Electrical biosensor

Outline the role of biosensors in addressing the challenge of chronopharmacology. What are the present limitations of using electrical biosensors ... 

Luo X, Davis JJ. Electrical biosensors and the label free detection of protein disease biomarkers. Chemical Society Reviews 2013 42 5944-62. http //dx.doi.org/ 10.1039/c3cs60077g. 

R.Somenath. Z.Gao (2009), Nanostructure-based electrical biosensors, Journal of Nano today 4,pp.318-334... 

A number of FET-based biosensors have been developed to study biomolecular interactions, which are the key drivers of biological responses in in vitro or in vivo systems. Among the many different biosensing systems, the FET-type biosensor is one of the most attractive electrical biosensors due to its advantages of sensitive measurements, portable instrumentation, easy operation with a small sample requirements, low cost... 

Kim et al. [226] reported on fabrication of electrical biosensors based on functionalized ZnO nanorod surfaces with biotin, a water soluble B-complex vitamin, for highly sensitive detection of biomolecule streptavidin that has an extraordinarily strong affinity for biotin. The biotin-modified ZnO nanorod FET exhibited drastic conductance increase to 17 tS after exposition to a 250 nm streptavidin solution, presumably due to the biotin-streptavidin binding. 

Functionalized conducting monomers can be deposited on electrode surfaces aiming for covalent attachment or entrapment of sensor components. Electrically conductive polymers (qv), eg, polypyrrole, polyaniline [25233-30-17, and polythiophene/23 2JJ-J4-j5y, can be formed at the anode by electrochemical polymerization. For integration of bioselective compounds or redox polymers into conductive polymers, functionalization of conductive polymer films, whether before or after polymerization, is essential. In Figure 7, a schematic representation of an amperomethc biosensor where the enzyme is covalendy bound to a functionalized conductive polymer, eg, P-amino (polypyrrole) or poly[A/-(4-aminophenyl)-2,2 -dithienyl]pyrrole, is shown. Entrapment of ferrocene-modified GOD within polypyrrole is shown in Figure 7. 

Individual polyethers exhibit varying specificities for cations. Some polyethers have found appHcation as components in ion-selective electrodes for use in clinical medicine or in laboratory studies involving transport studies or measurement of transmembrane electrical potential (4). The methyl ester of monensin [28636-21 -7] i2ls been incorporated into a membrane sHde assembly used for the assay of semm sodium (see Biosensors) (5). Studies directed toward the design of a lithium selective electrode resulted in the synthesis of a derivative of monensin lactone that is highly specific for lithium (6). 

Electrical conductivity measurements revealed that ionic conductivity of Ag-starch nanocomposites increased as a function of temperature (Fig.l7) which is an indication of a thermally activated conduction mechanism [40]. This behavior is attributed to increase of charge carrier (Ag+ ions) energy with rise in temperature. It is also foimd to increase with increasing concentration of Ag ion precursor (inset of Fig.l7). This potentiality can lead to development of novel biosensors for biotechnological applications such as DNA detection. 

Breer H. (1994). Signal recognition and chemo-electrical transduction in olfaction. Biosensors Bioelectron 9, 625-632. 

MWNTs favored the detection of insecticide from 1.5 to 80 nM with a detection limit of InM at an inhibition of 10% (Fig. 2.7). Bucur et al. [58] employed two kinds of AChE, wild type Drosophila melanogaster and a mutant E69W, for the pesticide detection using flow injection analysis. Mutant AChE showed lower detection limit (1 X 10-7 M) than the wild type (1 X 10 6 M) for omethoate. An amperometric FIA biosensor was reported by immobilizing OPH on aminopropyl control pore glass beads [27], The amperometric response of the biosensor was linear up to 120 and 140 pM for paraoxon and methyl-parathion, respectively, with a detection limit of 20 nM (for both the pesticides). Neufeld et al. [59] reported a sensitive, rapid, small, and inexpensive amperometric microflow injection electrochemical biosensor for the identification and quantification of dimethyl 2,2 -dichlorovinyl phosphate (DDVP) on the spot. The electrochemical cell was made up of a screen-printed electrode covered with an enzymatic membrane and combined with a flow cell and computer-controlled potentiostat. Potassium hexacyanoferrate (III) was used as mediator to generate very sharp, rapid, and reproducible electric signals. Other reports on pesticide biosensors could be found in review [17],... 

CNTs offer an exciting possibility for developing ultrasensitive electrochemical biosensors because of their unique electrical properties and biocompatible nanostructures. Luong et al. have fabricated a glucose biosensor based on the immobilization of GOx on CNTs solubilized in 3-aminopropyltriethoxysilane (APTES). The as-prepared CNT-based biosensor using a carbon fiber has achieved a picoamperometric response current with the response time of less than 5 s and a detection limit of 5-10 pM [109], When Nation is used to solubilize CNTs and combine with platinum nanoparticles, it displays strong interactions with Pt nanoparticles to form a network that connects Pt nanoparticles to the electrode surface. The Pt-CNT nanohybrid-based glucose biosensor... 

In recent years many efforts have been made to develop immunochemical techniques integrating the recognition elements and the detection components, in order to obtain small devices with the ability to carry out direct, selective, and continuous measurements of one or several analytes present in the sample. In this context biosensors can fulfill these requirements. Biosensors are analytical devices consisting of a biological component (enzyme, receptor, DNA, cell, Ab, etc.) in intimate contact with a physical transducer that converts the biorecognition process into a measurable signal (electrical or optical) (see Fig. 4). In... 

Currently, a large spectrum of microbial biosensors have been developed that enable the monitoring of pollutants by measuring light, fluorescence, colour or electric current and electrochemical signal [60]. A recent study [19] shows that whole-cell biosensors based on the detection of changes in gene... 

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