On the lifespan of Enchytraeus crypticus - impact of iron (nanomaterial and salt) on aging

Abstract

Iron oxide nanomaterials (Fe₃O₄ NMs) have important biomedical and environmental applications, e.g. drug delivery, chemotherapy, magnetic resonance imaging contrast agents, etc. However, the environmental risks of such Fe₃O₄ are not fully assessed, particularly for soil living invertebrates, which are among the ones in the first line of exposure. Research has showed that longer-term exposure time is required to assess hazards of NMs, not predicted when based on shorter time and are therefore recommended. Thus, in the present study the effects of Fe₃O₄ NMs and FeCl₃ were assessed in the terrestrial environment, using the soil model species Enchytraeus crypticus (Oligochaeta), throughout its entire lifespan (202 days). Two animals' density were used: 1 (D1) and 40 (D40) animals per replicate, in LUFA 2.2 soil. The endpoints were survival and reproduction monitored over-time, up to 202 days. Results showed that density clearly affected the toxicity response, with higher toxicity and lower lifespan in D1 compared to D40. Overall, FeCl₃ was more toxic than Fe₃O₄ NM in terms of reproduction, however, adult animals can be at higher (long-term) risk when exposed to Fe₃O₄ NM. Differences might be linked to slower Fe kinetics for the Fe₃O₄ NMs, i.e., slower Fe dissolution and release of ions.

Keywords: aging; long-term; magnetite; nanobiomaterial; survival.

Figure 1

Results from lifespan test with Enchytraeus crypticus when exposed to FeCl₃ and Fe₃O₄ NM, in LUFA 2.2 soil, at the density of 1 adult organism per replicate, in terms of survival (top row: values expressed as cumulative number) and reproductive output (down row: values are expressed as average ± standard error). Lines represent the models fit to data. *: p<0.05 (Dunnett’s), grey asterisk: 200 mg Fe/kg soil, black asterisk: 400 mg Fe/kg soil.

Figure 2

Results from lifespan test with Enchytraeus crypticus when exposed to FeCl₃ and Fe₃O₄ NM, in LUFA 2.2 soil, at the density of 40 adult organism per replicate, in terms of survival (top row) and reproductive output per surviving adult (down row). All the values are expressed as average ± standard error. Lines represent the models fit to data. *: p<0.05 (Dunnett’s), grey asterisk: 200 mg Fe/kg soil, black asterisk: 400 mg Fe/kg soil.