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Quantification of biological or biochemical processes are critical for medical, biological and biotechnological applications. However, the conversion of biological information to an electronic signal to facilitate subsequent processing is a challenge due to the complexity of the connection of an electronic device directly to a biological environment.

Biosensors are attractive devices for analyzing the content of a biological sample due to the direct conversion of a biological event into an electronic signal.

A biosensor consists of a biological recognition element, a transducer and an electronic system. In a complex sample, the biological recognition element is able to discriminate between the various components therein and interact with the compound to be analyzed. Also called analyte. Once produced the interaction the transducer converts the energy produced by this into an electrical signal. Finally the electronic records and processes the signal.

These devices can be classified according to: the type of interaction established between the recognition element and the analyte; the method used to detect this interaction; the nature of the recognition element; or transduction system.

The main desirable features biosensors are: high sensitivity, high selectivity, high reliability, long lifetime, low cost, short analysis time, sample pretreatment unnecessary, easy to use, portable, real-time analysis, automatable , miniaturized, etc …
A wide variety of different biosensors and not all have each of the abovementioned features. The combination of several of them could put many of these devices in an advantageous position compared to conventional analysis techniques.

There are multiple recognition elements and transduction system. Theoretically these components support various combinations. In practice, the choice of the biological / biomimetic material depends on the characteristics of the analyte. For example, when trying to detect antibodies an allergenic substance are used.

In the types of interaction we have: biocatalytic sensors, are the best known and most applied biosensors; and bioaffinity sensors.

A key step in the construction of a biosensor is the immobilization of the recognition element on a membrane or matrix, which in turn is fixed to the transducer surface.

There are several types transducers: electrochemical, optical, piezoelectric (mass, gravimetric, acoustic), and nanomechanical thermometric. Depending on the nature of the interaction between the recognition element and the species of interest can be used one type of transducer or another.

The first biosensor was a glucose analyzer developed by Clark and Lyons in 1962. But the term was first used biosensor from 1977, when the first device using live microorganisms immobilized on the surface of a sensitive ammonia electrode was developed. This device was used to detect the amino acid arginine.

The development of biosensors since been focused mainly on the field of clinical diagnosis (with great success biosensors for glucose) and there is a more recent interest in environmental and military fields, chemical, pharmaceutical.

The number of scientific publications and patents reviews biosensors developed in recent years is very high, reflecting the great interest in this topic in the scientific community.

Compared to conventional technologies such as mass spectrometry or various chromatographies, are expensive equipment which analyze compounds broad spectra, biosensors are specifically designed for the detection and / or quantification of one or a few analytes, in response to problems concrete.

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