Cell adhesion and focal contact formation on linear RGD molecular gradients: study of non-linear concentration dependence effects

Cell adhesion onto bioengineered surfaces is affected by a number of variables, including the former substrate derivatization process. In this investigation, we studied the correlation between cell adhesion and cell–adhesive ligand surface concentration and organization due to substrate modification. For this purpose, Arg-Gly-Asp (RGD) gradient surfaces were created on poly(methyl methacrylate) substrates by continuous hydrolysis and were then grafted with biotin-PEG-RGD molecules. Cell culture showed that adhesion behavior changes in a nonlinear way in the narrow range of RGD surface densities assayed (2.8 to 4.4 pmol/cm2), with a threshold value of 4.0 pmol/cm2 for successful cell attachment and spreading. This nonlinear dependence may be explained by nonhomogeneous RGD surface distribution at the nanometre scale, conditioned by the stochastic nature of the hydrolysis process. Atomic force microscopy analysis of the gradient surface showed an evolution of surface morphology compatible with this hypothesis.From the Clinical EditorThe authors observed by AFM nonlinear dependence of cell adhesion on RGD gradient surfaces with different surface densities. The nonlinear characteristics may be explained by non-homogeneous RGD surface distribution at the nanometer scale, conditioned by the stochastic nature of the hydrolysis process.

Graphical AbstractThe Table of Contents image selected shows the plot of the percentage of adhered cells onto the gradient surface against the RGD density values for each sample position. Images superimposed denote how the clustering degree of the adhesive ligands (RGD), which varies along the gradient, may affect cell behavior: threshold observed in cell adhesion at the narrow range of RGD densities of 2.8 to 4.4 pmol/cm2.Figure optionsDownload high-quality image (123 K)Download as PowerPoint slide