Binding Characteristics of Avidin and Surface Immobilized Octylbiotin - Implications for the Development of Dynamically Modified Optical-Fiber Sensors

by Wang, Yunlong; Bobbitt II, Donald R.

Specific sensing ligands can be immobilized onto C-18,, derivatized optical fibers by a dynamic modification protocol as part of a general strategy for producing optical fiber sensors. To investigate the influence of the hydrophobic surface and accessibility of the sensing ligand on the binding characteristics of the ligand and target analyte, an optical fiber sensor for fluorescently labeled avidin has been developed. Biotin's hydrophobicity is enhanced through the attachment of a C-8 moiety which allows it to be associated with the C-18 modified optical 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 process decreases the binding strength relative to that observed in homogeneous solution. When compared to previous studies in which a lipid-derivatized biotin was associated in an LB film, the association constant is reduced by 2-3 orders-of-magnitude. These results, in combination with the lipid-derivatized biotin/LB film studies suggest that spacers can be used to enhance the accessibility of the biotin moiety thereby leading to improved binding characteristics. This result has important implications for the design and development of dynamically modified, optical fiber sensors.

Analytica Chimica Acta
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1873-4324; 0003-2670