Antibacterial surfaces: the quest for a new generation of biomaterials Jafar Hasan, Russell J. Crawford, and Elena P. Ivanova Faculty of Life and Social Sciences, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria, 3122, Australia In this review we attempt to clarify the notion of what is meant by the term antibacterial surfaces and categorise the approaches that are commonly used in the design of antibacterial surfaces. Application of surface coatings and the modification of the surface chemistry of substra- ta are generally considered to be a chemical approach to surface modification (as are surface polymerisation, functionalisation, and derivatisation), whereas, modifi- cation of the surface architecture of a substrate can be considered a physical approach. Here, the antifouling and bactericidal effects of antibacterial surfaces are brief- ly discussed. Finally, several recent efforts to design a new generation of antibacterial surfaces, which are based on mimicking the surface nanotopography of natural surfaces, are considered. Antibacterial surfaces Despite considerable recent progress in the development of nanobiotechnology and nanofabrication techniques, the quest to design and fabricate new antibacterial surfaces (see Glossary) as an integral component of advanced biomaterials remains a high research priority [1–3]. Micro- organisms are the oldest life form on our planet and over the millions of years of their existence they have developed versatile adaptive mechanisms for the colonisation of sur- faces [4]. The colonisation of surfaces by bacteria is known to adversely affect the function of a variety of specific interfaces, such as those found in petroleum pipelines and aquatic flow systems, textiles, contact lenses, and medical implants [2,3]. In order to eliminate or substantially reduce the extent of bacterial attachment and biofilm formation on these sur- faces, intensive efforts have been focused on the fabrication of new surfaces, or on the improvement of the performance of existing antibacterial surfaces by, for example, the applica- tion of surface coatings, or modification and/or alteration of the surface architecture [2,5]. In this review we attempt to clarify the definition of the term antibacterial surface and categorise the approaches that are commonly used in the design of antibacterial surfaces. It is suggested that anti- bacterial surfaces should be categorised as being either antibiofouling or bactericidal, depending on the effect that these surfaces have on biological systems with which they have contact. An array of antibacterial surfaces can be categorised according to the surface coating or surface chemistry modifications to which they have been subjected, for example, surface functionalisation, polymerisation, and derivatisation (i.e., chemical modification) or modification to the surface topography (physical modification). Several re- cent efforts to design a new generation of antibacterial surfaces, which are based on mimicking the surface nano- topography of natural surfaces, are also reported. The concept of antibacterial surfaces The paradigm of bacterial attachment and proliferation on surfaces was first recognised in the 1930s [6]. It was established that bacteria prefer to colonise a solid sub- strate that may be present rather than dwell in a plank- tonic state [7]. The formation of biofilms has been extensively studied over the past decades in an attempt to develop several surface modification approaches to pre- vent or reduce the extent of bacterial attachment using biocides, antibiotics, and surface treatment processes [1,2,8,9]. The rationale for these approaches was to design an antibacterial surface, which would prevent the initial attachment of bacteria, therefore preventing the subse- quent formation of a biofilm. Antibiofouling and bactericidal surfaces Antibacterial surfaces may repel or resist the initial at- tachment of bacteria by either exhibiting an antibiofouling affect or by inactivating any cells coming into contact with the surface, causing cell death, therefore exhibiting a bactericidal effect. Antibacterial surfaces therefore can be broadly classified as either an antibiofouling [10] or bactericidal [1,11]. Antibiofouling surfaces may resist or prevent cellular attachment due to the presence of an unfavourable surface topography or surface chemistry with respect to the micro- organisms [12,13]. Bactericidal surfaces disrupt the cell on contact, causing cell death [1]. In some instances, an antibacterial surface may exhibit both antibiofouling Review Glossary Antibacterial surfaces: Surfaces that are capable of reducing the extent of attachment and proliferation of bacteria. They could be classified as antibiofouling and bactericidal surfaces. Antibiofouling: Antibiofouling generally implies repelling bacterial cells from attaching onto the surfaces; this is achieved through unfavourable conditions on the surfaces. Bactericidal surfaces: Surfaces that inactivate the bacterial cells largely through chemical mechanisms or agents. 0167-7799/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/ j.tibtech.2013.01.017 Corresponding author: Ivanova, E.P. (eivanova@swin.edu.au). Keywords: antibacterial; antibiofouling; bactericidal; surface chemistry; topography; nanotopography. Trends in Biotechnology, May 2013, Vol. 31, No. 5 295