Double Enhancement Photoelectrochemical Immunosensors Based on BiOBr/ZnCdS Heterojunction and LSPR for Liver Cancer Detection

Liver cancer has a high rate of recurrence and requires long-term monitoring and treatment. Protein induced by vitamin K absence or antagonist-II (PIVKA-II) is an early sensitive liver cancer marker. Therefore, it is essential to develop analytical methods for detecting trace PIVKA-II to enable screening and assessment of liver cancer. Here, a sandwich-type photoelectrochemical (PEC) immunosensor based on a “dual-signal” amplification strategy was proposed to quantitatively detect PIVKA-II in human blood. The ternary p-n heterojunction BiOBr/ZnCdS was first prepared on conductive glass fluorine-doped tin oxide (FTO), and the synergistic effect of BiOBr and ZnCdS significantly improved photocurrent response. After functionalization of the photoelectrode by chitosan and glutaraldehyde, the capture antibody (Ab1) of PIVKA-II can be successfully modified on the photoelectrode. In addition, the detection antibody (Ab2) for PIVKA-II was immunoreacted with PIVKA-II after In2S3@Au labeling. Due to the excellent photoelectric properties of In2S3 and the localized surface plasmon resonance (LSPR) of gold nanoparticles, the photocurrent response can be further amplified. The proposed PEC immunosensor for detecting PIVKA-II provides a wide linear range from 0.1 pg/mL to 100 ng/mL and a detection limit [limit of detection (LOD)] of 0.064 pg/mL (${S}/{N}=3$) under optimal experimental conditions. Besides, the immunosensor demonstrated reasonable specificity, stability, reproducibility, and potentiality of clinical applications.