Earth and environmental sciences

At Diamond Light Source, we are committed to deliver world class science and enhance our research activities that benefits society and the economy. A recent project conducted by researchers at the UK’s national synchrotron facility on its Hard X-ray Nanoprobe (I14 beamline), looked at how microplastics waste may interact with zinc oxide (ZnO) nanomaterials in both freshwater and seawater scenarios. Their work published in Global Challenges and echoed in Labmate, revealed worrying environmental implications for aquatic organisms in the food chain.

In recent decades, there has been a dramatic increase in the manufacture of engineered nanomaterials (tiny, tiny particles about 1000 times thinner than a human hair), which has inevitably led to their environmental release. Similarly, Zinc oxide (ZnO) is among the more abundant nanomaterials fabricated due to its advantageous use in electronics, semiconducting, and for antibacterial purposes. At the same time, plastic waste has become ubiquitous and may break down into smaller pieces called microplastics. These also are tiny, but ~100 times bigger than the nanomaterials. Because both these components are getting disposed more often, Dr Miguel Gomez-Gonzalez et al. decided to study their fate when they are potentially being combined in freshwater and oceans and to help make environmental risk assessments more accurate.

The ability of zinc oxide, both pure nanomaterials and those released from a sunscreen, to stick to very small pieces of plastic has big implications. These plastics can even come from everyday items like exfoliating facial cleansers. In this study, we found the microplastics can carry even smaller particles of zinc from place to place. As a consequence, fish or other aquatic organisms could swallow these microplastics, ingesting zinc particles at the same time.

In a broader effort to investigate the fate of even smaller pieces of plastics, we have teamed up with Dr Nathaniel Clark - University of Plymouth, to become project partners of ADVANCE: ADvanced Visualisation And Nano-scale Characterisation of Exposure.

Micro- and nanoplastics are increasingly found in human organs, including the liver. However, a critical barrier to understanding their health impact is our inability to reliably see these particles inside human tissues. Unlike metal-based nanoparticles, whose cellular trafficking and clearance are well understood, nanoplastics remain effectively invisible under most analytical systems.

This project will develop the first multimodal, label-free nanoscale imaging workflow to visualise plastic particles in human liver models. By integrating advanced imaging methods with spatial biology approaches, this research will map when, where and how micro- and nanoplastics interact with liver cells, allowing us to understand their biological significance and potential contribution to liver disease. The ultimate goal is seeing the Invisible, by understanding how plastics enter human tissues.

Preliminary research has localised europium-labelled nanoplastics (Eu-NPs) in macrophage cells by TEM microscopy, inside membrane-bound compartments (Fig. a). Complementary measurements at the I14 beamline further highlighted areas of Eu accumulation (Fig. b). However, these approaches cannot verify its chemical identity—an essential requirement, especially when analysing real-world samples such as biopsies, where other particles will be present.

Figure 2. Europium-labelled nanoplastics (Eu-NPs) in macrophage cells by TEM microscopy, inside membrane-bound compartments

Figure: a) Suspected Eu NP internalisation inside of macrophage cells following a 24-hour exposure, where nanoplastic clusters surrounded by membrane vesicles were revealed by TEM analysis (blue arrows). b) Nano XRF map measured at I14 showing the Eu-signal (orange colour dots, signalled by red arrows) over the K-signal for the macrophage (green colour). Note, the Eu-label is roughly 1-8% of the particle mass.