Materials Science and Engineering B 123 (2005) 123–129 Structural and biological properties of carbon nanotube composite films Roger J. Narayan a,∗ , C.J. Berry b , R.L. Brigmon b a School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, USA b Environmental Biotechnology Section, Savannah River National Laboratory, Aiken, SC 29808, USA Received 2 June 2004; received in revised form 5 July 2005; accepted 9 July 2005 Abstract Carbon nanotube composite films have been developed that exhibit unusual structural and biological properties. These novel materials have been created by pulsed laser ablation of graphite and bombardment of nitrogen ions at temperatures between 600 and 700 ◦ C. High- resolution transmission electron microscopy and radial distribution function analysis demonstrate that this material consists of sp 2 -bonded concentric ribbons that are wrapped approximately 15 ◦ normal to the silicon substrate. The interlayer order in this material extends to approximately 15–30 ˚ A. X-ray photoelectron spectroscopy and Raman spectroscopy data suggest that this material is predominantly trigonally coordinated. The carbon nanotube composite structure results from the use of energetic ions, which allow for non-equilibrium growth of graphitic planes. In vitro testing has revealed significant antimicrobial activity of carbon nanotube composite films against Staphylococcus aureus and Staphylococcus warneri colonization. Carbon nanotube composite films may be useful for inhibiting microorganism attachment and biofilm formation in hemodialysis catheters and other medical devices. © 2005 Elsevier B.V. All rights reserved. Keywords: Pulsed laser deposition; Kaufman ion source; Antimicrobial materials 1. Introduction A major concern in the treatment of hospitalized or chron- ically ill individuals is medical device infection. Infection of hemodialysis catheters is especially troublesome because these infections may quickly progress from the device site to involve other organs (e.g. endocarditis) or the entire body (e.g. septicemia). Colonization of polytetrafluoroethylene ultra- filtration materials may occur if dialysis membranes are exposed to persistent microbial contamination. There is con- siderable risk of bacteria and endotoxin discharge from bac- teria, algae and/or fungi biofilms, which serve as reservoirs for continuous contamination. A recent study of tubing drawn from dialysis machine fluid pathways has demonstrated that these materials are often covered with biofilms that con- ∗ Corresponding author at: Department of Biomedical Engineering, Uni- versity of North Carolina, Chapel Hill, NC 27599-7575, USA. Tel.: +1 404 894 2823; fax: +1 404 894 9140. E-mail address: roger.narayan@mse.gatech.edu (R.J. Narayan). tain high concentrations of bacteria (1.10 3 –1.10 6 cm 2 ), algae and endotoxins (1–12 endotoxin units cm -2 ) [1]. In addition, dialysis catheter infection can cause other systemic diseases, including inflammation of the blood vessel endothelium and atherogenesis (blood vessel closure). For example, vascular access infections have been correlated with both an increase in the serum concentration of atherogenic proteins and an increase in mortality from cardiovascular disease [2]. Antimicrobial treatments for hemodialysis catheter bio- materials can greatly improve human health by reducing device infection and secondary disease [3]. Traditional strate- gies for disinfecting the fluid-containing vessels of hemodial- ysis machines involve the use of microbicidal solutions. Typ- ical treatments include 500–750 ppm sodium hypochlorite solution for 30–40 min and 1.5–2.0% formaldehyde solu- tion overnight. These treatments provide 10 5 -fold reduc- tions in microbial counts; however, they do not always result in complete microbial elimination [4]. Some work has been done on treating planktonic cells and aged biofilm cells of Pseudomonas aeruginosa and Staphylococcus aureus 0921-5107/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2005.07.007