Toxicity Evaluation of One-Dimensional Nanoparticles Using Caenorhabditis elegans: A Comparative Study of Halloysite Nanotubes and Chitin Nanocrystals

In this study, the toxicity of two one-dimensional (1D) nanoparticles, halloysite nanotubes (HNTs) and chitin whiskers (ChNCs), was investigated in detail. Both in vitro and in vivo models were applied to evaluate the toxicity by cell viability staining, apoptosis assay, and reactive oxygen species generation. Particularly, the toxicity of HNTs and ChNCs was compared using an in vivo model Caenorhabditis elegans; their toxicity was assessed using the in vitro models, mouse bone marrow mesenchymal stem cells (mBMSCs) and rat osteosarcoma cells (UMR-106). In vitro, both HNTs and ChNCs exhibited low toxicity at concentrations lower than 50 μg/mL, but HNTs showed higher toxicity than ChNCs at higher concentrations such as 200 μg/mL. Cell viabilities of mBMSCs and UMR-106 were 73.4 and 77.1% at the HNT concentration of 200 μg/mL, while these were 96.2 and 99.8% at the ChNC concentration of 200 μg/mL, respectively. In vivo, HNTs exhibited a side effect on the C. elegans reproduction but did not influence the lifespan and other phenotypes, which suggested that HNTs had no long-term toxicity effects. While ChNCs did not result in obvious alterations in the phenotype of worms below the concentration of 2.5 mg/mL, the brood size of C. elegans decreased at ChNC concentrations of 10 and 50 mg/mL. Moreover, ChNCs had the side effect on the development of C. elegans at the high level. However, ChNC exposure at the concentrations of 10 and 50 mg/mL induced the longer fast movement periods and extended lifespan of C. elegans. It demonstrated that both HNTs and ChNCs had good biocompatibility below the concentration of 2.5 mg/mL. The toxicity studies of these two 1D nanoparticles contributed to their great significance for various biomedical applications.