Reversible Accumulation of PEGylated Single-Walled Carbon Nanotubes in the Mammalian Nucleus

Abstract

Carbon nanotubes (CNTs) have been shown to cross cell membranes and can mediate the internalization of macromolecules. These characteristics have constituted CNTs as an exciting new tool for drug delivery and biological sensing. While CNTs exhibit great potential in biomedical and pharmaceutical applications, neither the cell penetration mechanism of CNTs nor the intracellular fate of the internalized CNTs are fully understood. In this study, time-lapse fluorescence microscopy was used to investigate the intracellular distribution of FITC labeled PEGylated single-walled CNTs (FITC-PEG-SWCNTs) in living cells and shown that PEGylated SWCNTs entered the nucleus of several mammalian cell lines in an energy-dependent process. The presence of FITC-PEG-SWCNTs in the cell nucleus did not cause discernible changes in the nuclear organization and had no effect on the growth kinetics and cell cycle distribution for up to 5 days. Remarkably, upon removal of the FITC-PEG-SWCNTs from the culture medium, the internalized FITC-PEG-SWCNTs rapidly moved out of the nucleus and were released from the cells. Thus, the intracellular PEGylated SWCNTs were highly dynamic and the cell penetration of PEGylated SWCNTs appeared as bidirectional. These observations suggest SWCNTs may be used as an ideal nanovector in biomedical and pharmaceutical applications.

Insights into the biomedical effects of carboxylated single-wall carbon nanotubes on telomerase and telomeres

“…Moreover, it has also been demonstrated that the nature of the functional group on the CNT surface does not determine whether functionalized CNTs are internalized or not 25 . To further determine the localization of SWNTs within cells, we modified the SWNTs with PEG 1500N and labelled with fluorescein isothocyanate (FITC) as described previously 27 (Supplementary Methods and Supplementary Figs S5-S7). As shown in Fig.…”

“…Carboxyl-modified SWNTs were further used to attach aminopolymers polyethylene glycol (PEG 1500N ) to the nanotubes via amide linkages 27 . The PEG-SWNTs were then labelled with fluorescent dye FITC to facilitate biological imaging.…”

Triple functionalisation of single-walled carbon nanotubes with doxorubicin, a monoclonal antibody, and a fluorescent marker for targeted cancer therapy

“…Furthermore, Cheng et al recently showed that FITC-PEG-SWCNTs accumulated in the nuclei of several mammalian cell lines [29]. This indicates that the ability of CNTs to cross cellular barriers, such as the nuclear envelope, is dependent on the type of functionalisation.…”

Development and evaluation of pH-responsive single-walled carbon nanotube-doxorubicin complexes in cancer cells

“…Of note, SWNTs themselves at the concentrations used for SWNT-HBA-DOX and SWNT-DOX formulations did not affect the survival of HepG2 cells after exposure to PEGylated SWNTs for up to 72 hours (data not shown), which is similar to previous reports. 9,29 The cytotoxicity of two-drug formulations against HeLa cells was also evaluated using MTT assay (Supplementary Figure 2). The SWNT-HBA-DOX also showed higher cytotoxicity to HeLa cells than that of SWNT-DOX conjugate under the same experimental conditions.…”

“…7 Functionalized water-soluble CNTs (f-CNTs) were suggested to be compatible and nontoxic at the cellular level. 8,9 Furthermore, the one-dimensional structure of CNTs may have advantages over existing delivery vectors, including an enhanced capacity to penetrate cellular membranes and high surface area to provide sites to carry multiple moieties at high density. [10][11][12] These properties made f-CNTs a promising candidate for drug delivery system.…”