Photoinduced self-initiated graft polymerization of methacrylate monomers on poly(ether ether ketone) substrates and surface parameters for controlling cell adhesion

One of the super engineering plastics, poly(ether ether ketone) (PEEK), was functionalized by photoinduced self-initiated graft polymerization of various methacrylate monomers. Anionic, cationic, zwitterionic, nonionic hydrophilic, and nonionic hydrophobic polymer layers were formed onto PEEK substrates. Physical and chemical surface characterizations of the resultant polymer-grafted PEEK substrates were performed through measurements of their surface free energies and zeta potentials. The values of these parameters varied in the ranges of 39-71 mJ/m(2) and -69 to 46 mV, respectively. These parameters reflected the chemical structures of the grafted polymers. To understand the effects of these surface parameters on cell adhesion behavior at the substrate surface, the amount of fibronectin adsorbed on the plasma-contacting surface and the density of fibroblast cells adhered to the surface were determined. The adherent cell density showed a good linear correlation with the amount of fibronectin adsorbed on the plasma-contacting surface. The polymer surface with zero zeta potential showed a lower adsorbed fibronectin density. Both anionic and cationic polymer layers had increased cell adhesion compared with that on the original PEEK substrate, whereas the zwitterionic polymer layers significantly prevented cell adhesion. In conclusion, grafting zwitterionic polymers onto a PEEK substrate is anticipated to be useful in the development of a biomedical PEEK substrate.