High-throughput transcriptomics reveals mechanisms of nanopesticides – nanoformulation vs conventional pesticides and active ingredient – a case study with Enchytraeus crypticus

Nanoformulations are developed to offer controlled release of active ingredients (a.i.) and thus aim to keep functionality while having a smaller environmental footprint. However, the toxic effects of nanoformulations, particularly to non-target organisms, is poorly known, and even more so at the mechanistic level. The aim of the present study was to investigate the mechanisms of toxicity of atrazine when delivered as a nanoformulation of atrazine (nano_ATZ), a commercial atrazine-based formulation (Gesaprim), and the pure a.i. (ATZ). The high-throughput gene expression microarray (4 x 44K) was used to assess transcriptomics in Enchytraeus crypticus (a non-target species). Organisms were exposed, in soil, to equitoxic reproduction effect concentrations (EC10 and EC50) for 3 and 7 days. Results showed activation of both general and well-known mechanisms of detoxification (e.g. cytochrome P450 and GST) for all the atrazine forms, and it also showed effects on energy metabolism pathways. Common to all, was also the effect on arachidonic acid metabolism, which was linked to reproductive effects. Uniquely activated by nano_ATZ were changes in the processes cell death and immune system response, which was associated to increased cellular ROS generation. Further, effects of nano_ATZ on transcripts linked to secretion, translocation and vesicle trafficking, suggested that differentiated - nano-specific - uptake and/or cellular transport was taking place. In summary, this study on the transcriptomics of a nanoformulation, the first so far, suggested differentiated mechanisms of toxicity among the nanoformulation, the a.i. and the conventional pesticides, shedding light onto the issues of sustainability and safer-by-design for the agrochemical industry. Gene expression profile of Enchytraeus crypticus was analysed after 3 and 7 days of exposure to atrazine based pesticides: nanoformulation of atrazine (nano_ATZ), a commercial atrazine-based formulation (Gesaprim), and the pure a.i. (ATZ), in two different concentrations that reduce reproduction in 10 and 50% (EC10 and EC50). The exposure was performed in LUFA 2.2 soil. Three biological replicates per test treatment and controls (control: un-spiked soil for nano_ATZ and Gesaprim; and control-acetone for ATZ treatments) were used.