Xiuzhen Wang

Electrochemical DNA biosensor with chitosan-Co3O4 nanorod-graphene composite for the sensitive detection of staphylococcus aureus nuc gene sequence

In this paper a novel nanocomposite material prepared by Co(3)O(4) nanorods (nano-Co(3)O(4)), graphene (GR) and chitosan (CTS) was fabricated and further modified on carbon ionic liquid electrode (CILE), which was used as the substrate electrode to construct a new electrochemical DNA biosensor. The single-stranded DNA (ssDNA) probe was immobilized on the CTS-Co(3)O(4)-GR/CILE surface by electrostatic attraction, which could hybridize with the target ssDNA sequence under the selected conditions. By using methylene blue (MB) as the electrochemical indicator, the hybridization reactions were monitored with the reduction peak current. By combining the biocompatibility of Co(3)O(4) nanorods, excellent electron transfer ability and big surface of GR, good film-forming ability of CTS and the high conductivity of CILE, the amount of ssDNA adsorbed on the electrode surface was increased and the electrochemical response of MB was accelerated. Under the optimal conditions differential pulse voltammetric responses of MB were in linear with the specific target ssDNA sequence in the concentration range from 1.0×10(-12) to 1.0×10(-6)M with the detection limit as 4.3×10(-13)M (3σ). Good discrimination ability to the one-base and three-base mismatched ssDNA sequences could be achieved and the polymerase chain reaction (PCR) amplification products of Staphylococcus aureus nuc gene sequence were detected with satisfactory results.

Direct electrochemistry of hemoglobin on graphene and titanium dioxide nanorods composite modified electrode and itselectrocatalysis

A biocompatible sensing platform based on graphene (GR) and titanium dioxide (TiO₂) nanorods for the immobilization of hemoglobin (Hb) was adopted in this paper. The GR-TiO₂-Hb composite-modified carbon ionic liquid electrode was constructed through a simple casting method with Nafion as the film forming material. UV-Vis and FT-IR spectra confirmed that Hb retained its native structure in the composite film. Direct electron transfer of Hb incorporated into the composite was realized with a pair of quasi-reversible redox waves appeared, indicating that the presence of GR-TiO₂ nanocomposite on the electrode surface could facilitate the electron transfer rate between the electroactive center of Hb and the substrate electrode. Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 0.6 to 21.0 mmol L⁻¹. These results indicated that GR-TiO₂ nanocomposite could be a friendly biocompatible interface for immobilizing biomolecules and keeping their native structure. The fabricated biosensor displayed the advantages such as high sensitivity, good reproducibility and long-term stability.

Simultaneous electrochemical determination of guanosine and adenosine with graphene–ZrO2 nanocomposite modified carbon ionic liquid electrode

In this paper an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was fabricated and used as the basal electrode, which was further modified by graphene (GR) and ZrO2 nanoparticle with chitosan (CTS) film to immobilize the nanocomposite. The modified electrode was denoted as CTS-GR-ZrO2/CILE and further used for the simultaneous detection of adenosine and guanosine. Electrochemical performances of the modified electrode were greatly enhanced due to the presence of GR-ZrO2 nanocomposite, and the direct electro-oxidation behaviors of adenosine and guanosine were carefully investigated. Both adenosine and guanosine exhibited an increase of the oxidation peak currents with the negative shift of the oxidation peak potentials on the modified electrode, which indicated the electrocatalytic activity of GR-ZrO2 nanocomposite on the electrode surface. Electrochemical parameters of adenosine and guanosine on CTS-GR-ZrO2/CILE were calculated respectively, and a new electroanalytical method for the simultaneous determination of adenosine and guanosine was further established with the peak-to-peak separation (ΔEp) as 0.225V. The proposed method was successfully applied to detect adenosine and guanosine in human urine samples with satisfactory results.

Electrochemical behavior and determination of guanosine-5′-monophosphate on a ionic liquid modified carbon electrode

A carbon ionic liquid electrode (CILE) was constructed by using ionic liquid 1-butyl-3-meth-ylimidazolium dihydrogen phosphate, (BMIM)H2PO4, as modifier and further employed as a novel working electrode for the determination of guanosine-5′-monophosphate (GMP). The study of electrochemical behavior of GMP on the CILE showed a single well-defined irreversible oxidation peak on the cyclic voltammogram. Under the selected conditions the oxidation peak current was proportional to GMP concentration in the range from 5.0 to 1000 μM with the limit of detection of 1.3 μM (3σ) by differential pulse voltammetry. The proposed method showed good selectivity to the GMP detection without the interferences of coexisting substances.