*Article* **Dietary Transfer of Zinc Oxide Nanoparticles Induces Locomotive Defects Associated with GABAergic Motor Neuron Damage in** *Caenorhabditis elegans*

**Chun Ming How 1 and Chi-Wei Huang 2,\***


**Abstract:** The widespread use of zinc oxide nanoparticles (ZnO-NPs) and their release into the environment have raised concerns about the potential toxicity caused by dietary transfer. However, the toxic effects and the mechanisms of dietary transfer of ZnO-NPs have rarely been investigated. We employed the bacteria-feeding nematode *Caenorhabditis elegans* as the model organism to investigate the neurotoxicity induced by exposure to ZnO-NPs via trophic transfer. Our results showed that ZnO-NPs accumulated in the intestine of *C. elegans* and also in *Escherichia coli* OP50 that they ingested. Additionally, impairment of locomotive behaviors, including decreased body bending and head thrashing frequencies, were observed in *C. elegans* that were fed *E. coli* pre-treated with ZnO-NPs, which might have occurred because of damage to the D-type GABAergic motor neurons. However, these toxic effects were not apparent in *C. elegans* that were fed *E. coli* pre-treated with zinc chloride (ZnCl2). Therefore, ZnO-NPs particulates, rather than released Zn ions, damage the D-type GABAergic motor neurons and adversely affect the locomotive behaviors of *C. elegans* via dietary transfer.

**Keywords:** ZnO nanoparticles; trophic transfer; neurotoxicity; GABAergic motor neuron; neuron damage
