A workflow to investigate the impacts of weathered multi-walled carbon nanotubes to the mud snail Lymnaea stagnalis

Abstract

Although the development and application of nanomaterials is a growing industry, little data is available on the ecotoxicological effects on aquatic organisms. Therefore, we set up a workflow to address the potential uptake of weathered multi-walled carbon nanotubes (wMWCNTs) by a model organism, the pulmonary mud snail Lymnaea stagnalis (L. stagnalis), which plays an important role in the food web. It represents a suitable organism for this approach because as a grazer it potentially ingests large amounts of sedimented wMWCNTs. As food source for L. stagnalis, benthic biofilm was investigated by the use of a transmission electron microscope (TEM) and a scanning electron microscope (SEM) after exposure with wMWCNTs. In addition, isotopic labeling was applied with 14C-wMWCNTs (0.1 mg/L) to quantify fate, behavior, and enrichment of 14C-wMWCNTs in benthic biofilm and in L. stagnalis. Enrichment in benthic biofilm amounted to 529.0 µg wMWCNTs/g dry weight and in L. stagnalis to 79.6 µg wMWCNTs/g dry weight. A bioconcentration factor (BCF) for L. stagnalis was calculated (3500 L/kg). We demonstrate the accumulation of wMWCNTs (10 mg/L) in the digestive tract of L. stagnalis in an effect study. Moreover, the physiological markers glycogen and triglycerides as indicators for the physiological state, as well as the RNA/DNA ratio as growth indicator, were examined. No significant differences between exposed and control animals were analyzed for glycogen and triglycerides after 24 days of exposure, but a decreasing trend is recognizable for triglycerides. In contrast, the significant reduction in the RNA/DNA ratio of L. stagnalis indicated an inhibition of growth with a following recovery after depuration. The described workflow enables a comprehensive determination of the fate and the behavior of wMWCNTs specifically and in general all kinds of CNTs in the aquatic environment and therefore contributes to a holistic risk assessment of wMWCNTs.

Impact of weathered multi-walled carbon nanotubes on the epithelial cells of the intestinal tract in the freshwater grazers Lymnaea stagnalis and Rhithrogena semicolorata

“…Finally, after 28 days of depuration, no wMWCNTs were detected in the gut or digestive glands. Thus, we show the fate of wMWCNTs entering the cells of L. stagnalis, but after a period of depuration, the snails are able to recover (see also Weise et al 2021). There might be greater risk if there is no depuration phase, and the wMWCNTs are ingested over a long period of time.…”

“…In the midgut lumen, large bundles of wMWCNTs can be found (Fig. 4a, b, see also Weise et al 2021), but no wMWCNTs could be detected in its epithelial cells. This is consistent with observations by Petersen et al (2009) who showed the presence of MWCNTs in the intestinal lumen of D. magna, The digestive epithelium with B-cells which contain many phagocytic granules of different sizes (e.g.…”

“…The applied test substance wMWCNT (Baytubes C 150 P, BTS, Leverkusen, Germany) was synthesized and purchased from Bayer MaterialScience AG 2007 and is described precisely by Politowski et al (2021aPolitowski et al ( , 2021b and Weise et al (2021).…”

Multiwalled Carbon Nanotubes Promote Bacterial Conjugative Plasmid Transfer

“…A detailed description and characterization of MWCNTs can be found in Politowski et al ( 40 , 41 ) and Weise et al ( 27 ). Agglomerates with their typical cross-link structure and single strands of MWCNTs displaying a spiral shape with some irregularities were identified ( Fig.…”

“…Further, particles without antibacterial properties, such as microplastics, are able to promote plasmid transfer due to providing novel surfaces for biofilm formation and hence donor-recipient interactions with intense cell-cell contact ( 25 ). Garacci et al ( 26 ) and Weise et al ( 27 ) demonstrated a type of network formation between graphene and MWCNTs with the extracellular polymeric substances of benthic organisms. Accordingly, it is also possible that bacteria colonize MWCNT agglomerates, which could facilitate biofilm formation or promote bacterial agglomeration ( 28 ), thus promoting horizontal gene transfer.…”