AVS 53rd International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuA

Paper BI-TuA5
Integrin-Ligand Affinity Affects Neuron Outgrowth

Tuesday, November 14, 2006, 3:20 pm, Room 2001

Session: Cells at Surfaces
Presenter: T.P. Beebe Jr, University of Delaware
Authors: Z. Zhang, University of Delaware
J. Zheng, Alfred I. duPont Hospital for Children
Y. Leng, University of Delaware
K.W. Dabney, Alfred I. duPont Hospital for Children
J.L. Twiss, Alfred I. duPont Hospital for Children
T.P. Beebe Jr, University of Delaware
Correspondent: Click to Email
The role of ligand-receptor affinity on the outgrowth of neuronal processes was studied directly on postnatal day-1 primary cultures of living neurons by atomic force microscopy (AFM). To accomplish this, micropatterned test substrates were created and analyzed using contact angle measurement, AFM, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) at each step of the multistep surface functionalization process, for both substrates and AFM tips. The affinity force between an individual fibronectin molecule (Fn) and an individual growth cone integrin receptor was found to be 106 ± 8 pN, while that between the GRGDSY peptide and an individual integrin receptor was 170 ± 10 pN when measured under the same physiological conditions. In a conventional outgrowth assay on the same substrates, although both the Fn- and peptide-modified substrates supported significantly greater neurite outgrowth than controls, and outgrowth on both substrates was inhibited by the addition of soluble RGD peptide, ~30% longer neurite extension was observed on Fn-modified substrates than on GRGDSY-modified substrates. This implies that integrin-ligand affinity plays an important role in neurite outgrowth in vitro, and that adhesivity represents a balance between the formation and breakage of cell-substratum contacts. Neurite outgrowth involves the formation of new attachments at the front of the advancing growth cone, and the breakage of previous attachments now at the rear or the advancing growth cone. The higher binding affinity between a neurite's integrin receptors and the GRGDSY ligand implies a reduced rate of ligand-receptor breakage.