Biosensors molecular recognition elements

The use of additional membranes, which selectively convert nonionic analytes into ionic species that can be determined via ISEs is another common approach. An abundance of ingenious designs make use of biocatalysts for the development of potentiometric biosensors. Much of the earlier designs have made use of enzymes as the molecular recognition element. The products that are associated with such enzyme-catalyzed reactions can be readily monitored with the potentiometric transducer by coating the traditional electrodes with the enzyme. 

The flow-through sensors described in this Section comply essentially with the definition of biosensor. This word, like every term used to designate devices of scientific and popular note, has been the object of a number of definitions of both generic and specific scope. In a broad sense, a biosensor is any instrument or technique that measures biomolecules. In stricter terms, Rechnitz defines a biosensor as "a device that incorporates a biochemical or biological component as a molecular recognition element and yields an analytical signal in response to biomolecules" [10]. In between these two... 

A DNA-electrochemical biosensor is formed by a DNA film, which constitutes the molecular recognition element (the probe), directly immobilized on the electrochemical transducer. The performance, sensitivity and reliability of the DNA biosensor and the electrochemical response are dictated by the DNA immobilization procedure. The DNA biophysical properties, such as flexibility, and DNA-drug interactions, are influenced... 

Two different systems for the detection of dopamine and uric acid, respectively, have recently been reported in the literature. Both are based on the same detection technique, that of chemiluminescence (CL). In the first one, a chemiluminescence biosensor has been assembled using whole vegetable tissue (fresh mature potato root) as molecular recognition element [155]. 

A very broad research activity in recent years is focused on investigation of possibilities of applications of nucleic acids for biosensing, especially DNA. As DNAs in organisms function as carrier of genetic information, for biosensors employing DNA as molecular recognition element a name genosensors appears recently in analytical literature. 

The term receptor was introduced by Aizawa (1983) for that part of a biosensor which recognizes the analyte on the molecular level. In this broadened sense, it agrees with the definition by Scheler (1985). Recently Rechnitz (1987) introduced the term molecular recognition element for the biocomponent of biosensors. 

Bush, D. L., Rechnitz, G. A., Comparison of Antibodies as Molecular Recognition Elements for Biosensors Design , Analytical Letters 21 (11) (1988) 1947. 

Molecular recognition is central to biosensor technology. Receptors, enzymes, antibodies, aptamers, molecular beacons, and nucleic acids are mainly used as molecular recognition elements in biosensor development (Chambers etal., 2008). Since 1990, nucleic acids, especially deoxyribonucleic acid (DNA) have been used as biorecognition elements in biosensor technology. These biosensors are named as DNA-based biosensors. 

Cao s group in 2011 designed an ECL biosensor based on the construction of triplex DNA for the detection of adenosine which employs an aptamer as a molecular recognition element and quenches ECL of Ru(bpy)3 by ferrocene monocarboxylic acid (FcA) G ig. 6.5). In the presence of adenosine, the aptamer sequence (Ru-DNA-1) more likely forms the aptamer—adenosine complex with hairpin configuration and the switch of the DNA-1 occurs in conjunction with the... 

Aptamers are oligonucleic acid or peptide molecules that can selectively bind a specific target molecule. Recently, for the determination of a small-molecule drug, a highly sensitive ECL aptamer-based biosensor has been constructed based on two components a cocaine-binding aptamer as molecular recognition element and as a model analyte and a Ru(II) complex as an ECL label [153]. 

Enzymes were historically the first molecular recognition elements [2-6] included in biosensors and continue to be the basis for a significant number of pubUcations in this field. Amperometric biosensors based on glucose oxidase (GOx) are the most famous example of biosensors applied to medical diagnostic. The three modes of oxidation reactions that occur in redox enzyme-based biosensors, like GOx, are referred to as first, second, and third generation as follows [7] ... 

FIGURE 1-7 Chemical sensor, The sensor consists of a molecular recognition element and a transducer. A wide variety of recognition elements are possible. Shown here are some fairly selective recognition elements particularly useful with biosensors. The recognition phase converts the information of interest into a detectable characteristic, such as another chemical, mass, light, or heat. The transducer converts the characteristic into an electrical signal that can be measured. 

Bush D.L. and Rechnitz G.A. (1988) Comparison of antibodies as molecular recognition elements for biosensor design. Anal. Letters,21, 1947-1967. 

A Biosensor is a device where a coupling has been realized between a biological element responsible for the molecular recognition and tire element responsible for the transduction of the signal. 

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