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Upconverting vs. fluorescent labels for visualizing distribution and uptake of nanoplastics: a Daphnia magna case study
Summary
Scientists studying how tiny plastic particles (nanoplastics) get absorbed by living creatures have struggled to actually "see" these particles inside body tissue, because normal glow-in-the-dark tracking dyes get lost in the body's natural glow. This study created a new type of glowing tag that only lights up under special infrared light, allowing researchers to clearly track nanoplastics moving through a small water organism's gut for the first time. This matters because better tools to see where nanoplastics travel in living bodies could eventually help scientists understand how these particles might affect human health too, since we're exposed to the same types of plastics through food
Micro- and nanoplastics (MNPLs) are pervasive environmental contaminants, raising concerns for ecosystems and human health. Nanoplastics (NPLs), in particular, present unique analytical challenges due to their minute size, which makes their detection and study in complex biological systems difficult. Consequently, toxicological studies frequently use commercially available fluorescent polystyrene (PS) particles as model NPLs. These models, however, mainly have two drawbacks: limited environmental relevance and inadequate visualization in biological tissues, largely due to overlapping tissue autofluorescence. In this study, we address these issues by preparing surfactant-free model NPLs (UC-PS) labeled with Yb3+,Er3+-doped upconverting nanoparticles (UCNPs) that convert near-infrared excitation to visible emission. UC-PS were compared with a commercial NPL labeled with a fluorescent dye (fluo-PS). Both types consisted of spherical particles of ~100 nm in diameter, but exhibited distinct luminescent properties, as shown by spectroscopy and fluorescence microscopy. UC-PS and fluo-PS at concentrations of 0-100 µg/mL did not affect Daphnia magna’s growth rate after 72-h exposure. Importantly, unlike fluo-PS, UC-PS was clearly visualized within Daphnia magna’s intestine despite strong tissue autofluorescence. This work demonstrates the advantages of UCNP-labeled NPL models over conventional fluorescent NPLs and recommends their use for accurate visualization of MNPLs uptake in aquatic organisms.