Lihui Tian

Ultrasensitive sandwich-type electrochemical immunosensor based on trimetallic nanocomposite signal amplification strategy for the ultrasensitive detection of CEA.

A novel and ultrasensitive sandwich-type electrochemical immunosensor was designed for the quantitative detection of carcino-embryonic antigen (CEA). This immunosensor was developed by using the trimetallic NiAuPt nanoparticles on graphene nanosheets (NGs) nanosheets (NiAuPt-NGs) as excellent labels and β-cyclodextrin functionalized reduced graphene oxide nanosheets (CD-NGs) as the platform. The CD-NGs with high specific surface area good biocompatibility and the ideal dispersibility was used to capture the primary antibodies (Ab1) efficiently. The trimetallic NiAuPt-NGs nanocomposites were used as the labels for signal amplification, showing better electrocatalytic activity towards the reduction of hydrogen peroxide (H2O2), which is much better than that the monometallic Pt-NGs, bimetallic NiPt-NGs and AuPt-NGs due to the synergetic effect presented in NiAuPt-NGs. The NiAuPt-NGs nanocomposites consist of tightly coupled nanostructures of Au, Ni and Pt, which have neither an alloy nor a core-shell structure. Under the optimal conditions, a linear range from 0.001–100 ng/mL and a low detection limit of 0.27 pg/mL were obtained for CEA. The proposed electrochemical sandwich-type immunosensor may have a promising application in bioassay and it enriches the electrochemical immunoassays.

3D sandwich-type prostate specific antigen (PSA) immunosensor based on rGO–MWCNT–Pd nanocomposite

In this work, a novel and ultrasensitive sandwich-type electrochemical immunosensor was developed for the quantitative detection of prostate specific antigen (PSA), a well-known prostatic tumor biomarker. A 3D-structured reduced graphene oxide–multiwalled carbon nanotube–palladium nanoparticle (NP) nanocomposite (rGO–MWCNT–Pd) was prepared in a simple and environmentally friendly way and utilized for the adsorption of secondary antibodies (Ab2). It is used as a novel enzyme-mimicking label to develop a sandwich-type electrochemical immunosensor for signal amplification, and shows better electrocatalytic activity for the reduction of hydrogen peroxide (H2O2) than rGO–CNT or rGO–Pd due to the synergetic effect of the rGO–MWCNT–Pd nanocomposite. The nanocomposite of Au NPs decorated on aminated graphene (Au–NH2–GS) is used as a platform for the immobilization of primary antibobies (Ab1) via an amide reaction between the –NH2 group of the Au–NH2–GS and the –COOH groups of Ab1. Due to the excellent electrocatalytic activity of rGO–MWCNT–Pd for the reduction of H2O2, electrochemical amperometric changes at different concentrations of PSA were studied after the immunoreaction. Under the optimum experimental conditions, the proposed electrochemical sandwich-type immunosensor exhibits a low detection limit (0.17 pg mL−1), and a wide linear range (from 0.5 pg mL−1 to 15 ng mL−1) for the detection of PSA. It also shows high sensitivity, good selectivity and stability, and has great potential in clinical and diagnostic applications.

An ultrasensitive sandwich-type electrochemical immunosensor based on δ-MnO2 and palladium nanoparticles covered natural halloysite nanotubes for the detection of hepatitis B surface antigen

A sensitive sandwich-type electrochemical immunosensor for the quantitative detection of hepatitis B surface antigen (HBsAg) was proposed and the nanocomposite of palladium nanoparticles/δ-manganese dioxide/halloysite nanotubes (Pd/δ-MnO2/HNTs) was used as a novel signal amplification strategy. δ-MnO2 could absorb a large amount of palladium nanoparticles (Pd NPs) due to their advantages of large surface area, good adsorption capacity and environmentally friendly. The earth possesses abundant HNTs, which could deter the agglomeration of δ-MnO2 and preserve the advantages of δ-MnO2 once loaded on HNTs. With high electrical catalytic activity of Pd NPs and δ-MnO2, the Pd/δ-MnO2/HNT nanocomposite could improve the analytical signal and achieve high sensitivity. The electroplated gold nanoparticles (Au NPs) as the platform of the immunosensor could immobilize the primary antibodies tightly and enhance the electron transfer efficiently. Under the optimal conditions, the immunosensor exhibited an extremely low detection limit of 0.3 pg mL−1 and a wide linear range from 0.001 ng mL−1 to 20 ng mL−1 for HBsAg. Moreover, it revealed good selectivity, acceptable reproducibility and stability, and exhibited application potentiality in clinical diagnosis.

An electrochemical immunosensor for ultrasensitive detection of HBsAg based on platinum nanoparticles loaded on natural montmorillonite

A sensitive and facile electrochemical immunosensor for ultrasensitive detection of hepatitis B surface antigen (HBsAg) was designed, which was based on platinum nanoparticle decorated amino silane functionalized montmorillonite (Pt–NH2–MMT). As it is a luminosilicate clay mineral, the advantages of montmorillonite (MMT), such as a large specific surface area, good adsorption/ion exchange capacity and innocuousness, endow Pt–NH2–MMT with better sensing performance. The platinum nanoparticles (Pt NPs) also play an important role due to their good biological compatibility, electron transport rate and catalytic activity. Pt NPs and the available amine group of second HBsAg-antibody could be bound strongly to each other. And the covalent bond between NH2–MMT and the carboxyl group of primary HBsAg-antibody could be formed by the activation of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide. Under optimal conditions, the Pt–NH2–MMT showed high electrocatalytic activity toward hydrogen peroxide reduction. Under optimal conditions, the immunosensor showed a wide linear response to HBsAg ranging from 0.5 pg mL−1 to 20 ng mL−1 with a low detection limit of 2.0 × 10−4 ng mL−1. The designed immunosensor displayed high sensitivity, stability and reproducibility for the analysis of HBsAg.

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.