Influence of Silver Fiber Morphology on the Dose–Response Relationship and Enrichment in Daphnia magna Studied by Elemental Imaging with LA-ICP-TOF-MS

This study aims to
enhance the understanding of the environmental
risks associated with nanomaterials, particularly nanofibers. Previous
research suggested that silver fibers exhibit higher toxicity (EC50/48h 1.6–8.5 μg/L) compared to spherical silver
particles (EC50/48h 43 μg/L). To investigate the
hypothesis that toxicity is influenced by the morphology and size
of nanomaterials, various silver nanofibers with different dimensions
(length and diameter) were selected. The study assessed their toxicity
toward Daphnia magna using the 48 h
immobilization assay. The EC50 values for the different
fibers ranged from 122 to 614 μg/L. Subsequently, the study
quantified the uptake and distribution of two representative nanofibers
in D. magna neonates by employing digestion
and imaging mass spectrometry in the form of laser-ablation-ICP-MS.
A novel sample preparation method was utilized, allowing the analysis
of whole, intact daphnids, which facilitated the localization of silver
material and prevented artifacts. The results revealed that, despite
the similar ecotoxicity of the silver fibers, the amount of silver
associated with the neonates differed by a factor of 2–3. However,
both types of nanofibers were primarily found in the gut of the organisms.
In conclusion, the findings of this study do not support the expectation
that the morphology or size of silver materials affect their toxicity
to D. magna.

本研究旨在加深对纳米材料（nanomaterials），尤其是纳米纤维（nanofibers）相关环境风险的认知。先前研究表明，与球形银颗粒相比，银纳米纤维的毒性更高：银纳米纤维的48小时半数效应浓度（EC50/48h）为1.6~8.5 μg/L，而球形银颗粒的EC50/48h为43 μg/L。为验证“纳米材料的形态与尺寸会影响其毒性”这一假说，本研究选取了不同维度（长度与直径）的多款银纳米纤维。本研究采用48小时静止急性毒性试验法，评估了这些银纳米纤维对大型溞（Daphnia magna）的毒性，不同银纳米纤维的EC50值介于122~614 μg/L之间。随后，本研究通过消解及激光剥蚀-电感耦合等离子体质谱（laser-ablation-ICP-MS）成像质谱技术，定量分析了两种代表性纳米纤维在大型溞幼体体内的摄取与分布情况。本研究采用了一种新型样品前处理方法，可对完整无损的大型溞个体进行分析，这不仅便于定位银基材料，还能避免实验伪影的产生。研究结果显示，尽管各银纳米纤维的生态毒性相近，但大型溞幼体所富集的银含量差异可达2~3倍。不过，两种纳米纤维均主要分布在受试生物的肠道内。综上，本研究结果并不支持“银材料的形态或尺寸会影响其对大型溞的毒性”这一推测。