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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]

Abstract: A label-free electrochemiluminescence (ECL) immunosensor based on functionalized Santa Barbara Amorphous-15 (SBA-15) has been developed for detection of cancer antigen 15-3 (CA15-3). The functionalized SBA-15 was prepared by decoration of citrate-capped Ag nanoparticles and incorporation of Ru(bpy)3 2+on SBA-15. The Ag nanoparticles show remarkable enhancement effect on ECL properties of Ru(bpy)3 2+. In order to incorporate more Ru(bpy)3 2+, anionic surfactant sodium dodecyl sulfate (SDS) was used to increase the negative charge of the composite matrix. Chitosan–ionic liquid (CHIT–IL) were also used to increase the conductivity and film stability. The functionalized SBA-15 was used to label the anti-CA15-3 based on the covalent interaction between Ag nanoparticles and the amines of anti-CA15-3. The ECL immunosensor that used to detect breast cancer biomarker CA15-3 exhibits high ECL intensity, good biocompatibility and long-term stability. The results show that the ECL immunosensor has high sensitivity for CA15-3 with a linear range from 0.01U/mL to 100U/mL and a detection limit of 0.004U/mL (S/N=3). [Copyright &y& Elsevier]

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]