Published: May 18, 2011 r2011 American Chemical Society 1933 dx.doi.org/10.1021/am200150t | ACS Appl. Mater. Interfaces 2011, 3, 1933–1939 RESEARCH ARTICLE www.acsami.org StructureÀActivity Relationship for Quaternary Ammonium Compounds Hybridized with Poly(methyl methacrylate) Leticia D. Melo, †,‡ Renata R. Palombo, † Denise F. S. Petri, § Michael Bruns, ^ Edla M. A. Pereira, †,§ and Ana M. Carmona-Ribeiro* ,†,‡ † Biocolloids Lab, Departamento de Bioquímica, Instituto de Química, Universidade de S~ ao Paulo, CP 26077, CEP 05513-970, S ~ ao Paulo/SP, Brazil. ‡ Departamento de An alises Clínicas e Toxicol ogicas, Faculdade de Ci ^ encias Farmac^ euticas, Universidade de S ~ ao Paulo, CEP 05508-900, S ~ ao Paulo/SP, Brazil. § Departamento de Química Fundamental, Instituto de Química, Universidade de S ~ ao Paulo, S~ ao Paulo/SP, Caixa Postal 26077, CEP 05513-970, Brazil. ^ Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-WPT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany. b S Supporting Information ’ INTRODUCTION Polymeric devices and biomaterials play an important role in the transmission of infectious diseases because of formation of biofilms on their surfaces. 1 Bacteria from the biofilm may often initiate infection in adjacent regions. 2 These surface-associated contaminants organized as biofilms exhibit increased resistance to detergents, disinfectants, or antibiotics and provide microbial protection against immunological defenses. 1,2 Much work has been devoted to hybrid antimicrobial materials with improved properties. Three types of antimicrobial surfaces have been developed: (1) those killing microorganisms upon contact; 3,4 (2) those preventing microbial adhesion onto the surface; 5 (3) those leaching antibacterial agents. 6 Antimicrobial materials have been designed in form of particles, 7 coatings or films, 4 or permanent nonleaching antibacterial surfaces able to prevent contamination. 8À10 A variety of cationic antimicrobials have been effective such as peptides 11 and long-chained surfactants and lipids. 12À14 Molecules with a net positive charge killed microorganisms both in solution 11 or upon adsorption 4,7 or grafting to flat surfaces or particles. 3,9,10 Antimicrobial coatings have been prepared by different stra- tegies such as the layer-by-layer deposition, 7 grafting or covalent binding of antimicrobial moieties to surfaces 3,9,10 or spin-coating technique to impregnate thin polymeric films with dioctadecyl- dimethylammonium bromide (DODAB). 4 The last approach was based on solubility of polymer and antimicrobial agent in a common solvent, e.g., chloroform and spin-coating of the solu- tion on a supporting surface yielding thin, smooth and homo- geneous films. Thereby the antimicrobial DODAB properties 13 were transferred to the hybrid polymer/DODAB coating and Escherichia coli was effectively killed upon contact. 4 Poly (methyl methacrylate) (PMMA) has been widely used in medical and dentistry devices, 15,16 where formation of biofilms was frequently reported. 17 In this work, spin-coated hybrid films prepared from PMMA and one of three different QACs, DO- DAB, cetyltrimethylammonium bromide (CTAB) or tetrapro- pylammonium bromide (TPAB) (see Scheme 1 for chemical Received: February 3, 2011 Accepted: May 18, 2011 ABSTRACT: Hybrid films from poly (methylmethacrylate) (PMMA) and dioctadecyldimethylammonium bromide (DODAB), cetyltri- methylammonium bromide (CTAB), or tetrapropylammonium bro- mide (TPAB) were characterized by determination of wettability, ellipsometry, atomic force microscopy, active compounds diffusion to water, X-ray photoelectron spectroscopy (XPS) with determination of atomic composition on the films surface, and biocidal activity against Pseudomonas aeruginosa or Staphylococcus aureus. QAC mobility in the films increased from DODAB to CTAB to TPAB. Diffusion and optimal hydrophobicÀhydrophilic balance imparted the highest bioactivity to CTAB. DODAB sustained immobilization at the film surface killed bacteria upon contact. TPAB ability to diffuse was useless because of its unfavorable hydrophobicÀhydrophilic balance for bioactivity. KEYWORDS: hybrid antimicrobial surfaces, dioctadecyldimethylammonium bromide, cetyltrimethylammonium bromide, tetra- propylammonium bromide, poly (methyl methacrylate), XPS