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.