Objective     To fabricate Pt@GR nanocomposite-based electrochemical immunosensor for detecting alphafetoprotein (AFP) with high sensitivity.  Methods      The proposed immunosensor was prepared firstly by using the Pt@GR hybrid self-assembled onto the electrode surface. Then gold nanoparticles were immobilized to the surface of modified electrode via covalent-bonding interaction. Finally

antibody could be absorbed to the electrode by specific binding to antigen. The experimental conditions was optimized by methods of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The effects of experimental parameters and performance of the immunosensor such as reproducibility

sensitivity and stability were investigated. In addition

characteristics of the Pt@GR based immunosensor was compared with another constructed by coating Prussian blue on the graphene nanosheets .  Results     The optimal immunoreaction time and pH value of the detection solution were 24 min and 6.5

respectively. Under the optimal experimental conditions

the current was decreased by 5.1% after 100 cycles of consecutive scanning. The relative standard deviation (RSD) of 5 electrode-measurements was 8.1%

and the recovery rate of the immunosensor was in the range of 96.4% to 102.49%. After addition of hydrogen peroxide in the detection solution

the prepared immunosensor displayed a liner relationship within the range of 0.1~100 ng/mL with a detection limit of 0.026 ng/mL.  Conclusion     The high sensitivity and stability of Pt@GR complex-based immunosensor is applicable for the detection of AFP with low concentration.