Faying Li

An ultrasensitive sandwich-type electrochemical immunosensor based on signal amplification strategy of gold nanoparticles functionalized magnetic multi-walled carbon nanotubes loaded with lead ions.

In this study, a novel and ultrasensitive sandwich-type electrochemical immunosensor was prepared for the quantitative detection of alpha fetoprotein (AFP), a well-known hepatocellular carcinoma biomarker. Gold nanoparticles (Au NPs) functionalized magnetic multi-walled carbon nanotubes (MWCNTs-Fe3O4) were prepared and utilized for the adsorption of lead ions (Pb(2+)) and the secondary antibodies (Ab2). The resultant nanocomposites (Pb(2+)@Au@MWCNTs-Fe3O4) were used as the label for signal amplification, showing better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) than MWCNTs, MWCNTs-Fe3O4 or Au@MWCNTs-Fe3O4 due to the synergetic effect presented in Pb(2+)@Au@MWCNTs-Fe3O4. Moreover, Au NPs were electrodeposited on the surface of glassy carbon electrode (GCE) for the effective immobilization of primary antibodies (Ab1). Under the optimal conditions, a linear range from 10 fg/mL to 100 ng/mL and a detection limit of 3.33 fg/mL were obtained. The proposed electrochemical sandwich-type immunosensor shows high sensitivity, good selectivity and stability for the quantitative detection of AFP, holding a great potential in clinical and diagnostic applications.

Ultrasensitive non-enzymatic immunosensor for carcino-embryonic antigen based on palladium hybrid vanadium pentoxide/multiwalled carbon nanotubes

A novel and sensitive sandwich-type non-enzymatic electrochemical immunosensor was fabricated for quantitative monitoring of carcino-embryonic antigen (CEA). Nanocomposite of stannic oxide/reduced graphene oxide was used as substrate material to increase the specific surface area and enhance the conductivity of the glassy carbon electrode. Gold nanoparticles (Au NPs) were introduced to link substrate materials and primary antibodies (Ab1) and accelerate the electron transfer in this system. At the same time, the palladium nanoparticles (Pd NPs)-vanadium pentoxide (V2O5)/multiwalled carbon nanotubes (MWCNTs) were used as the label of secondary antibodies (Ab2). This composite label has shown excellent catalytic activity towards the reduction of H2O2. The nanomaterial-based signal amplification can improve the sensitivity and lower the limit of detection. The proposed immunosensor showed wide linear range from 0.5 pgmL(-1) to 25 ngmL(-1) with limit of detection of 0.17 pgmL(-1). This novel immunosensor was used to analyze serum sample. The results indicated that this immunosensor may find huge potential application for quantitative detection of CEA in the clinical diagnosis.

An ultrasensitive sandwich-type electrochemical immunosensor based on the signal amplification strategy of mesoporous core–shell Pd@Pt nanoparticles/amino group functionalized graphene nanocomposite

Herein, a novel and sensitive sandwich-type electrochemical immunosensor was fabricated for quantitative monitoring of prostate specific antigen (PSA). The sulfo group functionalized multi-walled carbon nanotubes (MWCNTs-SO3H) were used as substrate material to increase the specific surface area and enhance the conductivity of the glassy carbon electrode. Gold nanoparticles (Au NPs) were introduced to enhance the load capacity of the substrate material for primary antibodies (Ab1) and accelerate the electron transfer on the electrode interface. The mesoporous core-shell Pd@Pt nanoparticle loaded by amino group functionalized graphene (M-Pd@Pt/NH2-GS) with high specific surface area, high indexed facets, and good biocompatibility was not only as the carriers of secondary antibodies (Ab2) but also catalyzed the reduction of hydrogen peroxide (H2O2), which effectually amplified the current signal in detection of PSA. The as-proposed immunosensor exhibited high sensitivity and stability on the detection of PSA. A linear relationship between current signals and the concentrations of PSA was obtained in the range from 10fg/mL to 50ng/mL and the detection limit of PSA was 3.3fg/mL (signal-to-noise ratio of 3). Furthermore, the as-proposed immunosensor showed excellent performance in detection of human serum samples. The results suggest that the proposed immunosensor will be promising in the diagnostics application for accurately quantitative detection of PSA.

Ultrasensitive amperometric immunosensor for PSA detection based on Cu2O@CeO2-Au nanocomposites as integrated triple signal amplification strategy.

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of prostate specific antigen (PSA). To this end, the amino functionalized cuprous oxide @ ceric dioxide (Cu2O@CeO2-NH2) core-shell nanocomposites were prepared to bond gold nanoparticles (Au NPs) by constructing stable Au-N bond between Au NPs and -NH2. Because the synergetic effect presents in Cu2O@CeO2 core-shell loaded with Au NPs (Cu2O@CeO2-Au), it shows better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) than single Cu2O, Au NPs and Cu2O@CeO2. Featured by large specific surface area, good biocompatibility and good electrochemical properties which can greatly improve the electronic transmission rate, Cu2O@CeO2-Au was used as transducing materials to achieve efficiently capture antibodies and triple signal amplification of the proposed immunosensor. Under the optimal conditions, the proposed immunosensor exhibited a wide linear range from 0.1pg/mL to 100ng/mL with a low detection limit of 0.03pg/mL (S/N=3). Furthermore, the proposed label-free immunosensor has been used to determine PSA in human serum with satisfactory results. Meanwhile, it displayed good reproducibility, acceptable selectivity, and long-term stability, which had promising application in bioassay analysis.

Ultrasensitive electrochemical immunosensor for quantitative detection of SCCA using Co3O4@CeO2-Au@Pt nanocomposite as enzyme-mimetic labels

Recently early diagnosis of squamous cell carcinoma antigen (SCCA) as a tumor maker of various cancers has increasingly attracted a lot of attention with heightening of incidence rate of cancer. The SCCA with low concentration in human serum should be diluted before detecting. Thus, an immunoassay with high sensitivity is significant for early detecting SCCA. Therefore, a nonenzymatic sandwich-type electrochemical immunosensor herein was conducted to quantitative detection of squamous cell carcinoma antigen (SCCA). The amino functionalized cobaltosic oxide @ ceric dioxide nanocubes with core-shell morphology were prepared to combine sea-urchin like gold @ platinum nanoparticles (Co3O4@CeO2-Au@Pt), and used as labels to conjugate with secondary antibodies for signal amplification. Due to the synergetic effect, excellent electrochemical property and superior auxiliary catalytic activity of Co3O4@CeO2-Au@Pt, high electrocatalytic current responses toward the reduction of hydrogen peroxide (H2O2) were achieved. Besides, the electrodeposited gold nanoparticles (D-Au NPs) which were modified on glassy carbon electrodes (GCE) were used as antibodies carriers and sensing platforms. With the well cooperation of Co3O4@CeO2-Au@Pt and D-Au NPs, a broad linear range from 100fg/mL to 80ng/mL with a low detection limit of 33 fg/mL for detecting SCCA was achieved. In addition, the immunosensor displayed with good reproducibility, high selectivity and stability. The results are satisfactory when the proposed method has been applied to analyze human serum samples, indicating that the potential application is promising in clinical monitoring of tumor markers.

A novel sandwich-type electrochemical immunosensor for PSA detection based on PtCu bimetallic hybrid (2D/2D) rGO/g-C3N4.

In this work, a sensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of prostate-specific antigen (PSA) by amperometric i-t. The Au loaded on thionine functionalized graphene oxide (Au@Th/GO) was used as a platform to immobilize primary antibodies (Ab1) and accelerate the electron transfer on the electrode interface. PtCu bimetallic hybrid were loaded on 2D/2D reduced graphene oxide/graphitic carbon nitride (PtCu@rGO/g-C3N4) with large surface area and biocompatibility, which were employed as labels for combining secondary antibodies (Ab2) and amplifying signals to improve the sensitivity of the designed immunosensor which attributes to its good activity for the reduction of hydrogen peroxide (H2O2). Under optimal conditions, the designed immunosensor exhibited a linear concentration range from 50fg/mL to 40ng/mL, with a low detection limit of 16.6fg/mL (S/N=3) for PSA. Additionally, the designed immunosensor showed acceptable selectivity, reproducibility and stability. The satisfactory results in analyze human serum samples indicated potential application promising in clinical monitoring of tumor markers.

A label-free amperometric immunosensor for the detection of carcinoembryonic antigen based on novel magnetic carbon and gold nanocomposites

In this work, a novel label-free electrochemical immunosensor was developed for the quantitative detection of carcinoembryonic antigen (CEA). To this end, gold nanoparticle (Au NP) functionalized magnetic multi-walled carbon nanotubes (MWCNTs–Fe3O4) were prepared and applied to lead ion (Pb2+) adsorption. Because of the synergetic effect present in Pb2+@Au@MWCNTs–Fe3O4, they show better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2) than MWCNTs, MWCNTs–Fe3O4 or Au@MWCNTs–Fe3O4. Featuring a large specific surface area, good biocompatibility and excellent electrical conductivity, Pb2+@Au@MWCNTs–Fe3O4 were used as transducing materials to achieve efficient conjugation of capture antibodies and signal amplification of the proposed immunosensor. Cyclic voltammetry and the amperometric i–t technique were used to record the change of electrochemical signal when the electrodes were modified with different concentrations of CEA. Under optimal conditions, the label-free immunosensor exhibited a wide linear range from 5 fg mL−1 to 50 ng mL−1 with a low detection limit of 1.7 fg mL−1 for CEA. The proposed immunosensor displays high electrochemical performance with good reproducibility, selectivity and stability, and has great potential in clinical and diagnostic applications.

An ultrasensitive label-free electrochemical immunosensor based on signal amplification strategy of multifunctional magnetic graphene loaded with cadmium ions

Herein, a novel and ultrasensitive label-free electrochemical immunosensor was proposed for quantitative detection of human Immunoglobulin G (IgG). The amino functionalized magnetic graphenes nanocomposites (NH2-GS-Fe3O4) were prepared to bond gold and silver core-shell nanoparticles (Au@Ag NPs) by constructing stable Au-N and Ag-N bond between Au@Ag NPs and -NH2. Subsequently, the Au@Ag/GS-Fe3O4 was applied to absorb cadmium ion (Cd2+) due to the large surface area, high conductivity and exceptional adsorption capability. The functional nanocomposites of gold and silver core-shell magnetic graphene loaded with cadmium ion (Au@Ag/GS-Fe3O4/Cd2+) can not only increase the electrocatalytic activity towards hydrogen peroxide (H2O2) but also improve the effective immobilization of antibodies because of synergistic effect presented in Au@Ag/GS-Fe3O4/Cd2+, which greatly extended the scope of detection. Under the optimal conditions, the proposed immunosensor was used for the detection of IgG with good linear relation in the range from 5 fg/mL to 50 ng/mL with a low detection limit of 2 fg/mL (S/N = 3). Furthermore, the proposed immunosensor showed high sensitivity, special selectivity and long-term stability, which had promising application in bioassay analysis.

An optionality further amplification of an sandwich-type electrochemical immunosensor based on biotin–streptavidin–biotin strategy for detection of alpha fetoprotein

An optionality further amplification of sandwich-type electrochemical immunosensor based on Au NPs as platform and biotin-functionalized amination magnetic nanoparticle composite (B-APTES@Fe3O4) as label was designed for detection of alpha fetoprotein (AFP) in this work. The cross-shaped SA has one free biotin-binding site available for carrying a B-Ab2, and the other three binding sites are conjugated with a 3 equimolar ratio of B-APTES@Fe3O4. Thus, further signal amplification could be achieved as SA and B-APTES@Fe3O4 are added layer by layer on the electrode successively. Of the active biotins that were modified on the surface of APTES@Fe3O4, a part of biotins are bound to the SA and the remaining biotins can be used for further connection, which can present a dendritic spread outward. Therefore, the proposed electrochemical immunosensor has wider application range than before. Under optimal conditions, the designed immunosensor exhibited a wide linear range from 1 pg mL−1 to 10 ng mL−1 with a low detection limit of 0.33 pg mL−1 (S/N = 3) for HIgG. The proposed immunosensor provides a promising application for the quantitative detection of biomolecules in serum samples.

Electrochemical determination of bisphenol A using a polyacrylamide–multiwalled carbon nanotube-modified glassy carbon electrode

A novel electrochemical sensor was fabricated for the determination of bisphenol A (BPA) based on a signal amplification strategy with polyacrylamide and multiwalled carbon nanotubes (PAM–MWCNTs). The modified electrode significantly enhanced the oxidation peak current and lowered the oxidation overpotential to improve the sensitivity. Several important parameters which can influence the performance of the sensor were studied and optimized. The sensor showed a fast and sensitive response for the quantitative determination of BPA under optimum conditions. It exhibited a good linear relationship range from 5.0 nmol L−1 to 20 μmol L−1 and the detection limit was 1.7 nmol L−1, (S/N = 3). The sensor exhibited remarkable sensitivity (3.830 μA (μmol L−1)−1). Furthermore, the fabricated sensor showed an excellent result for the detection of BPA in milk samples.