Split-type photoelectrochemical immunoassay of detecting carcinoembryonic antigen for colorectal cancer with ultrathin Bi2MoO6 nanosheets

Abstract

Colorectal cancer is currently one of the most life-threatening gastrointestinal malignant tumors with high global morbidity and mortality, and carcinoembryonic antigen (CEA) is a clinically crucial biomarker for its screening and auxiliary diagnosis. Herein, a split-type photoelectrochemical (PEC) immunosensor for CEA detection was constructed using ultrathin Bi2MoO6 nanosheets (UBMO NSs) with strong and stable photocurrent as photoactive materials. This platform was integrated with an alkaline phosphatase (ALP)-mediated enzymatic catalytic amplification strategy for synergistic signal enhancement. In the presence of target CEA, a specific sandwich immunocomplex forms, and the ALP immobilized on the complex catalyzes L-ascorbic acid phosphate (AAP) hydrolysis to generate L-ascorbic acid (AA). As an efficient hole scavenger, AA promotes the separation of photogenerated electron-hole pairs in UBMO NSs, inducing a CEA concentration-dependent PEC signal enhancement. After systematic parameter optimization, the sensor exhibited a favorable linear response to CEA from 0.001 ng mL-1 to 100 ng mL-1 with a low limit of detection (LOD) of 0.43 pg mL-1. It also maintained excellent performance in serially diluted human serum samples. Thus, this work provides a sensitive and reliable platform for clinical colorectal cancer screening.