Molecular recognitions element

Medley et al. have shown the use of aptamer-conjugated nanoparticles for cancer cell detection [50]. Herr et al. [51] have shown the rapid collection and detection of leukemia cells using a novel two-nanoparticle assay with aptamers as the molecular recognition element. 

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. 

Members of the Caliciviridae family can hardly be examined in cell culture or animal models. Therefore, so-called virus-Hke particles (VLP) are employed in current experiments. These particles are expressed recombinantly in insect cells using a baculovirus system and do not carry infectious viral RNA [70-72]. It has been shown by single particle tracking studies that VLPs are internalized into the cells in a similar fashion to native viruses [73]. VLPs are believed to present identical molecular recognition elements to the outside world as do native viruses. 

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... 

Chitosan has also been grafted with saccharide-based ligands as molecular recognition elements to promote receptor-mediated endocytosis for cell specific... 

Interest in the development of synthetic schemes and approaches to create molecular recognition elements has blossomed during the past half century for a number of reasons. In contrast to biologically based receptors, artificial mimics have the potential advantages of being less costly, more stable, and better able to withstand harsher conditions.7-12 Furthermore, synthetic methodologies can be used to create receptors for molecules for which an artificial receptor does not exist. These designer materials have enormous potential in catalysis, clinical and pharmaceutical applications, chemical sensors, separation science, and electronics.7-12... 

In addition to antibodies, it is possible to use artificial nucleic acids ligands, known as aptamers, for the selective detection of proteins. The tight binding properties make aptamers attractive candidates as molecular recognition elements in a wide range of bioassays and for the development of protein arrays. Electrochemistry has been shown useful for monitoring aptamer-protein interactions (66). 

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]. 

During the initial stage of development of UA sensor, researchers used uricase enzyme (UOx) based electrodes for the determination of UA where UOx serves as a molecular recognition element. In the enzyme based electrodes UOx will oxidize UA to allantoin in the presence of 02 and gives away C02 and H202 as side products. The equation for the enzymatic oxidation of UA is ... 

Table 5.6 shows a number of molecular recognition elements which can be monitored using detectors in transducers to measure specific parameters. The electrical signal may be displayed in a number of different ways, depending on the application requirement. 

---