Ying Wu

A novel reagentless amperometric immunosensor based on gold nanoparticles/TMB/Nafion-modified electrode

A novel reagentless immunosensor was fabricated by immobilization of redox mediator 3,3,5,5-tetramethylbenzidine (TMB) on the Nafion (Nf) film modified glassy carbon electrode. Gold nanoparticles were assembled onto the TMB/Nafion film modified electrode to provide active sites for the immobilization of antibody molecules. The antibody (anti-MIgG), in the present study, was fixed on the electrode for the rapid detection of antigen molecules (MIgG as a model analyte). The results showed that the immunosensor based on the immobilized TMB redox mediator exhibited good electrochemical response. A good linear relationship between peak current and the concentration of the MIgG was obtained in the concentration range from 4 to 120ng/mL. The detection limit was estimated to be 1ng/ml. Under the optimized conditions, the immunosensor exhibits good sensitivity, reproducibility and stability.

Disposable superoxide anion biosensor based on superoxide dismutase entrapped in silica sol-gel matrix at gold nanoparticles modified ITO electrode

A novel disposable biosensor based on direct electron transfer of superoxide dismutase (SOD) was fabricated for the determination of superoxide anion. The biosensor was constructed by electrodeposition of gold nanoparticles (GNPs) on the indium tin oxide (ITO) electrode and then immobilization of SOD in silica sol–gel (SG) network in the presence of cysteine on GNPs/ITO modified electrode surface. The distribution of GNPs on ITO electrode surface was examined by scanning electron microscopy (SEM). The immobilized SOD exhibited high catalytical activity towards superoxide anion. Parameters affecting the performance of the biosensor were also investigated. A linear calibration curve was obtained over the range from 0.08 to 0.64xa0μM with a correlation coefficient of 0.9937. The resulted biosensors were demonstrated to possess striking analytical properties for superoxide anion determination, such as high sensitivity, good accuracy, and long-term stability. It provides a promising platform for the fabrication of disposable biosensors.

Synthesis of strongly fluorescent carbon quantum dots modified with polyamidoamine and a triethoxysilane as quenchable fluorescent probes for mercury(II)

AbstractThis article reports on the synthesis of water dispersible carbon quantum dots (CDs) by a one-step hydrothermal method using polyamidoamine (PAMAM) and (3-aminopropyl)triethoxysilane (APTES) asxa0a platform and passivant. The resulting CDs are highly uniform and finely dispersed. The synergistic effect between PAMAM and APTES on the surface of the CDs results in a fluorescence that is much brighter than that of CDs modified with either APTES or PAMAM only. The fluorescence of the co-modified CDs is quenched by Hg(II) ions at fairly low concentrations. Under the optimum conditions, the intensity of quenched fluorescence drops with Hg(II) concentration in the range from 0.2xa0nM to 10xa0μM, and the detection limit is 87 fM. The effect of potentially interfering cations on the fluorescence revealed a high selectivity for Hg2+. The fluorescent probe was applied to the determination of Hg(II) in (spiked) waters and milk and gave recoveries between 95.6 and 107xa0%, with relative standard deviation between 4.4 and 6.0xa0%.n Graphical abstractStrongly fluorescent carbon quantum dots (CDs) modified with polyamidoamine (PAMAM) and 3-aminopropyltriethoxysilane (APTES) were synthesized by one-step hydrothermal strategy. The resulting co-modified CD s were used as fluorescent probe for sensitive and selective detection of Hg2+.

Ultrasensitive electrochemiluminescent immunoassay for morphine using a gold electrode modified with CdS quantum dots, polyamidoamine, and gold nanoparticles

AbstractWe report on a novel electrochemiluminescent (ECL) immunoassay for the ultrasensitive determination of morphine by making use of a gold electrode which was modified with a nanocomposite film containing self-assembled polyamidoamine (PAMAM) CdS quantum dots and electrodeposited gold nanoparticles (Au-NPs). The highly uniform and well-dispersed quantum dots were capped with PAMAM dendrimers. Due to the synergistic effect of the modified quantum dots and the electrodeposited Au-NPs, the ECL response is dramatically enhanced. Under optimal experimental conditions, the immunoreaction between morphine and anti-morphine antibody resulted in a decrease of the ECL signal because of steric hindrance. The calibration plot is linear in the morphine concentration range from 0.2 to 180xa0ng•mL−1, with a detection limit as low as 67xa0pg•mL−1. The sensor was successfully applied to the determination of morphine in blood plasma. This kind of assay is expected to pave new avenues in label-free drug assays.n Figureᅟ

Electrochemiluminescence immunosensor for ketamine detection based on polyamidoamine-coated carbon dot film

In this work, we reported the synthesis of water-soluble carbon dots (CDs) by a one-step hydrothermal synthetic route using polyamidoamine (PAMAM) as platform and passivant, where the formation of CDs capped with PAMAM and the surface passivation were realized simultaneously. As a result, the prepared PAMAM-CDs were uniform, monodispersed sphere particles with an approximate diameter of about 2xa0nm, and the fluorescence and electrochemiluminescence (ECL) response of the nanocomposite film were enhanced. By combining the high sensitivity of ECL and the selectivity of immunoreactions, an ECL immunosensor for facile, rapid, and ultrasensitive detecting of ketamine was constructed, and the further application of the immunoassay was investigated. Under optimal experimental conditions, the obtained immunosensor showed a wide linear detection range from 0.2 to 200xa0ngxa0mL−1 with a detection limit at 0.067xa0ngxa0mL−1 in 0.1xa0M phosphate buffer solutions (pH 7.4). The immunosensor was successfully applied to the determination of ketamine in blood plasma. This kind of assay is expected to pave new avenues in label-free drug assays.

Enhanced direct electron transfer of glucose oxidase based on a protic ionic liquid modified electrode and its biosensing application

A novel glucose oxidase (GOD) biosensor was fabricated with a protic ionic liquid (PIL) N-ethylimidazolium trifluoromethanesulfonate ([EIm][TfO]) as the modifier of a carbon electrode. Due to the excellent conductivity and the conformational changes of the microenvironment around the GOD, the electrochemical and biocatalytic properties of GOD immobilized on the PIL-based electrode were dramatically enhanced. A couple of well-defined redox peaks could be observed, with a formal potential of −0.476xa0V. The GOD biosensor presented good catalytic activity to the oxidation of glucose in oxygen-saturated phosphate buffer solutions. The cathodic peak currents of GOD decreased along with glucose concentrations. A linear response in the range 0.005–2.8xa0mM was obtained with a detection limit of 2.5xa0μM. The sensitivity and the apparent Michaelis–Menten constant (Km) were estimated to be 14.96xa0μAxa0mM−1 and 1.53xa0μM, respectively. In addition, the biosensor remained stable over 30xa0days, indicating its good chemical and mechanical stability. The glucose content of several serum samples was determined by using the newly developed biosensor, and the results were in good agreement with those obtained by hospital measurements. All results suggested that PILs were a good media for supporting biocatalytic processes on the bioelectrode.

The use of gold-silver core-shell nanorods self-assembled on a glass substrate can substantially improve the performance of plasmonic affinity biosensors

AbstractWe report on an effective strategy for the enhancement in the sensitivity of localized surface plasmon resonance (LSPR). It is based on the use of gold-silver core-shell nanorods (Au-Ag-cs-NRs) immobilized on a glass substrate. The nanorods arrange themselves by self-assembly, and the resulting LSPR band of the Au-Ag-cs-NRs becomes sharper and more intense. The sensitivity to refractive index (RI) of the Au-Ag-cs-NRs on the glass support is ~281xa0nm per RI unit, which is better by about 30xa0% compared to gold nanorods immobilized on glass substrate. The system was applied to study the streptavidin-biotin affinity system which is widely used in biosciences. It is found that the red-shift of the LSPR peak linearly increases with the concentration of streptavidin in the 95xa0pM to 1.7xa0μM concentration range. The detection limit (at an S/N ratio of 3) is at 35xa0pM. The results reveal the merits of this approach in terms of label-free optical affinity sensing.n FigureAu-Ag core-shell nanorods self-assembled on glass substrates. The refractive index sensitivity was enhanced obviously. A strategy to amplify the response and fabricate a label-free optical biosensor

Determination of Dopamine with a Modified Carbon Dot Electrode

A facile and green synthesis was employed to synthesize water-soluble carbon dots that were shown to be uniform monodisperse spheres with an average diameter of approximately 4 nanometers. Because of their strong adsorption, the carbon dots were assembled on a glassy carbon electrode without a bridging agent. The modified electrode was employed for the sensitive determination of dopamine. In 0.1 mole per liter phosphate buffer at pH 6.0, the peak currents of dopamine increased at the modified electrode. A calibration curve for dopamine was obtained from 1.5 × 10−7 to 1.5 × 10−4 mole per liter with a limit of detection of 2.6 × 10−8 mole per liter. The sensor was employed to determine dopamine in human plasma without interferences from uric acid and ascorbic acid. The carbon dot modified electrode also exhibited high stability and excellent precision. The results demonstrate the facile fabrication of a carbon dot-based sensor and a sensitive method for the determination of dopamine.

A cathodic photoelectrochemical sensor for chromium(VI) based on the use of PbS quantum dot semiconductors on an ITO electrode

AbstractUnder visible-light irradiation, a cathodic photoelectrochemical (PEC) sensor is presented for highly sensitive determination of Cr(VI) at axa0potential of −0.25xa0V (vs SCE). PbS quantum dotsxa0(QDs)xa0were capped with mercaptoacetic acid and assembled on the surface of anxa0indium tin oxide (ITO) electrode via the linker poly(diallyl dimethyl ammonium chloride) providing a photoactive sensor. Cr(VI) accepts the photoelectrons generated by the PbS QDs. This promotes the separation of electron holes and enhances the cathodic photocurrent generated by a 470-nm LED. The sensor has 10 pM detection limit and a linear working range from 0.02xa0nM to 2xa0μMxa0of chromate. The method was successfully applied to the determination of Cr(VI) and total chromium in spiked environmental water samples.n Graphical abstractSchematic illustration of the photocurrent enhancement response of ITO/PbS toward chromium(VI). In the presence of Cr(VI) (red line), Cr(VI) accepts the photoelectrons generated by the PbS QDs under 470-nm LED irradiation, resulting in improved photocurrent of ITO/PbS.

Formation and electrochemical behaviour of polyoxometalate-capped gold nanoparticles assembly electrode

The functionalized gold nanoparticles capped with polyoxometalates were prepared by a simple photoreduction technique in the presence of phosphododecamolybdate (PMo12) to serve as reducing reagents, photocatalysts, and stabilizers. Monolayer and multilayer structures of the negatively charged PMo12-capped gold nanoparticles (PMo12-NGs) were constructed on a polyvinylpyridine-derivatized indium-doped tin oxide (ITO) electrode through layer-by-layer self-assembly technique. The PMo12-NGs modified ITO electrode exhibits the characteristic electrochemical behaviour of the surface confined PMo12: multi-step reversible redox reactions. Excellent catalytic activity for the reduction of iodate was obtained on the modified electrode.