Platinum–zinc oxide as a super signal amplifier for ultrasensitive electrochemical immunodetection of CEA

Electrochemical immunosensors are essential for disease screening, diagnosis, treatment and monitoring. In this study, a novel sandwich-type electrochemical immunosensor has been constructed for the sensitive detection of tumor marker carcinoembryonic antigen (CEA) based on platinum‑zinc oxide (Pt-ZnO) nanoparticles as a signal amplification platform. Pt-ZnO has outstanding peroxidase-like activity that enables efficient catalysis of the H₂O₂ reaction, leading to effective amplification of the current signal through numerous electron transfers. Its high specific surface area and excellent dispersion allow for immobilization with secondary antibodies through the PtN bond. Moreover, graphene quantum dots–chitosan possesses outstanding electrical conductivity and biocompatibility, enabling it to improve interfacial electron transfer and capture more primary antibodies on its surface. The Pt-ZnO signal amplification system has achieved a wide linear range for the CEA detection, which spanned from 10 fg mL⁻¹ to 100 ng mL⁻¹ with the limit of detection (LOD) of 1.02 fg mL⁻¹. The LOD of the electrochemical immunosensor was seven orders of magnitude lower than that of the traditional enzyme-linked immunosorbent assay. Furthermore, it has viable reproducibility, stability and practicality. Hence the Pt-ZnO electrochemical immunosensor has great potential for the clinical identification of CEA.