Using avidin-mediated binding to enhance initial endothelial cell attachment and spreading

Binding between the protein avidin and the vitamin biotin was used as an extrinsic, high affinity receptor-ligand system to augment the intrinsic integrin-dependent cellular adhesion mechanism. Glass substrates were coupled with avidin receptors through an adsorbed film of biotinylated bovine serum albumin (b-BSA). The avidin-treated slides then were seeded with biotinylated bovine aortic endothelial cells (BAEC). A 3:1 ratio of BSA:b-BSA provided the best results in terms of specific cellular attachment, growth, and spreading. Control surfaces consisted of bare glass or glass with adsorbed BSA. Attachment of unmodified BAEC to glass decreased in the presence of anti-beta 1 integrin antibody. Adhesion of biotinylated BAEC to avidin-treated slides was not affected by anti-beta 1 integrin antibody, consistent with integrin-independent avidin-mediated adhesion. The initial rate of cell spreading was greatest for avidin-biotin-mediated adhesion (80.0 +/- 25.6 microns2/h), followed by integrin-dependent cellular adhesion on plain glass (35.7 +/- 7.7 microns2/h) and, finally, by adhesion on BSA-coated protein surfaces (10.2 +/- 0.3 microns2/h). Biotinylated and unmodified BAEC, cultured for 1 h in serum-containing media, were subjected to laminar flow in a variable-height flow chamber that provided a range of shear stresses from 0.2 to 75 dynes/cm2. The critical shear stress required to detach 50% of the cells in serum-containing media increased from 4.6 +/- 0.8 dynes/cm2 for integrin-dependent adhesion to 12.6 +/- 1.2 dynes/cm2 for avidin-biotin-mediated adhesion. Avidin-mediated attachment for biotinylated BAEC increased initial cellular spreading rates and strength of attachment (i.e., at 1 h) by a factor of two and three, respectively. These results support the hypothesis that integrin-mediated cell attachment and spreading can be enhanced using high affinity integrin-independent binding.