Jintao Liang

Ultrasensitive cholesterol biosensor based on enzymatic silver deposition on gold nanoparticles modified screen-printed carbon electrode

Cholesterol is one of the essential structural constituents of cell membranes. Determination of cholesterol is of great importance in clinical analysis because the level of cholesterol in serum is an indicator in the diagnosis and prevention of heart diseases. In this work, a simple and ultrasensitive cholesterol biosensor based on enzymatic silver deposition was designed by immobilizing cholesterol oxidase (CHOD) and cholesterol esterase (CHER) onto the surface of gold nanoparticles (Au NPs) modified screen-printed carbon electrode (SPE). By the catalytic action of CHER and CHOD, the cholesterol was hydrolyzed to generate hydrogen peroxide (H2O2) which can reduced the silver (Ag) ions in the solution for the deposition of metallic Ag on the surface of Au NPs modified SPE. The ultrasensitive detection of cholesterol was achieved by anodic stripping voltammetry (ASV) measurement of the enzymatically deposited Ag. The influence of relevant experimental variables was optimized. The anodic stripping peak current of Ag depended linearly on the concentration of cholesterol in the range of 5-5000μg/mL with the regression correlation coefficient of 0.9983. A detection limit of 3.0μg/mL was attained by 3 sigma-rule. In addition, the ultrasensitive cholesterol biosensor exhibited higher specificity, acceptable reproducibility and excellent recoveries for cholesterol detection.

Highly sensitive covalently functionalized light-addressable potentiometric sensor for determination of biomarker.

A biomarker is related to the biological status of a living organism and shows great promise for the early prediction of a related disease. Herein we presented a novel structured light-addressable potentiometric sensor (LAPS) for the determination of a model biomarker, human immunoglobulin G (hIgG). In this system, the goat anti-human immunoglobulin G antibody was used as recognition element and covalently immobilized on the surface of light-addressable potentiometric sensor chip to capture human immunoglobulin G. Due to the light addressable capability of light-addressable potentiometric sensor, human immunoglobulin G dissolved in the supporting electrolyte solution can be detected by monitoring the potential shifts of the sensor. In order to produce a stable photocurrent, the laser diode controlled by field-programmable gate array was used as the light emitter to drive the light-addressable potentiometric sensor. A linear correlation between the potential shift response and the concentration of human immunoglobulin G was achieved and the corresponding regression equation was ΔV (V)=0.00714ChIgG (μg/mL)-0.0147 with a correlation coefficient of 0.9968 over a range 0-150 μg/mL. Moreover, the light-addressable potentiometric sensor system also showed acceptable stability and reproducibility. All the results demonstrated that the system was more applicable to detection of disease biomarkers with simple operation, multiple-sample format and might hold great promise in various environmental, food, and clinical applications.

Graphene and Au NPs co-mediated enzymatic silver deposition for the ultrasensitive electrochemical detection of cholesterol

Cholesterol is an essential ingredient in mammals, and serum cholesterol is a major component of atherosclerotic plaques. The level of cholesterol in human serum has become an important index for clinical diagnosis and prevention of cardiovascular disease. In this paper, a simple and ultrasensitive cholesterol biosensor based on graphene oxide (GO) and gold nanoparticles (Au NPs) co-mediated enzymatic silver deposition was designed by immobilizing cholesterol oxidase (CHOD), cholesterol esterase (CHER) and GO onto the surface of Au NPs modified screen-printed carbon electrode (SPE). Under the synergistic effect of CHER, CHOD and GO, the cholesterol was hydrolyzed to generate hydrogen peroxide, which can reduce the silver (Ag) ions in the solution to metallic Ag which deposited on the surface of Au NPs modified SPE. The ultrasensitive detection of cholesterol was achieved by anodic stripping voltammetry measurement of the enzymatically deposited Ag. Under optimal conditions, the anodic stripping peak current of Ag increased with the increasing cholesterol concentration in the range from 0.01μg/mL to 5000μg/mL with a limit of detection of 0.001μg/mL (S/N = 3). In addition, the ultrasensitive cholesterol biosensor exhibited higher specificity, acceptable reproducibility and excellent recoveries for cholesterol detection.

Label-free electrochemical aptasensor for detection of alpha-fetoprotein based on AFP-aptamer and thionin/reduced graphene oxide/gold nanoparticles

Sensitive and accurate detection of tumor markers is critical to early diagnosis, point-of-care and portable medical supervision. Alpha fetoprotein (AFP) is an important clinical tumor marker for hepatocellular carcinoma (HCC), and the concentration of AFP in human serum is related to the stage of HCC. In this paper, a label-free electrochemical aptasensor for AFP detection was fabricated using AFP-aptamer as the recognition molecule and thionin/reduced graphene oxide/gold nanoparticles (TH/RGO/Au NPs) as the sensor platform. With high electrocatalytic property and large specific surface area, RGO and Au NPs were employed on the screen-printed carbon electrode to load TH molecules. The TH not only acted as a bridging molecule to effectively capture and immobilize AFP-aptamer, but as the electron transfer mediator to provide the electrochemical signal. The AFP detection was based on the monitoring of the electrochemical current response change of TH by the differential pulse voltammetry. Under optimal conditions, the electrochemical responses were proportional to the AFP concentration in the range of 0.1-100.0 μg/mL. The limit of detection was 0.050 μg/mL at a signal-to-noise ratio of 3. The proposed method may provide a promising application of aptamer with the properties of facile procedure, low cost, high selectivity in clinic.

Non-enzymatic electrochemical hydrogen peroxide biosensor based on reduction graphene oxide-persimmon tannin‑platinum nanocomposite

Hydrogen peroxide (H2O2) is one of the most universal and essential ingredients in distinct biological tissues. Herein, a novel non-enzymatic sensor based on reduction graphene oxide-persimmon tannin‑platinum nanocomposite (RGO-PT-Pt) was exploited for H2O2 detection. RGO-PT-Pt nanocomposite was prepared by reduction procedure with ascorbic acid as reducing agent and characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV-vis) and Fourier infrared spectroscopy (FT-IR). Taking advantage of high electro-catalytic efficiency of Pt nanoparticles, high electronic conductivity and large surface area of RGO, and significant adsorption ability of PT on metal ions and its prevention of agglomeration to promote RGO dispersion, RGO-PT-Pt nanocomposite revealed better catalytic ability towards H2O2 via a synergistic effect. Under the optimal conditions, the RGO-PT-Pt non-enzymatic biosensor exhibited outstanding electrocatalytic activity towards H2O2 reduction. The amperometric response demonstrated a linear relationship with H2O2 concentration from 1.0 to100 μM with the correlation coefficient of 0.9931. The limit of detection was 0.26 μM (S/N = 3) and the response time was 3 s. Furthermore, the fabricated sensor exhibited a practical applicability in the quantification of H2O2 in human serum samples with an excellent recovery rate. Due to excellent performance such as fast response time, low detection limit, high stability and selectivity, the RGO-PT-Pt non-enzymatic biosensor has potential application in clinical diagnostics.

Preparation, characterisation and in vitro cytotoxicity studies of chelerythrine-loaded magnetic Fe3O4@O-carboxymethylchitosan nanoparticles

In this work, a novel, active tumour-targeting system (Fe3O4@OCMCS-CHE) was designed by surface-modifying superparamagnetic iron oxide nanoparticles (Fe3O4) with O-carboxymethylchitosan (OCMCS) to improve their biocompatibility and ability to target specific tumour cells. The chelerythrine (CHE) was used as the model of anti-tumour drug in this system. The optimised formulation was characterised and confirmed by scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), in vitro drug release and so on. It was found that the synthesised nanoparticles were spherical in shape with an average size of 60 nm, the drug loading content and entrapment efficiency were 8.32 ± 0.25% (w/w) and 90.65 ± 0.46% (w/w), respectively, and the saturated magnetisation reached 27.06 emu/g. The in vitro drug-release behaviour from nanoparticles displayed a biphasic drug-release pattern with initial burst release and consequently sustained release. Also, the effect of magnetic targeted nanoparticles on the proliferation of human hepatoma cell line (HepG2) in vitro was investigated. The results from 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and Hochest assays suggested that the Fe3O4@OCMCS-CHE nanoparticles could effectively inhibit the proliferation of HepG2 cells, which displayed time-dependent and concentration-dependent manner. All these results indicated that the multifunctional Fe3O4@OCMCS nanoparticles possess a high drug loading efficiency, have low cytotoxicity, and are promising candidates for targeted drug delivery.