Biosensor biological component

Biosensors ai e widely used to the detection of hazardous contaminants in foodstuffs, soil and fresh waters. Due to high sensitivity, simple design, low cost and real-time measurement mode biosensors ai e considered as an alternative to conventional analytical techniques, e.g. GC or HPLC. Although the sensitivity and selectivity of contaminant detection is mainly determined by a biological component, i.e. enzyme or antibodies, the biosensor performance can be efficiently controlled by the optimization of its assembly and working conditions. In this report, the prospects to the improvement of pesticide detection with cholinesterase sensors based on modified screen-printed electrodes are summarized. The following opportunities for the controlled improvement of analytical characteristics of anticholinesterase pesticides ai e discussed ... 

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... 

Biosensors are analytical devices that incorporate a biological component and a transducer. These must be in close proximity with one another and preferably in intimate contact, i.e. the biological component immobilized on to the transducer. Such devices are available in disposable forms, e.g. for measurement of blood glucose in diabetic patients, evaluation of the freshness of uncooked meat. Other designs are suitable for continuous use, e.g. on-line monitoring of fermentation processes, the detection of toxic substances. 

The possible biological components fall into two main categories (Table 4.5) and their function is to recognize and bind a specific analyte. It is the properties of the biological component that give specificity to biosensors and make them suitable for the analysis of samples without pre-treatment. 

Electrochemical biosensors are the most common especially when the biological component is an enzyme. Many enzyme reactions involve electroactive species being either consumed or generated and can be monitored by ampero-metric, potentiometric or conductimetric techniques, although the latter are the least developed and will not be discussed further. 

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... 

All these requirements can be met with biosensors. Biosensors are the combination of a biological component consisting of microorganisms, enzymes, an-... 

The search for new approaches which can give increasing sensitivity to S PR-based biosensors is associated with the optimization of immobilization of the biological components on the transducer surface. 

Panel (a) shows 8 test strips impregnated with genetically engineered E. coli bacteria whose genes are turned on by arsenite (HAsO ). When the strips are exposed to drinking water, a blue spot develops whose size increases with the concentration of arsenite in the water. By comparing the spot with a set of standards, we can estimate whether arsenic is above or below 50 ppb. We call the test strip a biosensor, because it uses biological components in its operation. 

In amperometry, we measure the electric current between a pair of electrodes that are driving an electrolysis reaction. One reactant is the intended analyte and the measured current is proportional to the concentration of analyte. The measurement of dissolved 02 with the Clark electrode in Box 17-1 is based on amperometry. Numerous biosensors also employ amperometry. Biosensors8-11 use biological components such as enzymes, antibodies, or DNA for highly selective response to one analyte. Biosensors can be based on any kind of analytical signal, but electrical and optical signals are most common. A different kind of sensor based on conductivity—the electronic nose —is described in Box 17-2 (page 360). 

Use of microorganisms and plant and animal tissues as a biological component of biosensor are also described in the literature (9, 10). The principle is based on the use of the natural bio-reactive systems. They have several advantages over the isolated enzymes and receptors. Isolation of enzymes and receptors are often required to increase the response time. Enzymes and receptors retained in the cells are more stable and have longer lifetimes. Cell-based biosensors are also economical as no purification step is required. 

Types of biosensors can be named either by the biological components, physical transducing devices, or the measured analytes. Researchers were originally using biological components to define types of biosensors (Table 2). Types of transducers had also been included in the name to identify the physical transducing device, i.e., enzyme electrodes, acoustic-immunosensors, optical biosensors, piezoelectric-immunosensors, and biochips. 

Bioanalyzer can be considered another version of commercial biosensors for off-line analysis. It was developed to have capabilities of complete analysis, short response time, specificity, and sensitivity that allows a quick clinical test. Abbott Vision, Boehringer-Mannheim Reflectron, and Kodak Ektachem DT60 (IBI Biolyzer is the new name) are used for cholesterol measurement in doctors offices. Bioanalyzer consists of biological and transducing component that are not physically connected. The uniqueness of this separation provides the versatility of analysis, i.e., use of disposable and different biological component for multi-components measurements. In authors laboratory, Kodak Ektachem DT60 was used successfully to determine cholesterol in some food matrices as well as in off-line process control. The analysis time was only 10 minutes compared to 1-2 days for the GC and HPLC methods. Complicated... 

For biosensor devices these problems are aggravated because of the additional integration of a biological component on a planar device surface [50]. 

A biosensor utilizes a biological component to translate the concentration of a specific analyte of interest into a signal detectable by some chemical or physical means (7). Successful operation of a biosensor requires that the biological component and the signal it transduces be localized to and concentrated within a region in close proximity to the detection system. Immobilization of enzymes within a polymeric matrix ensures concentration and localization of the enzymic reaction, and creates a convective barrier, thus preventing dilution and convective removal of the product species before it is detected. Enzymes immobilized on or near the detection system are frequently used as the... 

A biosensor can be described as a complex device for the detection of analytes that combines a biological component with a physicochemical detector component [2, 3]. This device, depending on how it functions, may take up a variety of forms from 2D surface based approaches to 3D micro and nanoplatforms. Examples of 3D... 

The basic requirement in biosensor development is ascribed to the successful attachment of the recognition material, a process governed by various interactions between the biological component and the sensor interface. Advanced immobilization technologies capable of depositing biologically active material onto or in close proximity of the transducer surface have been reported. In this context, the choice of a biocompatible electrode material is essential. The material surfaces (support) include almost all material tjrpes metals, ceramics, polymers, composites and carbon materials [8]. In most cases, when a native material does not meet all the requirements for... 

Spacecraft environments are particularly vulnerable to upsets due to their closed loop nature. The release and accumulation of toxic chemicals in the breathable atmosphere or the biological contamination of food and water supplies rapidly become detrimental to crew safety. Consequently, instrumentation for environmental monitoring is a prerequisite for mission success. Although seemingly uncomplicated, the additional requirements that these instruments use minimal space, mass, power, and crew time makes their successful development and application challenging. One potential solution may be to use biosensors as environmental monitors. Biosensors consist of a biological component (bioreporter) that... 

A biosensor is a device that combines a biological component a recognition layer) and a physico-chemical detector component (a transducer). The transduction unit can be electrochemical, optical, piezoelectric, magnetic, or calorimetric (1). Two groups of recognition molecules form the majority of biosensors affinity-based and catalytic-based biosensors. Affinity-based biosensors are used to bind molecular species of interest, irreversibly and noncatalytically. Examples include antibodies, nucleic acids, and... 

Biosensors are a class of sensors designed from the combination of three basic components. The first is a biological component, possessing the specificity and efficiency resulting from its evolutionary history. It represents the molecular recognition or sensing element and may be enzyme or protein, nucleic acid, or living cell. The second component is some molecular method... 

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