Label-free alpha fetoprotein immunosensor established by the facile synthesis of a palladium-graphene nanocomposite

In this study, we established a sensitive label-free immunosensor by palladium-reduced graphene oxide (Pd-rGO), which was prepared by one-pot synthesis under the reduction of extra-injected CO gas. The Pd-rGO nanocomposite structure has been confirmed by TEM, SEM, X-ray diffraction, and UV-vis spectroscopy. The Pd-rGO nanocomposite exhibited excellent stability in aqueous dispersion. The Pd-rGO-based label-free electrochemical immunosensor was used for detection of the hepatocellular carcinoma (HCC) biomarker alpha fetoprotein (AFP). The immunosensor determination was based on the fact that due to the formation of antigen-antibody immunocomplex, the decreased response amperometric currents of H2O2 were directly proportional to the concentrations of AFP. The limit of detection of this immunosensor for AFP detection is 5 pg/mL, and is linear from 0.01 to 12 ng/mL. The proposed immunosensor has been used to determine AFP in clinical serum samples with satisfactory results. This suggests the sensor may have great potential utility in the clinic.