title: Cell adhesion and focal contact formation on linear RGD molecular gradients: study of non-linear concentration dependence effects.
abstract: 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/cm(2)), with a threshold value of 4.0 pmol/cm(2) 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.
  
  
  BACKGROUND
  The 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.
authors.affiliation: Centro de Investigación Biomédica en Red. Bioingeniería, Biomateriales y Nanomedicina, Zaragoza, Spain. alagunas@ibecbarcelona.eu
authors.forename: Anna
authors.initials: A
authors.lastname: Lagunas
authors.forename: Jordi
authors.initials: J
authors.lastname: Comelles
authors.forename: Elena
authors.initials: E
authors.lastname: Martínez
authors.forename: Elisabet
authors.initials: E
authors.lastname: Prats-Alfonso
authors.forename: Gerardo A
authors.initials: GA
authors.lastname: Acosta
authors.forename: Fernando
authors.initials: F
authors.lastname: Albericio
authors.forename: Josep
authors.initials: J
authors.lastname: Samitier
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D022001:Focal Adhesions / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D009842:Oligopeptides / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid