Accumulation Kinetics and Gut Microenvironment Responses to Environmentally Relevant Doses of Micro/Nanoplastics by Zooplankton Daphnia Magna

Abstract

Microplastics are emerging pollutants that have been widely reported in aquatic ecosystems. Based on the analysis of environmentally relevant concentrations of microplastics in global freshwater systems, herein, we employed aggregated-induced emission (AIE) microplastic fluorogens and imaged and quantified the bioaccumulation of differentially charged micro-(20 μm)/ nano-(200 nm) plastics (MNPs) in zooplankton Daphnia magna. We found that all particles of different sizes and charges were readily ingested, especially larger-sized and positively charged MNPs, with over 50% of the ingested particles accumulating in the gut. Bioaccumulation of MNPs reached 50% of steady-state condition within 1 h. The presence of algae inhibited the ingestion and depuration of MNPs. To further demonstrate the effects of such accumulation on gut health, we further applied the AIE probes for visualizing the pH and esterase in the digestive tract, as well as the gut inflammation. An accumulation of MNPs in D. magna significantly and rapidly induced the acidification of gut pH while inducing esterase activity. The NPs apparently induced gut inflammation in contrast to the MPs, demonstrating the size-dependent effects on oxidative stress. Our results highlighted that MNP exposure at environmentally relevant concentrations perturbed the microenvironments of zooplankton guts, which may significantly affect their digestion and assimilation of food materials as well as contaminant uptake.

Near-Infrared-II In Vivo Visualization and Quantitative Tracking of Micro/Nanoplastics in Fish

“…The DLS results confirmed the stability of the exposure system (Figure G). This was similar to previous results of the stability of AIEgens-containing PS particles, , showing that NIR-AIE-MNPs overcome the fluorescent quenching and photobleaching of fluorescent plastics dyed with organic dyes , and are a stable MNPs model.…”

“…For in vivo imaging of microplastics and nanoplastics (MNPs) in fish, the near-infrared (NIR) aggregation-induced emission fluorogen (AIEgen)-containing microplastics (NIR-AIE-MPs) and nanoplastics (NIR-AIE-NPs) were synthesized based on the NIR-AIE technique. , AIEgen-containing polymer-based MNPs were produced by batch emulsion polymerization using styrene. The polymer particle size was determined by the mass of the emulsifier sodium dodecyl benzenesulfonate (SDBS).…”

“…The exposure concentrations were 100 μg/L (L-MPs) and 1000 μg/L (H-MPs) for NIR-AIE-MPs, and 100 μg/L (L-NPs) and 1000 μg/L (H-NPs) for NIR-AIE-NPs, respectively. The exposure concentrations were chosen to correspond to low ambient concentrations and high ambient concentrations of microplastics in freshwater environment. , Each treatment contained 4 biological replicates. To minimize the drop in the nominal concentration of MNPs, the exposure solution was renewed every day, and the MNPs concentrations in the solution were monitored every day.…”

“…Recently, a class of materials with aggregation-induced emission (AIE) characteristics that generate strong and stable fluorescence after aggregation has made them stand out in the field of detection of MNPs. AIE fluorogen-containing MNPs particles have unparalleled photostability and fluorescence intensity and have made significant progress in studying algae and Daphnia . , However, these earlier AIEs were still limited to fluorescence imaging at visible wavelengths and inherent limitations of the imaging instruments mentioned above. Promisingly, near-infrared (NIR) imaging is a rising biomedical imaging modality for preclinical animal research and clinical diagnostics and interventions, especially in the second near-infrared (NIR-II) window (1000–1700 nm). , It solves many problems of fluorescence imaging at visible wavelengths, such as autofluorescence, light absorption, photon scattering and low tissue penetration depths. , In principle, combining near-infrared fluorogen and plastic particles to synthesize MNPs models would provide an unparalleled opportunity to study the uptake, depuration, and distributions of MNPs in various organisms.…”

Mechanistic Understanding toward the Maternal Transfer of Nanoplastics in Daphnia magna

“…Nanoplastics with smaller sizes, stronger surface reactivity, and higher mobility could result in higher environmental risk than microplastics . For example, nanoplastics exhibited a higher toxicity to aquatic organisms (such as algae, zooplankton, fish, and bivalves) than microplastics. However, nanoplastics have not attracted as much attention as microplastics, and a better understanding of their ecotoxicological risks is certainly warranted …”