Label-free electrochemical immunosensor based on enhanced signal amplification between Au@Pd and CoFe2O4/graphene nanohybrid

The improvement of sensitivity of electrochemical immunosensor can be achieved via two approaches: increasing loading capacities of antibody and enlarging responding electrochemical signals. Based on these, CoFe 2 O 4 /graphene nanohybrid (CoFe 2 O 4 /rGO) as support was firstly used for preparing electrochemical biosensor, and with the addition of Au@Pd nanorods (NRs) as mimic enzyme, a label-free electrochemical immunosensor was prepared. Due to the high electrical conductivity, open porous structure and large loading capacities of CoFe 2 O 4 /rGO, the enhanced signal amplification between Au@Pd NRs and CoFe 2 O 4 /rGO was studied. Fabricated as a novel substrate, the prepared immunosensor had a good analytical performance and exhibited a wide linear range from 0.01 to 18.0 ng·mL −1 with a low detection limit of 3.3 pg·mL −1 for estradiol, which was succeeded in applying to detect estradiol in the natural water.