Table 2.

Summary of Articles on CNT Cellular Internalization Mechanisms

Types of Carbon Nanotubes	Length (L)/Diameter (D)	Surface-Modified Complex	Cell Types	Mechanisms	Ref.
SWCNTs	L: >1 µm	Pluronic- F108:CNT	Macrophage cells	Phagocytosis	[156]
SWCNTs MWCNTs	30–400 nm	–	Murine macrophage RAW264.7 cells	Phagocytosis	[62]
MWCNT	L: 453.5 ± 6.2	C6-CNTPC	A549 cells	Phagocytosis	[20]
SWCNTs	L:195–630 nm	–	Murine macrophage cells	Macropinocytosis	[60]
MWCNTs	L: >300 nm	p(4VP)-MWCNTs	TT1 cells	Macropinocytosis	[7]
SWCNTs	L: <500 nm/D: 1–2 nm	AO–SWCNTs	Hela cells	Clathrin-mediated endocytosis	[157]
MWCNTs	L:10 µm/D: 60 nm	–	BEAS-2B cells, HBEpCs	Clathrin- and caveolae-mediated endocytosis	[158]
SWNTs	L: 0.05–0.2 μm/<1 μm	SWNT-DNA, SWNT- proteins	HeLa cell	Clathrin-dependent endocytosis	[159]
MWCNTs	D: ~200 nm	Oxidized -MWCNTs	Caco-2 cell	Clathrin-dependent endocytosis	[160]
CNTs	L: 250–400 nm	PEG-CNT-ABT737 nanodrug	A549 non-small cell lung cancer cells	Clathrin-mediated endocytosis	[87]
SWNTs	L: 100–200 nm/D: 1–3 nm	FA-SWNTs	HepG2 cells	Folate receptor mediated endocytosis	[161]
SWNTs	L:50–100 nm/D: 1–3 nm	FA- SWNTs	HepG2 cells	Folate receptor mediated endocytosis	[162]
MWCNTs	L: 3 lm to 10 lm/D: 50 nm – 300 nm	–	Human neonatal epidermal keratinocytes (HEK)	Lectin receptor mediated endocytic pathway	[163]
SWCNTs	L: 50–200 nm/D: 1–3 nm	FA-SWCNTs	HepG2 cells	Passive diffusion for 50 nm or less SWNTs Clathrin-mediated endocytosis for 100–200 nm SWNTs	[164]
MWCNTs	D: 20–30 nm	FITC- MWCNTs	Plant cells	Passive diffusion	[165]

Abbreviations: HBEpCs, human bronchial epithelial cells; FA, folate acid; C6-CNTPC, coumarin-6 loaded TPGS conjugated MWCNT.