Abstract
BackgroundCarbon nanotubes are increasingly being tested for use in cellular applications. Determining the mode of entry is essential to control and regulate specific interactions with cells, to understand toxicological effects of nanotubes, and to develop nanotube-based cellular technologies. We investigated cellular uptake of Pluronic copolymer-stabilized, purified ~145 nm long single wall carbon nanotubes (SWCNTs) through a series of complementary cellular, cell-mimetic, and in vitro model membrane experiments.ResultsSWCNTs localized within fluorescently labeled endosomes, and confocal Raman spectroscopy showed a dramatic reduction in SWCNT uptake into cells at 4°C compared with 37°C. These data suggest energy-dependent endocytosis, as shown previously. We also examined the possibility for non-specific physical penetration of SWCNTs through the plasma membrane. Electrochemical impedance spectroscopy and Langmuir monolayer film balance measurements showed that Pluronic-stabilized SWCNTs associated with membranes but did not possess sufficient insertion energy to penetrate through the membrane. SWCNTs associated with vesicles made from plasma membranes but did not rupture the vesicles.ConclusionsThese measurements, combined, demonstrate that Pluronic-stabilized SWCNTs only enter cells via energy-dependent endocytosis, and association of SWCNTs to membrane likely increases uptake.
Highlights
Carbon nanotubes are increasingly being tested for use in cellular applications
single wall carbon nanotube (SWCNT) added to the extracellular media localize within cells We confocally imaged the Raman spectra inside HeLa cells to visualize the sub-cellular localization of Pluronic F-127 (PF-127) stabilized SWCNTs
Lipid bilayer association of SWCNTs To determine if SWCNTs perforate bilayers, and by a similar mechanism might penetrate the plasma membrane of the cell, we examined SWCNT interactions with synthetic lipid bilayers
Summary
Carbon nanotubes are increasingly being tested for use in cellular applications. Determining the mode of entry is essential to control and regulate specific interactions with cells, to understand toxicological effects of nanotubes, and to develop nanotube-based cellular technologies. We investigated cellular uptake of Pluronic copolymer-stabilized, purified ~145 nm long single wall carbon nanotubes (SWCNTs) through a series of complementary cellular, cell-mimetic, and in vitro model membrane experiments. Carbon nanotubes (CNTs) have recently been explored for potential uses in biology and medicine Their small size, high surface area, inert chemical composition, and unique physical properties have made them extensively investigated for transport of DNA[1], nucleic acids[2], drugs[3], and a variety of other potential therapeutics[4]. Theoretical and simulation studies on CNT uptake into cells provided contradictory results: some theoretical reports have suggested that CNTs may not be able to trigger endocytosis due to their small diameter and the kinetics of endosome formation[15,16]. Alteration or disruption of sub-cellular membranous structures or CNT affinity to membranes may be responsible for altering cellular uptake and architecture
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