Applying Luminescent Nanoparticles in Biological Research of Nano- and Microplastics

Speaker: Prof. dr hab. Tomasz Grzyb

Faculty of Chemistry, AMU Poznan, POLAND

Abstract:  Nano- and microplastics are among the most intensively studied environmental hazards today. Recent scientific findings have revealed a world contaminated at multiple levels by residues from plastic degradation. These particles have been detected in environments ranging from the oceans’ depths to Antarctica’s glaciers. However, the field of monitoring nano- and microplastic transmission is still developing and requires more research. Many established analytical techniques fail to accurately determine how these particles form and migrate within the natural environment.One promising method for visualizing nano- and microplastics in plants and invertebrates is the use of labeled particles with luminescent dyes. Detecting their luminescent signals makes it possible to confirm the presence of nano- and microplastics in biological systems under investigation. Unfortunately, autofluorescence from biological materials often interferes with accurately detecting such labeled particles, especially when tagged with organic dyes. This limitation arises because the excitation wavelengths required for organic dyes are frequently absorbed by compounds naturally present in biological samples.A highly effective solution to this challenge is the application of luminescent nanoparticles, such as upconversion nanoparticles (UCNPs), e.g., NaYF4:Yb3+/Er3+@NaYF4 type. These particles can be excited in the near-infrared region (975 nm), where biological materials exhibit lower absorption than in the UV-VIS range. This enables the visualization of nano- and microplastics containing UCNPs in biological samples without interference from autofluorescence.Another promising approach for tracking the uptake of nano- and microplastics by terrestrial plants or aquatic organisms, such as Daphnia magna, involves using polymers containing nanoparticles showing persistent luminescence. These materials emit light for several seconds after the cessation of excitation, allowing the use of fluorescence microscopy to detect whether the studied organism has absorbed plastic particles without activating autofluorescence. Nanoparticles like ZnAl2O4:Cr3+ (ZGO) are particularly well-suited for this purpose due to their emission within the first biological window, which is crucial for studying biological materials.In this study, UCNPs- and ZGO-labeled polystyrene (PS) and polyethylene terephthalate (PET) nano- and microplastics were employed to visualize their uptake by selected plants (wheat, Triticum aestivum) and simple aquatic organisms, including the cladoceran Daphnia magna and Daphnia longispina. The materials were characterized in terms of their structural, morphological, and spectroscopic properties. Imaging was conducted using a modified Nikon ECLIPSE Ti2 Inverted Microscope and an Upcon® plate reader. The findings demonstrate the feasibility of visualizing luminescently labeled nano- and microplastics, thereby broadening the scope of laboratory research on this globally significant issue.

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