An electrochemical immunosensor for AFP measurement based on the magnetic Fe₃O₄@Au@CS nanomaterials

An ultrasensitive electrochemical immunosensor was fabricated based on the magnetic Fe₃O₄@Au@CS nanomaterials for alpha fetoprotein (AFP). First, the Fe₃O₄@Au@CS nanocomposites were prepared with Fe₃O₄@Au NPs as the core and chitosan (CS) as the shell. Then, The human AFP antibody (Ab1) was immobilized on Fe₃O₄@Au@CS as the capture probe, the mouse anti-human AFP antibody (Ab2) and horseradish peroxidase (HRP) were conjugated on the gold nanoparticles (Au NPs) as the detection probe. In the presence of AFP, the immunosensor Fe₃O₄@Au@CS-Ab1@AFP@Ab2-Au-HRP was formed via specific recognition of antigen and antibody. Due to the immobilized HRP catalyzed the decomposition of H₂O₂ resulting in a substantial current, the response signal of the sensor was recorded by the amperometric (i-t) method. The current response presented the linear relationship to the concentration of AFP, a dynamic range from 0.01 to 8 μg/mL, with the detection limit of 1.78 ng/mL. (paper)