AVS 46th International Symposium
    Biomaterial Interfaces Group Thursday Sessions
       Session BI-ThM

Invited Paper BI-ThM3
Synthesis and Surface Characterization of Peptide-Modified Interpenetrating Polymer Networks that Control Biomineralization

Thursday, October 28, 1999, 9:00 am, Room 613/614

Session: Biomineralization
Presenter: K.E. Healy, Northwestern University
Authors: K.E. Healy, Northwestern University
T. Barber, Northwestern University
D.G. Castner, University of Washington
S.L. Golledge, University of Washington
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A major limitation in the performance of materials used in the medical device and pharmaceutical industries is that they lack the ability to integrate with biological systems through either a molecular or cellular pathway. We have designed and synthesized interfacial interpenetrating polymer networks (IPNs) that resist non-specific protein adsorption, and can be modified to tether bioactive groups such as peptides that mimic cell binding domains found on ECM molecules. An IPN was created by sequential photoinitiated synthesis of a thin layer of poly(acrylamide) [P(AAm)] followed by a secondary photoinitiation step using poly(ethylene glycol) [PEG] based monomers to create the network. Tethering of peptides was achieved by photoinitiated synthesis of PEG-monomethyl ether monomethacrylate, acrylic acid (AAc) and N,N-methylene-bis-acrylamide into the P(AAm) layer. A spacer of bisamino PEG (3400 MW) was then bonded to the AAc through a carbodiimide reaction. As a specific example of coupling bioactive molecules to the surface, peptides from the cell binding domain [CGGNGEPRGDTYRAY] and heparin binding domain [FHRRIKA] of bone sialoprotein were tethered to the remaining free PEG amine moiety via a sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate cross linker. Surfaces were characterized by contact angle measurements, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. The surface characterization confirmed the formation of the IPN and subsequent immobilization of the peptide. These surfaces resisted protein deposition and neither supported cell attachment nor growth without immobilization of the RGD-based biomimetic peptide from bone sialoprotein. Molecular modification of the non-adhesive IPN using a RGD-containing peptide led to rapid bone cell attachment independent of the presence of serum proteins, and subsequently to normal cell proliferation and normal phenotypic expression (e.g., synthesis of mineralized matrix).