▎ 摘　　要

Surface plasmon resonance imaging (SPRi) is one of the powerful tools for immunoassays with advantages of label-free, real-time, and high-throughput; however, it often suffers from limited sensitivity. Herein we report a dual signal amplification strategy utilizing polydopamine (PDA) functionalization of reduced graphene oxide (PDA-rGO) nanosheets for sensitive SPRi immunoassay in serum. The PDA-rGO nanosheet is synthesized by oxidative polymerization of dopamine in a gentle alkaline solution in the presence of graphene oxide (GO) sheets and then is antibody-conjugated via a spontaneous reaction between the protein and the PDA component. In the dual amplification mode, the first signal comes from capture of the antibody-conjugated PDA-rGO to form sandwiched immunocomplexes on the SPRi chip, followed by a PDA-induced spontaneous gold reductive deposition on PDA-rGO to further enhance the SPRi signal. The detection limit as low as 500 pg mL(-1) is achieved on a nonfouling SPRi chip with high specificity and a wide dynamic range for a model biomarker, carcinoembryonic antigen (CEA) in 10% human serum.