Electrochemical Cytosensor with Dual-Site Recognition Fabricated by In Situ Catalase-Encapsulated Metal-Organic Frameworks for Isolation and Detection of Circulating Tumor Cells in Whole Blood.

Circulating tumor cells (CTCs) are critical biomarkers for cancer prognosis and treatment monitoring, yet their detection remains challenging due to low abundance and phenotypic heterogeneity. Herein, we developed a dual-aptamer-conjugated electrochemical cytosensor using an in situ catalase (CAT)-encapsulated nanozyme CAT@Fe(SS)MOF-EpCAM/MUC1 (CMA) with a core-shell structure (64.8% catalase encapsulation efficiency) and magnetic nanoparticles Fe3O4-EpCAM/MUC1 (FA) for highly specific CTC capture. The CMA probe achieved 85.5% aptamer grafting efficiency and exhibited enhanced peroxidase (POD)-like activity through CAT-Fe(SS)MOF synergistic catalysis, significantly amplifying the differential pulse voltammetry (DPV) signal. The cytosensor achieved a detection limit of 2 cells/mL in 1 mL of whole blood, taking 95 min, with a wide linear range from 2 to 40 cells/mL. It demonstrated high specificity toward dual-antigen-expressing CTCs and showed promising clinical utility in discriminating lung cancer patients from healthy donors. The system demonstrated good anticoagulant properties, hemolysis rates of <5%, and IC50 values of 558 μg/mL (CMA) and >700 μg/mL (FA) for RAW264.7. This novel electrochemical cytosensor offers a portable and efficient platform for CTCs detection, thereby paving the way for its meaningful integration into clinical practice.