Ultrasensitive Electrochemiluminescence Immunosensor Research Articles

“Sugarcoated haws on a stick”-like MWNTs–Fe3O4–C coaxial nanomaterial: Synthesis, characterization and application in electrochemiluminescence immunoassays

In this paper, a carbon coated magnetic nanoparticle (Fe3O4–C) was first synthesized via solvothermal reaction and carbonization of glucose under hydrothermal condition. The electrochemiluminescence (ECL) property of Fe3O4–C was studied, and exhibited a peak at 1.21V. In the goal to amplify the ECL intensity for sensitive detection, a novel coaxial carbon coated magnetic nanomaterial (MWNTs–Fe3O4–C) was synthesized. Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), powder X-ray diffraction (XRD) and powder X-ray photoelectron spectrometry (XPS) were applied as powerful tools to characterize and to demonstrate the named nanomaterial. MWNTs–Fe3O4–C showed better ECL property than Fe3O4–C. Furthermore, an ultrasensitive ECL immunosensor based on MWNTs–Fe3O4–C was developed for the determination of carcinoembryonic antigen (CEA). The prepared ECL immunosensor exhibited high sensitivity, good reproducibility, long-term stability, and acceptable precision on the detection of CEA in clinical human serum samples.

Reagentless electrochemiluminescent detection of protein biomarker using graphene-based magnetic nanoprobes and poly-l-lysine as co-reactant

This work described the construction of a reagentless and ultrasensitive electrochemiluminescence (ECL) immunosensor using poly-l-lysine as a co-reactant with Ru(bpy)32+ for signal amplification and magnetic Fe3O4 loaded graphene nanosheet as nanoprobes, which can achieve an impressive detection limit of 0.03pg/mL human total 3,3′,5-triiodothyronine (T3), a kind of diagnostic markers of thyroid disease. The bionanoprobes were prepared based on the coimmobilization of Ru(bpy)32+ and T3 detection antibody on the Fe3O4 loaded graphene nanosheet and the sensing interface was achieved by assembling T3 capture antibody on the gold nanoparticles (AuNPs) loaded electro-deposited l-lysine film modified bare glass carbon electrode (GCE). ECL responses were generated from the modified electrodes described above by just immersing them in phosphate buffer solutions (PBS) based on the sandwich-type immunoreactions. T3 was measured quantitatively in the range from 0.1pg/mL to 10ng/mL, which exhibits sufficiently high sensitivity and stability. The reagentless ECL immunoassay is a promising approach for the detection of a wide range of molecular analytes.

Core–shell Fe3O4–Au magnetic nanoparticles based nonenzymatic ultrasensitive electrochemiluminescence immunosensor using quantum dots functionalized graphene sheet as labels

In this paper, a novel, low-cost electrochemiluminescence (ECL) immunosensor using core–shell Fe3O4–Au magnetic nanoparticles (AuMNPs) as the carriers of the primary antibody of carbohydrate antigen 125 (CA125) was designed. Graphene sheet (GS) with property of good conductivity and large surface area was a captivating candidate to amplify ECL signal. We successively synthesized functionalized GS by loading large amounts of quantum dots (QDs) onto the poly (diallyldimethyl-ammonium chloride) (PDDA) coated graphene sheet (P-GS@QDs) via self-assembly electrostatic reactions, which were used to label secondary antibodies. The ECL immunosensors coupled with a microfluidic strategy exhibited a wide detection range (0.005–50UmL−1) and a low detection limit (1.2mUmL−1) with the help of an external magnetic field to gather immunosensors. The method was evaluated with clinical serum sample, receiving good correlation with results from commercially available analytical procedure.

Ultrasensitive electrochemiluminescence immunosensor based on nanoporous gold electrode and Ru-AuNPs/graphene as signal labels

In the paper, a simple and sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was proposed for the detection of cancer antigen 125 (CA 125) on a nanoporous gold (NPG) modified glassy carbon electrode (GCE). The NPG was easily prepared by a selective dissolution of silver from silver/gold alloy in nitric acid. The fabrication of Ru(bpy)32+-gold nanoparticles (Ru-AuNPs) aggregates was owing to the electrostatic interactions between citrate-capped AuNPs and Ru in aqueous medium. The Ru-AuNPs composite assembled with poly(diallyldimethylammonium chloride) functionalized graphene nanosheets (GR) (Ru-AuNPs/GR) was used as ECL labels, which has large surface area, good biocompatibility and electronic conductivity. The ECL intensity observed by the application of as-prepared Ru-AuNPs/GR composites was enhanced 6-fold compared to those of Ru-AuNPs. The primary antibody of CA 125 (Ab1) was first immobilized on the NPG modified electrode, then the antigen and the secondary antibody (Ab2) were conjugated to form a sandwich-type immunocomplex through the specific interaction. The proposed ECL immunosensor provided a wide linear response range over 0.01–100UmL−1 with a detection limit of 0.005UmL−1. The ECL immunosensor showed high sensitivity, good reproducibility, satisfied regeneration and selectivity, and may exhibit an attractive approach for other analyte determination.

Ultrasensitive detection of trace amount of clenbuterol residue in swine urine utilizing an electrochemiluminescent immunosensor

Abstract As a familiar β 2 -agonist, clenbuterol (CLB) was frequently reported to be illegally abused as a “lean meat agent” for livestock breeding, since it could improve growth rate and inhibit fat synthesis. Due to its potential hazard to human health, it has been forbidden as growth promoter for food-producing animal feeding in most countries. Therefore, the routine monitoring of CLB abuse is exceedingly necessary for food safety purpose. We herein report an ultrasensitive electrochemiluminescent immunosensor, which is firstly applied for assay of trace amount of CLB residue in swine urine. In this investigation, gold nanoparticles doped chitosan composite film was utilized for antigen immobilization, and Ru(bpy) 3 2+ -labeled antibody was utilized as the tracer antibody. With a competitive immunoassay format, good analytical performance was obtained. The proposed method shows a linear range of 0.010–1.0 ng/mL, with a limit of detection of 0.0050 ng/mL for CLB, which is evidently lower than that of most previous reports. This method is suitable for screening of trace amount of CLB residue, due to its simple manipulation, short assay time, and high detection sensitivity, and exhibits great promise in food safety and agonist monitoring.

Ultrasensitive detection of carcinoembryonic antigen based on electrochemiluminescence quenching of Ru(bpy)32+ by quantum dots

An ultrasensitive electrochemiluminescence (ECL) immunosensor for the detection of carcinoembryonic antigen (CEA) in serum and saliva was developed. Ru(bpy)32+-graphene-Nafion composite was first coated on the glassy carbon electrode surface in this ECL immunosensor. The sandwich-type immunoreactions between the first antibody and the second antibody bridged the donors Ru(bpy)32+ and acceptors QDs, which led to the occurrence of ECL quenching of Ru(bpy)32+ by QDs. Based on the efficient ECL quenching, ultrasensitive CEA detection was realized. Under optimal conditions, the ECL signal depended linearly on the logarithm of the CEA concentration within a range from 0.005 to 0.5 pg/mL, and the detection limit of CEA was 0.002 pg/mL. Moreover, the proposed ECL immunosensor provides a stable, specific, and highly sensitive immunoassay protocol for CEA detection at very low levels, which might hold a promise for clinical application.

Ultrasensitive electrochemiluminescence immunosensor using PtAg@carbon nanocrystals composites as labels and carbon nanotubes-chitosan/gold nanoparticles as enhancer

An ultrasensitive electrochemiluminescence (ECL) immunosensor was developed using PtAg@carbon nanocrystals (CNCs) as excellent labels based on carbon nanotubes-chitosan/AuNPs (CNT-CHIT/AuNPs) composite modified screen-printed carbon electrodes (SPCEs) for prostate protein antigen (PSA) detection. The CNCs were obtained simply by electro-oxidation of graphite with abundant carboxyl groups at their surfaces. The PtAg bimetallic nanocomposites with hierarchically hollow structures were fabricated through simple replacement reaction using dealloyed nanoporous silver (NPS) as both a template and reducing agent. Structure characterization was obtained by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) images. The PtAg@CNCs composites exhibit a 6 times higher ECL intensity than the pure CNCs labeled anti-PSA. The as-prepared CNT-CHIT/AuNPs composite can attach more antibody than pure CNTs. Due to the dual-amplification techniques, the concentrations of PSA were obtained in the range from 1 pg mL(-1) to 50 ng mL(-1) with a detection limit of 0.6 pg mL(-1). Finally, the as-proposed ECL immunosensor has the advantages of high sensitivity, specificity and stability and could become a promising technique for tumor marker detection.

Double-Conjugated Ru(bpy)<sub>3</sub><sup>2+</sup> Complexes for Enhanced Electrochemiluminescence Immunoanalysis

A new method was established to construct a ultrasensitive electrochemiluminescence (ECL) immunosensor by using Ru@SiO2 (Ru(bpy)3 2+ doped silica) - doped Au (Ru@SiO2-Au) composite nanoparticles to label Ru-Ab2 (monoclonal α-fetoprotein (AFP) antibody labeled with Ru(bpy)32+). The primary antibody, anti-AFP was first immobilized on the multi-walled carbon nanotubes (MCNTs) modified with gold nanoparticles (MCNTs-Au) modified glassy carbon electrode due to the covalent conjugation, then the antigen and the Ru@SiO2-Au composite nanoparticles labeled Ru-Ab2 (Ru@SiO2-Au~Ru-Ab2)was conjugated successively to form a double-conjugated Ru(bpy)32+ sandwich-type immunocomplex through the specific interaction. Accordingly, through the ECL response of Ru@SiO2-Au~Ru-Ab2 and tripropylamine (TPA), a strong ECL signal was obtained and an amplification analysis of protein interaction was achieved. The present immunosensor performed high sensitivity and wide liner for detection α-fetoprotein (AFP) in the range of 0.05-80 ng mL−1 and the limit detection was 0.025 ng mL−1(defined as S/N=3). The morphologies of MCNTs, MCNTs-Au, Ru@SiO2 and Ru@SiO2-Au nanoparticles were characterized by using transmission electronic microscopy (TEM). The developed label and method is versatile, offers enhanced performances, and can be easily extended to other protein detection.

Ultrasensitive electrochemiluminescence immunosensor based on luminol functionalized gold nanoparticle labeling

An ultrasensitive electrochemiluminescence (ECL) immunosensor based on luminol functionalized gold nanoparticle (AuNP) labeling was developed using human immunoglobulin G (hIgG) as a model analyte. The primary antibody biotin-conjugated goat-anti-human IgG was first immobilized on a streptavidin coated AuNP modified electrode, then the antigen (human IgG) and the luminol functionalized AuNP-labeled second antibody were conjugated successively to form a sandwich-type immunocomplex, i.e. immunosensor. ECL was carried out with a double-step potential in carbonate buffer solution containing 1.0 mmol/L H 2O 2. Since thousand of luminol molecules were coated on the surface of AuNPs to realize labeling of multiple molecules with CL activity at a single antibody and the amplification of AuNPs and biotin–streptavidin system was utilized, luminol ECL signal could be enhanced greatly, finally resulting in extremely high sensitivity. The ECL method shows a detection limit of 1.0 pg/mL (S/N = 3) for hIgG, which is superior to all previously reported methods for the determination of hIgG. Moreover, the proposed method is also simple, stable, specific, and time-saving, avoiding the complicated stripping procedure during CL detection and the uncontrollable synthesis of irregular nanoparticles compared with other chemiluminescence immunoassay based on AuNP labeling. Additionally, the labeling procedure is also superior to that of other reported multilabeling strategies, such as Ru complex-encapsulated polymer microspheres, and most of Ru complex-encapsulated liposomes in simplicity, stability, labeling property and practical applicability. Finally, the proposed method has been successfully applied to the detection of hIgG in human serums.