Microelectrodes nanoparticle detection

To fulfill both the requirement of CFME for the practical applications and the necessity of Au substrate to assemble so-called promoters to construct the third-generation biosensor, Tian el al. have combined the electrochemical deposition of Au nanoparticles (Au-NPs) onto carbon fiber microelectrodes with the self-assembly of a monolayer on these Au-NPs to facilitate the direct electron transfer of SOD at the carbon fiber microelectrode. The strategy enabled a third-generation amperometric 02 biosensor to be readily fabricated on the carbon fiber microelectrode. This CFME-based biosensor is envisaged to have great potential for (he detection of 02" in biological systems [158],... 

The analysis of the current-time curves at electrodes or microelectrodes of different geometries has also a great interest in detecting the presence of small particles or nanoparticles at its surface or even single nanoparticles events through the current due to the electro-oxidation (or reduction) of the particles (see Fig. 2.18) or to a electrocatalytic reaction on the nanoparticle surface when this comes into contact with the electrode and transiently sticks to it [62-65]. 

Varshney M, Li YB, Srinivasan B, Tung S (2007) A label-free, microlluidics and interdigitated array microelectrode-based impedance biosensor in combi-natirm with nanoparticles immunoseparation for detection of Escherichia coli 0157 H7 in food samples. Sensor Actual B Chem 128 99-107... 

Nanoparticle-induced changes in the conductivity across a microelectrode gap can also be exploited for highly sensitive and selective electronic detection of DNA hybridization [45, 46]. The capture of the nanoparticle-tagged DNA targets by probes confined to the gap between the two microelectrodes, and a subsequent silver enlargement, results in a conductive metal layer across the gap, and leads to a measurable conductivity signal. Target DNA concentrations down to 500 fmol can, thus, be detected with remarkable... 

Adams, K.L., B.K. Jena, S.J. Percival, and B. Zhang. 2011. Highly sensitive detection of exocytotic dopamine release using a gold-nanoparticle-network microelectrode. Anal. Chem. 83 920-927. 

Finally, SECM studies on single HeLa cells have also focused on their interaction with silver nanoparticles. The detection scheme relied on the interaction of an iridium hexachloride couple with silver nanoparticles. When the microelectrode approached the HeLa cells, two mechanisms competed with IrCV regeneration from IrClg by the silver nanoparticles adsorbed on the ceU surface IrCl " diffusing across the intracellular space and IrCI transported in the intracellular lumen where it could subsequently be reduced by an intracellular redox species or silver nanoparticles segregated in the nucleus (Eigure 12.23). 

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