One‐Step Electrochemical Immunoassay for Carcinoembryonic Antigen in Human via Back‐Filling Immobilization of Gold Nanoparticles on DNA‐Modified Gold Electrodes

A new amperometric immunobiosensor for carcinoembryonic antigen (CEA) determination in human serum was developed via encapsulation of horseradish peroxidase‐labeled carcinoembryonic antibody (HRP‐anti‐CEA) in a gold nanoparticles/DNA composite architecture. The presences of gold nanoparticles provided a congenial microenvironment for the immobilized biomolecules and decreased the electron transfer impedance, leading to a direct electrochemical behavior of the immobilized HRP. The formation of the antibody–antigen complex by a simple one‐step immunoreaction between the immobilized HRP‐anti‐CEA and CEA in sample solution introduced a barrier of direct electrical communication between the immobilized HRP and the gold electrode surface. Under optimal conditions, the current change obtained from the labeled HRP relative to H₂O₂ system was proportional to the CEA concentration in two linear ranges from 0.5 to 15 ng/mL and 15 to 300 ng/mL with a detection limit of 0.1 ng/mL (at 3δ). The precision and reproducibility are acceptable with the intraassay CV of 6.3% and 4.7% at 8 and 60 ng/mL CEA, respectively. The storage stability of the proposed immunosensor is acceptable in a pH 7.0 PBS at 4 °C for 9 days. Moreover, the proposed immunosensors were used to analyze CEA in human serum specimens. Analytical results of clinical samples show the developed immunoassay has a promising alternative approach for detecting CEA in the clinical diagnosis.     

Electrochemical Biosensor Based on Nanocomposites Film of Thiol Graphene‐Thiol Chitosan/Nano Gold for the Detection of Carcinoembryonic Antigen

In this paper, a thiol graphene‐thiol chitosan‐gold nanoparticles (thGP‐thCTS‐AuNPs) nanocomposites film with porous structure was fabricated by electrochemically depositing on glassy carbon electrode (GCE), which exhibited good biocompatibility and improved conductivity, to construct immunosensor free label for detection of carcinoembryonic antigen (CEA). The electrochemical behavior of this immunosensor was investigated by cyclic voltammetry. Under the optimum conditions, the immunosensor revealed a good amperometric response to CEA in two linear ranges (0.3–8.0 ng mL^?1 and 8.0–100 ng mL^?1) with a detection limit of 0.03 ng mL^?1. The results indicated that the immunosensor has the advantages of good selectivity, high sensitivity, and good stability for the determination of CEA.     

One-step electrochemical immunosensing for simultaneous detection of two biomarkers using thionine and ferrocene as distinguishable signal tags

We report on a new kind of electrochemical immunosensors for simultaneous determination of the biomarkers carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP). Thionine and ferrocene were applied as distinguishable electrochemical tags (and mediators) which were covalently conjugated on anti-AFP and anti-CEA antibodies, respectively, via carboxy groups. The resulting conjugates were co-immobilized on a glassy carbon electrode functionalized with gold nanoparticles. Finally, horseradish peroxidase (HRP) was immobilized onto the modified electrode. Labeled thionine and ferrocene, respectively, act as distinguishable tags for simultaneous determination of AFP and CEA due to the difference in the location of their voltammetric peaks. With a one-step immunoassay format, the analytes in the sample produced transparent immunoaffinity reaction with the corresponding antibodies on the electrode. Once the immunocomplex is formed, it partially inhibits the active center of the immobilized HRP, and this decreased the activity of HRP in terms of reduction of hydrogen peroxide. This immunosensor enables the simultaneous determination of AFP and CEA in a single run and within the same dynamic range (0.01–50?ng?mL^?1) and the same lower detection limit (0.01?ng?mL^?1). The reproducibility and stability of the immunosensors are acceptable. The dual immunosensor was applied to evaluate several specimens, and the assay results are in acceptable agreement with clinical data.

Electrochemical Immunoanalysis for Carcinoembryonic Antigen Based on Multilayer Architectures of Gold Nanoparticles and Polycation Biomimetic Interface on Glassy Carbon Electrode

This paper describes a layer‐by‐layer (LBL) self‐assembly process of chitosan (CTS) and gold nanoparticles (Au) on the pretreated negatively charged glassy carbon (GC) electrode to fabricate electrochemistry immunosensor with a nontoxic biomimetic interface, which provided an environment similar to a native system and allowed more freedom in orientation for immobilization of carcinoembryonic antibody (anti‐CEA) to monitor carcinoembryonic antigen (CEA). UV‐vis spectroscope, atomic force microscopy (AFM), and cyclic voltammetric (CV) measurements were used to follow the multilayer film formation. The performance of the biominetic interface and factors influencing the assay system were investigated in detail. The differential pulse voltammetry (DPV) current response is used for the CEA concentration assay. The dynamic range was from 0.50 to 80.00 ng mL^?1 with a detection limit of 0.27 ng mL^?1 at 3σ. In addition, the experiment results indicate that immobilization described in this proposed method exhibits a good sensitivity, selectivity, and stability.     

A Sensitive Electrochemical Immunosensor for α‐Fetoprotein Detection with Colloidal Gold‐Based Dentritical Enzyme Complex Amplification

A sensitive and specific electrochemical immunosensor was developed with α‐fetoprotein (AFP) as the model analyte by using gold nanoparticle label for enzymatic catalytic amplification. A self‐assembled monolayer membrane of mercaptopropionic acid (MPA) was firstly formed on the electrode surface through gold‐sulfur interaction. Monoclonal mouse anti‐human AFP was covalently immobilized to serve as the capture antibody. In the presence of the target human AFP, gold nanoparticles coated with polyclonal rabbit anti‐human AFP were bound to the electrode via the formation of a sandwiched complex. With the introduction of goat anti‐rabbit IgG conjugated with alkaline phosphatase, the dentritical enzyme complex was formed through selective interaction of the secondary antibodies with the colloidal gold‐based primary antibody at the electrode, thus affording the possibility of signal amplification for AFP detection. Current response arising from the oxidation of enzymatic product was significantly amplified by the dentritical enzyme complex. The current signal was proportional to the concentration of AFP from 1.0 ng mL^?1 to 500 ng mL^?1 with a detection limit of 0.8 ng mL^?1. This system could be extended to detect other target molecules with the corresponding antibody pairs.     

High Sensitive Detection of Prostate Specific Antigen by Using Ferrocene Cored Asymmetric PAMAM Dendrimer Interface Screen Printed Electrodes

In this study, electrochemical immunosensors were developed for the detection of prostate specific antigen (PSA) using ferrocene (Fc) and polyamidoamine dendrimer (PAMAM) constructs. The biosensor fabrication was designed by modifying the screen‐printed gold electrode (Au) with ferrocene cored dendrimers (FcPAMAM) synthesized in three different generations. The self‐assembled monolayer principle was followed, to obtain sensitive, selective and disposable electrodes. Therefore, the Au electrodes were modified with cysteamine (Cys) to obtain a functional surface for FcPAMAM dendrimers to bind. Dendrimer generations were attached to this surface using a cross‐linker (glutaraldehyde) so that a suitable surface was obtained for binding of biological components. The Monoclonal PSA antibody (anti‐PSA) was immobilized on the Au electrode surface which coated with dendrimer, and (Au/Cys/FcPAMAM/anti‐PSA) biosensing electrode was obtained. The PSA detection performances of electrochemical impedance spectroscopy (EIS) and Amperometry based immunosensors exhibited very low detection limits; 0.001 ng mL^?1 and 0.1 pg mL^?1, respectively. In addition, EIS and Amperometry based biosensors using Au/Cys/FcPAMAM/anti‐PSA sensing electrode were represented excellent linear ranges of 0.01 ng mL^?1 to 100 ng mL^?1 and 0.001 ng mL^?1 to 100 ng mL^?1. In order to determine the applicability recovery and selectivity tests were performed using three different proteins in human serum.     

Ag−Co3O4 @ Nr GO Material Synthesized by One‐pot Hydrothermal Method for Carcinoembryonic Antigen (CEA) Detection of Enzyme‐mimetic Electrochemical Immunosensor

A high‐sensitivity carcinoembryonic antigen immunosensor was successfully prepared via a one‐step hydrothermal method, wherein nitrogen‐doped graphene oxide (Nr GO) loaded Ag and Co₃O₄ nanomaterials were synthesized using ammonia as the nitrogen source. Doping nitrogen atoms into the graphene structure forms a new type of N‐type semiconductor with an increased number of graphene layers and more active sites for bonding with chemicals, thereby providing excellent in biocompatibility and good electrical conductivity. The electrical signal of the sensor is further amplified due to the good catalytic effect of Co₃O₄ and Ag NPs on H₂O₂. The signal probe requires neither pretreatment nor acid treatment, and can be easy to loaded with metal‐immobilized antibodies, which greatly simplifies the detection step not shorten the detection time. The sensor has good sensitivity to detecting carcinoembryonic antigen (CEA) and can easily operate, and requires mild reaction conditions. Under optimal experimental conditions, the linear range of the sensor is 0.001–200 ng ? mL^?1, the detection limit is 0.18 pg ? mL^?1, and the linear correlation coefficient is 0.991, which can be used for CEA determination of the actual sample.     

基于酶标抗体和媒介体共吸附于金胶壳聚糖膜的PSA免疫传感器的制备

本文研制了一种用金胶壳聚糖仿生膜来同时固定四甲基联苯胺（TMB）和酶标抗体的新型电化学免疫传感器,用于检测血清肿瘤标志物前列腺特异性抗原（PSA）的含量。固定的TMB作为电子传递媒介体,在扫速小于45 mV/s时,电极表现为一个表面控制过程,而在扫速大于45 mV/s时则表现为一个扩散控制过程。将固定有酶标抗体和TMB的免疫传感器与待测PSA抗原一起培育,在该传感器上形成的免疫复合物通过TMB-H₂O₂-HRP电化学体系进行了测定。在优化实验条件下,PSA的线性检测范围为5-30 ng·mL^-1,检测限为1.0 ng·mL^-1。该PSA免疫传感器制备方法简单,成本低廉,具有较好的稳定性和重现性。     

Ultrasensitive electrochemical immunoassay for carcinoembryonic antigen based on three-dimensional macroporous gold nanoparticles/graphene composite platform and multienzyme functionalized nanoporous silver label

Three-dimensional macroporous gold nanoparticles/graphene composites (3D-AuNPs/GN) were synthesized through a simple two-step process, and were used to modify working electrode sensing platform, based on which a facile electrochemical immunoassay for sensitive detection of carcinoembryonic antigen (CEA) in human serum was developed. In the proposed 3D-AuNPs/GN, AuNPs were distributed not just on the surface, but also on the inside of graphene. And this distribution property increased the area of sensing surface, resulting in capturing more primary antibodies as well as improving the electronic transmission rate. In the presence of CEA, a sandwich-type immune composite was formed on the sensing platform, and the horseradish peroxidase-labeled anti-CEA antibody (HRP-Ab₂)/thionine/nanoporous silver (HRP-Ab₂/TH/NPS) signal label was captured. Under optimal conditions, the electrochemical immunosensor exhibited excellent analytical performance: the detection range of CEA is from 0.001 to 10 ng mL⁻¹ with low detection limit of 0.35 pg mL⁻¹ and low limit of quantitation (LOQ) of 0.85 pg mL⁻¹. The electrochemical immunosensor showed good precision, acceptable stability and reproducibility, and could be used for the detection of CEA in real samples. The proposed method provides a promising platform of clinical immunoassay for other biomolecules     

Carbon Nanomaterials‐based Electrochemical Immunoassay with β‐Galactosidase as Labels for Carcinoembryonic Antigen

In this study, a novel signal‐amplified strategy for sensitive electrochemical sandwiched immunoassay of carcinoembryonic antigen (CEA) was constructed based on aminofunctionalized graphene oxide (GO‐NH₂) supported AgNPs used as catalytic labels of secondary anti‐CEA and β‐galactosidase (β‐Gal), Meanwhile, sulfhydrylation single‐wall carbon nanotubes (SWCNTs‐SH) as substrate materials embellished gold electrode through Au‐SH and connected with gold nanoparticles to form anti‐CEA/AuNPs/SWCNTs‐SH/Au sensing platform through layer‐by‐layer. In the presence of analyte CEA, a sandwich‐type immunoassay format was employed for determination of CEA by using the labeled β‐Gal toward the reduction of p‐aminophenyl galactopyranoside (PAPG) and the redox reaction of AgNPs. Under optimal conditions, the increase in the current was proportional to the concentration of CEA from 0.1 pg/mL to 200 ng/mL. The detection limit (LOD) was 0.036 pg/mL CEA at 3σ. The electrochemical immunoassay displayed an acceptable precision, selectivity, stability. Clinical serum specimens were assayed with the method, and the results were in acceptable agreement with those obtained from the referenced electrochemiluminescent method.     

Ultrasensitive Electrochemical Immunosensor for Detection of Tumor Necrosis Factor‐α Based on Functionalized MWCNT‐Gold Nanoparticle/Ionic Liquid Nanocomposite

A novel and highly sensitive electrochemical immunosensor was developed for the detection of protein biomarker tumor necrosis factor‐alpha (TNF‐α) based on immobilization of TNF‐α‐antibody (anti‐TNF‐α) onto robust nanocomposite containing gold nanoparticles (AuNP), multiwalled carbon nanotubes (MWCNTs) and ionic liquid (1‐buthyl‐3‐methylimidazolium bis (trifluoromethyl sulfonyl)imide). Functionalized MWCNT‐gold nanoparticle was produced by one‐step synthesis based on the direct redox reaction. The electrochemical properties of nanocomposite were characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The anti‐TNF‐α was immobilized or entrapped in the nanocomposite and used in a sandwich type complex immunoassay with anti‐TNF‐α labeled with horseradish peroxidase as secondary antibody. Under optimum conditions, the immunosensor could detect TNF‐α in a linear range from 6.0 to 100 pg mL^?1 with a low detection limit of 2.0 pg mL^?1. The simple fabrication method, high sensitivity, good reproducibility, stability, as well as acceptable accuracy for TNF‐α detection in human serum samples are the main advantages of this immunosensor, which might have broad applications in protein diagnostics and bioassay.     

Fabrication of Immunosensor Based on Polyaniline,Fullerene‐C60 and Palladium Nanoparticles Nanocomposite: An Electrochemical Detection Tool for Prostate Cancer

Present work demonstrates the fabrication of new and facile sandwich‐type electrochemical immunosensor based on palladium nanoparticles (PdNPs), polyaniline (PANI) and fullerene‐C₆₀ nanocomposite film modified glassy carbon electrode (PdNP@PANI‐C₆₀/GCE) for ultrasensitive detection of Prostate‐specific antigen (PSA) biomarker. PdNP@PANI‐C₆₀ was electrochemically synthesized on GCE and used as an electroactive substrate. PdNP@PANI‐C₆₀ was characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Primary antibody anti‐PSA (Ab1) was covalently immobilized on PdNP@PANI‐C₆₀/GCE using NHS/EDC linkers. In the presence of PSA antigen, horseradish peroxidase secondary antibody (HRP‐Ab2) was brought into the surface of the electrode, developing stable amplified signals of H₂O₂ reduction. Under the optimal conditions, a linear curve for determination of PSA at the proposed immunosensor was 1.6×10^?4 ng.mL^?1 to 38 ng.mL^?1 with a limit of detection (LOD) of 1.95×10^?5 ng.mL^?1. The proposed immunosensor was successfully validated in serum and urine samples towards PSA detection with satisfactory and acceptable results.     

Voltammetric Immunoassay for the Detection of Protein Biomarkers

A strategy for a fast (ca. 20 min), specific, electrochemical immunoassay for the cardiac biomarker creatine kinase (CK) and the human cytokine interleukin 10 (IL10) has been developed in this paper. The polyaniline modified gold surface formed from electrochemical reduction of diazonium salt supplies a solid substrate to link the activated carboxylic acid groups from the antibodies, which were labelled with ferrocene. The direct electrochemistry of ferrocene allows the analysis of protein markers with good sensitivity. The creatine kinase sensor demonstrates limit of detection of 0.5 pg mL^?1 in a physiological Krebs‐Henseleit solution. The anti‐IL10 antibody retained fluorescence activity after further coupling to ferrocene and covalent immobilization on to a gold electrode, showing a linear detection range for IL‐10 from 0.001 ng mL^?1 to 50 ng mL^?1 in PBS. We attribute the high sensitivity to the well‐controlled modified surface which results in end–on antibodies that can specifically capture the antigen with ease.     

Electrochemical immunosensor for carcinoembryonic antigen based on antigen immobilization in gold nanoparticles modified chitosan membrane.

A disposable electrochemical immunosensor for carcinoembryonic antigen (CEA) was proposed based on the antigen immobilized in a colloidal gold nanoparticles modified chitosan membrane on the surface of an indium-tin oxide (ITO) electrode. The different membranes were characterized by scanning electron microscope and electrochemical methods. Based on a competitive immunoassay format, the immobilized antigen of the immunosensor was incubated with a horseradish peroxidase (HRP) labeled antibody and sample CEA antigen, and the formed immunoconjugate in the immunosensor was detected by an o-phenylenediamine-H(2)O(2)-HRP electrochemical system. Under the optimal experimental conditions, the electrocatalytic current decreased linearly with the competitive mechanism. CEA could be determined in the linear range from 2.0 to 20 ng/ml with a detection limit of 1.0 ng/ml. The prepared CEA immunosensor is not only economic due to the low-cost ITO electrode obtained from industrial mass production, but is also capable with good stability and reproducibility for batch fabrication.     

Nanosilver-doped DNA polyion complex membrane for electrochemical immunoassay of carcinoembryonic antigen using nanogold-labeled secondary antibodies

A simple and sensitive electrochemical immunoassay protocol was developed for the detection of carcinoembryonic antigen (CEA) using nanosilver-doped DNA polyion complex membrane (PIC) as sensing interface. To construct such an immunosensor, double-stranded DNA was initially assembled onto the surface of thionine/Nafion-modified screen-printed carbon electrode to adsorb silver ions with positive charges, then silver ions were reduced to nanosilver particles with the aid of NaBH₄, and then anti-CEA antibodies were immobilized on the nanosilver surface. Gold nanoparticles conjugated with horseradish peroxidase-labeled anti-CEA were employed as signal antibodies for the detection of CEA with a sandwich-type assay format. Under optimal conditions, the immunosensor exhibited a dynamic range of 0.03-32 ng mL⁻¹ with a low detection limit of 10 pg mL⁻¹ CEA. Intra- and inter-assay imprecision (CVs) were <9.5% and 6.5%, respectively. The response could remain 90.1% of the original current at 30th day. 50 real samples were evaluated using the immunosensor and the enzyme-linked immunosorbent assay, respectively, and received in accordance with those two methods.     

Nanoporous gold as a solid support for protein immobilization and development of an electrochemical immunoassay for prostate specific antigen and carcinoembryonic antigen

Nanoporous gold (NPG) was utilized as a support for immobilizing alkaline phosphatase (ALP) conjugated to monoclonal antibodies against either prostate specific antigen (PSA) or carcinoembryonic antigen (CEA). The antibody-ALP conjugates were coupled to self-assembled monolayers of lipoic acid and used in direct kinetic assays. Using the enzyme substrate p-aminophenylphosphate, the product p-aminophenol was detected by its oxidation near 0.1?V (vs. Ag|AgCl) using square wave voltammetry. The difference in peak current arising from oxidation of p-aminophenol before and after incubation with biomarker increased with biomarker concentration. The response to these two biomarkers was linear up to 10?ng mL^?1 for CEA and up to 30?ng mL^?1 for PSA. The effect of interference on the PSA assay was studied using bovine serum albumin (BSA) as a model albumin protein. The effect of interference from a serum matrix was examined for the PSA assay using newborn calf serum. A competitive version of the immunoassay using antigen immobilized onto the NPG surface was highly sensitive at lower antigen concentration. Estimates of the surface coverage of the antibody-ALP conjugates on the NPG surface are presented.

Electro‐nano Diagnostic Platforms for Simultaneous Detection of Multiple Cancer Biomarkers

In this study, a bimetallic nanomaterial‐based electrochemical immunosensor was developed for the detection of carcinoembryonic antigen (CEA) and vascular endothelial growth factor (VEGF) cancer biomarkers at the same time. CEA and VEGF biomarkers are indicators for colon and breast cancers and stomach cancers, respectively. During the study, gold nanoparticle (AuNp), lead nanoparticle (PbNp), copper nanoparticle (CuNp) and magnetic gamma iron(III)oxide (γFe₂O₃ Np) were synthesized, characterized and used together for the first time in the structure of an electrochemical biosensor based on anti‐CEA and anti‐VEGF. For this purpose, Au SPE based sandwich immunosensor was fabricated by using labeled anti‐CEA (labeled with Pb⁺²) and labeled anti‐VEGF (labeled with Cu⁺²). As a result, CEA and VEGF biomarkers were detected following the oxidation peaks of label metals (Pb⁺² and Cu⁺²) by using differential pulse voltammetry. After the experimental parameters were optimized, the linear range was found in the concentration range between 25 ng/mL and 600 ng/mL with the relative standard deviation (RSD) value of (n=3 for 600 ng/mL) 3.33 % and limit of detection (LOD) value of 4.31 ng/mL for CEA biomarker. On the other hand, the linear range was found in the concentration range between 0.2 ng/mL and 12.5 ng/mL with the RSD value of (n=3 for 12.5 ng/mL) 5.31 % and LOD value of 0.014 ng/mL for VEGF biomarker. Lastly, sample application studies for synthetic plasma sample and interference studies with dopamine, ascorbic acid, BSA, cysteine and IgG were carried out.     

Label‐free Electrochemical Aptasensor for Carcino‐embryonic Antigen Based on Ternary Nanocomposite of Gold Nanoparticles,Hemin and Graphene

In this report, a label‐free electrochemical aptasensor for carcino‐embryonic antigen (CEA) was successfully developed based on a ternary nanocomposite of gold nanoparticles, hemin and graphene nanosheets (AuNPs‐HGNs). This nanocomposite was prepared by decorating gold nanoparticles on the surface of hemin functionalized graphene nanosheets via a simple wet‐chemical strategy. The aptamer can be assembled on the surface of AuNPs‐HGNs/GCE (glassy carbon electrode) through Au‐S covalent bond to form the sensing interface. Hemin absorbed on the graphene nanosheets not only acts as a protective agent of graphene sheets, but also as an in situ probe base on its excellent redox properties. Gold nanoparticles provide with both numerous binding sites for loading CEA binding aptamer (CBA) and good conductivity to promote the electron transfer. The current changes, which are caused by CEA specifically binding on the modified electrode, are exploited for the label‐free detection of CEA in a very rapid and convenient protocol. Therefore, the method has advantages of high sensitivity, wide linear range (0.0001–10 ng mL^?1), low detection limit (40 fg mL^?1) and attractive specificity. The results illustrate that the proposed label‐free electrochemical aptasensor has a potential application in the biological or clinical target analysis for its simple operation and low cost.     

Electrochemical Immunosensor for α‐Fetoprotein Based on Gold Nanoparticles/Graphene‐Prussian Blue

The electrochemical immunosensor for α‐fetoprotein (AFP) was fabricated based on the platform of gold nanoparticles (GNP)/graphene (Gr)‐prussian blue (PB). By electrodeposition, GNP were modified on the surface of the prepared Gr‐PB. The anti‐AFP‐1,1′‐ferrocenedicarboxylic acid (FcDA) as label was directly immobilized on the platform of GNP/Gr‐PB. And after the immunoreactions, the formed complex inhibited the electron transfer and decreased the catalytic current of FcDA toward the reduction of H₂O₂. And in the range of 10–3200 pg·mL^?1, the decreased current is linear with the concentration of AFP, with a detection limit of 3 pg·mL^?1. The developed immunoassay method showed good precision, high sensitivity, acceptable stability and reproducibility, and could be used for the detection of real samples with consistent results in comparison with those obtained by the enzyme linked immunosorbent assay (ELISA) method.     

Voltammetric immunoassay for the carcinoembryonic antigen by using a glassy carbon electrode modified with poly(3,4-ethylenedioxythiophene) doped with tannic acid and grafted with poly(ethylene glycol)

The authors describe a voltammetric immunoassay for the carcinoembryonic antigen (CEA). A GCE was modified by electrodeposition of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with tannic acid (TA). Subsequently, four-armed poly(ethylene glycol) (PEG) was assembled onto the modified surface through hydrogen bonding. The fabrication steps were characterized by scanning electron microscopy, energy dispersive spectroscopy, fourier transform infrared spectroscopy, contact angle measurements, electrochemical impedance spectroscopy and differential pulse voltammetry. The PEG/TA-PEDOT surface is shown be super-hydrophilic and to possess anti-fouling capability. Antibody against CEA was then covalently immobilized on the electrode. By using hexacyanoferrate as an electrochemical probe and at a working potential of 0.18 V vs SCE, the amperometric response is linear in the 10 ag·mL^?1 to 1.0 ng·mL^?1 CEA concentration range, and the detection limit is as low as 4.8 ag·mL^?1 (at an S/N ratio of 3). The assay was applied to the quantification of CEA in 1:10 diluted human serum samples. Recoveries ranged from 103.7 to 108.7%, and relative standard deviations from 2.9 to 4.8%.

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Graphical abstract Schematic of an electrochemical immunosensor for the carcinoembryonic antigen (CEA). It is based on the use of tannic acid (TA) and poly(ethylene glycol) (PEG), both deposited on a glassy carbon electrode (GCE), and using hexacyanoferrate as the electrochemical probe. The sensor has a wide linear range and a 4.8 ag·mL^?1 detection limit.