Biosensor Principle

A biosensor is generally defined as a measurement system that consists of a probe with a biological recognition element, often called a bioreceptor, and a transducer [3, 18, 22]. Two fundamental operating principles of a biosensor are: (1) "biological recognition," and (2) "sensing." Therefore, a biosensor can be generally defined as a device that consists of two basic components connected in series: (1) a biological recognition system, often called a bioreceptor, and (2) a transducer. The basic principle of a biosensor is to detect this molecular recognition, and to transform it into another type of signal using a transducer. The main purpose of the recognition system is to provide the sensor with a high degree of selectivity for the analyte to be measured. The interaction of the analyte with the bioreceptor is designed to produce an effect measured by the transducer, which converts the information into a measurable effect, such as an electrical signal.

Biosensors can be classified based on the transduction methods they employ. Transduction can be accomplished through a large variety of methods. Most forms of trans-duction can be categorized in one of three main classes: (1) optical detection methods, (2) electrochemical detection methods, and (3) mass-based detection methods. Other detection methods include voltaic and magnetic methods. New types of transducers are constantly being developed for use in biosensors. Each of these three main classes contains many different subclasses, creating a large number of possible transduction methods or combinations of methods. Special emphasis will be placed on the description of optical transducing principles, which is the focus of this chapter. Figure 1 illustrates the conceptual principle of the biosens-ing process using an antibody as the bioreceptor probe and fluorescence as the detection method.

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