Nanoscale surface of carbon nanotube fibers for medical applications: Structure and chemistry revealed by TOF-SIMS analysis S. Polizu a, * , M. Maugey b , S. Poulin c , P. Poulin b , L’Hocine Yahia a a LIAB, 2900 E ´ douard-Montpetit, E ´ cole Polytechnique, Montre ´al, Que., Canada H3T 1J4 b Centre de Recherche Paul Pascal, CNRS, Bordeaux, F-33600, France c LASM, 2900 E ´ douard-Montpetit, E ´ cole Polytechnique, Montre ´al, Que., Canada H3T 1J4 Received 12 September 2005; accepted 15 February 2006 Available online 15 May 2006 Abstract Surface structure and related chemistry understanding is a vital element in the design of high biocompatible materials since adsorption and adhesion of biological components are involved. These features are even more important in the case of nanostructured materials such as carbon nanotubes (CNTs) fibers. In our preliminary work we synthesised CNTs based fibers for medical applications. This new hybrid system combines polyvinyl alcohol (PVA) with CNTs and polylactic-co-glycolic acid (PLGA), a biodegradable copolymer. The surface properties of this material are investigated in order to guarantee a biocompatible response. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was found to be an ideal tool for fiber characterisation owing to its capacity to provide chemical specificity combined with detection limits beyond the reach of techniques previously used. Complementary morphological information is provided by atomic force microscopy (AFM). The corroboration of both data enables us to define the chemistry and structure of this new formulation. # 2006 Elsevier B.V. All rights reserved. Keywords: Carbon nanotubes; PLGA; Fibers; Biocompatibility; TOF-SIMS; AFM 1. Introduction A growing interest toward the field of hybrid materials is currently observed in the biomedical world. The hybrid approach provides great fabrication versatility and encourages the creation of new materials with unique properties, depending on the nature of the incorporated functional segments. CNTs are emerging materials, which capture a great interest in the biomaterial field [1]. It is noteworthy that the effectiveness of CNT in hybrid materials strongly depends on the ability to disperse the nanotubes homogenously through the matrix while maintaining their integrity and ensure bonding between components [2–4]. We engineer CNTs fibers applying particle coagulation spinning (PCS) method, which forms macroscopic fibers with a very good alignment of nanotubes [2]. Using CNT dispersion based on a non-covalent stabilisation mechanism, in aqueous solution, we ensure the preservation of both the nanotube structure and its properties. Incorporation of PLGA in CNTs dispersion strengthens the network effect and further increases the biocompatible response [5]. When constructing fibers for biomedical application, surface chemistry and morphological homogeneity are of particular significance for such complex materials since they directly influence biological interactions [1,6]. Indeed, the structural features and the chemical composition at the fiber surface are crucial for understanding specific functional properties which have a great impact on tissue regeneration [1]. TOF-SIMS has great surface specificity and high detection limit and shows differences in spectra for different states of the various components of the fiber biomaterials [6]. The present study is concerned with the nanoscale surface characteristics of CNTs based fibers. The properties of the studied hybrid structure, in terms of biocompatibility, strongly depend on the components’ chemistry such as CNT, PLGA and PVA, as well as on the fibers’ structure. A variety of other reports refer to the characterisation of CNTs based materials using various techniques [2–4]. In this frame of investigation, surface www.elsevier.com/locate/apsusc Applied Surface Science 252 (2006) 6750–6753 * Corresponding author at: LIAB, E ´ cole Polytechnique de Montre ´al, C.P. 6079, succ. Centre-ville, Montre ´al, Que., Canada H3T 1J4. Fax: +1 514 340 5867. E-mail address: stefania.polizu@polymtl.ca (S. Polizu). 0169-4332/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2006.02.262