Contents lists available at ScienceDirect Materials Today Communications journal homepage: www.elsevier.com/locate/mtcomm Improvement in antimicrobial properties of titanium by diethyl phosphite plasma-based surface modification Gizem Kaleli-Can a , Hatice Ferda Özgüzar b , Selahattin Kahriman c , Miranda Türkal c , Jülide Sedef Göçmen d , Erkan Yurtçu e , Mehmet Mutlu b,c,1, * a Department of Biomedical Engineering, İzmir Democracy University, İzmir 35140, Turkey b Plasma Aided Biomedical Research Group (pabmed), Biomedical Engineering Division, Graduate School of Science and Technology, TOBB University of Economics and Technology, Ankara 06560, Turkey c Plasma Aided Biomedical Research Group (pabmed), Biomedical Engineering Department, Engineering Faculty, TOBB University of Economics and Technology, Ankara 06560, Turkey d Department of Medical Microbiology, Faculty of Medicine, TOBB University of Economics and Technology, Ankara 06560, Turkey e Department of Medical Biology, School of Medicine, Baskent University, Ankara 06790, Turkey ARTICLE INFO Keywords: Plasma polymerization Amphoteric polymer Titanium Antimicrobial coating Fungicidal activity Antibacterial activity ABSTRACT Titanium (Ti) has been commonly used as a biomaterial for dental applications. However, they have struggled with the formation of polymicrobial infections leading to peri-implantitis. In this research, antimicrobial activity of titanium modified via diethyl phosphite (DEP) plasma onto Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans), the two most frequently encountered pathogens in peri-implantitis, were investigated. Surface modification with DEP was achieved with plasma polymerization technique in a low-pressure/radio- frequency plasma using 75 W of plasma power and 10 min of exposure time under 0.15 mbar. Hydrophilicity, surface energy and roughness of Ti surface was increased and anionic Ti surface became amphoteric after surface modification according to physical and chemical examinations. This process significantly enhanced the anti- microbial efficiency of Ti towards S. aureus and C. albicans cells compared to control groups via contact killing. Moreover, DEP coating shown excellent compatibility with 93 % of L929 fibroblast cell viability. These findings revealed that amphoteric plasma polymer prepared from DEP offers promising solution for preventing biofilm formation on Ti. 1. Introduction Titanium (Ti) and its alloy-based materials have been widely used as crowns, brackets and implants to replace missing teeth in dental ap- plications, due to their ultimate biological compatibility, superior me- chanical strength and high corrosion resistance [1–3]. However, peri- implantitis may occur after implantation in spite of hygiene standards in hospitals and this situation interrupts the long-term usage of oral implants in clinic [4–6]. Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) are naturally present in the mouth and nasal cavity and these microorganisms are the two most frequently found in peri- implantitis microflora [7–11]. Therefore, alternative strategies to pre- vent the adhesion and/or colonization of these microorganisms on ti- tanium implant need to be developed. Surface coating is one of the most effective ways to develop anti- infective biomaterial/medical devices. Several researches, used various chemical approaches such as self-assembled monolayers, polymer- based coatings and liquid infused nanostructured surfaces have been conducted to produce antimicrobial surface [12–16]. These approaches are restricted to a certain biomaterial chemistry and/or pre-treatment of surfaces including the sequence of chemical reactions and these chemical processes are often time-consuming, complex, in need of or- ganic reagent and most importantly can damage the implant [17–19]. Plasma technology has been started to replace chemical processes for the surface modification of materials due to shorter reaction times, environmental safety and the ability to change the surface properties of the material without affecting the bulk properties. Furthermore, thin films, produced with plasma process, showed enhanced features like https://doi.org/10.1016/j.mtcomm.2020.101565 Received 28 May 2020; Received in revised form 23 July 2020; Accepted 10 August 2020 Abbreviations: DEP, diethyl phosphite; pp(DEP)-Ti, DEP-coated Ti surfaces; cfu, colony forming units; XPS, X-ray photoelectron spectroscopy; SEM, scanning electron microscope; EDS, electron dispersive X-ray; SDA, sabouraud dextrose agar; SDB, sabouraud dextrose broth ⁎ Corresponding author. E-mail Address: mehmet.mutlu@ostimteknik.edu.tr (M. Mutlu). E-mail address: mehmet.mutlu@ostimteknik.edu.tr (M. Mutlu). 1 Current address: Department of Mechanical Engineering, Ostim Technical University, Ankara 06374, Turkey Materials Today Communications 25 (2020) 101565 Available online 15 August 2020 2352-4928/ © 2020 Published by Elsevier Ltd. T