Mechanics of Cellular Adhesion to Artificial Artery Templates

¹ The University of Queensland

^* To whom correspondence should be addressed. E-mail: halina{at}physics.uq.edu.au.

Submitted on October 17, 2005
Revised on January 9, 2006
Accepted on 28 June 2006

	Abstract

We are using polymer templates to grow artificial artery grafts in vivo for the replacement of diseased blood vessels. We have previously shown that adhesion of macrophages to the template starts the graft formation. We present a study of the mechanics of macrophage adhesion to these templates on a single cell and single bond level with optical tweezers. For whole cells, in vitro cell adhesion densities decreased significantly from polymer templates polyethylene to silicone to Tygon (167, 135 and 65 cells/mm²). These cell densities were correlated with the graft formation success rate (50%, 25% and 0%). Single bond rupture forces at a loading rate of 450 pN/s were quantified by adhesion of trapped 2µm spheres to macrophages. Rupture force distributions were dominated by nonspecific adhesion (forces <40pN). On polystyrene, preadsorption of fibronectin or presence of serum proteins in the cell medium significantly enhanced adhesion strength from a mean rupture force of 20pN to 28pN or 33pN, respectively. The enhancement of adhesion by fibronectin and serum is additive (mean rupture force of 43pN). The fraction of specific binding forces in the presence of serum was similar for polystyrene and PMMA, but these forces were not observed for silica. Again, we found correlation to in vivo experiments, where the density of adherent cells is higher on polystyrene than on silica templates, and can be further enhanced by fibronectin adsorption. These findings show that in vitro adhesion testing can be used for template optimization and to substitute in vivo experiments.

Key Words: adhesion, artificial artery, macrophage, optical tweezers, rupture force, template