Wanzhi Wei

Bioremediation of heavy metals by growing hyperaccumulaor endophytic bacterium Bacillus sp. L14

Heavy metal bioremediation by a multi-metal resistant endophytic bacteria L14 (EB L14) isolated from the cadmium hyperaccumulator Solanum nigrum L. was characterized for its potential application in metal treatment. 16S rDNA analysis revealed that this endophyte belonged to Bacillus sp. The hormesis of EB L14 were observed in presence of divalent heavy metals (Cu (II), Cd (II) and Pb (II)) at a relatively lower concentration (10mg/L). Such hormesis was the side effect of abnormal activities increases of ATPase which was planned to provide energy to help EB L14 reduce the toxicity of heavy metals by exporting the cations. Within 24h incubation, EB L14 could specifically uptake 75.78%, 80.48%, 21.25% of Cd (II), Pb (II) and Cu (II) under the initial concentration of 10mg/L. However, nearly no chromium uptake was observed. The mechanism study indicated that its remediation efficiencies may be greatly promoted through inhibiting the activities of ATPase. The excellent adaptation abilities and promising remediation efficiencies strongly indicated the superiority of this endophyte in heavy metal bioremediation at low concentrations, which could be useful for developing efficient metal removal system.

Biosorption of cadmium by endophytic fungus (EF) Microsphaeropsis sp. LSE10 isolated from cadmium hyperaccumulator Solanum nigrum L.

A novel technology to obtain highly efficient biosorbent from the endophytes of a hyperaccumulator is reported. This technology is more convenient than the traditional method of obtaining biosorbents by experimentally screening many types of biomass by trial and error. Using this technology, endophytic fungus (EF) LSE10 was isolated from the cadmium hyperaccumulator Solanum nigrum L. It was identified as Microsphaeropsis sp. When cultured in vitro, the biomass yield of this EF was more than twice that of none-endophytic fungus (NEF) Rhizopus cohnii. Subsequently, it was used as a biosorbent for biosorption of cadmium from the aqueous solution. The results showed that the maximum biosorption capacity was 247.5mg/g (2.2 mmol/g) which was much higher than those of other adsorbents, including biosorbents and activated carbon. Carboxyl, amino, sulphonate and hydroxyl groups on EF LSE10 surface were responsible for the biosorption of cadmium.

Electrodeposition of chitosan–ionic liquid–glucose oxidase biocomposite onto nano-gold electrode for amperometric glucose sensing

A sensitive glucose biosensor was fabricated by electrodepositing chitosan-ionic liquid-glucose oxidase biocomposite onto nano-gold electrode. First, nano-gold electrode was constructed by electrochemically depositing gold nanoparticles onto a flat gold electrode surface. Then the nano-gold electrode was immersed in the bath containing p-benzoquinone (BQ), chitosan (CS), glucose oxidase (GOD) and ionic liquid (IL) for electrodeposition of enzymatic electrode. The proton consumption during electroreduction of BQ increased the local solution pH near the electrode surface and led to the deposition of CS hydrogel on the electrode surface. Co-deposition of GOD and IL with the CS hydrogel was achieved. The proposed biosensor exhibited a fast amperometric response (<5 s) to glucose. Under the optimal conditions, the proposed biosensor exhibited a high current sensitivity (14.33 microA mM(-1) cm(-2)), which was 2.8 times of the biosensor prepared by electrodepositing CS-IL-GOD biocomposite on flat gold electrode. The detection limit for glucose was 1.5 microM, which was 20-fold lower compared to the biosensor prepared on flat gold electrode. The linear range for glucose detection was wide from 3.0 microM to 9.0 mM. Moreover, the proposed biosensor exhibited high reproducibility, long-time storage stability and satisfactory anti-interference ability. The applicability of the proposed biosensor to serum samples analysis was also evaluated.

Determination of microorganisms with a quartz crystal microbalance sensor

A technique using a quartz crystal microbalance sensor coated with a thin culture medium film was developed and successfully applied to determine the number of Staphylococcus epidermidis (S. epidermidis) in the range of 1 × 102 −4.1 × 107 cells ml−1, based on a good linear relationship between the turning point time and the number of S. epidermidis. The technique is fast and accurate for detection of microorganisms due to the thin culture film and the sharp turning point of the response. The experimental conditions were discussed in detail.

Effects of conductive polyaniline (PANI) preparation and platinum electrodeposition on electroactivity of methanol oxidation

A modified galvanostatic method, termed the ‘pulse galvanostatic method’ (PGM) was used to synthesize nanofibular polyaniline (PANI). In contrast to granular PANI prepared by the conventional galvanostatic method (GM), nanofibular PANI has better conductivity and higher specific surface area. The nanofibular PANI electrode modified by Pt microparticles, at the same Pt loading, exhibits a considerably higher electrocatalytic activity on the methanol oxidation than that of the granular PANI electrode modified by Pt microparticles. Furthermore, the PGM method can be used as a good method for Pt microparticle electrodeposition. The composite electrode composed of PANI and Pt microparticles has the best electrocatalytic activity in the experimental range. The effects of Pt loading and methanol concentration, on the electrocatalytic activity for methanol oxidation have also been researched.

A third-generation hydrogen peroxide biosensor based on horseradish peroxidase immobilized on DNA functionalized carbon nanotubes

In this paper, DNA functionalized SWCNTs were used to immobilize horseradish peroxidase (HRP) on glassy carbon (GC) electrode. Cyclic voltammetry showed that the direct electrochemistry of HRP immobilized on DNA-SWCNTs hybrids was achieved. The DNA interlayer between the SWCNTs and HRP could be used to keep the activity of HRP. Compared with HRP-SWCNTs/GC and HRP-DNA/GC electrodes, the prepared HRP-DNA-SWCNTs/GC electrode exhibited more excellent electrochemical properties. Thus, the prepared HRP-DNA-SWCNTs/GC electrode was proposed as a third-generation H(2)O(2) biosensor. The effect of pH and applied potential on the performance of the biosensor was discussed in detail. Under the optimal conditions, a wide linear range of the propose biosensor for the detection of H(2)O(2) was observed from 6.0x10(-7) to 1.8 x10(-3)M. The detection limit was found to be 3.0 x10(-7)M at a signal-to-noise ratio of 3. Furthermore, the proposed biosensor displayed rapid response, high stability, very good reproducibility and high sensitivity for the detection of H(2)O(2). Determination H(2)O(2) concentration in disinfector sample by the proposed biosensor also showed satisfactory result.

A new antibody immobilization strategy based on electrodeposition of nanometer-sized hydroxyapatite for label-free capacitive immunosensor.

A new antibody immobilization strategy was proposed for the fabrication of a label-free capacitive immunosensor based on electrodeposition of nanometer-sized bioactive hydroxyapatite (HAP). By a procedure of constant current cathodal electrodeposition, a nano-HAP film with bioactivity was formed on a self-assembled beta-mercaptoethanol monolayer-modified gold electrode. A suitable amount of chitosan was added into the electrodeposition solution with the aim of obtaining a strong and homogeneous HAP-coating film. After blocking with long-chain alkylthiol and then embedding antibody by coupling with divinylsulphone, the electrode was possessed of a higher initial capacitance value, which was suitable for capacitive transduction. The sensitive layer was characterized by Fourier transform infrared spectrum, scanning electron microscopy and electrochemical method. Human transferrin immunoassay was selected as the testing system. The linear response range of the sensor for transferrin was between 1 and 100ng/mL with a detection limit of 0.15ng/mL. After simply rinsing with subacidity solution, the regenerated sensor achieved up to 10 assay cycles without significant loss of sensitivity.

Immobilization of DNA on silver surface of bulk acoustic wave sensor and its application to the study of UV-C damage

Abstract A simple, inexpensive, on-line bulk acoustic wave (BAW) DNA biosensor is proposed. DNA is immobilized onto an Ag-plated surface rather than the conventional Au surface. Thioglycollic (TGC) acid is used as an active coating for DNA immobilization. The immobilization of DNA and the different binding behavior of ds-DNA and ss-DNA are investigated. The result of the enzyme immunoassay also verifies that DNA is successfully immobilized onto the Ag surface. The experimental relationship between Δfs and the amount of added DNA on the TGC acid modified BAW sensor surface is presented. This novel DNA biosensor is used to monitor the whole process of UV-C induced DNA damage in vitro and to get the real-time frequency response curves. Results show that the UV-C damage in aqueous solution exhibits an apparent tendency towards strand breaks.

Amperometric glucose biosensor with remarkable acid stability based on glucose oxidase entrapped in colloidal gold-modified carbon ionic liquid electrode.

A colloidal gold-modified carbon ionic liquid electrode was constructed by mixing colloidal gold-modified graphite powder with a solid room temperature ionic liquid n-octyl-pyridinium hexafluorophosphate (OPPF(6)). Glucose oxidase (GOD) was entrapped in this composite matrix and maintained its bioactivity well and displayed excellent stability. The effect conditions of pH, applied potential and GOD loading were examined. Especially, the glucose oxidase entrapped in this carbon ionic liquid electrode fully retained its activity upon stressing in strongly acidic conditions (pH 2.0) for over one hour. The proposed biosensor responds to glucose linearly over concentration range of 5.0x10(-6) to 1.2x10(-3) and 2.6x10(-3) to 1.3x10(-2) M, and the detection limit is 3.5x10(-6) M. The response time of the biosensor is fast (within 10s), and the life time is over two months. The effects of electroactive interferents, such as ascorbic acid, uric acid, can be significantly reduced by a Nafion film casting on the surface of resulting biosensor.

Fabrication of DNA functionalized carbon nanotubes/Cu2+ complex by one-step electrodeposition and its sensitive determination of nitrite

In this paper, DNA functionalized single-wall carbon nanotubes/Cu(2+) (DNA-CNTs/Cu(2+)) complex was one-step electrodeposited onto the glassy carbon electrode (GCE), which fabricated a DNA-CNTs/Cu(2+)/GCE sensor to detect nitrite. Cyclic voltammogram of DNA-CNTs/Cu(2+)/GCE showed a pair of well-defined redox peaks for Cu(2+)/Cu(+). Compared with DNA-CNTs/GCE and DNA-Cu(2+)/GCE, the prepared DNA-CNTs/Cu(2+)/GCE exhibited more excellent electrochemical properties. Thus, the prepared DNA-CNTs/Cu(2+)/GCE was proposed as nitrite sensor. The effects of Cu(2+), CNTs and DNA concentration in the mixture together with electrodeposition time and determination conditions such as applied potential, pH value on the current response of DNA-CNTs/Cu(2+)/GCE toward nitrite were optimized to obtain the maximal sensitivity. In addition, electrochemical experiments revealed that the modified electrode showed high electrocatalytic activity to the reduction of nitrite ion (NO(2)(-)). The linear range for the detection of NO(2)(-) was 3x10(-8) to 2.6x10(-3)M, and the response was very fast (less than 3s). A low detection limit of 3x10(-8)M (S/N=3) for NO(2)(-) was achieved.