Responses of Caenorhabditis elegans to various surface modifications of alumina nanoparticles

The surface modifications of nanoparticles (NPs), are well-recognized parameters that affect the toxicity, while there has no study on toxicity of Al 2 O 3 NPs with different surface modification. Therefore, for the first time, this study pays attention to evaluating the toxicity and potential mechanism of pristine Al 2 O 3 NPs (p-Al 2 O 3 ), hydrophilic (w-Al 2 O 3 ) and lipophilic (o-Al 2 O 3 ) modifications of Al 2 O 3 NPs both in vitro and in vivo . Applied concentrations of 10, 20, 40, 80,100 and 200 μg/mL for 24 h exposure on Caenorhabditis elegans ( C. elegans ), while 100 μg/mL of Al 2 O 3 NPs significantly decreased the survival rate. Using multiple toxicological endpoints, we found that o-Al 2 O 3 NPs (100 μg/mL) could induce more severe toxicity than p-Al 2 O 3 and w-Al 2 O 3 NPs. After uptake by C. elegans , o-Al 2 O 3 NPs increased the intestinal permeability, easily swallow and further destroy the intestinal membrane cells. Besides, cytotoxicity evaluation revealed that o-Al 2 O 3 NPs (100 μg/mL) are more toxic than p-Al 2 O 3 and w-Al 2 O 3 . Once inside the cell, o-Al 2 O 3 NPs could attack mitochondria and induce the over-production of reactive oxygen species (ROS), which destroy the intracellular redox balance and lead to apoptosis. Furthermore, the transcriptome sequencing and RT-qPCR data also demonstrated that the toxicity of o-Al 2 O 3 NPs is highly related to the damage of cell membrane and the imbalance of intracellular redox. Generally, our study has offered a comprehensive sight to the adverse effects of different surface modifications of Al 2 O 3 NPs on environmental organisms and the possible underlying mechanisms.