Influence of Biotin Lipid Surface Density and Accessibility on Avidin Binding to the Tip of an Optical Fiber Sensor

LB films doped with biotin lipids were deposited at the tip of an evanescent fiber optic (EFO) sensor, and the fluorescence intensity of FITC-labeled avidin bound to the sensor tip was monitored. The influence of receptor density and receptor surface accessibility on avidin binding to, and desorption from, the sensor surface was investigated. This was accomplished by varying the doping density from 0 to 100 mol % of two biotinylated phosphatidylethanolamines B-DPPE and B-X-DPPE, where B-X-DPPE is essentially identical to B-DPPE, except B-X-DPPE has a six carbon amino acid spacer interposed between the DPPE and the biotin hapten. In general, increasing the biotin lipid surface density or the biotin hapten accessibility increased both the affinity and amount of avidin bound to the sensor tip. Increasing the biotin lipid doping density also hastened the binding of avidin to a relatively inaccessible B-DPPE hapten, but slowed the binding of avidin to the more accessible B-X-DPPE hapten. Overall, avidin bound to the biotin-doped sensor surface 3-4 orders of magnitude slower and dissociated from the sensor surface considerably faster than that observed for avidin/biotin binding and dissociation in solution, particularly at low biotin doping densities. These observations suggest a sterically hindered binding of avidin to the biotin lipids at the sensor surface. © 1992, American Chemical Society. All rights reserved.

Duke Scholars

Author William M. Reichert Biomedical Engineering