# Safety and Potential Neuromodulatory Effects of Multi-Wall Carbon Nanotubes in Vertebrate and Invertebrate Animal Models In Vivo

## TL;DR

This study investigates the safety and effects of multi-wall carbon nanotubes on neurons in rats and lifespan in worms, finding them biocompatible and potentially useful for neuromodulation.

## Contribution

The study demonstrates the biocompatibility and neuromodulatory potential of multi-wall carbon nanotubes in both vertebrate and invertebrate models.

## Key findings

- Neither MWCNT sample was cytotoxic to hippocampal neurons in rats.
- Electro-conductive a-MWCNTs interacted with mitochondrial proteins TOM20 and CytC in rat olfactory bulbs.
- MWCNT-treated C. elegans showed delayed aging without affecting lifespan or reproduction.

## Abstract

Multi-Wall Carbon Nanotubes (MWCNTs) are under investigation for their use in biomedical applications, especially in neurological diseases, due to their electrochemical properties. Nevertheless, conflicting results have cast doubt on their safety. To advance their translational potential, we evaluated the cytotoxicity of two MWCNT samples in vivo in both vertebrate and invertebrate animal models. Pristine MWCNTs were, in part, used as prepared (MWCNTs), and, in part, annealed at 2400 °C (a-MWCNTs). The two samples differ in their electrochemical properties: MWCNTs are not electro-conductive, while a-MWCNTs are electro-conductive and negatively charged on their surface. We evaluated the effects of both intranasally delivered MWCNTs on several key markers of cell viability in the olfactory bulbs and hippocampus from healthy adult Wistar rats, as well as their impact on lifespan, genotoxicity, oxidative stress, and aging-related functional markers in the nematode Caenorhabditis elegans. Neither of the two MWCNT samples was cytotoxic towards neuronal cells in the hippocampus. In olfactory bulbs, only electro-conductive a-MWCNTs interacted with two positively charged mitochondrial proteins: Translocase of Outer Mitochondrial Membrane 20 (TOM20) and Cytochrome C (CytC). In C. elegans, neither type of MWCNT affected lifespan or brood size, and cytosolic ROS levels remained unchanged. Notably, treated worms exhibited a significantly delayed aging phenotype. Metallic MWCNTs are biocompatible in living organisms and possess the potential to modulate neural cells functioning in vivo.