Adhesion of alpha(5)beta(1) receptors to biomimetic substrates constructedfrom peptide amphiphiles

Biomimetic membrane surfaces functionalized with Fragments of the extracell ular matrix protein, fibronectin, are constructed from mixtures of peptide and polyethylene glycol(PEG) amphiphiles. Peptides from the primary binding loop, GRGDSP, were used in conjunction with the synergy site peptide, PHSR N, in the III9-10 sites of human fibronectin. These peptides were attached to dialkyl lipid tails to form peptide amphiphiles. PEG amphiphiles were mi xed in the layer to minimize non-specific adhesion in the background. GRGDS P acid PEG amphiphiles or GRGDSP, PHSRN- and PEG amphiphiles were mixed in various ratios and deposited on solid substrates from the air-water interfa ce using Langmuir-Blodgett techniques. In this method, peptide composition, density, and presentation could be controlled accurately. The effectivenes s of these substrates to mimic native fibronectin is evaluated by their abi lity to generate adhesive forces when they are in contact with purified act ivated alpha (5)beta (1) integrin receptors that are immobilized on an oppo sing surface. Adhesion is measured using a contact mechanical approach (JKR experiment). The effects of membrane composition, density, temperature, an d peptide conformation on adhesion to activated integrins in this simulated cell adhesion setup were determined. Addition of the synergy site, PHSRN, was found to increase adhesion of alpha (5)beta (1) to biomimetic substrate s markedly. Increased peptide mobility (due to increased experimental tempe rature) increased integrin adhesion markedly at low peptide concentrations. A balance between peptide density and steric accessibility of the receptor binding race to alpha (5)beta (1), integrin was required for highest adhes ion. (C) 2001 Elsevier Science Ltd. All rights reserved.