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

A novel and sensitive sandwich-type photoelectrochemical (PEC) immunosensor was developed for the quantitative detection of beta-amyloid protein (A beta). 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)(3)(2+)) 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)(3)(2+)/Ce-CdS was 70 times that of pure ZnO. The aminofunctionalized polystyrene (PS) microspheres coated with copper sulfide (CuS) was linked with a secondary antibody (Ab(2)) for the first time for the AP detection by the immunosensor. The good insulation and steric resistance of the as-prepared polystyrene@CuS-Ab(2) (PS@CuS-Ab(2)) composite significantly weakened the photocurrent response of the immunosensor in the specific immune recognition. Under the optimal conditions, the quantitative detection of A beta 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.