Residual metals in carbon nanotubes suppress the proliferation of neural stem cells

Abstract

Carbon nanotubes (CNTs) are used in many fields; however, little is known about the effects of CNTs on the central nervous system (CNS). In this study, we found that extracts of sonicated CNTs suppressed the proliferation of neural stem cells (NSCs). Single-walled CNTs (SWCNTs) and multiple-walled CNTs (MWCNTs) were suspended in PBS (1 mg/mL) and sonicated for 5 hr using a water bath sonicator. Supernatants from both types of CNTs suppressed NSC proliferation. The effects weakened in a dilution-ratio-dependent manner and strengthened in a sonication time-dependent manner. Metal concentrations extracted from SCNTs and MCNTs after 5-hr of sonication were determined using inductively coupled plasma mass spectrometry. Mn, Rb, Cs, Tl, and Fe were detected in the SWCNT supernatant, and Mn, Cs, W, and Tl were detected in the MWCNT supernatant. The concentration of Mn, Rb, and Fe eluted from the SWCNTs and Rb eluted from MWCNTs following sonication were sufficient to suppress NSC proliferation alone. N-acetyl cysteine (NAC) and ascorbic acid (AA) reversed the effects of Mn and Fe and restored NSC proliferation. The effects of Rb and Tl were not affected by the antioxidants. Both antioxidants largely restored the suppression of NSC proliferation induced by the SWCNT and MWCNT supernatants. These results suggest that metals extracted from CNTs via a strong vibration energy can suppress NSC proliferation through ROS production by the extracted metals.

Characterization of functionalized multiwalled carbon nanotubes and comparison of their cellular toxicity between HEK 293 cells and zebra fish in vivo.

“…Co, Fe, Ni, Mo, etc., are commonly used in the synthesis process of these CNTs and those get entrapped at the edges of the newly synthesized CNTs. These are difficult to remove and still persists in the CNT after harsh treatment of CNTs with inorganic acids [27, 28, 29]. Thus, it becomes difficult to remove these entrapped metals in case of pristine MWCNTs.…”

Phagocytosis-dependent and independent mechanisms underlie the microglial cell damage caused by carbon nanotube agglomerates

“…CNTs #1, #2, #3, #4, and #5 were suspended in PBS at 1 mg/mL and sonicated in a water-bath sonicator for 30 min as in our previous report (Shigemoto-Mogami et al, 2014b). The visual appearance of these suspensions immediately after the sonication is shown in Fig.…”

“…It has also been reported that nanoparticles themselves induce the generation of ROS and stimulate inflammatory factors in microglia in the absence of phagocytosis (Wang et al, 2011). We and other groups have reported that some CNTs cause cytotoxicity and genotoxicity (Pumera, 2007;Liu et al, 2008;Shigemoto-Mogami et al, 2014b) by ROS production via metal residues that were used as catalysts (Ding et al, 2008;Yazyev and Pasquarello, 2008;Banhart, 2009;Tyagi et al, 2011). The cytotoxicity of the CNT #1 and #2 agglomerates may have been caused via ROS production.…”

“…Furthermore, it has been shown that nanoparticles cross the blood-brain barrier (BBB) and infiltrate the brain (Sharma and Sharma, 2007). We recently determined that residual metals extracted from CNTs possibly suppress the proliferation of neural stem cells via the production of reactive oxygen species (ROS) (Shigemoto-Mogami et al, 2014b).…”

Differential Responses of Bacterial and Fungal Communities to Siderophore Supplementation in Soil Affected by Tobacco Bacterial Wilt (Ralstonia solanacearum)

“…In the natural environment, soil and crust are rich in iron, an essential element for plants and microorganisms [ 7 ]. Iron plays a vital role in the process of information transmission and physiological metabolism in cells [ 8 ].…”