An amplified electrochemical aptasensor for thrombin detection based on pseudobienzymic Fe3O4–Au nanocomposites and electroactive hemin/G-quadruplex as signal enhancers

Abstract

A sensitive and selective electrochemical aptasensor for thrombin detection was constructed based on hemin/G-quadruplex as the signal label and Fe₃O₄–Au nanocomposites with glucose oxidase (GOx-) and peroxide-mimicking enzyme activity as the signal enhancers. Due to their large surface area and good biocompatibility, Fe₃O₄–Au nanocomposites were employed to immobilize electroactive hemin/G-quadruplex, which was formed by the conjugation between a single-stranded guanine-rich nucleic acid and hemin. Based on the GOx-mimicking enzyme activity, Au nanoparticles on the surface of the Fe₃O₄–Au nanocomposites effectively catalyzed the oxidization of glucose in the presence of dissolved O₂, accompanied by the production of H₂O₂. Both the Fe₃O₄ cores of Fe₃O₄–Au nanocomposites and hemin/G-quadruplex with H₂O₂-mimicking enzyme activity could catalyze the reduction of the generated H₂O₂, which promoted the electron transfer of hemin and amplified the electrochemical signal. The proposed electrochemical aptasensor had a wide dynamic linear range of 0.1 pM to 20 nM with a lower detection limit of 0.013 pM, which provided a promising method for a sensitive assay for the detection of proteins in electrochemical aptasensors.