title: Aqueous cationic, anionic and non-ionic multi-walled carbon nanotubes, functionalised with minimal framework damage, for biomedical application.
abstract: The use of a thermochemical grafting approach provides a versatile means to functionalise as-synthesised, bulk multi-walled carbon nanotubes (MWNTs) without altering their inherent structure. The associated retention of properties is desirable for a wide range of commercial applications, including for drug delivery and medical purposes; it is also pertinent to studies of intrinsic toxicology. A systematic series of water-compatible MWNTs, with diameter around 12 nm have been prepared, to provide structurally-equivalent samples predominantly stabilised by anionic, cationic, or non-ionic groups. The surface charge of MWNTs was controlled by varying the grafting reagents and subsequent post-functionalisation modifications. The degree of grafting was established by thermal analysis (TGA). High resolution transmission electron microscope (HRTEM) and Raman measurements confirmed that the structural framework of the MWNTs was unaffected by the thermochemical treatment, in contrast to a conventional acid-oxidised control which was severely damaged. The effectiveness of the surface modification was demonstrated by significantly improved solubility and stability in both water and cell culture medium, and further quantified by zeta-potential analysis. The grafted MWNTs exhibited relatively low bioreactivity on transformed human alveolar epithelial type 1-like cells (TT1) following 24 h exposure as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase release (LDH) assays. The exposure of TT1 cells to MWNTs suppressed the release of the inflammatory mediators, interleukin 6 (IL-6) and interleukin 8 (IL-8). TEM cell uptake studies indicated efficient cellular entry of MWNTs into TT1 cells, via a range of mechanisms. Cationic MWNTs showed a more substantial interaction with TT1 cell membranes than anionic MWNTs, demonstrating a surface charge effect on cell uptake.
authors.affiliation: Department of Materials and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Chemistry and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Sheng
authors.initials: S
authors.lastname: Hu
authors.affiliation: National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK.
authors.forename: Elizabeth F
authors.initials: EF
authors.lastname: Smith
authors.affiliation: Department of Materials and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Pakatip
authors.initials: P
authors.lastname: Ruenraroengsak
authors.affiliation: National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Thorley
authors.affiliation: Department of Chemistry and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Menzel
authors.affiliation: Department of Materials and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Angela E
authors.initials: AE
authors.lastname: Goode
authors.affiliation: Department of Materials and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Mary P
authors.initials: MP
authors.lastname: Ryan
authors.affiliation: National Heart and Lung Institute, Imperial College London, Dovehouse Street, London SW3 6LY, UK.
authors.forename: Teresa D
authors.initials: TD
authors.lastname: Tetley
authors.affiliation: Department of Materials and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Porter
authors.affiliation: Department of Chemistry and London Centre for Nanotechnology, Imperial College London, Exhibition Road, London SW7 2AZ, UK. Electronic address: m.shaffer@imperial.ac.uk.
authors.forename: Milo S P
authors.initials: MS
authors.lastname: Shaffer
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004705:Endocytosis; D006801:Humans; D007477:Ions / Q000737:chemistry; D037742:Nanotubes, Carbon / Q000032:analysis / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D012995:Solubility; D055672:Static Electricity; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D007477:Ions; D037742:Nanotubes, Carbon; D014867:Water
keywords: Cell uptake; Cytotoxicity; Integrity structure; Multiwalled carbon nanotubes; Surface charge; Thermal chemical functionalisation