Polyaniline@Au organic-inorganic nanohybrids with thermometer readout for photothermal immunoassay of tumor marker.

A photothermal immunoassay using a thermometer as readout based on polyaniline@Au organic-inorganic nanohybrids was built. Temperature output is acquired due to the photothermal effect of the photothermal nanomaterial. Polyaniline@Au organic-inorganic nanohybrids were synthesized by interfacial reactions with high photothermal conversion efficiency. A sandwich structure of the immunocomplex was prepared on a microplate for determination of carcinoembryonic antigen (CEA) by polyaniline@Au organic-inorganic nanohybrids as nanolabel. The released heat based on light-to-heat conversion from the photothermal nanolabel under NIR irradiation is detectable using the thermometer. The increased temperature is directly proportional to CEA concentration. The linear range of the photothermal immunoassay is 0.20 to 25 ng mL-1 with determination limit of 0.17 ng mL-1. Polyaniline@Au organic-inorganic nanohybrids with high photothermal conversion efficiency was synthesized as labels to construct photothermal immunosensor. The sandwich-type immunoassay was built on 96 hole plate based on specific binding of antigen and antibody. Carcinoembryonic antigen in sample was detected quantitatively by thermometer readout.

Cysteine-assisted photoelectrochemical immunoassay for the carcinoembryonic antigen by using an ITO electrode modified with C3N4-BiOCl semiconductor and CuO nanoparticles as antibody labels.

A sensitive photoelectrochemical (PEC) immunoassay for the carcinoembryonic antigen (CEA) is described that is based on the use of C3N4-BiOCl semiconductor on an ITO electrode. The photocurrent of the modified electrode was measured under visible light illumination. It increased in presence of L-cysteine due to rapid separation of the photoexcited electrons and holes. A sandwich-type immunoassay in a 96-well microtiter plate format used CuO nanoparticles as label for the secondary antibody. The Cu2+ is released from the CuO in the sandwich complex by treatment with acid. The free Cu2+ combined with both the cysteine and the electron receptors of C3N4 and BiOCl. Under optimal conditions, this dual action immensely decreases the photocurrent of the PEC system, and the response is inversely proportional to the CEA concentrations from 0.1 pg mL-1 to 10 ng mL-1 at the working voltage of 0 V (vs. SCE). The detection limit is 0.1 pg mL-1, and the method is exhibited satisfactory selective, repeatable and stable. Graphical abstract Schematic representation of an immunoassay based on cysteine-assisted C3N4-BiOCl photoelectrochemical platform. CuO nanoparticles were utilized as labels in immunocomplex to release Cu2+ in acidic condition. Carcinoembryonic antigen in sample was detected sensitively by dual function of Cu2+ with cysteine and C3N4-BiOCl semiconductor.

TiO2/SnOx-Au nanocomposite catalyzed photochromic reaction for colorimetric immunoassay of tumor marker.

A simple colorimetric immunoassay based on visible light excitation for detection of carcinoembryonic antigen (CEA) was developed. Firstly, visible light photocatalysts of TiO2/SnOx-Au ternary heterostructures were prepared by in situ reduction method, which were characterized using transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD) and UV-vis diffuse reflectance spectroscopy (DRS). Then, a novel sandwich-type colorimetric immunoassay for quantitative analysis of CEA by using TiO2/SnOx-Au nanoparticle as signal tag was constructed. Under visible light irradiation (λ ≥ 420 nm), the color development of TMB was obtained. And the quantitative analysis was carried out in ABS buffer solution by ultraviolet spectrum scanning. Under optimal conditions, the absorbance values increased with the increasing of CEA levels in samples, which presented linear relationship in the range of 5 pg mL-1-2.5 ng mL-1 with a detection limit of 5 pg mL-1. Meanwhile, the colorimetric immunosensor owned acceptable specificity, stability and reproducibility.