Jiadi Sun

Electrochemical sensor based on molecularly imprinted film at Au nanoparticles-carbon nanotubes modified electrode for determination of cholesterol.

A novel electrochemical sensor for cholesterol (CHO) detection based on molecularly imprinted polymer (MIP) membranes on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWNTs) and Au nanoparticles (AuNPs) was constructed. p-Aminothiophenol (P-ATP) and CHO were assembled on the surface of the modified GCE by the formation of Au-S bonds and hydrogen-bonding interactions, and polymer membranes were formed by electropolymerization in a polymer solution containing p-ATP, HAuCl4, tetrabutylammonium perchlorate (TBAP) and the template molecule CHO. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements were used to monitor the electropolymerization process and its optimization, which was further characterized by scanning electron microscopy (SEM). The linear response range of the MIP sensor was between 1×10(-13) and 1×10(-9)molL(-1), and the limit of detection (LOD) were 3.3×10(-14)molL(-1). The proposed system has the potential for application in clinical diagnostics of cholesterol with high-speed real-time detection capability, low sample consumption, high sensitivity, low interference and good stability.

Surface-enhanced fluorescence immunosensor using Au nano-crosses for the detection of microcystin-LR.

A surface-enhanced fluorescence (SEF) immunosensor for the detection of microcystin-LR was developed using Au nano-crosses as fluorescence enhancement nanoparticles and cy5 as a fluorescence label molecule. The SEF effects of cy5 in the proximity of Au nanorods and gold nano-crosses was investigated by using Au nanorods or nano-crosses coated negative-charged glass surfaces. Fluorescence measurements indicated that SEF was influenced by the size, shape and distribution of the Au nanoparticles, with an appropriate spacer layer between the Au nanoparticles and the cy5. The enhancement factor was from 2.3- to 35-fold. Under optimal conditions, the SEF immunosensor exhibited a good linear response at microcystin-LR concentrations of 0.02-16 ng mL(-1) (R(2)=0.9981). The limit of detection was 0.007 ng mL(-1) with little adsorption of microcystin-RR, microcystin-LW, and microcystin-LF. High microcystin-LR recoveries were obtained from naturally contaminated fish samples. The SEF immunosensor allows the reliable detection of microcystin-LR in seafood, and has potential in simple, sensitive detection applications.

A novel molecularly imprinted electrochemical sensor modified with carbon dots, chitosan, gold nanoparticles for the determination of patulin

In this paper, molecular imprinting technique was applied to the electrochemical sensor. We used 2-oxindole as dummy template, ρ-Aminothiophenol (ρ-ATP) as functional monomers, combined with the high sensitivity of electrochemical detection, to achieve a specific and efficient detection of patulin in fruit juice. In addition, carbon dots and chitosan were used as the modifying material to improve electron-transfer rate, expand the electroactive surface of glassy carbon electrode and enhance strength of the signal. The Au-S bond and hydrogen bond were employed to complete the assembly of the ρ-ATP and 2-oxindole on the surface of the electrode. Then, polymer membranes were formed by electropolymerization in a polymer solution containing ρ-ATP, HAuCl4, tetrabutylammonium perchlorate (TBAP) and the template molecule 2- oxindole. After elution, the specific cavity can adsorb the target patulin. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements were performed to monitor the electropolymerization process and its optimization. Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) analyses were used for characterization. This was the first time that the molecularly imprinted polymer (MIP) technology combined with carbon dots, chitosan and Au nanoparticles modification and was applied in the electrochemical detection of patulin. The linear response range of the MIP sensor was from 1 × 10-12 to 1 × 10-9molL-1 and the limit of detection (LOD) was 7.57 × 10-13molL-1. The sensor had a high-speed real-time detection capability, low sample consumption, high sensitivity, low interference, good stability and could become a new promising method for the detection of patulin.

Metabolomics analysis to evaluate the anti-inflammatory effects of polyphenols: glabridin reversed metabolism change caused by LPS in RAW 264.7 cells.

Inflammation has been shown to play a critical role in the development of many diseases. In this study, we used metabolomics to evaluate the inflammatory effect of lipopolysaccharide (LPS) and the anti-inflammatory effect of glabridin (GB, a polyphenol from Glycurrhiza glabra L. roots) in RAW 264.7 cells. Multivariate statistical analysis showed that in comparison with the LPS group, the metabolic profile of the GB group was more similar to that of the control group. LPS impacted the amino acid, energy, and lipid metabolisms in RAW 264.7 cells, and metabolic pathway analysis showed that GB reversed some of those LPS impacts. Metabolomics analysis provided us with a new perspective to better understand the inflammatory response and the anti-inflammatory effects of GB. Metabolic pathway analysis can be an effective tool to elucidate the mechanism of inflammation and to potentially find new anti-inflammatory agents.

A novel recombinant cell fluorescence biosensor based on toxicity of pathway for rapid and simple evaluation of DON and ZEN

During an exposure, humans and animals are most often exposed to a mixture rather than individual mycotoxins. In this study, a Human Embryonic Kidney 293 cell (HEK-293) fluorescence sensor was developed to detect and evaluate mycotoxins, deoxynivalenol (DON) and zearalenone (ZEN) compounds, produced by Fusarium culmorum that are common food contaminants. TRE-copGFP (green fluorescent protein) and ERE-TagRFP (red fluorescent protein) plasmids were constructed and cotransfected into HEK-293 cells through a highly efficient, lipid-mediated, DNA-transfection procedure. Results show that fluorescence intensity was proportional to DON and ZEN concentrations, ranging from 2 to 40 ng/mL and 10 to 100 ng/mL respectively, with a detection limit of 0.75 ng/mL and 3.2 ng/mL respectively. The EC50 of DON and ZEN are 30.13 ng/mL and 76.63 ng/mL respectively. Additionally, ZEN may have a synergistic effect on enhancing AP-1 activity of the toxicity pathway of DON. These data indicate the high sensitivity and effectiveness of our biosensor system in the evaluation of the combined toxicity of ZEN, DON and their derivatives. In addition, this approach is suitable for an early warning method for the detection of ZEN and DON family mycotoxins contamination without higher-priced, conventional analytical chemistry methods.

Electrochemical behavior of a pheochromocytoma cell suspension and the effect of acrylamide on the voltammetric response

The electrochemical behavior of electroactive species in a pheochromocytoma cell (PC-12) suspension was studied to establish a simple and rapid measurement method to obtain strong and direct electrochemical responses that objectively reflect cell viability. Two electrochemical signals of the PC-12 suspension, caused by the oxidation of guanine, xanthine, adenine and hypoxanthine, were simultaneously detected by using a glass carbon electrode modified with a multi-walled carbon nanotube–graphene nanosheet hybrid film. The presence of the four purines in the PC-12 cell cytoplasm was verified by HPLC assay using a DAD system and LC-MS analysis. Additionally, a linear relationship between the peak currents of purines in the cell suspension and culture time was found, which is in accord with the cell counts. The cytotoxic effect of acrylamide (0.1 mM to 10 mM) on cells was evaluated by differential pulse voltammetry (DPV) analysis, which detected a decrease in the voltammetric response of purines in the cytoplasm, in agreement with that obtained by the MTT test and with morphological analysis. Therefore, the voltammetric response of the ultrasonicated PC-12 cell suspension could be used to monitor cell growth and to evaluate the effects of potential toxic hazards on cells, and in drug screening.

Explaining combinatorial effects of mycotoxins Deoxynivalenol and Zearalenone in mice with urinary metabolomic profiling

Urine metabolic profiling of mice was conducted utilizing gas chromatography-mass spectrometry (GC-MS) to investigate the combinatory effect of mycotoxins deoxynivalenol (DON) and zearalenone (ZEN) on the metabolism of the mice. Experiments were conducted by means of five-week-old mice which were individually exposed to 2 mg/kg DON, 20 mg/kg ZEN and the mixture of DON and ZEN (2 mg/kg and 20 mg/kg, respectively). The intragastric administration was applied for three weeks and urine samples were collected for metabolic analysis. Univariate and multivariate analysis were applied to data matrix processing along with respective pathway analysis by MetaMapp and CytoScape. The results showed that the combined DON and ZEN administration resulted in lower significant changes, compared to the individual mycotoxin treated groups verified by heatmap. Metabolic pathways network mapping indicated that the combined mycotoxins treated groups showed a little effect on the metabolites in most pathways, especially in glucose metabolism and its downstream amino acid metabolism. In glucose metabolism, the content of galactose, mannitol, galactonic acid, myo-inositol, tagatose was drastically down-regulated. Furthermore, the organic acids, pyruvate, and amino acids metabolism displayed the same phenomenon. In conclusion, the combined DON/ZEN administration might lead to an “antagonistic effect” in mice metabolism.

Cell Based-Green Fluorescent Biosensor using Cytotoxic Pathway for Bacterial Lipopolysaccharide Recognition

Lipopolysaccharide (LPS), a characteristic component of the outer membrane of Gram-negative bacteria, can be used as an effective biomarker to detect bacterial contamination. Here, we reported a 293/hTLR4A-MD2-CD14 cell-based fluorescent biosensor to detect and identify LPS, which is carried out in a 96-well microplate which is nondestructive, user-friendly, and highly efficient. The promoter sequence of the critical signaling pathway gene ZC3H12A (encoding MCPIP1 protein) and enhanced green fluorescence protein (EGFP) were combined to construct a recombinant plasmid, which was transferred into 293/hTLR4A-MD2-CD14 cells through lipid-mediated, DNA-transfection way. LPS was able to bind to TLR4 and coreceptors-induced signaling pathway could result in green fluorescent protein expression. Results show that stable transfected 293/hTLR4A-MD2-CD14 cells with LPS treatment could be directly and continually observed under a high content screening imaging system. The novel cell-based biosensor detects LPS at low concentration, along with the detection limit of 0.075 μg/mL. The cell-based biosensor was evaluated by differentiating Gram-negative and Gram-positive bacteria and detecting LPS in fruit juices as well. This proposed fluorescent biosensor has potential in sensing LPS optically in foodstuff and biological products, as well as bacteria identification, contributing to the control of foodborne diseases and ensurance of public food safety with its high throughput detection way.

A class-specific artificial receptor-based on molecularly imprinted polymer-coated quantum dot centers for the detection of signaling molecules, N-acyl-homoserine lactones present in gram-negative bacteria

Herein, a novel class-specific artificial receptor-based on molecularly imprinted polymer (MIP)-coated quantum dots (QDs@MIP) was synthesized, characterized, and used for the detection and quantification of the bacterial quorum signaling molecules N-acyl-homoserine lactones (AHLs), a class of autoinducers from Gram-negative bacteria. The QDs@MIP was prepared by surface imprinting technique under controlled conditions using CdSe/ZnS QDs as the signal transducing material. The synthesis of the QDs@MIP was characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, and fluorescence spectroscopy. After template elution, the obtained cavities sensitively and selectively recognized the target AHLs of interest. The fluorescence intensity of the QDs@MIP was significantly quenched compared to the control non-imprinted polymer (QDs@NIP) upon exposure to different AHL concentrations. It also had a good linearity in the range from 2 to 18 nM along with a detection limit of 0.66, 0.54, 0.88, 0.72 and 0.68 nM for DMHF, C4-HSL, C6-HSL, C8-HSL and N-3oxo-C6-HSL, respectively. Most interestingly, the proposed sensor exhibited high sensitivity, good stability and fast response (30 s) towards the target molecules due to successful formation of surface imprints. The practicability of the developed sensor in real samples was further confirmed through the analysis of bacterial supernatant samples with satisfactory recoveries ranging from 89 to 103%. According to these results, the as-prepared QDs@MIP can be used as a new potential supporting technique for the rapid and real-time detection of bacterial pathogens in food safety and healthcare facilities.

Pathway of 3-MCPD-induced apoptosis in human embryonic kidney cells

3-Chloropropane-1,2-diol (3-MCPD) is a heat-produced contaminant formed during the preparation of soy sauce worldwide. The present investigation was conducted to determine the molecular aspects of 3-MCPD toxicity on human embryonic kidney cells (HEK293). Cell viability and apoptosis were assessed in response to exposure to 3-MCPD using the MTT assay and high-content screening (HCS). DNA damage, intracellular reactive oxygen species (ROS) and apoptosis-related proteins were evaluated. Genes related with apoptosis were detected by qPCR-array for further understanding the 3-MCPD induced cell apoptosis signaling pathway. Our results clearly showed that 3-MCPD treatment inhibits cell proliferation and reactive oxygen species generation. qPCR-array indicated that nine apoptotic genes were up-regulated more than 2-fold and six down-regulated more than 2-fold. Genes associated with the mitochondrial apoptotic pathway, especially BCL2 family genes, changed significantly, indicating that the mitochondrial apoptotic pathway is activated. Death receptor pathway-related genes, TNFRSF11B and TNFRSF1A, changed significantly, indicating that the death receptor pathway is also activated, resulting in the inhibition of cell growth and proliferation as well as induction of apoptosis. To sum up, the experiment results indicated that 3-MCPD induced HEK293 cell toxicity through the death receptor pathway and mitochondrial pathway.