Search

Highlights • A novel signal-off ultrasensitive photoelectrochemical immunosensor was prepared for detection BNP. • The CeO 2 -CdS composites showed excellent visible-light activity benefited from the matched energy band. • SiO 2 /PDA-Ag NPs had dual-inhibition effect on the CeO 2 -CdS sensitivity structure. • The immunosensor showed a low detection limit of 0.05 pg mL−1. Abstract A novel sandwich photoelectrochemical (PEC) immunosensor was constructed for ultrasensitive brain natriuretic peptide (BNP) detection. In this work, CeO 2 -CdS was employed as excellent photoactive sensing platform, and SiO 2 /PDA-Ag nanocomposite was used as signal amplification element. CeO 2 -CdS, providing great photocurrent response due to the well matched energy band which effectively impeded the recombination of the electrons and holes. For SiO 2 , due to the poor electro-conductivity and easy modification, it could be well used as an excellent signal-off label. For the sake of improving sensitivity of the immunosensor, Ag nanoparticles (Ag NPs) was applied owing to the energy transfer between CdS, which could decrease the PEC response obviously for amplifying the change of signal value. Besides, Ag NPs could anchor plenty of the detection antibodies by the chemical bonding between Ag NPs and –NH 2 of antibodies. Using PDA to connected SiO 2 and Ag NPs because of it great biocompatibility and reducing capacity. The well-established PEC immunosensor exhibited a low detection limit of 0.05 pg mL−1 (S/N = 3) with a linear range from 0.1 pg mL−1−5 ng mL−1 for BNP detection. In addition, the immunosensor also exhibited good stability, satisfactory reproducibility and acceptable specificity, which could be applied to detect other biomarkers. [ABSTRACT FROM AUTHOR]

In this work, a label-free electrochemical immunosensor was developed for the quantitative detection of carcinoembryonic antigen (CEA). Flower-like Ag/MoS 2 /rGO nanocomposites were employed as the signal amplification platform of the designed immunosensor for the first time. Due to the synergistic effect between molybdenum disulfide (MoS 2 ), reduced graphene oxide (rGO) and Ag nanoparticles (NPs), Ag/MoS 2 /rGO nanocomposites could provide a high sensitivity for the label-free electrochemical immunosensor. The detection mechanism was based on the monitoring of the electrocatalytic current response change towards the reduction of hydrogen peroxide (H 2 O 2 ) when immunoreaction occurred on the surface of the electrode modified with Ag/MoS 2 /rGO nanocomposites. Using amperometric i-t curve to record the electrocatalytic process, the proposed immunosensor achieved an ultrasensitive and specific detection of CEA with a low detection limit of 1.6 fg/mL. Under optimal conditions, the fabricated immunosensor exhibited acceptable reproducibility, selectivity and excellent stability. This designed immunosensor could provide an effective method in the clinical diagnosis of other tumor markers. [ABSTRACT FROM AUTHOR]

In this work, silver nanoparticles functionalized cuprous oxide nanowires (Ag@Cu 2 O) nanocomposites were synthesized by a simple method. The nanostructure of it could be well confirmed by a scanning electron microscope (SEM) image. Due to the good synergistic effect between silver nanoparticles (Ag NPs) and cuprous oxide nanowires (Cu 2 O NWs), Ag@Cu 2 O nanocomposites displayed a good electrocatalytic performance towards the reduction of hydrogen peroxide (H 2 O 2 ). Cyclic voltammograms (CVs) were employed to investigate electrocatalytic mechanism of it. Using Ag@Cu 2 O nanocomposites as the labels, a novel and ultrasensitive sandwich-type electrochemical immunosensor was developed for the quantitative detection of carcinoembryonic antigen (CEA). Due to the special electrochemical performance of Ag@Cu 2 O nanocomposites, the facile and sensitive fabrication of the designed immunosensor was achieved. Under optimal conditions, the designed immunosensor exhibited a wide linear range with a low detection limit. It also displayed an electrochemical performance with good reproducibility, selectivity and stability, which would provide potential applications in the clinical diagnosis of other tumor markers. [ABSTRACT FROM AUTHOR]

Detection of tissue polypeptide antigen (TPA) in human serum plays an important role in monitoring the occurrence of cancers. In this work, a sandwich-type electrochemical immunosensor based on a novel dual signal amplification strategy was employed for quantitative detection of TPA. Multifunctional graphene nanocomposites (Au@MGN) were designed as labels to achieve a high sensitivity and low limit of detection (LOD), which dominated the dual signal amplification strategy. On one hand, introduction of graphene could accelerate the electron transfer capability of magnetic graphene nanocomposites (MGN) than single ferriferrous oxide nanoparticles (Fe 3 O 4 NPs). On the other hand, introduction of gold nanoparticles (Au NPs) could build a synergetic effect between Fe 3 O 4 NPs and Au NPs, which resulted in the increasing of electrocatalytic properties of Au@MGN. In short, due to the excellent electrochemical property of Au@MGN, high electrocatalytic current responses toward the reduction of hydrogen peroxide (H 2 O 2 ) were achieved. Under optimum conditions, the proposed sandwich-type electrochemical immunosensor exhibited a wide linear range from 10 −5 ng/mL to 10 2 ng/mL with a low LOD of 7.5 fg/mL for TPA. The designed immunosensor displayed an excellent analytical performance with good reproducibility, high selectivity and stability, indicating potential application promising in clinical monitoring of tumor markers. [ABSTRACT FROM AUTHOR]

Abstract: A novel label-free electrochemical immunosensor for the detection of alpha fetoprotein (AFP) has been developed by immobilizing anti-AFP on graphene sheet (GS) and thionine (TH) modified glassy carbon electrode. The modification procedure was characterized by cyclic voltammetry (CV). The detection is based on the peak current change of the modified electrode before and after the antigen–antibody reaction. Tests relating to the detection of AFP demonstrated that the immunosensor exhibited high sensitivity, wide linear range (0.05–2.00ngmL−1), low detection limit (5.77pgmL−1 based S/N =3) and good long-term stability. The reliability of the developed immunosensor has been proved by the detection of AFP in serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]