A visible light photoelectrochemical sensor for tumor marker detection using tin dioxide quantum dot–graphene as labels

Abstract

In this paper, a simple and sensitive sandwich-type photoelectrochemical (PEC) immunosensor for measurement of biomarkers on a gold nanoparticle-modified indium tin oxide (ITO) electrode through electrodeposition for point-of-care testing was developed by using a tin dioxide quantum dot–graphene nanocomposite (G–SnO₂) as an excellent label with amplification techniques. The capture antibody (Ab1) was firstly immobilized on the gold nanoparticle-modified ITO electrode due to the covalent conjugation, then the antigen and the AuNP/PDDA–G–SnO₂ nanocomposite nanoparticle labeled signal antibody (Ab2) were conjugated successively to form a sandwich-type immunocomplex through a specific interaction. Under irradiation with a common ultraviolet lamp (∼365 nm, price $50), the SnO₂ NPs were excited and underwent charge-separation to yield electrons (e⁻) and holes (h⁺). As the holes were scavenged by ascorbic acid (AA), the electrons were transferred to the ITO electrode through RGO to generate a photocurrent. The photocurrents were proportional to the CEA concentrations, and the linear range of the developed immunosensor was from 0.005 to 10 ng mL⁻¹ with a detection limit of 0.036 pg mL⁻¹. The proposed sensor shows high sensitivity, stability, reproducibility, and can become a promising platform for other biomolecular detection.