Enzyme-free electrochemical immunosensor configured with Au-Pd nanocrystals and N-doped graphene sheets for sensitive detection of AFP

A novel electrochemical immunosensor capable of enzyme-free detection of alpha fetoprotein (AFP) is reported. This immunosensor was fabricated in a sandwich-like format where catalytic Au-Pd nanocrystals and highly conductive N-doped graphene sheets were incorporated. The significant catalysis by Au-Pd nanocrystals toward hydrogen peroxide, along with the increased electron transfer by graphene sheets, caused signal generation and increased sensitivity, which enables the enzyme-free detection of AFP. With a low detection limit at 0.005 ng mL−1, this novel immunosensor worked well over the broad linear range of 0.05-30 ng mL−1. Unlike previously reported enzyme-based electrochemical immunosensors, which often involve the complicated steps for enzyme loading and necessary treatments to keep the activity of enzyme, this novel immunosensor is simple in nature and employed catalytic Au-Pd nanoparticles and highly conductive graphene, which thus enables reliable and sensitive detection for clinic usage.