Chunyong Xia

A novel DNA biosensor integrated with Polypyrrole/streptavidin and Au-PAMAM-CP bionanocomposite probes to detect the rs4839469 locus of the vangl1 gene for dysontogenesis prediction

The single nucleotide polymorphism (SNP) of the vangl1 gene is highly correlated with Neural Tube Defects (NTDs), a group of severe congenital malformations. It is hindered by the lack of a quantitative detection method. We first propose the use of a DNA biosensor to detect the missense single nucleotide polymorphism (rs4839469 c.346G>A p.Ala116Thr) of the vangl1 gene in this work. Polypyrrole (PPy) and streptavidin were integrated to modify a gold electrode. We took advantage of the PPys good biocompatibility and excellent conductivity. To further accelerate the electron transfer process at the electrode surface, polyamidoamine dendrimer-encapsulated gold nanoparticles (Au-PAMAM) were used, because Au-PAMAM possess a large number of amino groups to load capture probes (CP). Using the biotin-streptavidin system, the Au-PAMAM-CP bionanocomposite probe, which can detect the target DNA, was conjugated to the electrode surface. Under optimal conditions, the DNA biosensor exhibited a wide linear range of 0.1-100 nM with a low detection limit of 0.033 nM (S/N=3). The results suggest that this approach has the potential to be used 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.

Rapidly accomplished femtomole soluble CD40 ligand detection in human serum: a “green” homobifunctional agent coupled with reduced graphene oxide-tetraethylene pentamine as platform

The analysis of soluble CD40 ligand (sCD40L), which is present at significant levels in the blood of patients with cardiovascular disease, can reveal the severity of the disease at its early stage. However, the current biomarker detection techniques exhibit poor detection limits. To accomplish this main challenge, herein, we demonstrate an assay based on a novel modified electrochemical immunosensor for the ultrasensitive assay of sCD40L in human serum, which uses β-cyclodextrin (CD) and reduced graphene oxide-tetraethylene (rGO-TEPA) as a platform. rGO-TEPA contains a great number of amino groups and has excellent conductivity, which makes it a promising material for application in electrochemical biosensor development. To further improve the solubility and stability of rGO-TEPA, CD was selected. The CD decorated rGO-TEPA film not only improved the electron transfer but also provided more amino-groups for the immobilization of antibodies. For speeding up the immobilization of antibodies, the amine-modified electrodes were functionalized by a “green” conjugation route using a lower toxicity homobifunctional 1,4-phenylene diisothiocyanate (PDITC) linker. This is the first study that challenges electrochemical immunosensors with CD-rGO-TEPA-PDITC as a platform for the detection of biomarkers. Under optimal conditions, sCD40L could be assayed in the range of 0.25 to 50 pg mL−1 with detection limits of 83.3 fg mL−1 (S/N = 3). We demonstrate excellent specificity and show that the proposed assay accurately detects the protein of interest. The results were in agreement with an enzyme linked immunosorbent assay, suggesting that the electrochemical immunosensor may possess potential towards use in clinical applications of the proposed immunosensor.

Multi-purpose electrochemical biosensor based on a “green” homobifunctional cross-linker coupled with PAMAM dendrimer grafted p-MWCNTs as a platform: application to detect α2,3-sialylated glycans and α2,6-sialylated glycans in human serum

Sialylated glycans are crucial molecular targets for cancer diagnosis and clinical research. α2,3-Sialylated glycans and α2,6-sialylated glycans are the predominant sialic acids found in nature. Different expression of the quantity of glycans can result in development of different disease. However, there are no ideal methods for discriminating α2,3-sialylated glycans and α2,6-sialylated glycans. In this work, a multi-purpose biosensor is fabricated for sensitive detection of α2,3-sialylated glycans and α2,6-sialylated glycans. To improve the sensitivity of the biosensor, p-MWCNTs were integrated with PAMAM, as PAMAM has highly branched and abundant amino groups, providing a large available surface area for linking with other substances. To achieve distinguishable recognition, Maackia amurensis lectin (MAL) and Sambucus nigra agglutinin (SNA) were included. To facilitate the lectin fixation, PDITC, a kind of green homobifunctional cross-linker, was selected. Under optimized detection conditions, the linear range of detection for α2,3-sialylated glycans is 10 fg mL−1 to 50 ng mL−1 with a lower detection limit of 3 fg mL−1, and the linear range of detection for α2,6-sialylated glycans is 10 fg mL−1 to 50 ng mL−1 with a detection limit of 3 fg mL−1. This work not only provides a method for distinguishing detection of α2,3-sialylated glycans and α2,6-sialylated glycans, but also provides a reference for future clinical testing.

A switched catalysis qualified sealers capped one-step synthesis biocompatibility bimetallic scaffold film for Neu5Acα(2-6)Gal β MP Glycoside specific detection.

In this work, a novel label-free biosensor was designed for the sensitive and selective determination of Neu5Acα(2-6)Gal β MP Glycoside using AuPt-PPy(polypyrrole) conductive nanocomposite film as the sensor platform. The introduced AuPt-PPy nanocomposite provided a large surface area for the immobilization of Sambucus nigra agglutinis (SNA) through a coupling agent for specifically recognizing analytes and exhibited high electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2) as an analytical signal. Subsequently, to block the non-specific sites of the modified electrode, GOx was employed instead of the usual sealers. Most importantly, in the presence of glucose, these localized GOx further enhanced the electrochemical signal, which was achieved by the efficient catalysis of glucose. This study is the first that demonstrates the specific detection of Neu5Acα(2-6)Gal β MP Glycoside using AuPt-PPy as the electrocatalytic. Under optimal conditions, the electrochemical biosensor exhibited a wide linear range of 0.01 pgmL(-1)-800 ngmL(-1) with a low detection limit of 0.003 pgmL(-1) (S/N=3), due to the affinity between SNA and Neu5Acα(2-6)Gal β MP Glycoside. Therefore, the co-catalysis signal amplification approach has considerable potential in clinical applications and is suitable for the quantification of other biomarkers.