Sensitive Electrochemical Immunoassay Research Articles

Atomically Co-dispersed nitrogen-doped carbon for sensitive electrochemical immunoassay of breast cancer biomarker CA15-3.

The development of an ultrasensitive and precise measurement of a breast cancer biomarker (cancer antigen 15-3; CA15-3) in complex human serum is essential for the early diagnosis of cancer in groups of healthy populations and the treatment of patients. However, currently available testing technologies suffer from insufficient sensitivity toward CA15-3, which severely limits early large-scale screening of breast cancer patients. We report a versatile electrochemical immunoassay method based on atomically cobalt-dispersed nitrogen-doped carbon (Co-NC)-modified disposable screen-printed carbon electrode (SPCE) with alkaline phosphatase (ALP) and its metabolite, ascorbic acid 2-phosphate (AAP), as the electrochemical labeling and redox signaling unit for sensitive detection of low-abundance CA15-3. During electrochemical detection by differential pulse voltammetry (DPV), it was found that the Co-NC-SPCE electrode did not have a current signal response to the AAP substrate; however, it had an extremely favorable response current to ascorbic acid (AA). Based on the above principle, the target CA15-3-triggered immunoassay enriched ALP-catalyzed AAP produces a large amount of AA, resulting in a significant change in the system current signal, thereby realizing the highly sensitive detection of CA15-3. Under the optimal AAP substrate concentration and ALP catalysis time, the Co-NC-SPCE-based electrochemical immunoassay demonstrated a good DPV current for CA15-3 in the assay interval of 1.0 mU/mL to 10,000 mU/mL, with a calculated limit of detection of 0.38 mU/mL. Since Co-NC-SPCE has an excellent DPV current response to AA and employs split-type scheme, the constructed electrochemical immunoassay has the merits of high preciseness and anti-interference, and its clinical diagnostic results are comparable to those of commercial kits.

FeNC nanozyme-based electrochemical immunoassay for sensitive detection of human epidermal growth factor receptor 2.

Theproof-of-concept of sensitive electrochemical immunoassay for the quantitative monitoring of human epidermal growth factor receptor 2 (HER2)is reported. The assay is carried out on iron nitrogen-doped carbon (FeNC) nanozyme-modified screen-printed carbon electrode using chronoamperometry. Introduction of target HER2 can induce the sandwiched immunoreaction between anti-HER2 monoclonal antibody-coated microplate and biotinylated anti-HER2 polyclonal antibody. Thereafter, streptavidin-glucose oxidase (GOx) conjugate is bonded to the detection antibody. Upon addition of glucose, 3,3',5,5'-tetramethylbenzidine (TMB) is oxidized through the produced H2O2 with the assistance of GOx and FeNC nanozyme. The oxidized TMB is determined via chronoamperometry. Experimental results revealed that electrochemical immunosensing system exhibited good amperometricresponse, and allowed the detection of target HER2 as low as 4.5 pg/mL. High specificity and long-term stability are acquired with FeNC nanozyme-based sensing strategy. Importantly, our system provides a new opportunity for protein diagnostics.

Electrochemical biosensor based on antibody-modified Au nanoparticles for rapid and sensitive analysis of influenza A virus.

The online version contains supplementary material available at 10.1007/s11581-023-04944-w.

Biomimetic nanochannels for molybdate transport: application to sensitive electrochemical immunoassay for HER2

A nanochannel-based electrochemical immunoassay was developed for the detection of human epidermal growth factor receptor 2 (HER2), with molybdate as the reporter to explore the interaction occurring into the nanochannels. The presence of target increased steric hindrance of the antibody-functionalized nanochannels, thereby hindering the transport of molybdate. And the reporter could be monitored by working electrode modified with hydroxyapatite nanoparticles, based on the formation of the redox-active molybdophosphate. As a result, peak current obtained at ca. - 0.28V in square wave voltammograms could be applied to quantitative determination of HER2. The electrochemical signal increased linearly with the logarithm of the concentration of HER2 in a broad dynamic range of 0.1pg∙mL-1 to 10ng∙mL-1 with a detection limit of 0.05pg∙mL-1. The reliability of this immunoassay was validated by a recovery range of 99.5% to 111.7% for the detection of three different levels of HER2 in human serum samples. Integrating with multiple bionanochannels, this immunoassay is expected to provide a versatile approach for quantitative detection of various biomarkers in related disease diagnosis and therapy.

A sandwich-like configuration with a signal amplification strategy using a methylene blue/aptamer complex on a heterojunction 2D MoSe2/2D WSe2 electrode: Toward a portable and sensitive electrochemical alpha-fetoprotein immunoassay.

Liver cancer is one of the most common global health problems that features a high mortality rate. Alpha-fetoprotein (AFP) is a potential liver cancer biomarker for the diagnosis of liver cancer. The quantitative detection of AFP at an ultratrace level has important medical significance. Using the reaction of the antibody-antigen pair in an immunosensor enables the sensitive and selective AFP assay. Finding a strategy in signal generation and amplification is challenging to fabricate new sensitive electrochemical immunosensors for AFP detection. This study demonstrates the construction of a simple, reliable, and label-free immunosensor for the detection of AFP on a smart phone. Exfoliated two-dimensional (2D) molybdenum diselenide (MoSe2) and 2D tungsten diselenide (WSe2) were employed to modify the disposable screen-printed carbon electrode (SPCE) to use as the electrochemical platform, which is affixed to a small potentiostat connected to a smart phone. The modified electrode offers antibody immobilization and allows detection of AFP via an immunocomplex forming a sandwich-like configuration with the AFP-corresponding aptamer. A heterojunction 2D MoSe2/2D WSe2 composite improves the SPCE's reactivity and provides a large surface area and good adsorption capacity for the immobilizing antibodies. The signal generation for the immunosensor is from the electrochemical response of methylene blue (MB) intercalating into the aptamer bound on the electrode. The response for the proposed sandwich-like immunosensor is proportional to the AFP concentration (1.0-50,000 pg ml-1). The biosensor has potential for the development of a simple and robust point-of-care diagnostic platform for the clinical diagnosis of liver cancer, achieving a low limit of detection (0.85 pg ml-1), high sensitivity, high selectivity, good stability, and excellent reproducibility.

Highly Sensitive Electrochemical Immunoassay Using Signal Amplification of the Coagulation Cascade

Here, we report a highly sensitive immunoassay for human immunoglobulin G (IgG) that uses signal amplification of the coagulation cascade. Z-Phe-Pro-Lys-p-nitroaniline (FPK-pNA) was used as a substrate for thrombin activation in the last step of the coagulation cascade. During the coagulation cascade, pNA is liberated from FPK-pNA and can be detected electrochemically. Using square wave voltammetry with a glassy carbon electrode, we demonstrated that pNA can be quantified in a solution modeling the coagulation cascade prepared by mixing FPK-pNA and pNA. Characterization of the reactivity of thrombin toward FPK-pNA revealed that thrombin efficiently reacted with FPK-pNA. Subsequent characterization of factor XIa activity of factor XIa-labeled antibody revealed that factor XIa was not inactivated during labeling. Finally, a coagulation cascade-based immunoassay for human IgG was performed using a factor XIa-labeled antibody on magnetic beads. The limit of detection for human IgG was 5.0 pg/mL (33 fM) indicating that the coagulation cascade can amplify the immunoassay sensitivity compared to immunoassay using a thrombin-labeled antibody as a condition without a coagulation cascade. Coagulation cascade-based immunoassay was also highly selective. In the near future, we will report a highly sensitive immunoassay for the simultaneous detection of multiple analytes using a coagulation cascade-based immunoassay and Limulus amebocyte lysate reaction-based immunoassay we previously reported.

Toluidine blue-assisted synthesis of functionalized M (M = Cu, Co, Zn)-metal-organic frameworks for electrochemical immunoassay of proteins

• One-step TB-assisted synthesis strategy for fabricating functionalized MOFs. • The TB@Cu-MOFs, TB@Co-MOFs and TB@Zn-MOFs were synthesized. • A sensitive electrochemical immunoassay to detect IgG, MB and FMDV was developed. Toluidine blue (TB) as an electrochemically active molecule usually loads on metal organic frameworks (MOFs) surface to improve its electrochemical performance. In this paper, a simple synthesis strategy for one-step fabricating toluidine blue (TB)-functionalized metal organic frameworks (TB@MOFs) via the self-assembly approach was reported. This reaction of trimesic acid (H 3 BTC) as an organic ligand, TB as an electrochemical probe and a base for the deprotonation of H 3 BTC, and Zn 2+ , Cu 2+ or Co 2+ as the metal ion source leads to a rapid synthesis of three different MOFs, which all show exceptional electrochemical activity due to abundant TB molecules encapsulated in the MOFs. Varied instruments were used to characterize the TB@MOFs to verify the successful synthesis. Based on these three TB@MOFs sensing platforms, the sensitive label-free electrochemical immunosensors for the detection of pig immunoglobulin G (IgG), mycobacterium bovis (MB) and foot and mouth disease virus (FMDV) were developed with wide linear ranges and low detection limits. Furthermore, these immunosensors present good sensitivity, selectivity and stability in actual samples.

Electrochemical Immunoassay for the Detection of SARS-CoV-2 Nucleocapsid Protein in Nasopharyngeal Samples.

Point-of-care (POC) methods currently available for detecting SARS-CoV-2 infections still lack accuracy. Here, we report the development of a highly sensitive electrochemical immunoassay capable of quantitatively detecting the presence of the SARS-CoV-2 virus in patient nasopharyngeal samples using stencil-printed carbon electrodes (SPCEs) functionalized with capture antibodies targeting the SARS-CoV-2 nucleocapsid protein (N protein). Samples are added to the electrode surface, followed by horseradish peroxidase (HRP)-conjugated detection antibodies also targeting the SARS-CoV-2 N protein. The concentration of the virus in samples is quantified using chronoamperometry in the presence of 3,3′5,5′-tetramethylbenzidine. Limits of detection equivalent to less than 50 plaque forming units/mL (PFU/mL) were determined with virus sample volumes of 20 μL. No cross-reactivity was detected with the influenza virus and other coronavirus N proteins. Patient nasopharyngeal samples were tested as part of a proof-of-concept clinical study where samples were also tested using the gold-standard real-time quantitative polymerase chain reaction (RT-qPCR) method. Preliminary results from a data set of 22 samples demonstrated a clinical specificity of 100% (n = 9 negative samples according to RT-qPCR) and a clinical sensitivity of 70% for samples with RT-PCR cycle threshold (Ct) values under 30 (n = 10) and 100% for samples with Ct values under 25 (n = 5), which complies with the World Health Organization (WHO) criteria for POC COVID-19 diagnostic tests. Our functionalized SPCEs were also validated against standard plaque assays, and very good agreement was found between both methods (R2 = 0.9993, n = 6), suggesting that our assay could be used to assess patient infectivity. The assay currently takes 70 min from sampling to results.

Nitrogen‐doped TiO2 Nanocrystals for Highly Sensitive Electrochemical Immunoassay of Carcinoembryonic Antigen

AbstractNitrogen‐doped TiO2 nanocrystals (N−TiO2 NCs) were simply synthesized and then functionalized with streptavidin for highly sensitive electrochemical immunoassay of tumor marker. Scanning electron microscopy, transmission electron microscopy, static water contact angle, and cyclic voltametric measurement were adapted to examine the properties of N−TiO2 NCs and resultant immunosensor. The functionalized N−TiO2 NCs sensing platform shows high electrochemical conductivity, large surface area and excellent hydrophilicity. The features make them to produce high current response, capture more antibody molecules, and maintain the bioactivity of immobilized antibodies. By means of carcinoembryonic antigen (CEA) as model tumor marker, a wide linear range of 0.005–3 ng/mL and a low detection limit of 0.005 ng/mL (signal‐to‐noise ratio of 3) were achieved by the proposed CEA immunosensor. Furthermore, the resultant CEA immunosensor displays high specificity and was employed to determine CEA in clinical serum samples.

Hedgehog-like Bi2S3 nanostructures: a novel composite soft template route to the synthesis and sensitive electrochemical immunoassay of the liver cancer biomarker

An effective electrochemical immunosensor for detecting the liver cancer biomarker was developed based on the hedgehog-like Bi2S3 nanostructure, which was synthesized using novel CTAB-trimellitic acid as a composite soft template and thiourea as the sulfur source by a simple hydrothermal method with 20-fold sensitivity enhancement and one order of magnitude increase of linear range. The electrochemical immunosensor presented excellent performance, and could be applied to detect the cancer biomarker in clinical serum samples.

Magnetic beads combined with carbon black-based screen-printed electrodes for COVID-19: A reliable and miniaturized electrochemical immunosensor for SARS-CoV-2 detection in saliva

The diffusion of novel SARS-CoV-2 coronavirus over the world generated COVID-19 pandemic event as reported by World Health Organization on March 2020. The huge issue is the high infectivity and the absence of vaccine and customised drugs allowing for hard management of this outbreak, thus a rapid and on site analysis is a need to contain the spread of COVID-19. Herein, we developed an electrochemical immunoassay for rapid and smart detection of SARS-CoV-2 coronavirus in saliva. The electrochemical assay was conceived for Spike (S) protein or Nucleocapsid (N) protein detection using magnetic beads as support of immunological chain and secondary antibody with alkaline phosphatase as immunological label. The enzymatic by-product 1-naphtol was detected using screen-printed electrodes modified with carbon black nanomaterial. The analytical features of the electrochemical immunoassay were evaluated using the standard solution of S and N protein in buffer solution and untreated saliva with a detection limit equal to 19 ng/mL and 8 ng/mL in untreated saliva, respectively for S and N protein. Its effectiveness was assessed using cultured virus in biosafety level 3 and in saliva clinical samples comparing the data using the nasopharyngeal swab specimens tested with Real-Time PCR. The agreement of the data, the low detection limit achieved, the rapid analysis (30 min), the miniaturization, and portability of the instrument combined with the easiness to use and no-invasive sampling, confer to this analytical tool high potentiality for market entry as the first highly sensitive electrochemical immunoassay for SARS-CoV-2 detection in untreated saliva.

Efficient AuPd@GO-based electrochemical nanoprobe for sensitive detection of histone acetylase activity and its inhibitor.

Histone acetylase (HAT p300), which has aroused great concern in fundamental research and clinical applications, serves as one class of significant tumor markers. In our work, a sensitive electrochemical immunoassay for testing HAT p300 based on both graphene-assisted supported AuPd nanomaterial (AuPd@GO composite) and a typical amperometric i-t technique with fast response is developed favorably. The AuPd@GO-based sensing mechanisms are distributed as follows: the HAT p300 derived acetylation reaction occurs at the customized peptide-immobilized electrode; the AuPd@GO composite acts as carrier to immobilize acetyl antibody, thus constructing a sandwich-type electrochemical immunosensor via an antigen and antibody interaction; importantly, a distinct electrochemical signal could be caught due to the AuPd@GO nanomaterial with a favorable electrocatalytic property to the commercialized 3,3,5',5'-tetramethyl benzidine solution (TMB). Taking advantage of AuPd@GO composite, the established immunosensor displays a wide linear range from 1pM to 1000nM, and the detection limit is 0.5pM (S/N = 3) for HAT p300. Next, the biosensor is also used to analyze the inhibitor of HAT p300 successfully, which is promising for promoting the development of electrochemical HAT-related biodetection and drug discovery. Graphical abstract A sensitive electrochemical immunoassay for testing HAT p300 based on both graphene-assisted supported AuPd nanomaterial (AuPd@GO composite) and a typical amperometric i-t technique with fast response is developed favorably.

Electrochemical enzyme-linked immunosorbent assay (e-ELISA) for parasitic nematode Ostertagia ostertagi (brown stomach worm) infections in dairy cattle.

A sensitive electrochemical immunoassay (e-ELISA) has been developed for the detection of the gastrointestinal parasitic nematode Ostertagia ostertagi (brown stomach worm) in infected and control serum samples. An antigen-indirect immunoassay format was employed to detect the presence of O. ostertagi antibodies, coupled with an anti-species monoclonal horseradish peroxidase (HRP) conjugate. ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) and TMB (3,3',5,5'-tetramethylbenzidine/hydrogen peroxide) were investigated as both chromogenic visualising reagents for optical ELISA and electroactive substrates for electrochemical ELISA in the HRP catalysed oxidation reaction. Coulometry was applied for the detection of O. ostertagi antibodies (via TMB electrochemistry) and compared with the commercial optical ELISA (ABTS based SVANOVIR® O. ostertagi-Ab ELISA kit). Cost-effective in-house sensors were designed and fabricated using polyester and chemical adhesive materials with the aid of stencil printing and laser machining techniques. The performance of the electrochemical ELISA and sensor was evaluated by investigating redox mediators (ABTS vs. TMB), stop solutions (sodium dodecyl sulfate vs. sulfuric acid) and incubation times (150 min vs. 70 min vs. 25 min). For a total assay incubation time of 70 minutes, the TMB/H2SO4 based e-ELISA was able to differentiate between positive (P) and negative (N) control serum samples, with a P/N70 control ratio 1.6 times higher than that of optical ELISA (TMB/H2SO4 combination) and 2.9 times higher than that of the commercial ELISA kit (ABTS/SDS combination). Furthermore, the e-ELISA approach is quicker and required only 25 min (total incubation time) with even better response (P/N25 = 14.7), which is approximately 4-fold higher than the optical immunoassay (P/N25 = 3.8). The proposed e-ELISA is specific (selective Ab-Ag interactions) and highly sensitive - capable of detecting up to 16-fold dilutions of a positive control serum sample. The electrochemical ELISA approach has the potential for rapid sample screening in a portable, disposable format, contributing to the quest for effective prevention and control of parasitic Ostertagia ostertagi infections in cattle.

Sensitive and portable electrochemical immunoassay for lipoprotein-associated phospholipase A2 using BSA-doped CaCO3 nanospheres to regulate pH readout

A simple and sensitive electrochemical immunoassay method was developed for the quantitative monitoring of lipoprotein-associated phospholipase A2 (Lp-PLA2) on a low-cost microtiter plate by using a portable handheld pH meter.

Electrochemical sandwich immunoassay for Escherichia coli O157:H7 based on the use of magnetic nanoparticles and graphene functionalized with electrocatalytically active Au@Pt core/shell nanoparticles.

A highly sensitive electrochemical sandwich immunoassay is described fordetermination of Escherichia coli O157:H7 (E. coli O157:H7). Silica coated magnetite nanoparticles (Fe3O4) were modified with primary antibody to capture E. coli O157:H7. Gold-platinum core/shell nanoparticles (Au@Pt NPs) with different Pt shell thicknesses were prepared via changing the molar ratio of H2PtCl6 to HAuCl4 in the precursor solution. The optimized Au@Pt NPs exhibit enhanced activity in the electrocatalytic reduction of hydrogen peroxide (H2O2). The Au@Pt NPs were modified with graphene that was functionalized with Neutral Red, and then used as an electrochemical label for secondary antibodies and horseradish peroxidase (HRP). The sandwich immunocomplexes were magnetically absorbed on a 4-channel screen printed carbon electrode. Due to the catalysis of the Au@Pt NPs and HRP, the signal is strongly amplified in the presence of H2O2 when using thionine as the electron mediator. Under optimal conditions, the immunoassay has a linear response in the 4.0 × 102 to 4.0 × 108CFU·mL-1 concentration range, with a limit of detection of 91CFU·mL-1 (at an S/N ratio of 3). Graphical abstract Preparation of Au@Pt core/shell nanoparticles with different Pt shell thickness (A), rGO-NR (B), rGO-NR-Au@Pt-Ab2-HRP (C) and the preparation and the detection process of the immunoassay (D). rGO: reduced graphene oxide, GO: graphene oxide, NR: Neutral Red, HRP: horseradish peroxidase, AuNPs: gold nanoparticles, Fe3O4@SiO2: Silica coated magnetite nanoparticles, 4-SPCE: 4-channel screen printed carbon electrode.

Electrochemical immunoassay for lactalbumin based on the use of ferrocene-modified gold nanoparticles and lysozyme-modified magnetic beads.

The authors describe a method for electrochemical determination of the breast cancer biomarker α-lactalbumin (α-LA) using disposable screen-printed carbon electrodes (SPCEs). Lysozyme-conjugated Fe3O4 nanoparticles (Lys-Fe3O4NPs) were used to capture α-LA on the surface of the SPCEs which then is trapped in an immunosandwich using secondary antibodies labeled with ferrocene-modified gold nanoparticles. The amperometric response of ferrocene (recorded at +0.1V vs. silver pseudo-reference electrode) as well as the electrocatalytic activity of gold nanoparticles on the hydrogen evolution reaction (recorded at -1.0V Vs Ag pseudo-reference electrode) was exploited to sense α-LA. A sensitive voltammetric response is observed, with (a) a sensitivity of 0.8789μA·nM-1.cm-2, (b) a detection limit (LOD, atS/N = 3) as low as 0.07ng·mL-1, and (c) linear response in the 0.75 to 630ngmL-1 α-LA concentration range. The assay is selective and reproducible, and the SPCEs have good storage stability. The SPCEs were applied (a) to the analysis of (spiked) maternal milk, (b) of spiked serum from healthy and pregnant persons, and (c) of serum of patients suffering from breast cancer. Graphical abstract Schematic presentation of a sensitive electrochemical immunoassay platform based on ferrocene modified gold nanoparticles and lysozyme modified magnetic beads for the determination of alpha lactalbumin in human sera and breastmilk by the amperometric response of ferrocene and hydrogen evolution reaction.

Coupling antibody based recognition with DNA based signal amplification using an electrochemical probe modified with MnO2 nanosheets and gold nanoclusters: Application to the sensitive voltammetric determination of the cancer biomarker alpha fetoprotein.

The authors describe a sensitive electrochemical immunoassay for the cancer biomarker α-fetoprotein (AFP). It is based on a combination of an immunoassay with DNA-based signal amplification. Two-dimensional MnO2 nanosheets modified with gold nanoclusters (AuNC-MnO2) were synthesized through one-pot process and utilized as an electrochemical probe. Bovine serum albumin servedas templating agent to guide the formation and assembly of the modified sheets. The detection antibody against AFP and a polycytosine DNA sequence (dC20) were immobilized onto the modified nanosheets. The electrochemical assay follows the usual sandwich protocol. The antibodies on the nanosheets then bind to AFP, while dC20 causes signal amplification. The reaction of the phosphate backbone of dC20 with molybdate leads to the formation of redox-active molybdophosphate which generates an electrochemical current, typically measured at 0.20V (vs. Ag/AgCl). The method allows AFP to be determined in the 0.01 to 10ng·mL-1 concentration range, and the detection limit is as low as 5pg·mL-1. This strategy overcomes the drawbacks of conventional immunoassays whose sensitivity is often limited because many immunoassays are rather difficult to amplify. The method has a wide scope in that various other DNA signal amplification methods such as rolling circle amplification and hybridization chain reactions may also be applied. Graphical abstract Schematic of an electrochemical immunosensor for the detection of alpha fetoprotein (AFP) by combining an antibody based immunoassay with DNA based signal amplification utilizing gold clusters anchored 2D MnO2 (Au NCs-MnO2) nanosheets as electrochemical probe.

Application of antibody–nanogold–ionic liquid–carbon paste electrode for sensitive electrochemical immunoassay of thyroid-stimulating hormone

A novel electrochemical immunosensor based on carbon paste electrode (CPE) composed of ionic liquid (IL) and graphite was constructed. It demonstrated good efficiency for quick (each test in 30 s) determination of thyroid stimulating hormone (TSH). Electrode surface was modified by gold nanoparticles in order to immobilize of the thyroid stimulating hormone antibody (anti-TSH) on the CPE. The immunoassay structure was established by sandwiching the antigen (TSH) between the thyroid stimulating hormone antibody on the CPE surface modified with gold nanoparticles and the secondary antibody, polyclonal anti-human-TSH labeled with horseradish peroxidase (HRP-labeled anti-TSH). The signal of differential pulse voltammetry (DPV) was used as a basis for the determination of TSH concentration. This signal is generated by the reaction between O-aminophenol (OAP) and H2O2 catalyzed by HRP. The proposed immunosensor is able to measure the concentration of TSH in a linear range between 0.2 and 90.0 ng/mL with a detection limit 0.1 ± 0.02 ng/mL. In addition, high sensitivity and acceptable stability were achieved by this immunosensor which is promising in the clinical assay of TSH.

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

AbstractIn 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.

Detection of TSH, FT3, FT4, and TRAb in ovarian cancer with highly sensitive electrochemical immunoassay

To investigate the correlation between thyroid-stimulating hormone (TSH), free T3 (FT3), free T4 (FT4), thyroid-stimulating hormone receptor antibody (TRAb), and pathological parameters of ovarian cancer, we selected 122 patients with ovarian cancer and 70 patients with benign ovarian tumor. The differences in the positive rates of different pathological parameters, including TSH, FT3, FT4, and TRAb, in their serum were detected and compared through highly sensitive electrochemical immunoassay. We found that the positive rates of TSH, FT3, FT4, and TRAb in serous cystadenocarcinoma were higher than those of mucinous cystadenocarcinoma and other types of ovarian cancer. Meanwhile, the positive rates of FT3 and FT4 in stage III and IV ovarian cancer were lower than those in stage I and II ovarian cancer. However, the positive rates of FT3 and FT4 in poorly differentiated ovarian cancer were higher than those in moderately differentiated and well-differentiated ovarian cancer. The serum levels of TSH, FT3, FT4, and TRAb preoperatively, postoperatively, and after four cycles of ovarian cancer were significantly different from those in the control group. Thus, we conclude that TSH, FT3, FT4, and TRAb were abnormally expressed in the serum of ovarian cancer patients. And the application of highly sensitive electrochemical immunoassay for the detection of TSH, FT3, FT4, and TRAb in serum has important clinical value in the diagnosis of ovarian cancer.