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Developing electrochemical biosensor, particularly for high sensitive recognizing and detecting tumor marker at low level under benign conditions, is highly desired, but still remains a severe challenge. In this communication, we report a dual-signaling ratiometric method for sensitive detection of carcinoembryonic antigen (CEA) based on gold nanoparticles (Au NPs) functionalized Cu 2 S-CuS/graphene composite (Au-Cu 2 S-CuS/graphene) as the matrix material and carboxyl-Au nanoparticles (Au-COOH) functionalized mesoporous CeO 2 nanoparticles (Au-CeO 2 ) supported toluidine blue (TB) complex as signal label. The oxidation peak current of Cu 2 S-CuS decreases with the increase of CEA concentration, while the oxidation peak current of TB increases. The change of dual signals “Δ I = Δ I TB + |Δ I Cu2S-CuS |” (Δ I TB and |Δ I Cu2S-CuS | are the change values of the oxidation peak currents of TB and Cu 2 S-CuS, respectively) is used as the response signal for quantitative determination of CEA. Notably, the linear range is 0.001 ∼ 100 ng/mL with a detection limit of 0.78 pg/mL (S/N = 3). The ratiometric electrochemical system provides an extremely simple strategy for detecting tumor markers in a reliable, facile, sensitive, and specific manner, which has a promising application for quantitative detection of other tumor markers in clinical diagnosis. [ABSTRACT FROM AUTHOR]

A label-free photoelectrochemical (PEC) immunosensor for carcinoembryonic antigen (CEA) detection was developed using two-dimensional (2D) ultrathin graphitic carbon nitride (g-C 3 N 4 ) nanosheets hybridized with Zn 0.1 Cd 0.9 S nanocrystals as the photoactive matrix. The g-C 3 N 4 ultrathin nanosheets, which are 2D conjugated polymers, were synthesized through a thermal polymerization-exfoliation method that can generate a high specific surface area. Next, the Zn 0.1 Cd 0.9 S nanocrystals was successfully grown on the g-C 3 N 4 ultrathin nanosheets (Zn 0.1 Cd 0.9 S/g-C 3 N 4 ), forming a well-matched band structure where the presence of Zn 0.1 Cd 0.9 S/g-C 3 N 4 accelerated the separation and transfer of photogenerated electron-hole pairs. The as-synthesized Zn 0.1 Cd 0.9 S/g-C 3 N 4 composites showed excellent photoelectrochemical activity, considerably higher than that of pure Zn 0.1 Cd 0.9 S and g-C 3 N 4 . It was worth noting that the heterojunction with strong interfacial interaction formed between Zn 0.1 Cd 0.9 S and g-C 3 N 4 was adopted in the construction of an immunosensor for the first time. CEA antibody (anti-CEA) was immobilized on the surface of a modified electrode using a chemical bonding effect, with mercaptoacetic acid (MPA) and EDC/NHS being used as bridging media. The highly specific introduction of CEA resulted in increased steric hindrance via the antigen-antibody specific immunoreaction; Thus, the concentrations of CEA could be detected by observing the decrease in photocurrent. Under optimal conditions, the linear range for the immunosensor was from 0.005 ng mL −1 to 20 ng mL −1 . The detection limit was 1.4 pg mL −1 . [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 sensitive detection of kanamycin based on water-soluble graphene sheet (WGS)/prussian blue-chitosan (PB-CTS)/nanoporous gold (NPG) composited film has been reported. PB was selected as an electron transfer mediator, and was modified onto the electrode together with WGS through electrostatic adsorption. Then NPG was immobilized onto the as-prepared film for biomolecules anchoring. The electroactivity of PB was greatly enhanced in the presence of WGS and NPG. It could mainly be ascribed to the fact that the good conductivity of WGS and NPG promoted electron transfer and enhanced the sensitivity. kanamycin antibody, as a model, was immobilized onto the composite film for the detection of kanamycin. Under optimum conditions, the amperometric signal of PB decreased linearly with kanamycin concentration (0.02–14ngmL−1), a linear calibration plot (y =1.3817+4.7544x, r =0.9993), resulting in a low limit of detection (6.31pgmL−1). The novel immunosensor for the detection of kanamycin in real sample with satisfactory results has been proved. In addition, this method would be easily adapted for the detection of other residual antibiotics in animal derived foods. [Copyright &y& Elsevier]

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]