Sandwich-Type Electrochemical Sensor for Mucin-1 Detection Based on a Cysteine-Histidine-Cu@Cuprous Oxide Nanozyme

The sensitive detection of biomarkers is crucial for the early identification and treatment of cancer. In this study, a cysteine-histidine-Cu-modified jujube-like Cu₂O (CH-Cu@J-Cu₂O) nanozyme was synthesized and used to fabricate an electrochemical sensor for mucin-1 (MUC1) sensitive detection. Gold-modified reduced graphene oxide and CH-Cu@J-Cu₂O for the sensor were prepared and also characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The CH-Cu@J-Cu₂O nanozyme was used as a signal probe, containing two catalytic units of cysteine-histidine-Cu and jujube-like Cu₂O. The CH-Cu@J-Cu₂O nanozyme can potently catalyze the H₂O₂-driven oxidation of dopamine to aminochrome, leading to a high-level electrochemical signal. This electrochemical sensor was used to detect MUC1 with a linear range from 0.5 to 5000 pg·mL^-1, and the limit of detection was 0.085 pg·mL^-1, owing to the excellent catalytic activity of CH-Cu@J-Cu₂O. The expression of MUC1 on the surface of MCF-7 cells was further analyzed, and the results indicate that the proposed strategy is practical for the detection of biomarkers.