title: Translocation of Functionalized Multi-Walled Carbon Nanotubes across Human Pulmonary Alveolar Epithelium: Dominant Role of Epithelial Type 1 Cells.
abstract: Uptake and translocation of short functionalized multi-walled carbon nanotubes (short-fMWCNTs) through the pulmonary respiratory epithelial barrier depend on physicochemical property and cell type. Two monoculture models, immortalized human alveolar epithelial type 1 (TT1) cells and primary human alveolar epithelial type 2 cells (AT2), which constitute the alveolar epithelial barrier, were employed to investigate the uptake and transport of 300 and 700 nm in length, poly(4-vinylpyridine)-functionalized, multi-walled carbon nanotubes (p(4VP)-MWCNTs) using quantitative imaging and spectroscopy techniques. The p(4VP)-MWCNT exhibited no toxicity on TT1 and AT2 cells, but significantly decreased barrier integrity (*p < 0.01). Uptake of p(4VP)-MWCNTs was observed in 70% of TT1 cells, correlating with compromised barrier integrity and basolateral p(4VP)-MWCNT translocation. There was a small but significantly greater uptake of 300 nm p(4VP)-MWCNTs than 700 nm p(4VP)-MWCNTs by TT1 cells. Up to 3% of both the 300 and 700 nm p(4VP)-MWCNTs reach the basal chamber; this relatively low amount arose because the supporting transwell membrane minimized the amount of p(4VP)-MWCNT translocating to the basal chamber, seen trapped between the basolateral cell membrane and the membrane. Only 8% of AT2 cells internalized p(4VP)-MWCNT, accounting for 17% of applied p(4VP)-MWCNT), with transient effects on barrier function, which initially fell then returned to normal; there was no MWCNT basolateral translocation. The transport rate was MWCNT length modulated. The comparatively lower p(4VP)-MWCNT uptake by AT2 cells is proposed to reflect a primary barrier effect of type 2 cell secretions and the functional differences between the type 1 and type 2 alveolar epithelial cells.
authors.affiliation: Lung Cell Biology, Airways Disease, National Heart and Lung Institute, Imperial College London , Dovehouse Street, London, United Kingdom SW3 6LY.
authors.forename: Pakatip
authors.initials: P
authors.lastname: Ruenraroengsak
authors.forename: Shu
authors.initials: S
authors.lastname: Chen
authors.forename: Sheng
authors.initials: S
authors.lastname: Hu
authors.forename: Jodie
authors.initials: J
authors.lastname: Melbourne
authors.affiliation: Lung Cell Biology, Airways Disease, National Heart and Lung Institute, Imperial College London , Dovehouse Street, London, United Kingdom SW3 6LY.
authors.forename: Sinbad
authors.initials: S
authors.lastname: Sweeney
authors.affiliation: Lung Cell Biology, Airways Disease, National Heart and Lung Institute, Imperial College London , Dovehouse Street, London, United Kingdom SW3 6LY.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Thorley
authors.affiliation: Cambridge Advanced Imaging Centre, Department of Physiology, Development and Neuroscience, University of Cambridge , Cambridge, United Kingdom CB2 3DY.
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Skepper
authors.forename: Milo S P
authors.initials: MS
authors.lastname: Shaffer
authors.affiliation: Lung Cell Biology, Airways Disease, National Heart and Lung Institute, Imperial College London , Dovehouse Street, London, United Kingdom SW3 6LY.
authors.forename: Teresa D
authors.initials: TD
authors.lastname: Tetley
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Porter
mesh_terms: D018929:Cell Culture Techniques; D004847:Epithelial Cells; D006801:Humans; D008168:Lung / Q000166:cytology*; D037742:Nanotubes, Carbon; D011650:Pulmonary Alveoli / Q000166:cytology*; D020545:Respiratory Mucosa
chemical_list: D037742:Nanotubes, Carbon
keywords: alveolar epithelial barrier; electron microscopy; functionalized multi-walled carbon nanotubes; quantitative imaging technique; translocation; uptake