Translocation of Functionalized Multi-Walled Carbon Nanotubes across Human Pulmonary Alveolar Epithelium: Dominant Role of Epithelial Type 1 Cells

• Published in: ACS nano 2016-05, Vol.10 (5), p.5070-5085
• Main Authors: Ruenraroengsak, Pakatip, Chen, Shu, Hu, Sheng, Melbourne, Jodie, Sweeney, Sinbad, Thorley, Andrew J, Skepper, Jeremy N, Shaffer, Milo S. P, Tetley, Teresa D, Porter, Alexandra E
• Format: Article
• Language: English
• Subjects: Cell Culture Techniques; Epithelial Cells; Humans; Lung - cytology; Nanotubes, Carbon; Pulmonary Alveoli - cytology; Respiratory Mucosa
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.5b08218

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.