Ultrasensitive sandwich-type electrochemical immunosensor based on dual signal amplification strategy using multifunctional graphene nanocomposites as labels for quantitative detection of tissue polypeptide antigen

• An ultrasensitive sandwich-type immunosensor for the detection of TPA was fabricated.
• Multifunctional graphene nanocomposites (Au@MGN) were designed as labels.
• The introduction of graphene could accelerate the electron transfer capability.
• The introduction of gold nanoparticles could produce a synergetic effect.
• Au@MGN dominated the dual signal amplification strategy of the proposed immunosensor.

Detection of tissue polypeptide antigen (TPA) in human serum plays an important role in monitoring the occurrence of cancers. In this work, a sandwich-type electrochemical immunosensor based on a novel dual signal amplification strategy was employed for quantitative detection of TPA. Multifunctional graphene nanocomposites (Au@MGN) were designed as labels to achieve a high sensitivity and low limit of detection (LOD), which dominated the dual signal amplification strategy. On one hand, introduction of graphene could accelerate the electron transfer capability of magnetic graphene nanocomposites (MGN) than single ferriferrous oxide nanoparticles (Fe3O4 NPs). On the other hand, introduction of gold nanoparticles (Au NPs) could build a synergetic effect between Fe3O4 NPs and Au NPs, which resulted in the increasing of electrocatalytic properties of Au@MGN. In short, due to the excellent electrochemical property of Au@MGN, high electrocatalytic current responses toward the reduction of hydrogen peroxide (H2O2) were achieved. Under optimum conditions, the proposed sandwich-type electrochemical immunosensor exhibited a wide linear range from 10−5 ng/mL to 102 ng/mL with a low LOD of 7.5 fg/mL for TPA. The designed immunosensor displayed an excellent analytical performance with good reproducibility, high selectivity and stability, indicating potential application promising in clinical monitoring of tumor markers.