Biofilm behavior on sulfonated poly(ether-ether-ketone) (sPEEK) Juan F.D. Montero a , Henrique A. Tajiri b , Guilherme M.O. Barra b , Márcio C. Fredel b , Cesar A.M. Benfatti a , Ricardo S. Magini a , Andréa L. Pimenta c,d , Júlio C.M. Souza a,e, ⁎ a Center for Research on Dental Implants (CEPID), School of Dentistry (ODT), Federal University of Santa Catarina (UFSC), Florianópolis, SC 88040-900, Brazil b Department of Mechanical Engineering (EMC), Federal University of Santa Catarina (UFSC), Florianópolis, SC 88040-900, Brazil c Integrated Laboratories Technologies (InteLAB), Dept. Chemical Engineering (EQA), Federal University of Santa Catarina (UFSC), Florianópolis, SC 88040-970, Brazil 1 d Department of Biologie, Université de Cergy Pontoise, 2, Av. Adolphe Chauvin, 95302 Cergy Pontoise, France 2 e Center for Microelectromechanical Systems (CMEMS), Dept. Mechanical Engineering (DEM), Campus Azurém, 4800-058 Guimarães, Portugal abstract article info Article history: Received 15 May 2016 Received in revised form 15 August 2016 Accepted 6 September 2016 Available online 7 September 2016 Poly(ether-ether-ketone) (PEEK) has also shown to be very attractive for incorporating therapeutic compounds thanks to a sulfonation process which modifies the material structure resulting in a sulfonated-PEEK (sPEEK). Concerning biomedical applications, the objective of this work was to evaluate the influence of different sulfona- tion degree of sPEEK on the biofilm growth. PEEK samples were functionalized by using sulphuric acid (98%) and then dissolved into dimethyl-sulfoxide. A dip coating technique was used to synthesize sPEEK thin films. The sul- fonation degree of the materials was analyzed by FT-IR, H NMR, TG and IEC. The surfaces were characterized by scanning electron microscopy, profilometry and contact angle analyses. Subsequently, the biofilm formation on sulfonated-PEEK based on Streptococcus mutans and Enterococcus faecalis was measured by spectrophotometry, colony forming units (CFU mL -1 ) and SEM. Results obtained from thermal and chemical analyses showed an in- tensification in sulfonation degree for sPEEK at 2 and 2.5 h. The E. faecalis or S. mutans biofilm growth revealed statistically significant differences (p b 0.05) between 2 and 3 h sulfonation groups. A significant decrease (p b 0.05) in CFU mL -1 was recorded for S. mutans or E. faecalis biofilm grown on 2.5 or 3 h sPEEK. Regarding the thermal-chemical and microbiologic analyses, the sulfonation degree of sPEEK ranging from 2 up to 3 h was successful capable to decrease the biofilm growth. That revealed an alternative strategy to embed anti-bio- film and therapeutic compounds into PEEK avoiding infections in biomedical applications. © 2016 Elsevier B.V. All rights reserved. Keywords: Biofilm Enterococcus faecalis PEEK sPEEK Streptococcus mutans 1. Introduction Titanium and its alloys are widely used to synthesize biomedical de- vices and implants due to their excellent properties such as corrosion resistance, high mechanical strength and biocompatibility [1]. However, metallic biomaterials cannot satisfy all clinical requirements. Previous studies have reported the release of metallic nano- and micro-particles generated by wear and corrosion of prosthetic structures in the context of severe postoperative complications such as osteolysis and allergenic- ity [2,3]. In fact, the presence of metallic ions and particles in human tis- sues induces the activation of macrophages, neutrophils, and T- lymphocytes with elevation of cytokines and metallic proteinases that can promote bone resorption [3,7]. Concerning those biological limitations, one of the alternative mate- rials used as a choice of titanium in the biomedical field is the poly(ether-ether-ketone) (PEEK) [4]. PEEK has been classified as having a higher mechanical strength, chemical resistance and biocompatibility than those of other biocompatible polymers [4,5]. Also, PEEK maintains its structural stability at high temperature up to about 300 °C supporting machining and repeated sterilization processes [6], Thus, PEEK repre- sents an interesting material in dentistry considering it has already been used in dental implant systems [5,7,8]. However, the osseointegration process of biomaterials depends on the surface morphology and chemical composition. There have been ef- forts to enhance the osseointegration of biomaterials by increasing micro- and nano-roughness or modifying chemical composition and po- rosity of the surface [9]. The increase of roughness or porosity results in a higher bone-implant contact area for fibrin attachment and then en- hancing the activation of blood platelets which will produce density gradients of cytokines and bone growth factors such as platelet-derived growth factors (PDGF) and transforming growth factors beta (TGF-β) [10]. Porous surfaces play a critical role in the osteogenic cell migration and bone formation [10,11]. Many techniques have been used for the manufacturing of porous structures over metal surfaces, including Materials Science and Engineering C 70 (2017) 456–460 ⁎ Corresponding author at: Center for Research on Dental Implants (CEPID), School of Dentistry (ODT), Federal University of Santa Catarina (UFSC), Florianópolis, SC 88040- 900, Brazil. E-mail address: julio.c.m.souza@ufsc.br (J.C.M. Souza). 1 Present address. 2 Permanent address. http://dx.doi.org/10.1016/j.msec.2016.09.017 0928-4931/© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec