Liuliu Gao

Ultrasensitive electrochemical biosensor based on graphite oxide, Prussian blue, and PTC-NH2 for the detection of α2,6-sialylated glycans in human serum.

α2,6-Sialylated glycans are crucial molecular targets for cancer diagnosis and clinical research. In this work, a novel ultrasensitive electrochemical biosensor was fabricated based on a graphite oxide (GO), Prussian blue (PB), and PTC-NH2 (an ammonolysis product of 3,4,9,10-perylenetetracarboxylic dianhydride) nanocomposite for the selective detection of α2,6-sialylated glycans. To increase the sensitivity of the electrochemical biosensor, gold nanoparticles (GNPs) were immobilized on a GO-PB-PTC-NH2 modified glassy carbon electrode (GCE). Sambucus nigra agglutinins (SNAs), which specifically bind with α2,6-sialylated glycans, were covalently immobilized on GNPs for the sensitive detection of α2,6-sialylated glycans in serum. This proposed method can be applied to human serum, and it worked well over a broad linear range (0.1 pg mL(-1)-500 ng mL(-1)) with detection limits of 0.03 pg mL(-1). Moreover, recovery of the spiked samples ranged from 100.2% to 105.0%, suggesting that this excellent electrochemical biosensor can be used for the practical detection of α2,6-sialylated glycans.

A novel electrochemical immunosensor based on the rGO-TEPA-PTC-NH2 and AuPt modified C60 bimetallic nanoclusters for the detection of Vangl1, a potential biomarker for dysontogenesis

The aberrant expression of Vangl1 is highly correlated with dysontogenesis, especially for neural tube defects. Therefore, the ultrasensitive detection of Vangl1 would provide a new approach for the specific early diagnostics in dysembryoplasia. However, no quantitative detection method is currently available. Herein, we describe the development of a new approach to fill this assay gap. We utilized C60-templated AuPt bimetallic nanoclusters for signal amplification because the promising C60 nanomaterial provides a large surface area for the in site reduction of bimetallic nanocomposites as well as excellent conductivity. To further amplify the electrochemical signal, reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) and a derivative of 3,4,9,10-perylenetetracarboxylicdianhydride (PTC-NH2) were selected for modification of the electrode to provide more amino groups for the immobilization of antibodies and to enhance the conductivity. The electrochemical signal was primarily derived from the catalysis of H2O2 by C60-AuPt. Chronoamperometry was applied to record the electrochemical signals. Under optimal conditions, the prepared immunosensor exhibited a wide linear range from 0.1 pg mL(-1) to 450 pg mL(-1) and a low detection limit of 0.03 pg mL(-1). Moreover, the proposed method exhibited good stability and recovery, suggesting its potential for use in clinical research.

Ultrasensitive electrochemical immunosensor based on orderly oriented conductive wires for the detection of human monocyte chemotactic protein-1 in serum

For the first time, a simple, ultrasensitive and label-free electrochemical monocyte chemotactic protein-1 (MCP-1) immunosensor based on orderly oriented conductive wires has been developed. A conductive wire, which is similar to an electron-conducting tunnel, was designed with Au nanoparticles (AuNPs) joined to Au@Pt core-shell microspheres via a cysteamine (CA) crosslinker. To enhance the sensitivity of the immunosensor, Au nanoparticles were electrodeposited onto the gold electrode, and CA was self-assembled via strong Au-S covalent bonds, providing an appropriate surface and promoting electron transfer. Next, Au@Pt core-shell microspheres with large surface area were grafted onto the modified electrode to immobilize more MCP-1 antibodies. MCP-1 is an initiating factor and biomarker of atherosclerotic diseases. Under optimal experimental conditions, differential pulse voltammetry (DPV) current changes were used to detect MCP-1 with a broad linear range of 0.09-360 pg mL(-1) and a low detection limit of 0.03 pg mL(-1) (S/N=3). The proposed immunosensor exhibited good selectivity, reproducibility and reusability. When applied to spiked serum samples, the data for the developed immunosensor were in agreement with an enzyme linked immunosorbent assay, suggesting that the electrochemical immunosensor would be suitable for practical detection.

Ultrasensitive electrochemical detection of secretoneurin based on Pb2+-decorated reduced graphene oxide–tetraethylene pentamine as a label

In this work, a novel electrochemical immunosensor for the detection of secretoneurin (SN), which uses metal ion functionalised reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) as a label, is reported for the first time. rGO-TEPA contains a large number of amino groups, which makes it an ideal templet for the loading of metal ions. rGO-TEPA-Pb(2+) was employed to immobilise secondary secretoneurin (SN) antibody (Ab2), and the resulting nanocomposite (Ab2-rGO-TEPA-Pb(2+)) was used as a trace tag for signal amplification. A modified electrode consisting of functionalised graphene nanosheets (Au@GS) was used as a substrate to immobilise the antibodies. Under the optimal conditions, the immunoassay exhibited high sensitivity, acceptable stability and reproducibility with a wide linear range from 0.001 to 100ngmL(-1) (R=0.996), and an ultra-low detection limit of 0.33pgmL(-1) (S/N=3). Furthermore, the immunosensor could be employed to detect SN in clinical serum samples. The proposed sensing strategy enriches the electrochemical immunoassay and exhibits potential for the point-of-care diagnostic application of the clinical screening of biomarkers.

A novel ultrasensitive electrochemical immunosensor based on carboxy-endcapped conductive polypyrrole for the detection of gypican-3 in human serum

In this work, a novel, ultrasensitive electrochemical immunosensor has been fabricated for the determination of gypican-3 (GPC3) in human serum. A disposable indium tin oxide (ITO) glass array was used as the working electrode on which pyrrole-α-carboxylic acid (Py-α-COOH) was electropolymerised. This approach provided a high content of surface-confined carboxyl groups suitable for the direct covalent binding of GPC3 antibody. In the immunosensor system, the “fluorescence microscopy” technique was first used for the characterisation of carboxyl groups. Meanwhile, the electrode was characterised by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Using GPC3 as a model analyte, the immunoassay exhibited high sensitivity, acceptable stability and reproducibility with a wide linear range from 0.9 pg mL−1 to 9 ng mL−1 and an ultra-low detection limit of 0.3 pg mL−1 (S/N = 3). The results for real sample analysis in human serum demonstrated that the newly constructed immunosensor array provided a rapid, simple and cost-efficient immunoassay with high throughput and sufficiently low detection limits for clinical applications.