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Langmuir 2004, 20, 10718-10726
Synthesis of Copolymer Brushes Endowed with Adhesion to Stainless Steel Surfaces and Antibacterial Properties by Controlled Nitroxide-Mediated Radical Polymerization Milena Ignatova,†,‡ Samuel Voccia,† Bernard Gilbert,§ Nadya Markova,| Paola Sandra Mercuri,⊥ Moreno Galleni,⊥ Vale´rie Sciannamea,† Sandrine Lenoir,† Damien Cossement,O Rachel Gouttebaron,O Robert Je´roˆme,† and Christine Je´roˆme*,† Center for Education and Research on Macromolecules (CERM), University of Lie` ge, Sart-Tilman, B6, B-4000 Lie` ge, Belgium, Laboratory of Analytical Chemistry and Electrochemistry, University of Lie` ge, Sart-Tilman, B6, B-4000 Lie` ge, Belgium, Institute of Microbiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria, Biological Macromolecules, Center for Protein Engineering, University of Lie` ge, Sart-Tilman, B6, B-4000 Lie` ge, Belgium, and Service de Chimie Inorganique et Analytique LASSIE, University of Mons-Hainaut, Av. Nicolas Copernic, B-7000 Mons, Belgium Received July 2, 2004. In Final Form: September 13, 2004 Novel copolymer brushes have been synthesized by a two-step “grafting from” method that consists of the electrografting of poly(2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yloxy)-ethylacrylate) onto stainless steel, followed by the nitroxide-mediated radical polymerization of 2-(dimethylamino ethyl)acrylate and styrene or n-butyl acrylate, initiated from the electrografted polyacrylate chains. The grafted copolymers were quaternized in order to endow them with antibacterial properties. Peeling tests have confirmed the strong adhesion of the grafted copolymer onto the stainless steel substrate. Quartz crystal microbalance experiments have proven that fibrinogen adhesion is lower on the hydrophilic quaternized films compared to the nonionic counterpart. Such quaternized copolymers exhibit significant antibacterial activity against the Gram-positive bacteria S. aureus and the Gram-negative bacteria E. coli.
Introduction Adherence of microorganisms to the surface of polymeric or metallic implants followed by colonization on this exposed surface are the major initial steps in the pathogenesis of foreign body infections. The body reacts toward orthopedic implants by coating their surfaces with a film composed of various proteins (e.g., fibronectin, fibrinogen, laminin, fibrin, collagen, and immunoglobulins) which can act as receptors for colonizing bacteria.1,2 Therefore, one way to provide the surface with antiadhesive properties toward bacteria is to block protein adsorption. Different methods of surface modification have been developed recently to prepare protein inert surfaces. In particular, surface modification of substrates such as polyuretane, poly(tetrafluoroethylene), poly(vinyl chloride), cellulose, gold, and functionalized glass3-9 by hydrophilic poly(ethylene oxide) (PEO) chains is especially promising. Similarly, a significant decrease in protein adsorption has * To whom correspondence should be addressed. Phone: (32) 4-3663491. Fax: (32) 4-3663497. E-mail:
[email protected]. † CERM, University of Lie ` ge. ‡ Permanent address: Bulgarian Academy of Sciences, Institute of Polymers, bl.103A, Acad. G. Bontchev str., 1113 Sofia, Bulgaria. § Laboratory of Analytical Chemistry and Electrochemistry, University of Lie`ge. | Bulgarian Academy of Sciences. ⊥ Center for Protein Engineering, University of Lie ` ge. O University of Mons-Hainaut. (1) Gristina, A. G.; Naylor, P. T. Implant Associated Infection. In Biomaterials Science: An Introduction to Materials in Medicine; Ratner, B. D., Hoffman, A S., Schoen, F. J., Lemons, J. E., Eds.; Academic Press: San Diego, CA, 1996; p 205. (2) An, Y. H.; Friedman, R. J. J. Biomed. Mater. Res. 1998, 43, 338. (3) Sofia, S. J.; Merrill, E. W. Protein adsorption on poly(ethylene glycol)-grafted silicon surfaces. In Poly(Ethylene Glycol): Chemistry and Biological Applications; Harris, J. M., Zalipsky, S., Eds.; American Chemical Society: Washington, DC, 1997; Chapter 22.
been reported on poly(tetrafluoroethylene) fibers grafted by ionic and nonionic polymers.10 Grafting of poly(acrylic acid) at the surface of catheters is also effective in improving the frictional properties.11 Finally, plasma treatment of Vicryl sutures in the presence of dimethylaminoethyl methacrylate or acrylic acid results in a significant decrease in protein and bacteria attachment.12 Polymer coatings with antibacterial properties present an alternative approach for preventing surface-mediated infection. Antibacterial properties have been imparted to a variety of substrates (siliceous surfaces, natural and artificial fibers, and others) by treatment with quaternary ammonium containing alkoxysilane coupling agents.13-15 (4) Gombotz, W. R.; Guanghui, W.; Horbett, T. A.; Hoffman, A. S. Protein adsorption to and elution from polyether surfaces. In Poly(Ethylene Glycol) Chemistry Biotechnical and Biomedical Applications; Harris, J. M., Ed.; Plenum Press: New York, 1992; p 127. (5) Zhang, M.; Desai, T.; Ferrari, M. Biomaterials 1998, 19, 953. (6) McPherson, T.; Kidane, A.; Szleifer, I.; Park, K. Langmuir 1998, 14, 176. (7) Mrksich, M.; Whitesides, G. M. Using self-assembled monolayers that present oligo(ethylene glycol) groups to control the interactions of proteins with surfaces. In Poly(Ethylene Glycol): Chemistry and Biological Applications; Harris, J. M., Zalipsky, S., Eds.; American Chemical Society: Washington, DC, 1997; Chapter 23. (8) Mrksich, M.; Chen, C. S.; Xia, Y.; Dyke, L. E.; Ingber, D. E.; Whitesides, G. M. Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 10775. (9) Chapman, R. G.; Ostuni, E.; Liang, M. N.; Meluleni, G.; Kim, E.; Yan, L.; Pier, G.; Warren, H. S.; Whitesides, G. M. Langmuir 2001, 17, 1225. (10) Kato, K.; Sano, S.; Ikada, Y. Colloids Surf., B 1995, 4, 221. (11) Anders, C.; Gartner, R.; Steinert, V.; Voit, B.; Zschoche, S. J. Macromol. Sci., Chem. 1999, 36 (7/8), 1017. (12) Rad, A. Y.; Ayhan, H.; Piskin, E. J. Biomed. Mater. Res. 1998, 41, 349. (13) Isquith, A. J.; Abott, E. A.; Waters, P. A. Appl. Microbiol. 1972, 24, 859. (14) Walters, P. A.; Abbot, E. A.; Isquith, A. J. Appl. Microbiol. 1973, 25, 253.
10.1021/la048347t CCC: $27.50 © 2004 American Chemical Society Published on Web 10/29/2004
Synthesis of Copolymer Brushes by Controlled NMP
Cationic polymers with long alkyl chain quaternary ammonium (octyl or dodecyl) have been found very efficient in bacteria removal because of the contribution of the increased hydrophobicity to the cidal activity.16,17 It is now widely accepted that the target site of these cationic polymers is the cytoplasmic membrane of bacterial cells and that the crucial step in their lethal action is the disruption of the membrane followed by the rapid release of K+ ions and other cytoplasmic constituents.18,19 Two main techniques are known for chemically attaching polymer chains to a solid surface, that is, the “grafting to” method whereby preformed chains are bonded by reaction with surface reactive groups20,21 and the “grafting from” method based on the initiation of monomer polymerization from the surface.22-26 Whenever the solid substrate is electrically conducting, cathodic electropolymerization of (meth)acrylates has proved to be an efficient “grafting from” technique.27,28 However, because an insulating polymer film is deposited, the cathode is rapidly passivated, thereby restricting the film thickness to
