Engineered PtAgCu/MoS2 and hexagonal star-like nitrogen-doped carbon enabling highly efficient sandwich-type electrochemical immunosensing via multiple signal enhancement

Cardiac troponin I (cTnI), recognized as the gold-standard biomarker for acute myocardial infarction (AMI), plays a crucial role in the early diagnosis and clinical management. Herein, we present a rationally designed multiple signal enhancement strategy for an ultrasensitive electrochemical immunoassay of cTnI. This work integrates the superior catalytic activity of a wrinkled MoS 2 -supported PtAgCu ternary alloy (PtAgCu/MoS 2 ) with the excellent conductivity of hexagonal star-like nitrogen-doped carbon (HS-NC) modified by gold nanoparticles (Au@HS-NC). The PtAgCu alloy, featuring maximized atomic utilization and optimized d-orbital coupling, exhibits outstanding hydrogen peroxide (H 2 O 2 ) electroreduction activity and a large electrochemically active surface area, thereby effectively amplifying the sensing signal. Meanwhile, the precisely designed MoS 2 carrier not only offers abundant anchoring sites and facilitates charge transfer but also enriches H 2 O 2 reactant, thereby promoting the catalytic performance of the PtAgCu alloy. Furthermore, as an ideal substrate, the morphologically engineered HS-NC, enriched with nitrogen functionalities, offers a highly conductive framework with ultralarge surface area (1121.80 m 2  g −1 ), enabling efficient immobilization of primary antibodies (Ab 1 ) and stable, accelerated charge transfer, thereby synergistically amplifies the signal output. Benefiting from this multiple amplification strategy, the proposed immunosensor achieves a remarkably low limit of detection of 0.51 fg mL −1 , and an exceptionally broad dynamic range (from 10 fg mL −1 to 100 ng mL −1 ), while exhibits excellent selectivity in complex matrices, maintaining high reproducibility and stability. This work demonstrates a rational multi-amplification design paradigm for constructing high-performance immunosensors and highlights its promising application in AMI early diagnosis.