A novel sandwich-type photoelectrochemical immunosensor based on Ru(bpy)32+ and Ce-CdS co-sensitized hierarchical ZnO matrix and dual-inhibited polystyrene@CuS-Ab2 composites

Abstract

A novel and sensitive sandwich-type photoelectrochemical (PEC) immunosensor was developed for the quantitative detection of β-amyloid protein (Aβ). A ITO electrode was sequentially coated with hierarchical porous zinc oxide (ZnO) microspheres with a large specific area, sensitized with tris(bipyridine)ruthenium(II) ion (Ru(bpy)32+) to achieve high visible light absorption, and modified with cerium-doped cadmium sulfide (Ce-CdS) nanoparticles to enhance the PEC response. Under the stimulation of visible light and ascorbic acid as an efficient electron donor, the photoelectric signal of ZnO/Ru(bpy)32+/Ce-CdS was 70 times that of pure ZnO. The amino-functionalized polystyrene (PS) microspheres coated with copper sulfide (CuS) was linked with a secondary antibody (Ab2) for the first time for the Aβ detection by the immunosensor. The good insulation and steric resistance of the as-prepared polystyrene@CuS-Ab2 (PS@CuS-Ab2) composite significantly weakened the photocurrent response of the immunosensor in the specific immune recognition. Under the optimal conditions, the quantitative detection of Aβ was achieved within the range of 0.001–100 ng/mL with the detection limit of 0.37 pg/mL. In addition, the PEC immunosensor is easy to make, stable and selective, which has provided a good experimental platform for the detection of disease biomarkers.