BIOMOLECULAR MODIFICATION OF P(AAM-CO-EG AA) IPNS SUPPORTS OSTEOBLASTADHESION AND PHENOTYPIC-EXPRESSION/

Interpenetrating polymer networks (IPNs) were designed to resist mater ials fouling caused by non-specific protein adsorption, and indiscrimi nate cell or bacterial adhesion. These IPNs were thin adherent films ( similar to 20 nm) comprised of acrylamide (AAm), ethylene glycol (EG), and acrylic acid (AA) grafted to either silicon waters or quartz subs trates via photoinitiated free radical polymerization. These networks were further modified to promote specific cell adhesion by tethering b ioactive groups such as peptides that mimic cell-binding domains found on extracellular matrix molecules. As a specific example of biomolecu lar surface engineering, peptides from the cell-binding domain of bone sialoprotein were tethered to a p(AAm-co-EG/AA) IPN to control cell b ehavior at the surface. The networks were characterized by contact ang le measurements, spectroscopic ellipsometry, and X-ray photoelectron s pectroscopy to convey information on IPN wettability, thickness, and c hemistry. The surface characterization data supported the theory that the PEG/AA layer formed an IPN with the underlying p(AAm) network, and after graft modification of this IPN with diamino PEG (PEG(NH2)(2)), the PEG(NH2)(2) chains were enriched at the surface. Rat calvarial ost eoblasts attached to Alg-Gly-Asp (RGD) modified IPNs at levels signifi cantly greater than on clean quartz, Arg-Gly-Glu (RGE) modified, or th e PEG(NH2)(2) modified TPN, with or without serum in the media. Cells maintained in media containing 15% fetal bovine serum (FBS) proliferat ed, exhibited nodule formation, and generated sheets of mineralized ex tracellular matrix (ECM) with the addition on beta-glycerophosphate to the media. Cell adhesion and mineralized ECM formation were specifica lly dependent on the peptide sequence present at the surface.