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.

The Effects of Varying Degree of MWCNT Carboxylation on Bioactivity in Various In Vivo and In Vitro Exposure Models

“…There are several proposed reasons for why f-MWCNTs are taken up by epithelial cells. The first reason is the relative decrease in aggregation and the smaller size that results from carboxylation [ 14 , 34 ]. This study supports that conclusion with one caveat.…”

“…Lastly, surface charge and zeta potentials can be altered as a result of functionalization. Several studies indicate that this can make the particle variants more or less interactive with different cell types [ 15 , 16 , 34 ]. However, this may not appear to have been the case in this study, as there was no change in zeta potential with any MWCNT variant tested.…”

Review-Influence of Nanomaterials on Cellular Stress, and Cellular Behavior

“…The degree of multiwalled carbon nanotubes uptake with smaller length (300 nm) was higher than that of multiwalled carbon nanotubes with larger length (700nm). Even the translocation rates were different in the cell-type studied [48].…”

Advanced Functional Nanomaterials for Theranostics

“…[298] Besides in vivo applications, CNTs have been used for high resolution mapping activities of single cells. [299, 300] In 2014, Fakhri et al observed a new intermediate mode of transport with the kinesin-1 motor proteins combined with SWNTs. [301] …”