Binding and orientation of fibronectin to silanated glass surfaces using immobilized bacterial adhesin-related peptides

Previously, we have demonstrated the suitability of bacterial adhesin-related peptides, directly immobilized on polystyrene surfaces, to bind and orient fibronectin (FN). For these studies a method to bind the large protein FN in a desired orientation on a solid substratum was developed which utilizes a bacterial adhesin-related peptide (designated BRP-A), which is known to bind specifically to the NH3-terminus end of FN. Glass substrata was first coated with an amine-terminated silane, followed by streptavidin (SA), which was used as an intermediate tether to bind the biotinylated bacterial adhesin-related peptide. The BRP-A peptide, used for these studies was synthesized with a terminal biotin to assure irreversible coupling of the BRP-A to the streptavidin. The biotinylated BRP-A was next immobilized on the SA-silanated glass surfaces. 125I-FN was used to quantify the amount of FN binding to the (BRP-A):SA-silanated glass surface. Monoclonal antibodies, which react with specific epitopes at either the NH3– or –COOH-termini of FN, were used to quantify the binding and orientation of FN. The Results of these studies indicated: (1) FN bound to the BRP-A:SA-silanated glass surface; and (2) the bound FN was oriented such that NH2-terminal region of FN was bound towards the glass surface and the COOH-terminus was oriented away from the glass surface. These studies demonstrate that small peptides can be used to specifically bind and orient large proteins such as FN on the surfaces.