gold nanoparticles modification

A novel electrochemical aptasensor incorporating a signal enhancement for the determination of cocaine was designed. Gold nanoparticles were self-assembled onto the surface of a gold electrode through 1,6-hexanedithiol. A bifunctional derivative of the 32-base cocaine-binding aptamer with a redox-active ferrocene moiety and a thiol linker group at the termini of the strand was self-assembled onto the surface of gold nanoparticles. The oxidation peak current is linearly related to the concentration of cocaine from 1.0 to 15.0 mu M with a detection limit of 0.5 mu M. It was found that the sensitivity of the aptasensor with gold nanoparticles modification was ca. 10-fold higher than that of the aptasensor without gold nanoparticles modification. This work demonstrates that gold nanoparticles-assembled gold electrode provides a promising platform for immobilizing aptamer and enhancing the sensitivity.