Trapping method of antibodies on surfaces of polymerizing discs for enzyme immunoassay

Quenching study of Cu2S-MPA/NGODs composites in electrochemiluminescence detection by modulating resonance energy transfer and adsorption process

This study explores the principles of resonance energy transfer and adsorption modulation using composites of Cu2S-MPA/NGODs. These composites can efficiently control the quenching process of electrochemiluminescence (ECL). Mercaptopropionic acid (MPA) was added during the synthesis of Cu2S-MPA to enhance its attachment to nitrogen-doped graphene quantum dots (NGODs). The UV absorption peaks of NGODs coincided with the emission peaks of luminol ECL, enabling resonance energy transfer and enhancing the quenching capability of Cu2S-MPA. Meanwhile, there is another quenching strategy. When the readily reducible Cu+ ions underwent partial reduction to Cu when they were bound to NGODs. This weakened the electrocatalytic effect on reactive oxygen species (ROS) and had a detrimental impact on electron transfer. Under optimal conditions, the immunosensor ECL intensity decreased linearly with the logarithm of carcinoembryonic antigen (CEA) concentration in the range of 0.00001-40 ng/mL, with a detection limit of 0.269 fg/mL. The sensor was effectively utilized for the identification of CEA in actual serum samples.

Fabrication of an ultrasensitive and selective electrochemical aptasensor to detect carcinoembryonic antigen by using a new nanocomposite

A lable-free electrochemical aptasensor was successfully developed for the sensitive detection of carcinoembryonic antigen as a tumor biomarker. To do this, a ternary nanocomposite of hemin, graphene oxide and multi-walled carbon nanotubes was used. The aptamer can be attached to the surface of a hemin, graphene oxide and multi-walled carbon nanotubes glassy carbon electrode through -NHCO- covalent bonds to form a sensing surface. Through fourier transform infrared spectroscopy and scanning electron microscopy, it was indicated that hemin can be successfully incorporated into hemin, graphene oxide and multi-walled carbon nanotubes. Hemin, which protects graphene nanosheets, also serves as an in-situ probe owing to its well-defined redox properties. Multi-walled carbon nanotubes in the modifier enhance conductivity and facilitate the electron transfer between hemin and the glassy carbon electrode. In this study, carcinoembryonic antigen got specifically bound to the aptamer, and the current changes were used for selective and specific detection of that antigen. The devised aptasensor proved to have excellent performance with a wide linear range of 1.0 × 10^-15 - 1.0 × 10^-8 gmL^-1 and a detection limit of 0.82 fg mL^-1. The inter-day and intra-day values of RSD% were obtained in the range of 0.10-2.91 and 2.21-4.56 respectively. According to the experiments conducted on real samples, it may be claimed that the proposed label-free electrochemical aptasensor is capable enough of determining carcinoembryonic antigen in clinical diagnostics.

One-pot synthesis of multidimensional conducting polymer nanotubes for superior performance field-effect transistor-type carcinoembryonic antigen biosensors

Aptamer FET sensors based on carboxylated polypyrrole multidimensional nanotubes show ultrahigh sensitivity and selectivity toward CEA, and superior lifetimes.

Simplified aptamer-based colorimetric method using unmodified gold nanoparticles for the detection of carcinoma embryonic antigen

A new colorimetric aptasensor for the detection of CEA was developed. Aptamer-based colorimetric method with nanoparticles was used for the detection of CEA. The colorimetric aptasensor has potential for the detection of other proteins or nucleotides.

Electrochemical immunoassay of carcinoembryonic antigen based on a lead sulfide nanoparticle label

We describe a lead sulfide nanoparticle (PbS NP)-based electrochemical immunoassay to detect a tumor biomarker, carcinoembryonic antigen (CEA). Cubic PbS NPs were prepared and functionalized with thioglycolic acid (TGA), which stabilized the formed NPs and offered carboxyl groups to conjugate with CEA antibodies. PbS NP conjugated with monoclonal CEA antibody was used as a label in an immunorecognition event. After a complete sandwich immunoreaction among the primary CEA antibody (immobilized on the carboxyl-modified magnetic beads), CEA and the PbS-labeled secondary antibody (PbS-anti-CEA), PbS labels were captured to the magnetic-bead (MB) surface through the antibody-antigen immunocomplex. Electrochemical stripping analysis of the captured PbS was used to quantify the concentration of CEA after an acid-dissolution step. The MBs and the magnetic separation platform were used to integrate a facile antibody immobilization with immunoreactions and the isolation of immunocomplexes from reaction solutions in the immunoassay. The voltammetric response is highly linear over the range of 1-50 ng ml(-1) CEA, and the limit of detection is estimated to be 0.5 ng ml(-1). The performance of this nanoparticle-based electrochemical immunoassay was successfully evaluated with human serum spiked with CEA, indicating that this convenient and sensitive technique offers great promise for rapid, simple and cost-effective analysis of tumor biomarkers in biological fluids.

A disposable electrochemical immunosensor for flow injection immunoassay of carcinoembryonic antigen

A new simple immunoassay method for carcinoembryonic antigen (CEA) detection using a disposable immunosensor coupled with a flow injection system was developed. The immunosensor was prepared by coating CEA/colloid Au/chitosan membrane at a screen-printed carbon electrode (SPCE). Using a competitive immunoassay format, the immunosensor inserted in the flow system with an injection of sample and horseradish peroxidase (HRP)-labeled CEA antibody was used to trap the labeled antibody at room temperature for 35 min. The current response obtained from the labeled HRP to thionine-H(2)O(2) system decreased proportionally to the CEA concentration in the range of 0.50-25 ng/ml with a correlation coefficient of 0.9981 and a detection limit of 0.22 ng/ml (S/N=3). The immunoassay system could automatically control the incubation, washing and current measurement steps with good stability and acceptable accuracy. Thus, the proposed method proved its potential use in clinical immunoassay of CEA.

Flow injection immunoassay for carcinoembryonic antigen combined with time-resolved fluorometric detection

Time-resolved fluorescence has been developed for immunoassay to obtain higher sensitivity than usual immunoassays. In this paper, a simple, sensitive and specific method was developed for immunoassay of serum carcinoembryonic antigen (CEA) by combining time-resolved fluoroimmunoassay (TRFIA) and flow injection analysis. Based on a sandwich immunoassay format, a monoclonal antibody immobilized immunoaffinity column inserted in a flow system was used for immunoreactions. The cleaved solution was collected after the reaction between the immunocomplex in the immunoaffinity column and the enhancement solution that was used to cleave the Eu-labels from the immunocomplex, and then detected by time-resolved fluorescence. Serum CEA could be detected in the linear range from 2.5 to 100 ng/ml with a correlation coefficient of 0.997 and the detection limit of 1.0 ng/ml. Twenty human serum samples detected by this method were in good agreement with the results obtained by the electrochemiluminescence immunoassay. This method could be further developed for fast practical clinical detection of serum CEA levels.

Noncompetitive enzyme immunoassay for carcinoembryonic antigen by flow injection chemiluminescence

BACKGROUND

Recently, many automated immunoassay analyzers have been developed for carcinoembryonic antigen (CEA) to overcome the shortcomings in traditional immunoassay methods that are time-consuming and labor-intensive. Flow injection immunoassay (FIIA) has been increasingly applied to laboratory medicine due to its ease in automation, rapid speed and reproducible results. It is important to develop a FIIA method for CEA determination.

METHODS

Based on a noncompetitive immunoassay format, a CEA-immobilized immunoaffinity column inserted in the flow system was used to trap the unbound horseradish peroxidase (HRP)-labeled antibody after an off-line incubation of CEA and HRP-labeled anti-CEA. The trapped enzyme conjugate was detected by injecting substrates to produce an enhanced chemiluminescence (CL).

RESULTS

The linear range for CEA was 1.0-25 ng/ml with a correlation coefficient of 0.997 and a detection limit of 0.5 ng/ml. The sampling and chemiluminescence detection time for one sample was 5 min after a preincubation procedure of 25 min. Twenty five human serum samples detected by this method were in good agreement with the results obtained by immunoradiometric assay (IRMA).

CONCLUSIONS

This method could be used for rapid analysis of CEA and potentially other antigens.