Visualizing Nanoplastic and Microplastic Biodistribution in C. elegans Using Upconversion Probes

Maryam B, Wang Y, Li X, Asim M, Qayyum H, Zhang P, Liu X. Luminous Upconverted Nanoparticles as High-Sensitivity Optical Probes for Visualizing Nano- and Microplastics in Caenorhabditis elegans. Sensors 2025;25(11):3306. doi: 10.3390/s25113306.

Background: Plastic pollution has become a major global concern, with microplastics (MPs) and nanoplastics (NPs) posing particular risks to soil organisms. Conventional fluorescence imaging methods used to study plastic ingestion suffer from high background noise and low sensitivity. To overcome these limitations, this study developed luminous upconverted nanoparticles (UCNPs) as high-sensitivity optical probes to visualize the ingestion and biodistribution of polystyrene nano- and microplastics in Caenorhabditis elegans, a model organism for environmental toxicity assessment.

Hypothesis: This study hypothesized that NaYF₄:Yb³⁺/Er³⁺ upconverted nanoparticles can serve as efficient and non-invasive probes to detect, visualize and differentiate size-dependent ingestion and physiological effects of polystyrene nanoplastics and microplastics in C. elegans.

Methods: The authors synthesized PS@LUC-nano and PS@LUC-micro particles labeled with NaYF₄:Yb³⁺/Er³⁺ UCNPs and exposed C. elegans to 0.1–100 µg/L concentrations. Worm locomotion, growth and reproduction were analyzed using WormLab. Fluorescence visualization was performed under a 980 nm near-infrared excitation to minimize autofluorescence interference.

Results: Microscopy confirmed strong luminescence signals in worms exposed to higher doses, with microplastics localized in the intestine and nanoplastics penetrating intestinal walls and circulating systemically. PS-NP exposure caused greater reductions in head thrashes (−40%) and body bends (−44%) than PS-MPs. Growth and reproduction decreased by 49% and 41%, respectively, for PS-NPs, compared with 34% and 31% for PS-MPs, showing dose- and size-dependent toxicity.

Conclusions: Upconverted nanoparticles provided precise visualization of plastic ingestion and revealed that nanoplastics exhibit greater bioavailability and systemic toxicity than microplastics. This method offers a sensitive, non-invasive approach for tracking pollutant interactions and assessing nanoplastic risks in biological systems.