Abstract
Along with the rapidly increasing applications of nitrogen-doped graphene quantum dots (N-GQDs) in the field of biomedicine, the exposure of N-GQDs undoubtedly pose a risk to the health of human beings, especially in the nervous system. In view of the lack of data from in vivo studies, this study used the nematode Caenorhabditis elegans (C. elegans), which has become a valuable animal model in nanotoxicological studies due to its multiple advantages, to undertake a bio-safety assessment of N-GQDs in the nervous system with the assistance of a deep learning model. The findings suggested that accumulated N-GQDs in the nematodes’ bodies damaged their normal behavior in a dose- and time-dependent manner, and the impairments of the nervous system were obviously severe when the exposure dosages were above 100 μg/mL. When assessing the morphological changes of neurons caused by N-GQDs, a quantitative image-based analysis based on a deep neural network algorithm (YOLACT) was used because traditional image-based analysis is labor-intensive and limited to qualitative evaluation. The quantitative results indicated that N-GQDs damaged dopaminergic and glutamatergic neurons, which are involved in the neurotoxic effects of N-GQDs in the nematode C. elegans. This study not only suggests a fast and economic C. elegans model to undertake the risk assessment of nanomaterials in the nervous system, but also provides a valuable deep learning approach to quantitatively track subtle morphological changes of neurons at an unbiased level in a nanotoxicological study using C. elegans.
Highlights
Graphene quantum dots (GQDs) are a relatively new type of quantum dots (QDs), which have excellent properties of graphene, and novel characteristics of QDs, including quantum confinement effect and size effect
When nematodes were exposed to 200 μg/mL nitrogen-doped graphene quantum dots (N-GQDs) for 24 h, the fluorescence of N-GQDs showing blue, which is the color of spontaneous fluorescence from
N-GQDs, could be observed in the bodies, mainly accumulated in the intestinal system, while the fluorescent intensity in nematodes treated with N-GQDs at the same dose for 48 h were stronger than those for 24 h and fluorescence could be observed in the whole fluorescence of N-GQDs showing blue, which is the color of spontaneous fluorescence from N-GQDs, could be observed in the bodies, mainly accumulated in the intestinal system, while the fluorescent intensity in nematodes treated with N-GQDs at the same dose for 48 h were stronger than those for 24 h and fluorescence could be observed in the whole body, including the head (Figure 1)
Summary
Graphene quantum dots (GQDs) are a relatively new type of quantum dots (QDs), which have excellent properties of graphene, and novel characteristics of QDs, including quantum confinement effect and size effect. GQDs present significant potentials in the applications of environmental monitoring and pollutant detection due to their excellent properties, such as excellent optical properties, low toxicity, good biocompatibility and low preparation cost, among which optical properties, including strong photoluminescence (PL), fluorescent stability and tunable luminous color are key features, such they can be considered as a new class of fluorophores overcoming weaknesses of organic dyes commonly used as fluorophores but that suffer from photobleaching and do not allow long-term exposure to excitation sources [1,2]. GQDs that contains different functional groups could be useful candidates to be prepared for specific application requiring better stability and fluorescence intensity. Along with the increasing applications of N-GQDs, their exposure to the public in the environment undoubtedly pose a threat to human health. The information on the neurotoxicity of N-GQDs is rare
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