Differences in the Cytotoxic Effects of Multi-Walled Carbon Nanotubes on Two- and Three-Dimensionally Cultured Human Neural Precursor Cells and Rat Brain Slices

Carbon nanotubes (CNTs) are used in batteries, nano-electronic devices, fuel cells, and biosensors as they can be used to make these devices more biocompatible; moreover, various compounds can be attached to these CNTs. Although multi-walled carbon nanotubes (MWCNTs) have been used in biosensors for the detection of specific proteins and neurotransmitters, they are not well understood. The present study addressed the difference between the cytotoxic effects of different types of MWCNTs by testing them on two dimensional (2D) and 3D-cultivated human neural precursor cells (hNPCs). We also evaluated the apoptotic damage caused by these MWCNTs using rat brain slices. Our results confirmed that there was significant cytotoxic effect of MWCNT, as shown by the damage caused to the 2D cultured cells. However, the cell death seen in the 3D cultured cells treated with MWCNT was significantly lower than that of the 2D cultivated cells. Furthermore, the 3D cell cytotoxicity assay showed similar results after MWCNT 1/2 treatment and decreased slightly after MWCNT 3/4 treatment, except when treated with 10 ng/ml of MWCNT 3 and 1 g/ml of MWCNT 4. Western blot results using brain slices treated with MWCNTs showed that the expressions of SAPK/JNK, Caspase 3, and Caspase 8 were not significantly different compared to those in the control. In conclusion, MWCNTs had a stable effect on the 3D cultured cells or brain slices, consistent with the results seen in the in vivo system, but caused remarkable damage to the 2D cultured cells that were observed as a flat structure