Photoelectrochemical immunoassay for the breast cancer biomarker CA 15-3 based on In2O3/ZnIn2S4 heterojunctions

Abstract

The development of sensitive breast cancer biomarker (CA 15-3) measurement techniques is of great significance for the early diagnosis and therapeutic monitoring of breast cancer worldwide. Herein, we have designed a split-type photoelectrochemical (PEC) immunoassay platform for the ultrasensitive determination of CA 15-3 using In₂O₃/ZnIn₂S₄ heterojunctions with high photovoltaic conversion performance as a photoactive substrate. Efficient photocurrent-responsive In₂O₃/ZnIn₂S₄ was formed by surface loading narrow-bandgap ZnIn₂S₄ on MOF-derived wide bandgap In₂O₃ nanomaterials. Subsequently, a sandwich immunoreaction was performed using an alkaline phosphatase (ALP)-labeled secondary antibody as a signaling indicator to produce large amounts of ascorbic acid by enzymatic biocatalysis. Since ascorbic acid is an excellent electron donor capable of promoting photogenerated electron separation in semiconductor materials, it enhances the anodic photocurrent of In₂O₃/ZnIn₂S₄-modified electrodes. Under the optimal catalyst loading and immunoreaction time, the In₂O₃/ZnIn₂S₄-based PEC immunoassay showed a good photocurrent response to CA 15-3 over a wide detection range from 1.0 mU mL⁻¹ to 10 000 mU mL⁻¹ with a limit of detection of 0.45 mU mL⁻¹. Owing to the excellent photocurrent response of In₂O₃/ZnIn₂S₄ to ascorbic acid and the split-type immunoassay protocol, the constructed PEC immunosensing platform has the advantages of high precision, anti-interference, and acceptable accuracy, and the results are equivalent to those of commercial enzyme-linked immunosorbent assay (ELISA) kits.