Complex biological recognition elements

Biological receptors can include chemically and genetically modifled enzymes, new types of antibodies with high afiinity and selectivity for small molecules, natural or artiflcial receptors or complex biological recognition elements. 

Among the biological recognition elements enzymes are by far the most important. The reason for this lies in the fact that these molecules provide not only the recognition of analyte-substrate, but also have the catalytic function important for the amplification of the signal. Enzymes are quite flexible molecules and have various complex conformations with sometimes different catalytic activity. The biorecognition molecules can be integrated in biosensors with a variety of electrochemical transducers (Table 1). 

Another way to increase sensor specificity is offered by antibodies used as biological recognition element, but they have also some limitations due to the complexity of the assay that must be developed for each analyte. The development of sensor arrays to create multianalyte detection systems could be interesting not only in environmental but also in diagnostic and therapy monitoring. 

The main limitation towards the widespread application of MIPs as selective recognition elements in ILAs is that their performance is still not as brilliant as their biological counterparts. Their sensitivity and selectivity in aqueous media is, in most cases, lower than that of the antibodies. In fact there are not many examples so far of ILAs for the analysis of complex clinical, environmental or food samples. Moreover, the number of MIP-based validated methods described in the literature is still limited and this issue should be addressed before these materials can be considered as practical alternatives to the biological recognition entities. 

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