Length effects on the dynamic process of cellular uptake and exocytosis of single-walled carbon nanotubes in murine macrophage cells

Abstract

Cellular uptake and exocytosis of SWCNTs are fundamental processes determining their intracellular concentration and effects. Despite the great potential of acid-oxidized SWCNTs in biomedical field, understanding of the influencing factors on these processes needs to be deepened. Here, we quantitatively investigated uptake and exocytosis of SWCNTs in three lengths-630 (±171) nm (L-SWCNTs), 390 (±50) nm (M-SWCNTs), and 195 (±63) nm (S-MWCNTs) in macrophages. The results showed that the cellular accumulation of SWCNTs was a length-independent process and non-monotonic in time, with the most SWCNTs (3950 fg/cell) accumulated at 8 h and then intracellular SWCNTs dropped obviously with time. The uptake rate of SWCNTs decreased with increasing concentration, suggesting that intracellular SWCNTs accumulation is a saturable process. After refreshing culture medium, we found increasing SWCNTs in supernatant and decreasing intracellular SWCNTs over time, confirming the exocytosis occurred. Selective inhibition of endocytosis pathways showed that the internalization of SWCNTs involves several pathways, in the order of macropinocytosis> caveolae-mediated endocytosis> clathrin-dependent endocytosis. Intriguingly, clathrin-mediated endocytosis is relatively important for internalizing shorter SWCNTs. The dynamic processes of SWCNTs uptake and exocytosis and the mechanisms revealed by this study may render a better understanding on SWCNT toxicity and facilitate the design of CNT products with mitigated toxicity and desired functions.

Graphene Nanomaterials: Synthesis, Biocompatibility, and Cytotoxicity

“…However, cell penetrating nanotubes can also be harmful to biological cells because they induce appreciable toxicity and apoptosis [ 19 , 20 , 21 ]. Electron microscopic observations have revealed the presence of nanotubes in the cytoplasm, thereby inducing oxidative stress, reducing metabolic activity, and causing eventual cell death [ 22 , 23 ]. In this respect, the application of carbon nanotubes in clinical field is hampered by their biodistribution, size, and shape [ 19 , 20 , 21 ].…”

Transcriptomic and morphological response of SIM-A9 mouse microglia to carbon nanotube neuro-sensors

“…S2B). Previous studies of SWCNT internalization in mammalian cells have determined the internalization mechanism to be predominantly energy-dependent clathrin-mediated endocytosis (30,31). No correlation was found between degree of internalization and cell morphology at 2 h post exposure to SWCNTs (fig.…”

The Fate of SWCNTs in Mouse Peritoneal Macrophages: Exocytosis, Biodegradation, and Sustainable Retention

“…First, peritoneal macrophages were exposed with a low dose (10 µg/mL) SWCNTs. After incubation, SWCNTs uptake and preservation in primary macrophages was determined by SDS-PAGE according to the method described previously (Wang et al, 2009;Cui et al, 2017). Briefly, macrophages were washed three times with D-PBS to remove extra SWCNTs.…”

“…The exocytosis mechanism of SWCNTs mediated through the activation of P2×7 receptor, an ATP-gated membrane receptor in macrophages Raw264.7 (Cui et al, 2016). The intracellular SWCNTs in RAW264.7 showed a rapid excretion over time of exposure, short SWCNTs (195 nm) were expulsed faster than long (630 nm) and middle (390) length SWCNTs (Cui et al, 2017). In primary macrophages, the question that whether SWCNTs exocytosis is involved in the final fate of SWCNTs after CNTs exposure has not been explored.…”