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 intr insic integrin-dependent cellular adhesion mechanism. Glass substrates were coupled with avidin receptors through an adsorbed film of biotin ylated bovine serum albumin (b-BSA). The avidin-treated slides then we re 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 BA EC to glass decreased in the presence of anti-beta 1 integrin antibody . Adhesion of biotinylated BAEC to avidin-treated slides was not affec ted by anti-beta 1 integrin antibody, consistent with integrin-indepen dent avidin-mediated adhesion. The initial rate of cell spreading was greatest for avidin-biotin-mediated adhesion (80.0 +/- 25.6 mu m(2)/h) , followed by integrin-dependent cellular adhesion on plain glass (35. 7 +/- 7.7 mu m(2)/h) and, finally, by adhesion on BSA-coated protein s urfaces (10.2 +/- 0.3 mu m(2)/h). Biotinylated and unmodified BAEC, cu ltured for 1 h in serum-containing media, were subjected to laminar fl ow in a variable-height flow chamber that provided a range of shear st resses from 0.2 to 75 dynes/cm(2). The critical shear stress required to detach 50% of the cells in serum-containing media increased from 4. 6 +/- 0.8 dynes/cm(2) for integrin-dependent adhesion to 12.6 +/- 1.2 dynes/cm(2) for avidin-biotin-mediated adhesion. Avidin-mediated attac hment for biotinylated BAEC increased initial cellular spreading rates and strength of attachment (i.e., at 1 h) by a factor of two and thre e, respectively. These results support the hypothesis that integrin-me diated cell attachment and spreading can be enhanced using high affini ty integrin-independent binding. (C) 1998 John Wiley & Sons, Inc.