Electrochemical biosensor, structure

Similarly to the above-mentioned entrapment of proteins by biomimetic routes, the sol-gel procedure is a useful method for the encapsulation of enzymes and other biological material due to the mild conditions required for the preparation of the silica networks [54,55]. The confinement of the enzyme in the pores of the silica matrix preserves its catalytic activity, since it prevents irreversible structural deformations in the biomolecule. The silica matrix may exert a protective effect against enzyme denaturation even under harsh conditions, as recently reported by Frenkel-Mullerad and Avnir [56] for physically trapped phosphatase enzymes within silica matrices (Figure 1.3). A wide number of organoalkoxy- and alkoxy-silanes have been employed for this purpose, as extensively reviewed by Gill and Ballesteros [57], and the resulting materials have been applied in the construction of optical and electrochemical biosensor devices. Optimization of the sol-gel process is required to prevent denaturation of encapsulated enzymes. Alcohol released during the... 

The application of dendrimers in electrochemical biosensors is an emerging area of research. The structural homogeneity, biocompatibility, internal porosity, high surface area and ease of functionalization of dendrimers make them very desirable for biosensor applications. In the past ten years, there has been a steady and gradual development in the evaluation of the bionanocomposites of dendrimers for electrochemical sensors. The expanding interest in the development of novel electroactive dendrimers has enabled their viability for this application. 

Enzyme immobilization is considered as an important factor in biosensor technologies. Great attempts are in progress for finding novel materials for fabrication electrochemical biosensors. Due to electrical, optical, biocompatible properties, structure stability and small... 

BLM systems have been accepted as models of natural biomembranes for applications in medicine, industry, and clinical laboratories. BLMs have therefore been studied extensively in combination with various proteins, and are an excellent choice for the basis for development of electrochemical biosensors. The principles behind the development of BLM-based biosensors are quite simple. The sensing element should be biocompatible and should have a structure similar to a biomembrane. Chemically selective proteins may then be embedded into the membranes with substantial retention of binding activity. The simplest way to test transducer function is by using ligand-receptor binding interactions... 

Carbon materials have been used widely in the development of sensors and actuators, particularly for electrical or electrochemical biosensors. These applications critically rely on the unique chemical and electrical properties of specific carbon materials [1,2]. It is quite common that similar carbon materials present drastically different properties in the literature. The goal of this chapter is to describe the atomic structures of each carbon material and correlate these structures with their properties so that discrepancies in the literature can be understood. Readers can then optimize the material properties for specific sensing applications by tuning carbon structures. This is particularly important for graphitic carbon materials, which present inherent highly anisotropic properties. 

One can conclude that the use of amperometric and potenriometric biosensots has achieved a considerable progress in the determination of hydrogen peroxide. The redox-enzyme and electrode structure achieved by many provides the basis for electrochemical biosensors. Enzymes need to be modified either by mutagenesis, or site-specific reactions that would provide structures with readily accessible sites. Many of the latter could be accomplished with the aid of a mediator. 

The structural changes in redox-modified single-chain DNA have been applied in electrochemical biosensors. In one example, a hairpin structure on an electrode snrface places the ferrocene label on its free 5 end in close proximity to the electrode, thus allowing a constant electron flow (Fan et al., 2003). Hybridization with its target DNA leads to formation of the duplex, in which the distance between the redox label and the electrode surface is increased beyond the possibility of electron transfer. 

S. Zhang, J. Xia, and X. Li, Electrochemical biosensor for detection of adenosine based on structure-switching aptamer and amplification with reporter probe DNA modified Au nanoparticles. Anal Chem., 80, 8382-8388 [2008]. 

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