FIBER OPTIC BIOSENSING BASED ON RECEPTOR RECOGNITION

Abstract

Enzymes,ion carriers, and optically active receptors are shownto be useful for specific recognition and sensing of biologically important species including enzymesubstrates, metabolites, and drugs. In enzyme-based sensors, optical assays for substrates (such as glucose, lactate or cholesterol)have bee designed andare fairly established. The specificity of such sensorsis usually very high. However, quite a numberof assays cannot be performed with enzymes, and use has to be made ofion carriers and other recognition elements. A quite different situation is found in such cases. In contrast to enzymes which "digest" their substrates, receptors do not metabolize their substrates. They therefore offer an promising alternative for enzymatic recognition of substrates. However, most existing receptors lack the tremendousspecificity of enzymes. Neutral on carriers which may be considered as a kind of ion receptors, are a notable exception. If the receptoris enantio-selective(i.e. preferably binds one speciesoutofa pairof optical isomers)a fairly specific recognition of enantiomers of biogenic amines (such as some drugs and biogenic amines) becomes possible. In contrast to enzyme-based sensing where steady-state response is a result of kinetic equilibration, this type of substrate binding results in thermodynamicequilibration. Specific examples are given for new types sensors and sensors based on recognition by enzymes, neutralion carriers, charge-transfer interaction, and hydrogen bonding. Their respective merits and limitations are discussed.