Biological recognition system

More than half of all drugs on the market are asymmetric molecules. Many of these are administered as racemates. Since biological recognition systems are based on optically active molecules, the two enantiomers of a racemic drug may interact by different mechanisms with these systems. One of the enantiomers may exert pharmacologically different or unwanted side effects [1-3]. The same is true for racemic pesticides and herbicides often only one of the enantiomers possesses the desired activity. 

Biological recognition systems offer exquisite selectivity and sensitivity. A vast range of approaches has been described [42,43]. 

Despite their advantages of specificity and selectivity, biosensors suffer from a severe disadvantage, the instability of the biological recognition system, which makes storage and operation in harsh chemical environments problematic. This problem has been addressed using a newly developed sensor with injected recognition element biosensors (whose operational principle is based on the one time use... 

It is interesting to note that most biosensors use biological molecular recognition systems, but do not use the principles of natural transduction. Thus, biological recognition systems which do not induce any transduction in nature have been the primary elements used in the preparation of biosensors, while the principles of natural transduction have been only tentatively investigated from the standpoint of biosensor development. 

Biological Recognition Systems Without TVansduction and Chemical Conversion... 

The most versatile biological recognition system developed by higher animals is the immune system. It is capable of producing complementary structures even to molecules and shapes... 

As a biosensor, by definition, consists of a biological recognition system in intimate physical and functional contact with an artificial transducer, among the possible combinations the most efHcient ones have to be conceived with regard to the demands of the actual analytical problem. The choice will not only be determined by the optimum sensitivity or the response time to be attained, but also by the properties of the matrix and the concentration range of the substance to be monitored. This may be explained by means of an example. 

Glucose is the most common and most important substance to be determined, occurring in food, blood, and fermentation broths, and there is no other substrate for which so many kinds and variations of biosensors have been described. Most of them use glucose oxidase (GOD) as the biological recognition system. As will be derived from the following formula, many possibilities of transduction are possible, and all of them have been realized. 

A bioreceptor must be able to react specifically with an analyte of interest. For example, a bioreceptor for cholesterol should react only with cholesterol and not with any other compound in the sample. Biological recognition systems such as enzymes or antibodies offer this high specificity and, in addition, ensure high sensitivity and fast response. Usually, the bioreceptor molecules are immobilised at, or close to, the surface of the transducer. Immobilisation can be achieved by physical adsorption or entrapment by an inert membrane. The bioreceptor can also be covalently bound to functional groups on the surface of the transducer. 

A biosensor is defined as an analytical device that uses a biological recognition system to target molecules or macromolecules. Biosensors use a physiochemical transducer to convert the signal from the bio-recognition system into a detectable signal [1]. Biosensors consist of three components (1) the detector, which identifies the stimulus (2) the transducer, which converts this stimulus to an output and (3) the output system, which involves amplification and display of the output in an appropriate format [1]. 

Biosensors are analytical devices that combine a biological recognition system with a suitable transducer to enable detection or evaluation of the proceeding reaction or interaction. 

Perhaps the most unique component of a biosensor is the biological system that is utilized to identify specific molecules of interest in solutions of complex mixtures. The biological element of course is primarily responsible for the selectivity of biosensors. There are many different types of biological recognition systems that have been explored for sensors, ranging from the molecular scale— e.g., bioreceptors, enzymes, and antibodies— to cellular structures like mitochondria, and even immobilized whole cells and tissues. However, to date for practical reasons most commercially feasible biosensors have primarily utilized enzymes, and to a lesser extent antibodies. 

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