Electrode receptor-modified electrodes

While the variety of NPs used in catalytic and sensor applications is extensive, this chapter will primarily focus on metallic and semiconductor NPs. The term functional nanoparticle will refer to a nanoparticle that interacts with a complementary molecule and facilitate an electrochemical process, integrating supramolecular and redox function. The chapter will first concentrate on the role of exo-active surfaces and core-based materials within sensor applications. Exo-active surfaces will be evaluated based upon their types of molecular receptors, ability to incorporate multiple chemical functionalities, selectivity toward distinct analytes, versatility as nanoscale receptors, and ability to modify electrodes via nanocomposite assemblies. Core-based materials will focus on electrochemical labeling and tagging methods for biosensor applications, as well as biological processes that generate an electrochemical response at their core. Finally, this chapter will shift its focus toward the catalytic nature of NPs, discussing electrochemical reactions and enhancement in electron transfer. 

When natural or synthetic DNA molecules interact with electrode surfaces adsorption occurs. The knowledge about the adsorption of nucleic acids onto the electrode surface leads to the development of DNA-modified electrodes, also called electrochemical DNA biosensors [3-6,19-24], An electrochemical DNA biosensor is an integrated receptor-transducer device that uses DNA as the biomolecular recognition element to measure specific binding processes with DNA, using electrochemical transduction. 

A method for the preparation of thin films of Fe4[Ru(CN)6]3 ( ruthenium purple ) involving electrochemical reduction of K3[Ru(CN)6] in a solution of Fe2(S04)3 has been developed.28 This ruthenium purple modified electrode is claimed to be one of the best catalysts for evolution of oxygen and chlorine. Electrochemical studies on polyammonium macrocyclic complexes of [Ru(CN)6]4 indicate a 1 1 stoichiometry with a monoelectronic, reversible, oxidation for these complexes this illustrates the control of redox potential of anions by complexation with appropriate receptor molecules.29 The kinetics of oxidation of [Ru(CN)6]4 by [Mn04] in HC104 have been investigated by stopped-flow techniques. It is found that [Ru(CN)6]4" is quantitatively oxidized to [Ru(CN)6]3 in accordance with equation (1) and that two protonated intermediates [RuH(CN)6]3 and [RuH2(CN)6]3 are involved in the oxidation process.30... 

Ge. Y. Smith, D.K. Development of chemical sensors 126. based on redox-dependent receptors. Preparation and characterization of phenanthrenequiiione-modified electrodes. Anal. Chern. 2000. 72. 1860- 1865. 

Electrochemical biosensor A self-contained integrated device that is capable of providing specific quantitative or semiquantitative analjrtical information using a biological recognition element (biochemical receptor), which is retained in direct spatial contact with an electrochemical transduction element [6]. A biosensor with an electrochemical transducer may represent a chemically modified electrode. 

Key words Self-assembled mono-layers - binding sites - receptors -host-guest interactions - amphiphilic structures - sensors -voltammetry - modified electrodes... 

Buehfinann P, Aoki H, Xiao KP, Anemiya S, Tohda K, Umezawa Y (1998) Chemical sensing with chemically modified electrodes that mimic gating at biomembranes incorporating ion-channel receptors. Electroanalysis 10 1149-1158... 

Although at present their use has been restricted to redox-active sensors in solution, it should be possible to immobilise these receptors at an electrode, and we may then have a simple redox-active electrode whose behaviour in solution is modified by the presence of ions. The high sensitivity of electrochemical techniques would then give us a sensitive and selective method of anion detection. 

Electrode surfaces that have been properly modified with bioreactive layers (enzyme, antibody, receptor) can provide access to the in vivo investigation of biologically significant materials. Such devices offer simplicity, low cost, miniaturization, automation, and high sensitivity. Key research areas include... 

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