Signal-enhancement synergy in engineered NiOx/Pd@MoS2 and carbonized COF toward ultrasensitive electrochemical immunosensing

Abstract

Acute myocardial infarction (AMI) highly demands ultrasensitive and specific detection of the gold-standard biomarker cardiac troponin I (cTnI) for early diagnosis and precise intervention, especially at ultralow levels in complex biological samples. Herein, we present an engineered multiple signal enhancing strategy for ultrasensitive cTnI determination. This enhancement originates from the synergistic catalytic coupling of efficient wrinkled MoS2 nanospheres (NSs) supported NiOx/Pd nanocubes (NCs) (NiOx/Pd@MoS2) together with the superior conductivity of spherically porous carbonized covalent organic frameworks (C-COF). Atomically dispersed NiOx clusters induce strong electronic coupling with Pd centers, precisely tuning the electronic structure of the active sites, thereby markedly enhancing the hydrogen peroxide (H2O2) reduction. The wrinkled MoS2 NSs, featuring a graphene-like layered architecture, enables rapid charge transfer and high electrical conductivity while effectively concentrating H2O2, thereby boosting the electrocatalytic activity of NiOx/Pd NCs. Meanwhile, the elaborately controlled carbonized C-COF, with its enlarged surface area, hierarchical porosity and abundant nitrogen functionalities, provides sufficient binding sites for primary antibody (Ab1) immobilization, thus further cooperatively ensuring signal amplification. Benefiting from this rational multi-amplification design, the immunoassay achieved an ultralow detection limit of 1.588 fg mL- 1 across a wide linear range (10 fg mL- 1 to 100 ng mL-1) for cTnI. Moreover, excellent reproducibility, selectivity and recovery in human serum samples highlight its great potential for early AMI diagnosis and clinical monitoring.