Modulation of Apoptotic Pathways of Macrophages by Surface-Functionalized Multi-Walled Carbon Nanotubes

Abstract

Biomedical applications of carbon nanotubes (CNTs) often involve improving their hydrophilicity and dispersion in biological media by modifying them through noncovalent or covalent functionalization. However, the potential adverse effects of surface-functionalized CNTs have not been well characterized. In this study, we functionalized multi-walled CNTs (MWCNTs) via carboxylation, to produce MWCNTs-COOH, and via poly (ethylene glycol) linking, to produce MWCNTs-PEG. We used these functionalized MWCNTs to study the effect of surface functionalization on MWCNTs-induced toxicity to macrophages, and elucidate the underlying mechanisms of action. Our results revealed that MWCNTs-PEG were less cytotoxic and were associated with less apoptotic cell death of macrophages than MWCNTs-COOH. Additionally, MWCNTs-PEG induced less generation of reactive oxygen species (ROS) involving less activation of NADPH oxidase compared with MWCNTs-COOH, as evidenced by membrane translocation of p47phox and p67phox in macrophages. The less cytotoxic and apoptotic effect of MWCNTs-PEG compared with MWCNTs-COOH resulted from the lower cellular uptake of MWCNTs-PEG, which resulted in less activation of oxidative stress-responsive pathways, such as p38 mitogen-activated protein kinases (MAPK) and nuclear factor (NF)-κB. These results demonstrate that surface functionalization of CNTs may alter ROS-mediated cytotoxic and apoptotic response by modulating apoptotic signaling pathways. Our study thus provides new insights into the molecular basis for the surface properties affecting CNTs toxicity.

Anti-Cancer Cytotoxic Effects of Multiwalled Carbon Nanotubes

“…On the contrary, aggregated or poorly resuspended nanomaterials behave more like bulk material, being only phagocytized by cells of the reticulo-endothelial system. In particular, poorly functionalized CNTs aggregate into large, micrometric bundles that are phagocytized and accumulate intracellularly in macrophages, often killing these cells by the generation of reactive oxygen species that lead to oxidative stress [52,54,55,69,[78][79][80][81][82][83][89][90].…”

Polyhydroxylated fullerene attenuates oxidative stress-induced apoptosis via a fortifying Nrf2-regulated cellular antioxidant defence system

“…DCFH-DA enters the cells via passive diffusion, where it reacts with ROS, resulting in the formation of the highly fluorescent compound dichlorofluorescein (DCF). 23 Briefly, cells attached to plastic dishes were harvested by 0.25% trypsin, washed twice with cold PBS, and incubated with 10 µM DCFH-DA for 30 minutes at 37°C, and then analyzed using a flow cytometer (Beckman-Coulter Epics XL, Miami, FL, USA).…”

In Vivo Induction of Primary DNA Lesions upon Subchronic Oral Exposure to Multi-walled Carbon Nanotubes

“…They detected significant elevation in ROS level and MN frequency but primary DNA lesions (strand breaks) were not detected by the comet assay (21). The elevation of ROS level in different cells, tissues and organs upon MWCNT treatment was confirmed both in vitro (22,23) and in vivo (24,25) by several articles. In our previous in vivo (rat) studies involving urinary mutagenicity (Ames) test, sister chromatid exchange and MN analyses, SW-and MWCNT samples did not show any genotoxic effects (26).…”