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.     

Heparin‐gold Nanoparticles and Liquid Crystal Applied in Label‐free Electrochemical Immunosensor for Prostate‐specific Antigen

A label‐free electrochemical immunosensor based on the liquid crystal (E)‐1‐decyl‐4‐[(4‐decyloxyphenyl)diazenyl]pyridinium bromide (Br−Py), together with heparin‐stabilized gold nanoparticles (AuNP‐Hep) and Nafion is proposed for the determination of prostate‐specific antigen (PSA). The Br−Py liquid crystal presented redox properties and good film‐forming abilities on the electrode surface, and thus it is a suitable alternative as a redox probe for a label‐free electrochemical immunosensor, which could simplify the analysis methodology. The stepwise construction of the immunosensor and the incubation process (immunocomplex formation) were characterized by voltammetry and electrochemical impedance spectroscopy. The proposed immunosensor could directly detect PSA concentrations in the incubation samples, based on the suppression of the Br−Py redox peak (‘base peak’) current. After optimization, the immunosensor exhibited a linear response to PSA concentrations in the range of 0.1 to 50 ng mL⁻¹, with a calculated detection limit of 0.08 ng mL⁻¹. The reproducibility (coefficient of variance less than 3.0 %), selectivity and accuracy of the methodology were adequate. The immunosensor was satisfactorily applied in the quantification of PSA in human blood plasma samples.     

A Prostate Specific Antigen Immunosensor Based on Biotinylated‐Antibody/Cyclodextrin Inclusion Complex: Fabrication and Electrochemical Studies

Immobilization of biomolecules with a proper orientation is considered as a basis for diverse biotechnological applications. Herein, we report a host‐guest inclusion complexation between β‐cyclodextrin (β‐CD) and biotin as a versatile approach for the immobilization of biomolecules. As a practical application, a sandwich‐type electrochemical immunosensor was designed for the determination of prostate specific antigen (PSA). The immunosensor was fabricated by in situ electropolymerization of poly(N‐acetylaniline) onto a rGO‐modified Pt electrode. Then, β‐CD was covalently grafted onto the over‐oxidized polymer backbone. For improving the efficiency of the assay, AuNPs were casted on the polymeric film, on the surface of which thionine (TH) as an electron mediator was covalently immobilized. Using a host‐guest inclusion complexation between β‐CD and biotin, a β‐CD/biotin‐Ab₁/PSA/Ab₂‐horseradish peroxidase (HRP) sandwich was formed on the electrode surface. The analytical signal was produced via electrochemical reduction of TH_ox, generated by biocatalytic oxidation of the TH_red in the presence of HRP/H₂O₂. Under optimal conditions, the proposed sensor responded linearly to PSA in the range from 10.0 pg mL⁻¹ to 25.0 ng mL⁻¹, with a low detection limit of 6.7 pg mL⁻¹ (S/N=3). Kinetic parameters of the interaction of β‐CD with Ab₁ were also investigated. Finally, the applicability of the immunosensor was successfully investigated for the detection of PSA in human serum samples.     

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.     

An Amperometric Immunosensor for IgG Based on Conducting Polymer and Carbon Nanotube‐Linked Hydrazine Label

An amperometric immunosensor for IgG was developed by covalently immobilizing anti‐IgG on multiwall carbon nanotube‐embedded conducting polymer, poly‐5,2′ : 5′′,2′′‐terthiophene‐3′‐carboxylic acid (MWCNT/pTTCA). The MWCNT/pTTCA modified electrode was characterized by SEM, EIS, and XPS. A hydrazine‐labeled secondary antibody‐MWCNT conjugate (Hyd‐MWCNT‐Ab₂) was applied for detection. Hydrazine was used as a catalyst for the reduction of hydrogen peroxide, which was monitored at ?0.3 V vs. Ag/AgCl. The calibration plots showed a linear range of 0.1–10 ng/mL with a detection limit of 0.084±0.004 ng/mL. The proposed immunosensor was evaluated for clinical applications in a rabbit serum sample.     

Metal Enhanced Electrochemical Cyclooxygenase‐2 (COX‐2) Sensor for Biological Applications

Pain measurement is commonly required in biomedical and other emergency situations, yet there has been no pain biosensor reported in literature. Conventional approaches for pain measurement relies on Wong‐Baker face diagrams, which are grossly inadequate for situations involving children or unconscious people. We report a label‐free immunosensor for monitoring the pain biomarker cylooxygenase‐2 (COX‐2) in blood. The sensor is based on the concept of metal‐enhanced detection (MED). MED relies on the idea that the immobilization of underpotential deposition (upd) metallic films deposited either as a monolayer or electrostatically held onto a solid gold substrate could significantly amplify bimolecular recognition such as involving antigen‐antibody (Ab‐Ag) interactions. The surface bound Ab‐Ag complex insulates the electrode; causing a decrease in concentration‐dependent redox signals. A linear detection range of (3.64–3640.00)×10^?4 ng/mL was recorded with a detection limit of 0.25×10^?4 ng/mL, which was 4 orders of magnitude lower than that reported for ELISA for the same biomarker. The immunosensor exhibited selectivity of less than 6 % for potential interferents.     

Simultaneous electrochemical immunosensing of alpha-fetoprotein and prostate specific antigen using a glassy carbon electrode modified with gold nanoparticle-coated silica nanospheres and decorated with Azure A or ferrocenecarboxylic acid

We describe an electrochemical immunosensor for the simultaneous determination of alpha-fetoprotein (AFP) and prostate specific antigen (PSA) via a modified glassy carbon electrode. Silica nanoparticles (200–300 nm i.d.) with good monodispersity and uniform shape were synthesized, and the following species were then consecutively immobilized on their surface: gold nanoparticles (AuNPs; 5–15 nm i.d.), secondary antibody (Ab₂) and the redox-probes Azure A or ferrocenecarboxy acid (Fc). In parallel, two types of primary antibodies (Ab₁) were co-immobilized on the surface of the dissolved reduced graphene oxide sheets (rGO) that were also decorated with AuNPs. In the presence of antigens (AFP or PSA), the Ab₂/Si@AuNPs carrying Azure A and Fc are attached to the AuNP/rGO conjugate via a sandwich type immunoreaction. Differential pulse voltammetry (DPV) was employed to measure the resulting changes in the signal of Fc or Azure A. Two well-resolved oxidation peaks, one at −0.48 V (corresponding to Azure A) and other at + 0.12 V (corresponding to Fc; both vs. SCE) can be observed in the DPV curves. Under optimal conditions, AFP and PSA can be simultaneously determined in the range from 0.01 to 25 ng mL‾¹ for AFP, and from 0.012 to 25 ng mL‾¹ for PSA. The detection limits are 3.3 pg mL‾¹ for AFP and 4.0 pg mL‾¹ for PSA (at a signal-to-noise ratio of 3). The method was applied to (spiked) real sample analysis, and the recoveries are within 96.0 and 107.2 % for PSA, and within 100.9 and 105.8 % for AFP, indicating that this dual immunosensor matches the requirements of clinical analysis.

(A) Two types of signal labels preparation process. (B) The immunosensor preparation and detection process.

     

Gold nanoparticle‐enhanced capillary electrophoresis‐chemiluminescence assay of trace uric acid

A sensitive method based on gold nanoparticle‐enhanced CE‐chemiluminescence (CL) detection was developed for quantifying uric acid (UA) in serum. In this work, gold nanoparticles were added into the running buffer of CE to catalyze the post‐column CL reaction between luminol and hydrogen peroxide, achieving highly efficient CL emission. Negative peaks were produced due to the inhibitory effects on CL emission from UA eluted from the electrophoretic capillary. The decrease in CL intensity was proportional to the concentration of UA in the range of 2.5×10^?7–1.0×10^?5 M. Detection limit was 4.6×10^?8 M UA. Ten human serum samples were analyzed by the presented method. Serum level of UA was found to be in the range from 204 to 324 μM for healthy subjects (n=5), and from 464 to 497 μM for diabetic patients (n=5). The two groups were significantly different (p<0.05). The results suggested a potential application of the proposed assay in rapid primary diagnosis of diseases such as diabetes.     

Two‐step signal amplification for high‐sensitivity detection of biomarkers using gold nanoparticle–based conjugates

The measurement of biomarkers in bodily fluids is extremely important for diagnosing disease, monitoring disease progression, and evaluating treatment efficacy. In this paper, we present a highly sensitive and compatible gold nanoparticle (AuNP)‐based, two‐step signal amplification system for biomarker detection. First, AuNPs were coated onto the surfaces of 96‐well plates to generate rough surfaces, which enable immobilization of many more capture antibodies than a smooth substrate. As a result, detection sensitivity was enhanced significantly. Second, the horseradish peroxidase (HRP)‐conjugated detection antibodies were labeled on large‐size AuNPs, which increase the localized amounts of HRP and thus further lower the detection limit. Based on the consecutive signal amplification system, a high‐sensitivity assay was achieved, with a LOD of 0.07 ng/mL for prostate‐specific antigen (PSA). This assay was allowed to detect the PSA levels in clinical samples without changing the current standard immunoassay setups, showing great potential in many settings where immunoassays are needed.     

Sandwich-type electrochemiluminescence immunosensor based on Ru-silica@Au composite nanoparticles labeled anti-AFP

A simple and sensitive sandwich-type electrochemiluminescence immunosensor for α-1-fetoprotein (AFP) on a gold nanoparticles (nano-Au) modified glassy carbon electrode (GCE) was developed by using Ru-silica (Ru(bpy)₃²⁺-doped silica) doped Au (Ru-silica@Au) composite as labels. The primary antibody, anti-AFP was first immobilized on the gold nanoparticles modified electrode due to the covalent conjugation, then the antigen and the Ru-silica@Au composite nanoparticles labeled secondary antibody was conjugated successively to form a sandwich-type immunocomplex through the specific interaction. The surfaces of Ru-silica nanoparticles were modified via the assemble of Au nanoparticles. The prepared Ru-silica@Au composite nanoparticles own the large surface area, good biocompatibility and highly effective electrochemiluminescence properties. The morphologies of the Ru-silica@Au composite nanoparticles were investigated by using transmission electronic microscope (TEM). The Ru-silica@Au composite nanoparticles labeled anti-AFP/AFP/bovine serum albumin (BSA)/anti-AFP/nano-Au modified GCE electrode was evaluated by means of cyclic voltammetry (CV) and electrogenerated chemiluminescence (ECL). The immunosensor performed high sensitivity and wide liner for detection AFP in the range of 0.05-50 ng/mL and the limit detection was 0.03 ng/mL (defined as S/N = 3).     

Double‐Layer Nanogold and Poly(amidoamine) Dendrimer‐ Functionalized PVC Membrane Electrode for Enhanced Electrochemical Immunoassay of Total Prostate Specific Antigen

A simple and portable electrochemical immunosensor for the detection of total prostate specific antigen (t‐PSA) in human serum was developed using a double‐layer nanogold particles and dendrimer‐functionalized polyvinyl chloride (PVC) membrane as immunosensing interface. To fabricate such a multifunctional PVC electrode, an o‐phenylenediamine‐doped PVC membrane was initially constructed, then nanogold particles and poly(amidoamine) G4‐dendrimer with a sandwich‐type format were assembled onto the PVC membrane surface, and then t‐PSA antibodies (anti‐PSA) were adsorbed on the nanogold surface. The detection principle of the immunosensor is based on the change in the electric potential before and after the antigen‐antibody interaction. The experimental conditions and the factors influencing the performance of the immunosensor were investigated. Under optimal conditions, the proposed immunosensor exhibits good electrochemical behavior in the dynamic range of 0.5–18 ng/mL relative to t‐PSA concentration with a relative low detection limit of 0.1 ng/mL (S/N=3). The precision, reproducibility, and stability of the immunosensor are acceptable. In addition, 43 serum specimens were assayed by the as‐prepared immunosensor, and consistent results were obtained in comparison with those obtained by the standard enzyme‐linked immunosorbent assay (ELISA). Compared with the conventional ELISAs, the developed immunoassay system was simple and rapid without labeling and separation steps. Importantly, the immobilization and detection methodologies could be extended for the immobilization and detection of other biomarkers.     

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。     

Development of proof of concept for prostate cancer detection: an electrochemical immunosensor based on fullerene-C60 and copper nanoparticles composite film as diagnostic tool

Screening of Prostate-specific antigen (PSA) in human blood is the most common approach to diagnose prostate cancer. The joint application of biology and electrochemistry has shown a tremendous rise in research towards the development of electrochemical diagnostic tools for various diseases. The present study demonstrates the development of an effective immunosensing platform incorporating hydroquinone (HQ) immobilized, fullerene-C₆₀ and copper nanoparticles (CuNPs) composite film on glassy carbon electrode (HQ@CuNPs-reduced-fullerene-C₆₀/GCE) for the selective, quick and trace detection of PSA. In order to fabricate immunosensor sequential immobilization of primary antibody (Ab₁), blocking agent (bovine serum albumin (BSA)), antigen (prostate-specific antigen (PSA)) and secondary antibody (Ab₂) tagged with horseradish peroxide (HRP) was carried out on HQ@CuNPs-reduced-fullerene-C₆₀/GCE. Electrochemical characterization and the signal response of immunosensor were tested using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergetic effect of fullerene-C₆₀ and CuNPs, the novel nanocomposite film exhibited excellent catalytic activity towards hydrogen peroxide (H₂O₂) reduction for greatly amplified immunosensing signals. HQ@CuNPs-fullerene-C₆₀/GCE exhibited a well-defined redox peak and accelerated electrochemical reduction of H₂O₂ without any interference of dissolved oxygen and false-positive result in phosphate buffer solution (PBS) at pH 7.0. The parameters influencing the electrochemical response were optimized. Under the optimized conditions, wide linearity between PSA concentrations and current responses ranging from 0.005 ng/mL to 20 ng/mL with the lower detection limit of 0.002 ng/mL was obtained at the proposed immunosensor. The clinical applicability of the proposed immunosensor was successfully tested in serum and urine samples. Results revealed that the proposed immunosensor may create new boundaries in the identification of PSA in human blood samples.     

Phthalocyanine‐Sensitized Graphene–CdS Nanocomposites: An Enhanced Photoelectrochemical Immunosensing Platform

A novel strategy is developed for the fabrication of graphene–CdS (G–CdS) nanocomposites by in situ growth of CdS nanoparticles onto simultaneously reduced graphite oxide, which is noncovalently functionalized by sodium 1‐pyrene sulfonate through strong π–π stacking interactions. Subsequently, cobalt 2,9,16,23‐tetraaminophthalocyanine (CoTAPc) is self‐assembled on the G–CdS nanocomposites through electrostatic interactions to produce phthalocyanine‐sensitized G–CdS nanocomposites. The photoactive superstructure enhances the photocurrent generation capability, and presents an efficient photoelectrochemical immunosensing platform for the ultrasensitive detection of the prostate‐specific antigen (PSA). The quantitative measurement of PSA is based on the decrease in the photocurrent intensity of the phthalocyanine‐sensitized G–CdS nanocomposites, which results from an increase in the steric hindrance due to the formation of the immunocomplex. A linear relationship between the photocurrent decrease and the PSA concentration is obtained in the wide range from 1 pg mL^?1 to 5 μg mL^?1 with a detection limit of 0.63 pg mL^?1. The proposed sensor shows high sensitivity, stability, reproducibility, and can become a promising platform for other biomolecular detection.     

Label-free sandwich type of immunosensor for hepatitis C virus core antigen based on the use of gold nanoparticles on a nanostructured metal oxide surface

We report on the construction of a label-free electrochemical immunosensor for detecting the core antigen of the hepatitis C virus (HCV core antigen). A glassy carbon electrode (GCE) was modified with a nanocomposite made from gold nanoparticles, zirconia nanoparticles and chitosan, and prepared by in situ reduction. The zirconia nanoparticles were first dispersed in chitosan solution, and then AuNPs were prepared in situ on the ZrO₂-chitosan composite. In parallel, a nanocomposite was synthesized from AuNPs, silica nanoparticles and chitosan, and conjugated to a secondary antibody. The properties of the resulting nanocomposites were investigated by UV-visible photometry and transmission electron microscopy, and the stepwise assembly process was characterized by means of cyclic voltammetry and electrochemical impedance spectroscopy. An sandwich type of immunosensor was developed which displays high sensitivity to the HCV core antigen in the concentration range between 2 and 512?ng?mL^?1, with a detection limit of 0.17?ng?mL^?1 (at S/N?=?3). This immunosensor provides an alternative approach towards the diagnosis of HCV.

Photoelectrochemical immunoassay for microcystin-LR based on a fluorine-doped tin oxide glass electrode modified with a CdS-graphene composite

We report on a sensitive electrochemical aptasensor for the detection of human prostate specific antigen (PSA). It is based on the signal amplification of the biotin-avidin system using a sensing platform that is making use of a graphite electrode modified with gold nanoparticles that were covered with graphitized mesoporous carbon nanoparticles (AuNPs@GMCs). The AuNPs@GMCs hybrid was prepared by linking 1,6-hexanedithiol-functionalized GMCs and gold nanoparticles via Au-S groups. Then, streptavidin was immobilized on the electrode modified with the AuNPs@GMCs so to enlarge the amount of biotin-aptamer which led to enhanced detection sensitivity. If an PSA aptamer captures the target PSA on the electrode, the differential pulse voltammetric (DPV) signal of the hexacyanoferrate redox system decreases. Factors affecting the performance of the aptasensor were studied in detail. Under optimal conditions, the DPV signal changes could be used to quantitatively detect PSA in the concentration range from 0.25 to 200?ng?mL^?1, with a lowest limit of detection as small as 0.25?ng?mL^?1. The aptasensor is highly specific and displays acceptable precision, good stability and repeatability.     

Electrochemical Immunoassay for Free Prostate Specific Antigen (f‐PSA) Using Magnetic Beads

Prostate specific antigen (PSA) is a prominent marker for the prostate carcinoma. It is found in human blood in free (f‐PSA) and complex forms. These two forms together are called total PSA (t‐PSA). Estimation of both forms is essential to predict malignancy. In this study we report a unique and effective technique of electrochemical detection of f‐PSA using magnetic beads on a three‐electrode screen‐printed sensor. A magnetic bead enzyme linked immunosorbent assay (ELISA) was performed in a cuvette. Following the immunoassay, magnetic beads were recovered by a magnetic concentrator and transferred on the working electrode of the 3‐electrode assembly. The amperometric response, a measure of the amount of residual enzyme activity on the beads and hence the concentration of analyte in solution, was determined by addition of enzyme substrate. The device has a detection limit of <0.1 ng mL^?1 f‐PSA and a linear range of 0 to 1 ng mL^?1 f‐PSA.     

Simultaneous quantification of catecholamines in rat brain by high‐performance liquid chromatography with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence detection

A new method based on high‐performance liquid chromatography (HPLC) coupled with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence (CL) detection was developed for the simultaneous quantitation of catecholamines in rat brain. In the present CL system, gold nanoparticles were produced by the on‐line reaction of H₂O₂, NaHCO₃?Na₂CO₃ (buffer solution of luminol) and HAuCl_4. Norepinephrine (NE), epinephrine (EP) and dopamine (DA) could strongly enhance the CL signal of the on‐line gold nanoparticle‐catalyzed luminol system. The UV?visible absorption spectra and transmission electron microscopy studies were carried out, and the CL enhancement mechanism was proposed. Catecholamines promoted the on‐line formation of more gold nanoparticles, which better catalyzed the luminol–H₂O₂ CL reaction. The good separation of NE, EP and DA was achieved with isocratic elution using a mixture of methanol and 0.2% aqueous phosphoric acid (5:95, v/v) within 8.5 min. Under the optimized conditions, the detection limits, defined as a signal‐to‐noise ratio of 3, were in the range of 1.32–1.90 ng/mL, corresponding to 26.4?38.0 pg for 20 μL sample injection. The recoveries of catecholamines added to rat brain sample were >94.6%, with the precisions <5.5%. The validated HPLC?CL method was successfully applied to determine NE and DA in rat brain without prior sample purification. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

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.