BINDING CHARACTERISTICS OF AVIDIN AND SURFACE IMMOBILIZED OCTYLBIOTIN- IMPLICATIONS FOR THE DEVELOPMENT OF DYNAMICALLY MODIFIED OPTICAL-FIBER SENSORS

Specific sensing ligands can be immobilized onto C-18,, derivatized op tical fibers by a dynamic modification protocol as part of a general s trategy for producing optical fiber sensors. To investigate the influe nce of the hydrophobic surface and accessibility of the sensing ligand on the binding characteristics of the ligand and target analyte, an o ptical fiber sensor for fluorescently labeled avidin has been develope d. Biotin's hydrophobicity is enhanced through the attachment of a C-8 moiety which allows it to be associated with the C-18 modified optica l fiber surface through a hydrophobic interaction. Measurement of both the time dependence and K-assoc for the binding of FITC-avidin to the surface immobilized biotin show that the hydrophobic immobilization p rocess decreases the binding strength relative to that observed in hom ogeneous solution. When compared to previous studies in which a lipid- derivatized biotin was associated in an LB film, the association const ant is reduced by 2-3 orders-of-magnitude. These results, in combinati on with the lipid-derivatized biotin/LB film studies suggest that spac ers can be used to enhance the accessibility of the biotin moiety ther eby leading to improved binding characteristics. This result has impor tant implications for the design and development of dynamically modifi ed, optical fiber sensors.