Neuron-specific enolase (NSE) is a specific marker for small cell carcinoma (SCLC). Sandwich-type electrochemical immunosensors are powerful for biomarker analysis, and the electrocatalytic activity of the signal amplification platform and the performance of the substrate are critical to their sensitivity. In this work, N atom-doped graphene functionalized with hollow porous Pt-skin Ag-Pt alloy (HP-Ag/Pt/NGR) was designed as a dual signal amplifier. The hollow porous Pt skin structure improves the atomic utilization and the larger internal cavity spacing significantly increases the number of electroactive centers, thus exhibiting more extraordinary electrocatalytic activity and durability for H2O2 reduction. Using NGR with good catalytic activity as the support material of HP-Ag/Pt, the double amplification of the current signal is realized. For the substrate, polypyrrole-poly(3,4-ethylenedioxythiophene) (PPy-PEDOT) nanotubes were synthesized by a novel chemical polymerization route, which effectively increased the interfacial electron transfer rate. By coupling Au nanoparticles (Au NPs) with PPy-PEDOT, the immune activity of biomolecules is maintained and the conductivity is further enhanced. Under optimal conditions, the linear range was 50 fg mL-1 - 100 ng mL-1, and the limit of detection (LOD) was 18.5 fg mL-1. The results confirm that the developed immunosensor has great promise for the early clinical diagnosis of SCLC.

In this study, a sensitive and stable electrochemical sensor based on CuO-CeO2/MXene is constructed for the continuous detection of H2O2. CuO-CeO2 nanomaterials are applied as a catalyst to promote the electrolysis of H2O2 on the electrode surface as well as amplify the reduction current for the aim of H2O2 detection. MXene serves as a catalyst carrier for CuO-CeO2 and enhances the electron transfer rate during the reduction process of H2O2. Furthermore, the generation of hydroxyl radical during the decomposition of H2O2 is demonstrated by UV-vis spectrum and first-principles calculation to explore the reaction mechanism. The electrolysis rate of H2O2 is obtained as 0.61 × 103 M-1 s-1 by chronoamperometry. Based on the good properties, the electrochemical sensor fabricated by CuO-CeO2/MXene exhibits high sensitivity, stability, and reproducibility. A good linear relationship is ranged from 5.0 μM to 100 μM with a low detection limit of 1.67 μM for H2O2 detection. Besides, the current signal is stable and repeatable when continuously testing H2O2 content, which can calculate a reliable H2O2 concentration value for practical application. The proposed approach sheds light on the rational design and assembly of electrochemical sensors and its relevant catalytic mechanism study.

In this work, a sandwich-type electrochemical immunosensor was fabricated to the effective detection of hepatitis B surface antigen (HBsAg). The designed electrochemical immunosensor was based on Au core and Pd shell nanodendrites loaded on amino functionalized molybdenum dioxide nanosheets (Au@Pd NDS/NH2-MoO2 NSs) as the secondary antibody (Ab(2)) label and silver nanoparticles were loaded by electrodeposited (D-Ag NPs) on the surface of electrode as the platform. Because of the synergistic effect and abundant catalytic activity sites provided by surface dendrite structure, Au@Pd NDs were more effective than single gold and palladium nanoparticles in catalytic reduction of hydrogen peroxide (H2O2). MoO2 had the good catalytic capacity for reduction of H2O2 and favourable electrical conductivity. Hence, the obtained Au@Pd NDS/NH2-MoO2 NSs were more effective than Au@Pd NDs and NH2-MoO2 NSs in catalytic reduction of hydrogen peroxide attribute to a synergistic effect. Also, Ag NPs with admirable electrical conductivity and biocompatibility were used as sensing platforms and primary antibodies (Ab(1)) carriers, which can accelerate the electron transfer and improve the sensitivity of the immunosensor. Here, the proposed electrochemical immunosensor offered a wide linear interval from 10 fg mL(-1) to 100 ng mL(-1) and the lower limit of detection of 3.3 fg mL(-1) (S/N = 3) for detection of HBsAg under optimal experimental conditions. Furthermore, the accuracy of the actual serum sample analysis was satisfactory, which showed that the electrochemical immunosensor possessed a good application prospect in clinical detection. (C) 2020 Elsevier B.V. All rights reserved.

Changes in the concentration of neuron-specific enolase (NSE) can be used as an indicator for many diseases. Electrochemical immunosensor is a reliable tool for early diagnosis, but achieving ultrasensitive analysis is a pressing problem. In this work, graphene oxide doped poly (3,4-ethylenedioxythiophene) (PEDOT/GO) spindle-like nanorods prepared by liquid/liquid interface polymerization method have good stability and high conductivity. The sulfur atoms on the thiophene ring combine with gold nanoparticles (Au NPs) to further improve the efficiency of interface electron transfer. Besides, the exposed carboxyl groups and Au NPs on the surface of PEDOT/GO can effectively couple with the capture antibody (Ab1). Double-shelled Cu2O hollow spheres (Pd NPs@DSHSs-Cu2O) modified with palladium nanoparticles (Pd NPs) are used as signal markers. The abundant catalytic active sites and detection antibody (Ab2) binding sites rely on the double-shell hollow spheres to increase the specific surface area. The combined effect of Cu2O and Pd NPs can efficiently catalyze H2O2 to realize the amplification of electrical signals. The detection range of the immunosensor prepared by the above-mentioned sensing strategy was 50.0 fg ml−1 ∼ 100.0 ng ml−1, and the detection limit was 7.54 fg ml−1, which provides potential reference value for early clinical diagnosis.

In this study, a sandwich-type electrochemical immunosensor was developed for detecting carcinoembryonic antigen (CEA) effectively. The proposed electrochemical immunosensor was based on gold nanocrystals (Au NDs) as the substrate material for capturing primary antibodies and using palladium nanoscale cubics (Pd NCs) loaded on amino-functionalized MoO2 nanospheres (Pd NCs/NH2-MoO2 NSs) as a secondary antibody label. Au NDs had dendritic structures that were more conducive to capturing Ab1 and can accelerate electron transfer. MoO2 had the good catalytic capacity for reduction of H2O2 and favourable electrical conductivity. Similarly, Pd NCs had excellent catalytic performance for hydrogen peroxide reduction. Hence, the obtained Pd NCs/NH2-MoO2 NSs were more effective than Pd NCs and NH2-MoO2 NSs in catalytic reduction of hydrogen attribute to a synergistic effect, showing excellent catalysis. The proposed electrochemical immunosensor had a lower detection limit of 3.3 fg ml−1 jand a wider detection range from 10 fg ml−1 to 100 ng ml−1 (S/N = 3) for the detection of CEA under optimal experimental conditions. The proposed electrochemical immunosensor showed good sensitivity, stability, selectivity, reproducibility and its good detection performance of the immunosensor indicated that it had a broad application prospect in clinical detection.