ABSTRACT
Neurotransmitter receptor proteins are excellent candidates as sensing elements in biosensors because of their high affinity and selectivity for sepcific ligands. They can recognize families of chemicals of physiological, pharmacological and toxicological significance, that range from amino acids and peptides to therapeutics, drugs of abuse and toxicants. Although optic immunosensors which make use of total internal reflection fluorescence (i.e. evanescence) have been initially used in immunochemical biosensors (1,2), evanescent fluorosensors, with an appropriate indicator chemistry, can also provide a sensitive and stable transducer for a receptor-based biosensor (3). In this receptor-optical sensor, the incident light excites a fluorophore just outside the waveguide boundary (approximately 1000 Å), then a portion of the resultant fluoroescence becomes trapped and is transmitted back up the fiber. This technique is well suited to a receptor-based or immunochemical biosensor because the fluorescently-tagged ligand, or antibody bound to the receptor protein, which is immobilized at the fiber surface, can be monitored without interference from the ligand in bulk solution.
