Zixia Zhao

A novel nonenzymatic hydrogen peroxide sensor based on multi-wall carbon nanotube/silver nanoparticle nanohybrids modified gold electrode

A novel strategy to fabricate hydrogen peroxide (H(2)O(2)) sensor was developed based on multi-wall carbon nanotube/silver nanoparticle nanohybrids (MWCNT/Ag nanohybrids) modified gold electrode. The process to synthesize MWCNT/Ag nanohybrids was facile and efficient. In the presence of carboxyl groups functionalized multi-wall carbon nanotubes (MWCNTs), silver nanoparticles (Ag NPs) were in situ generated from AgNO(3) aqueous solution and readily attached to the MWCNTs convex surfaces at room temperature, without any additional reducing reagent or irradiation treatment. The formation of MWCNT/Ag nanohybrids product was observed by transmission electron microscope (TEM), and the electrochemical properties of MWCNT/Ag nanohybrids modified gold electrode were characterized by electrochemical measurements. The results showed that this sensor had a favorable catalytic ability for the reduction of H(2)O(2). The resulted sensor could detect H(2)O(2) in a linear range of 0.05-17 mM with a detection limit of 5x10(-7)M at a signal-to-noise ratio of 3. The sensitivity was calculated as 1.42 microA/mM at a potential of -0.2 V. Additionally, it exhibited good reproducibility, long-term stability and negligible interference of ascorbic acid (AA), uric acid (UA), and acetaminophen (AP).

A novel glucose biosensor based on the immobilization of glucose oxidase onto gold nanoparticles-modified Pb nanowires

A novel glucose biosensor was developed, based on the immobilization of glucose oxidase (GOD) with cross-linking in the matrix of bovine serum albumin (BSA) on a Pt electrode, which was modified with gold nanoparticles decorated Pb nanowires (GNPs-Pb NWs). Pb nanowires (Pb NWs) were synthesized by an L-cysteine-assisted self-assembly route, and then gold nanoparticles (GNPs) were attached onto the nanowire surface through -SH-Au specific interaction. The morphological characterization of GNPs-Pb NWs was examined by transmission electron microscopy (TEM). Cyclic voltammetry and chronoamperometry were used to study and to optimize the electrochemical performance of the resulting biosensor. The synergistic effect of Pb NWs and GNPs made the biosensor exhibit excellent electrocatalytic activity and good response performance to glucose. The effects of pH and applied potential on the amperometric response of the biosensor have been systemically studied. In pH 7.0, the biosensor showed the sensitivity of 135.5 microA mM(-1) cm(-2), the detection limit of 2 microM (S/N=3), and the response time <5 s with a linear range of 5-2200 microM. Furthermore, the biosensor exhibits good reproducibility, long-term stability and relative good anti-interference.

Amperometric choline biosensors prepared by layer-by-layer deposition of choline oxidase on the Prussian blue-modified platinum electrode

An amperometric choline biosensor was developed by immobilizing choline oxidase (ChOx) in a layer-by-layer (LBL) multilayer film on a platinum (Pt) electrode modified with Prussian blue (PB). 6-O-Ethoxytrimethylammoniochitosan chloride (EACC) was used to prepare the ChOx LBL films. The choline biosensor was used at 0.0V versus Ag/AgCl to detect choline and exhibited good characteristics such as relative low detection limit (5x10(-7)M), short response time (within 10s), high sensitivity (88.6muAmM(-1)cm(-2)) and a good selectivity. The results were explained based on the ultrathin nature of the LBL films and the low operating potential that could be due to the efficient catalytic reduction of H(2)O(2) by PB. In addition, the effects of pH, temperature and applied potential on the amperometric response of choline biosensor were evaluated. The apparent Michaelis-Menten constant was found to be (0.083+/-0.001)x10(-3)M. The biosensor showed excellent long-term storage stability, which originates from a strong adsorption of ChOx in the EACC multilayer film. When the present choline biosensor was applied to the analysis of phosphatidylcholine in serum samples, the measurement values agreed satisfactorily with those by a hospital method.

Self-assembled film of hydrophobins on gold surfaces and its application to electrochemical biosensing

Hydrophobins are small fungal proteins which self-assemble on interfaces and significantly change the surface wettability. The self-assembled film of hydrophobin HFBI on a gold surface improved the surface hydrophilicity with water contact angle changing from 73.8+/-1.8 degrees to 45.3+/-1.4 degrees . A quartz crystal microbalance (QCM) analysis indicated that the HFBI coverage density on a gold surface was 588 ng cm(-2), and the self-assembled film remained stable under different pH values ranging from 1 to 13. A hydrophilic protein such as choline oxidase (ChOx) was then successfully immobilized on the HFBI modified gold surface. To evaluate the bioactivity of immobilized enzyme, an amperometric choline biosensor was constructed based on the Gold/HFBI/ChOx electrode, which produced as large as 4578.27 nA response current by 0.238 microg immobilized ChOx, when saturated by choline substrate. Comparing with our choline biosensors previously reported, the HFBI self-assembled film exhibited excellent capability to preserve the bioactivity of ChOx, hence a great potential in electrochemical biosensing is suggested.

Noncovalently functionalized multi-wall carbon nanotubes in aqueous solution using the hydrophobin HFBI and their electroanalytical application

A novel noncovalent approach was developed for the functionalization of multi-wall carbon nanotubes (MWNTs) using the hydrophobin, HFBI. Owing to the amphipathic nature, HFBI can be adopted onto the surface of MWNTs to form HFBI-MWNTs nanocomposite with good dispersion in water. The HFBI-MWNTs nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and water contact angle measurements (WCA). Furthermore, a glucose biosensor was developed based on HFBI-MWNTs by a one-step casting method. The resulting biosensor displayed high sensitivity, wider linear range, low detection limit, and fast response for glucose detection, which implicated that the HFBI-MWNTs nanocomposite film holds great promise in the design of electrochemical devices, such as sensors and biosensors.

Horseradish peroxidase microcapsules based on layer-by-layer polyelectrolyte deposition.

Polyelectrolyte multilayer microcapsules have been prepared for encapsulating horseradish peroxidase (HRP). The CaCO3 microparticles containing HRP molecules were prepared and subsequently enwrapped with layer-by-layer (LbL) deposited multilayer films. The LbL films were constructed via an alternate electrostatic adsorption of poly(allylamine) and poly(styrene sulfonate). The CaCO3 templates were then dissolved in an ethylenediaminetetraacetic acid solution, leaving HRP in the microcapsules. Optical microscope and fluorescence microscope observations indicated that the microcapsules are homogeneous spheres with an average diameter about 7 μm. The encapsulated HRP showed catalytic activity in the oxidation of pyrogallol, suggesting the microcapsules provide a suitable environment for enzymatic reaction. A leakage of HRP from the microcapsules was negligibly small. Therefore, the HRP-containing microcapsules is promising for detection and treatment of phenolic compounds.

Comparison of a Resonant Mirror Biosensor (IAsys) and a Quartz Crystal Microbalance (QCM) for the Study on Interaction between Paeoniae Radix 801 and Endothelin-1

A resonant mirror biosensor, IAsys, and a quartz crystal microbalance (QCM) are known independently as surface sensitive analytical devices capable of label-free and in situ bioassays. In this study, an IAsys and a QCM are employed for a new study on the action mechanism of Paeoniae Radix 801 (P. radix 801) by detecting the specific interaction between P. radix 801 and endothelin-1 (ET-1). In the experiments, ET-1 was immobilized on the surfaces of the IAsys cuvette and the QCM substrate by surface modification techniques, and then P. radix 801 solution was contacted to the cuvette and the substrate, separately. Then, the binding and interaction process between P. radix 801 and ET-1 was monitored by IAsys and QCM, respectively. The experimental results showed that P. radix 801 binds ET-1 specifically. The IAsys and QCM response curves to the ET-1 immobilization and P. radix 801 binding are similar in reaction process, but different in binding profiles, reflecting different resonation principles. Although both IAsys and QCM could detect the interaction of P. radix 801 and ET-1 with high reproducibility and reliability through optimization of the ET-1 coating, the reproducibility and reliability obtained by IAsys are better than those obtained by QCM, since the QCM frequency is more sensitive to temperature fluctuations, atmospheric changes and mechanical disturbances. However, IAsys and QCM are generally potent and reliable tools to study the interaction of P. radix 801 and ET-1, and can conclusively be applied to the action mechanism of P. radix 801.