Effects of carbon nanotubes on primary neurons and glial cells

Carbon nanotubes (CNTs) are among the most promising novel nanomaterials and their unique chemical and physical properties suggest an enormous potential for many areas of research and applications. As a consequence, the production of CNT-based material and thus the occupational and public exposure to CNTs will increase steadily. Although there is evidence that nanoparticles (NPs) can enter the nervous system via the blood stream, olfactory nerves or sensory nerves in the skin, there is still only little knowledge about possible toxic effects of CNTs on cells of the nervous system. The goal of the present study was to analyse the influences of single-walled CNTs (SWCNTs) with different degrees of agglomeration on primary cultures derived from chicken embryonic spinal cord (SPC) or dorsal root ganglia (DRG). As measured by the Hoechst assay treatment of mixed neuro-glial cultures with up to 30mug/mL SWCNTs significantly decreased the overall DNA content. This effect was more pronounced if cells were exposed to highly agglomerated SWCNTs as compared to better dispersed SWCNT-bundles. Using a cell-based ELISA we found that SWCNTs reduce the amount of glial cells in both peripheral nervous system (PNS) and central nervous system (CNS) derived cultures. Neurons were only affected in DRG derived cultures, where SWCNT treatment resulted in a decreased number of sensory neurons, as measured by ELISA. Additionally, whole-cell patch recordings revealed a diminished inward conductivity and a more positive resting membrane potential of SWCNT treated DRG derived neurons compared to control samples. The SWCNT suspensions used in this study induced acute toxic effects in primary cultures from both, the central and peripheral nervous system of chicken embryos. The level of toxicity is at least partially dependent on the agglomeration state of the tubes. Thus if SWCNTs can enter the nervous system at sufficiently high concentrations, it is likely that adverse effects on glial cells and neurons might occur.