Confocal surface-enhanced Raman imaging of the intestine barrier crossing behavior of nanoplastics in Daphnia magna

Abstract

Due to their wider spread, higher concentrations, and bioavailability, nanoplastics (nPs) pose great ecological hazards both in the marine and freshwater ecosystems. To evaluate their toxicity in the model freshwater organism Daphnia magna, and how the nPs how the particles translocate from the intestine, the primary organ of accumulation, to the other body parts, is an important phenomenon. In the current effort, we addressed the phenomenon of inner organ translocation of the nPs and suggested plausible mechanism of the process with the help of a model nPS and confocal surface-enhances Raman mapping. We synthesized a polystyrene coated-nanogold ‘core-shell' particle (nPS@nAu), conjugated with a Raman reporter, 4-mercapto benzoic acid to the (4-MBA). This dual functional model nanoplastic (model nPS) fulfills the purpose of nP as well as surface-enhanced Raman scattering (SERS) nano-probe. Upon exposure, the Daphnia showed uptake of the model nPSs mainly in the intestine tract. Further exposure (beyond 4 h at model nPS concentration of 10 mg/L) exhibited inter organ migration of the model nPSs to other parts in the Daphnia body. Translocation of the model nPSs was observed with the help of multilayer stack Raman mapping of the SERS signals coming from the model nPSs.