Surface probe measurements of the elasticity of sectioned tissue, thin gels and polyelectrolyte multilayer films: Correlations between substrate stiffness and cell adhesion

Surface probe measurements of the elasticity of thin film matrices as well as biological samples prove generally important to understanding cell attachment across such systems. To illustrate this, sectioned arteries were probed by atomic force microscopy (AFM) within the smooth muscle cell (SMC)-rich medial layer, yielding an apparent Young’s modulus Emedia ∼ 5–8 kPa. Polyacrylamide gels with Egel spanning several-fold above and below this range were then cast 5–70 μm thick and coated with collagen: SMC spreading shows a hyperbolic dependence in projected cell area versus Egel. The modulus that gives half-max spreading is E1/2-spread ∼ 8–10 kPa, proving remarkably close to Emedia. More complex, layer-by-layer microfilms of poly(l-lysine)/hyaluronic acid were also tested and show equivalent trends of increased SMC spreading with increased stiffness. Adhesive spreading of cells thus seems to correlate broadly with the effective stiffness of synthetic materials and tissues.