# Luminous Upconverted Nanoparticles as High-Sensitivity Optical Probes for Visualizing Nano- and Microplastics in Caenorhabditis elegans

## TL;DR

This study introduces a new type of nanoparticle probe that improves the detection of microplastics and nanoplastics in nematodes, offering insights into their distribution and toxicity.

## Contribution

The novel use of luminous upconverted nanoparticles enables high-sensitivity and non-invasive visualization of plastic particles in living organisms.

## Key findings

- Upconverted nanoparticles effectively distinguish size-dependent plastic distribution in C. elegans.
- Nanoplastics penetrate intestinal walls and enter systemic circulation, showing higher bioavailability than microplastics.
- The probes provide a sensitive and non-invasive method for tracking pollutant interactions in biological systems.

## Abstract

With the increasing prevalence of plastic pollution, understanding its impact on soil nematodes is crucial for environmental sustainability and food security. Traditional fluorescence-based probes have the limitations of high background noise and interference from autofluorescence. In this study, the luminous upconverted NaYF4:Yb3+/Er3+ nanoparticles acted as high-sensitivity probes for real-time visualization of ingestion and biodistribution of polystyrene microplastics (PS-MPs) and nanoplastics (PS-NPs) in Caenorhabditis elegans. The novel probes enabled efficient near-infrared-to-visible light conversion. This approach improved the precision of nano- and microplastic detection in biological tissues. Microscopic imaging revealed that the probes effectively distinguished size-dependent plastic distribution patterns, with microplastics remaining in the digestive tract, whereas nanoparticles penetrated intestinal walls and entered systemic circulation. Quantitative fluorescence analysis confirmed that PS-NPs exhibited higher bioavailability and deeper tissue penetration, providing crucial insights into plastic behavior at the organismal level. The different toxicities of PS-NPs and PS-MPs were further confirmed by measurement of the locomotor impairments and the physiological disruptions. These findings emphasize the broader applications of upconverted nanoparticles as advanced bio-imaging probes, offering a sensitive and non-invasive tool for tracking pollutant interactions in environmental and biological systems.