Jiajia Wu

Graphene oxide sheet-mediated silver enhancement for application to electrochemical biosensors.

Functionalized graphene oxide (GO) sheets coupled with a signal amplification method based on the nanomaterial-promoted reduction of silver ions for the sensitive and selective detection of bacteria. This paper aims to develop an electrochemical route combined with GO sheet-mediated Ag enhancement for biological/chemical analyte detection. A linear relationship between the stripping response and the logarithm of the bacterial concentration was obtained using an electrochemical technique for concentrations ranging from 1.8 × 10(2) to 1.8 × 10(8) cfu mL(-1), with a slope of 15.28 and a correlation coefficient of 0.995. Dot blot assay was used as a conventional immunoassay method for comparison with the electrochemical method, as well as to observe the quality of the anti-sulfate-reducing bacteria (SRB) antibody (Ab) used in the immunosensor. The GO sheet-mediated silver enhancement holds great potential for the rapid analysis of protein, DNA, and pathogens.

Vancomycin-functionalised Ag@TiO2 phototoxicity for bacteria.

This study reports on the synthesis of vancomycin (Van)-functionalised Ag@TiO(2) nanoparticles and their enhanced bactericidal activities. Van-Ag@TiO(2) nanoparticles were prepared by nanoparticle deposition and chemical cross-linking reactions. The catalysts showed high efficiency for the degradation of methylene blue under ultraviolet (UV) illumination. The photocatalytic inactivation of the sulphate-reducing bacteria, Desulfotomaculum, was also studied under UV light irradiation and in the dark using aqueous mixtures of Ag, Ag@SiO(2), Ag@TiO(2), and Van-Ag@TiO(2). The Van-Ag@TiO(2) nanoparticles showed a capacity to target Van-sensitive bacteria. They also effectively prevented bacterial cell growth through the functionalised nanoparticles under UV irradiation for 1h. To investigate the specificity of the catalyst phototoxicity, a Van-resistant bacteria, Vibrio anguillarum, was used as the negative control. The results indicated that Van-Ag@TiO(2) nanoparticles had a higher selective phototoxicity for Van-sensitive bacteria. Therefore, the antibiotic molecule-functionalised core-shell nanoparticles allow for selective photokilling of pathogenic bacteria.

Controlled drug release characteristics and enhanced antibacterial effect of graphene oxide–drug intercalated layered double hydroxide hybrid films

Novel graphene oxide–benzylpenicillin (BP) anion intercalated Mg–Al layered double hydroxide (GO–BP-LDH) hybrid films were prepared via a simple solvent evaporation process. The release behaviour of BP anions and the antibacterial activity have also been investigated. The release time can be tailored by adjusting the film composition and increased by decreasing the GO/BP-LDH mass ratio. By applying release kinetic models to the drug release processes, the mechanism of release of BP anions from the GO–BP-LDH hybrid film was found to follow the first-order model. In addition, the hybrid film exhibited an enhanced synergistic antibacterial effect compared with the single GO film, which can be attributed to the combination of the antibacterial activity of GO and BP anions released from the hybrid film system.

Enhancement in Kinetics of the Oxygen Reduction Reaction on a Nitrogen-Doped Carbon Catalyst by Introduction of Iron via Electrochemical Methods

The iron (Fe) electrodeposition-electrochemical dissolution has been employed on nitrogen-doped carbon material (P-PI) prepared via multi-step pyrolysis of a polyimide precursor to achieve the introduction of Fe species, and its influence on the oxygen reduction reaction (ORR) is investigated by cyclic and rotating ring-disk electrode voltammetry in 0.5 M H2SO4. After the electrochemical treatment, the overpotential and H2O2 production percentage of ORR on the P-PI are decreased and the number of electrons transferred is increased in the meanwhile. In combination with the results of X-ray absorption fine structure spectra, the presence of Fe-Nx sites (Fe ions coordinated by nitrogen) is believed to be responsible for the improved ORR performance. Further kinetic analysis indicates that a two-electron reduction of O2 is predominant on the untreated P-PI with coexistence of a direct four-electron transformation of O2 to H2O, while the introduction of Fe species leads to a larger increase in the rate constant for the four-electron reduction than that for the two-electron process, being in good agreement with the view that Fe-Nx sites are active for four-electron ORR.

Electron transfer from sulfate-reducing becteria biofilm promoted by reduced graphene sheets

Reduced graphene sheets (RGSs) mediate electron transfer between sulfate-reducing bacteria (SRB) and solid electrodes, and promote the development of microbial fuel cells (MFC). We have investigated RSG-promoted electron transfer between SRB and a glassy carbon (GC) electrode. The RGSs were produced at high yield by a chemical sequence involving graphite oxidation, ultrasonic exfoliation of nanosheets, and N2H4 reduction. Cyclic voltammetric testing showed that the characteristic anodic peaks (around 0.3 V) might arise from the combination of bacterial membrane surface cytochrome c3 and the metabolic products of SRB. After 6 d, another anodic wave gradually increased to a maximum current peak and a third anodic signal became visible at around 0 V. The enhancements of two characteristic anodic peaks suggest that RSGs mediate electron-transfer kinetics between bacteria and the solid electrode. Manipulation of these recently-discovered electron-transport mechanisms will lead to significant advances in MFC engineering.