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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. [ABSTRACT FROM AUTHOR]

The hybrids, N -aminobutyl- N -ethylisoluminol (ABEI), horseradish peroxidase (HRP) and cancer antigen 125 s antibody (Ab2) immobilized graphene oxide (GO), were prepared, which exhibited excellent chemiluminescence (CL) activity. The zinc oxide nanorods (ZNRs) grew on reduced graphene oxide (RGO) modified paper working electrode (ZNRs-RGO/PWE) via an in situ growth method. The deposition of CdS quantum dots (QDs) on ZNRs/RGO-PWE resulted in an enhanced excitation and photo-to-electric conversion efficiency. The ABEI-GO@HRP/Ab2CL system was employed as an internal excited light source. A photoelectrochemical (PEC) immunosensor based on CdS-sensitized ZNRs anchored RGO as the photoactive matrix and ABEI-GO@HRP/Ab2 as the CL labels was established for sensitive detection of cancer antigen 125 (CA 125). As a model, sandwich CA 125-antibody was taken as molecular reorganization elements on this sensor for the sensitive determination of CA 125 in the linear range from 5.0 × 10 −4 U/mL to 500 U/mL with a detection limit of 2.0 × 10 −4 U/mL. The specificity, reproducibility, and stability of this sensor were also investigated. This proposed method might be attractive for clinical and biomedical applications. [ABSTRACT FROM AUTHOR]