"Near-zero background signal" sensing platform for tumor marker based on catalytic amplification strategy in chronocoulometry.

In practical applications, the long-term stability of electrochemical (EC) sensors during continuous monitoring of target substances is particularly critical. However, due to complex detection environments that readily cause background signal interference, achieving long-term stability and high-sensitivity detection still faces significant challenges. To solve this issue, a "near-zero background signal" approach was designed via a catalytic amplification strategy in chronocoulometry, constructing a sensitive and stable tumor marker sensing platform. Specifically, glucose oxidase (GOx) was encapsulated within the covalent organic frameworks (COFs) during the synthetic process of gold nanoparticles (AuNPs)/GOx@COFs. Subsequently, an environmentally tolerant immunoprobe was successfully prepared by conjugating AuNPs/GOx@COFs with antibodies. The surface of electrodes modified with AuNPs/multi-walled carbon nanotubes immobilized a large amount of the electroactive material ferrocene (Fc), achieving the first catalytic amplification of EC signals. Following the construction of the immunosandwich sensing interface on the electrode surface, glucose was catalyzed by GOx to generate hydrogen peroxide (H2O2), and Fc+/Fc catalyzed the decomposition of H2O2, enabling the second amplification of the EC signal. As a proof of concept, prostate-specific antigen (PSA) was selected as a model analyte for verification. The sensing interface demonstrated highly sensitive detection with a low limit of detection (LOD) of 11.96 fg mL-1 and maintained stability for up to 6 weeks (signal deviation rate of -2.48 %). This strategy effectively enhances EC signal response and exhibits stability, providing a universal and feasible concept for the precise, sensitive, and stable detection of tumor markers.