title: Biochemical functionalization of polymeric cell substrata can alter mechanical compliance.
abstract: Biochemical functionalization of surfaces is an increasingly utilized mechanism to promote or inhibit adhesion of cells. To promote mammalian cell adhesion, one common functionalization approach is surface conjugation of adhesion peptide sequences such as Arg-Gly-Asp (RGD), a ligand of transmembrane integrin molecules. It is generally assumed that such functionalization does not alter the local mechanical properties of the functionalized surface, as is important to interpretations of macromolecular mechanotransduction in cells. Here, we examine this assumption systematically, through nanomechanical measurement of the nominal elastic modulus of polymer multilayer films of nanoscale thickness, functionalized with RGD through different processing routes. We find that the method of biochemical functionalization can significantly alter mechanical compliance of polymeric substrata such as weak polyelectrolyte multilayers (PEMs), increasingly utilized materials for such studies. In particular, immersed adsorption of intermediate functionalization reagents significantly decreases compliance of the PEMs considered herein, whereas polymer-on-polymer stamping of these same reagents does not alter compliance of weak PEMs. This finding points to the potential unintended alteration of mechanical properties via surface functionalization and also suggests functionalization methods by which chemical and mechanical properties of cell substrata can be controlled independently.
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: M Todd
authors.initials: MT
authors.lastname: Thompson
authors.forename: Michael C
authors.initials: MC
authors.lastname: Berg
authors.forename: Irene S
authors.initials: IS
authors.lastname: Tobias
authors.forename: Jenny A
authors.initials: JA
authors.lastname: Lichter
authors.forename: Michael F
authors.initials: MF
authors.lastname: Rubner
authors.forename: Krystyn J
authors.initials: KJ
authors.lastname: Van Vliet
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D004548:Elasticity; D005347:Fibroblasts / Q000187:drug effects*; D008567:Membranes, Artificial; D051379:Mice; D041681:NIH 3T3 Cells; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D011073:Polyamines / Q000737:chemistry / Q000494:pharmacology; D013499:Surface Properties
chemical_list: D008567:Membranes, Artificial; D010455:Peptides; D011073:Polyamines; C065723:poly (arginyl-glycyl-aspartic acid); C063994:polyallylamine