Full-spectrum responsive photoelectrochemical immunoassay based on β-In2S3@carbon dot nanoflowers

Abstract This work designed a new photoelectrochemical (PEC) immunoassay for the ultrasensitive detection of alpha-fetoprotein (AFP) based on the flower-like β-In2S3@carbon dots (CDs). The photocurrent of the as-prepared heterogeneous nanostructure was enhanced significantly under ultraviolet (UV), visible (Vis) and near-infrared (NIR) irradiation thanks to the more generation of carriers and less electron-hole pairs recombination with CDs. The three-layer sandwich-like immunocomplex would be formed upon the target AFP existed, the ascorbic acid 2-phosphate (AA2P) was subsequently transformed into ascorbic acid (AA) owing to the catalysis of alkaline phosphatase-conjugated rabbit polyclonal anti-human AFP (ALP-Ab2). Without additional applied voltage, the photocurrent of the β-In2S3@CDs-modified electrode was positively correlated with the increasing AA level in the detection cell. Under optimal conditions, the developed PEC immunosensing platform exhibited good reproducibility and high sensitivity for the determination of target AFP within a dynamic working range from 0.5 to 50 ng mL−1 at a detection limit of 37.9 pg mL−1. In addition, the method accuracy relative to human AFP ELISA kit was evaluated by analyzing human serum specimens, and a good match between two methods was obtained. Such the increasing photocurrent through full-spectrum responsive mode gives a new horizon to develop highly sensitive PEC immunoassay in early clinical diagnosis by monitoring disease-related biomarkers.