Guanhui Zhao

Ultrasensitive electrochemical immunosensor for alpha fetoprotein detection based on platinum nanoparticles anchored on cobalt oxide/graphene nanosheets for signal amplification

An ultrasensitive sandwich-type electrochemical immunosensor was developed for quantitative monitoring of Alpha fetoprotein (AFP). To achieve this objective, an incorporated signal amplification strategy of platinum nanoparticles anchored on cobalt oxide/graphene nanosheets (Pt NPs/Co3O4/graphene) was proposed by acting as the label of secondary antibodies. The prepared label not only empowered by advantages of each component but exhibited better electrochemical performance than single Pt NPs, Co3O4 and graphene, which has shown large specific surface area and good catalytic activity towards the reduction of H2O2. Meanwhile, the nanocomposite of gold nanoparticles adhered on 3-mercaptopropyltriethoxysilane functionalized graphene sheets (Au@MPTES-GS) was used as matrix to accelerate electron transfer and immobilize primary antibodies in this system. The signal amplification mechanism of the matrix and the label were explored successfully. Under optimal conditions, the electrochemical immunosensor exhibited a wide linear range from 0.1xa0pgxa0mL-1 to 60xa0ngxa0mL-1 with a low detection limit of 0.029xa0pg mL-1for AFP. The proposed immunosensor may have promising application in the clinical diagnosis of AFP and other tumor markers.

Electrochemiluminescent competitive immunosensor based on polyethyleneimine capped SiO2 nanomaterials as labels to release Ru(bpy)32+ fixed in 3D Cu/Ni oxalate for the detection of aflatoxin B1

In this work, a highly-efficient competitive method-based electrochemiluminescence (ECL) immunosensor was proposed based on {[Ru(bpy)3][Cu2xNi2(1-x)(ox)3]}n (Cu/Ni/Ru) as luminophor to efficiently detect aflatoxins B1 (AFB1). Cu/Ni/Ru exhibited excellent ECL behavior. While polyethyleneimine capped silicon dioxide (PEI@SiO2) could decrease the ECL performance of Cu/Ni/Ru due that PEI could destroy the structure of Cu/Ni/Ru via producing the complex between PEI and metal ions (Cu(II)/Ni(II)), inducing the release of Ru(bpy)32+. Since Au nanoparticles can directly combine with antibody and antigen, the Cu/Ni/Ru and PEI@SiO2 was functionalized by Au nanoparticles. The quantitative detection of AFB1 was based on the competitive binding between AFB1-bovine serum albumin labeled Au-PEI@SiO2 (Au-PEI@SiO2-AFB1-BSA) and free AFB1 with antibody-AFB1 which immobilized on Au-Cu/Ni/Ru. The ECL signal increased with augmenting the concentrations of the free AFB1 due to less Au-PEI@SiO2-AFB1-BSA combining with antibodies. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01ngmL-1 to 100ngmL-1 with a detection limit of 0.0039ngmL-1 (S/N = 3). The proposed immunosensor also provides a promising approach for ultrasensitive detection of other mycotoxins.

Ultrasensitive competitive method-based electrochemiluminescence immunosensor for diethylstilbestrol detection based on Ru(bpy) 3 2+ as luminophor encapsulated in metal–organic frameworks UiO-67

In this work, Ru(bpy)32+ encapsulated in metal-organic frameworks (MOFs) UiO-67 (Ru(bpy)32+/UiO-67) as luminophor was easily prepared and firstly applied in constructing an electrochemiluminescence (ECL) immunosensor to efficiently estimate diethylstilbestrol (DES). The competitive method-based ECL immunosensor platform was fabricated by amino-silicon dioxide which possesses large surface area. The poriness of UiO-67 was splendid so that Ru(bpy)32+ could be easily encapsulated. Ru(bpy)32+/UiO-67 with excellent ECL luminescence signal existed large specific surface area for easily labeled with antibodies. DES competed with bovine serum albumin-diethylstilbestrol (BSA-DES) for binding to antibody-specific sites in the constructed immunosensor. However DES was micromolecule, which was easier to bond to antibodies than BSA-DES. The ECL signal was gradually decreases with the increase of the concentration of DES. Under optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.01u202fpgu202fmL-1 to 50u202fngu202fmL-1 with a low detetion limit of 3.27 fg mL-1 (S/Nu202f=u202f3). The novel fabricated immunosensor with interference immunity and high stability may cause an attractive approach for the other targets determination.

Dual-responsive electrochemical immunosensor for detection of insulin based on dual-functional zinc silicate spheres-palladium nanoparticles

In this study, described an electrochemical immunoassay for insulin that is based on the use of zinc silicate spheres loaded with palladium nanoparticles (Zn2SiO4-PdNPs) that act as dual-function labels. The Zn2SiO4-PdNPs display high electrocatalytic activity towards the reduction of H2O2 and high sensitivity in chronoamperometry. The Zn2SiO4-PdNPs decrease the electron transfer rate between the electrolyte and the surface of the electrode, which can increase the changed current and enhance the sensitivity of the immunosensor as detected by square wave voltammetry (SWV). Electrodeposited gold is used as the matrix material. The icosahedral gold nanocrystals are coated with the primary antibodies formed a 3D mode to against abundant of insulin. Under optimal conditions, the assay has a linear response in the 0.1pgmL-1 to 50ngmL-1 insulin concentration range, and the limit of detection of the SWV and CA methods are 0.25 fg mL-1 and 80 fg mL-1, respectively. Moreover, the immunosensor holds an outstanding analytical performance for the insulin detection and has promising potential in clinical diagnosis.

Sandwich-type electrochemical immunoassay based on Co 3 O 4 @MnO 2 -thionine and pseudo-ELISA method toward sensitive detection of alpha fetoprotein

In this study, a sensitive sandwich-type electrochemical immunosensor was fabricated for the detection of alpha fetoprotein (AFP) based on Co3O4@MnO2-thionine (Co3O4@MnO2-Th) and the screen printing technique. Meanwhile, the pseudo enzyme-linked immunosorbent assay (pseudo-ELISA) method was applied in fabricating the immunosensor. Screen-printed carbon electrode (SPCE) was applied for achieving the detection of AFP. Simultaneously, the amino functionalized Co3O4@MnO2-Th was employed as secondary label and could greatly improve the electrochemical response signal, which was beneficial for detecting AFP. Differential pulse voltammetry (DPV) was applied for the detection of AFP and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the immunosensor. Under optimal conditions, the immunosensor exhibited a linear response toward AFP in the range of 0.001-100u202fng/mL, with a low detection limit of 0.33u202fpg/mL. Simultaneously, the proposed immunosensor displayed acceptable selectivity, excellent stability and well reproducibility. Furthermore, this proposed strategy may open up new ideas and find many potential applications in the detection of other tumor markers.

A voltammetric immunoassay for the carcinoembryonic antigen using a self-assembled magnetic nanocomposite

AbstractThe authors describe a voltammetric immunoassay for the carcinoembryonic antigen (CEA). It is based on the use of a self-assembled magnetic nanocomposite as multifunctional signal amplification platform. The core of the nanocomposite consists of Fe3O4 microspheres, and the shell of zirconium hexacyanoferrate loaded with gold nanoparticles (AuNPs@ZrHCF@Fe3O4). The material was synthesized by an electrostatic self-assembly process which is caused by the strong interaction between cyano groups and AuNPs. The surface of the Fe3O4 microspheres was functionalized with amino groups to facilitate the immobilization of ZrHCF which acts as an electron mediator. The nanocomposite was placed on a glassy carbon electrode which then displays noteworthy electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2). The AuNPs serve as a support for the immobilization of antibodies by the interaction between AuNPs and amino groups on antibodies to construct a covalent Au-N bond. This facilitates electron transfer on the electrode surface using H2O2 as the electrochemical probe. Square wave voltammetry (measured typically at +0.2xa0V vs. SCE) was carried out to record the electrochemical behavior. Under the optimal conditions, a response is linear in the 0.5xa0pg·mL−1 to 50xa0ng·mL−1 CEA concentration range, and the detection limit is as low as 0.15xa0pg·mL−1 (S/Nxa0=u20093). The method is selective, highly stable and acceptably reproducible.n Graphical abstractA self-assembly magnetic nanocomposite for voltammetric immunoassay of CEA. GCE glassy carbon electrode; Au NPs gold nanoparticles; ZrHCF zirconium hexacyanoferrate; CEA carcinoembryonic antigen; Anti-CEA CEA antibody; BSA bovine serum albumin; SWV square wave voltammetry. A high sensitive voltammetric immunoassay method has been used for detecting CEA, It is based on a self-assembled magnetic nanocomposite (Au NPs@ZrHCF@Fe3O4) as multifunctional signal amplification platform.

Ultrasensitive photoelectrochemical immunosensor for the detection of amyloid β-protein based on SnO2/SnS2/Ag2S nanocomposites

An ultrasensitive label-free photoelectrochemical (PEC) immunosensor with high visible-light activity was developed for quantitative detection of amyloid β-protein (Aβ) by cross-linking anti-Aβ antibody onto the Ag2S sensitized SnO2/SnS2 nanocomposites. Specifically, SnO2 with flower-like porous nanostructure was innovatively applied in PEC immunosensor as a basal material. It could form a heterostructure with SnS2, which brought about the sensitization of SnO2 and enhanced the separation of photogenerated electrons and holes. Moreover, Ag2S was in-situ growth on the surface of SnO2/SnS2, which further enhanced the photocurrent response significantly. Therefore, SnO2/SnS2/Ag2S could form stepwise band-edge structure, which benefited the light harvesting and provided a good foundation for sensor construction and detection. Under optimal conditions, the PEC immunosensor was used to detect the content of Aβ and exhibited a wide linear concentration range from 0.5u202fpgu202fmL-1 to 100u202fngu202fmL-1, with low limit of detection (0.17u202fpgu202fmL-1) and limit of quantification (0.56u202fpgu202fmL-1). Additionally, the designed PEC immunosensor exhibited good reproducibility, specificity, and stability which may find potential applications in the biosensor, biomedicine, clinical diagnosis, photocatalysis and other related fields.

An electrochemical immunosensor based on a multiple signal amplification strategy for highly sensitive detection of prostate specific antigen

A sandwich-type electrochemical immunosensor was developed based on a multiple signal amplification strategy. To enable this objective, pompon-like palladium@platinum nanoparticles were attached onto a 3-aminopropyl-triethoxysilane functionalized cuprous oxide@cobalt oxide nanocomposite (Pd@Pt-APTES-Cu2O@Co3O4) by constructing Pt–N bonds. The nanocomposite exhibited better electrocatalytic activity towards the reduction of hydrogen peroxide than each component and was used as a multiple signal amplification label to capture secondary antibodies due to its splendid electrochemical performance. Meanwhile, a gold nanoparticle incorporated chitosan-graphene nanocomposite solution (Au-CS-Gr) was modified on a glassy carbon electrode and employed as an electron transfer facilitator and primary antibody carrier. The proposed electrochemical immunosensor showed a wide linear range from 0.01 pg mL−1 to 100 ng mL−1 and a low detection limit of 2.0 fg mL−1 for quantitative detection of PSA. It also exhibited high sensitivity, good stability and acceptable reproducibility. Furthermore, a favorable result was obtained when the proposed method was applied to the analysis of human serum samples, which indicated its potential application in clinical analysis of tumor markers.

Quenching Electrochemiluminescence Immunosensor Based on Resonance Energy Transfer between Ruthenium (II) Complex Incorporated in the UiO-67 Metal–Organic Framework and Gold Nanoparticles for Insulin Detection

This work describes a sandwich-type electrochemiluminescence (ECL) strategy for insulin detection by using Ru(bpy)32+ as the luminophore which was encapsulated in the UiO-67 metal-organic framework (UiO-67/Ru(bpy)32+). Because UiO-67 possesses the characteristics of large specific surface area and porosity, more Ru(bpy)32+ could be loaded onto its surface and holes, thus greatly improving the ECL efficiency. Furthermore, the ECL resonance energy transfer (ECL-RET) could occur between UiO-67/Ru(bpy)32+ (ECL donor) and Au@SiO2 nanoparticles (ECL acceptor), resulting in a conspicuously decreased ECL response. The ECL spectrum of UiO-67/Ru(bpy)32+ which exhibited strong ECL intensity has suitable spectral overlap with the absorption spectrum of Au@SiO2, which further proved the occurrence of the ECL-RET action. The ECL intensity decreased with the increase of the concentration of insulin. In addition, the sandwich-type ECL immunosensor was applied to insulin detection, and the ECL decrease efficiency was found to be logarithmically related to the concentration of the insulin antigen in the range of 0.0025 to 50 ng mL-1 with the limit of detection of 0.001 ng mL-1. Meanwhile, this work provides an important reference for the application of metal-organic frameworks in the ECL and ECL-RET study and also exhibits potential capability in the detection of other hormones.