(Nanowerk Spotlight) Plastic pollution has emerged as one of the most pressing environmental challenges of our time, with an estimated 400 million tons of plastic waste generated annually worldwide. Of particular concern are nanoplastics – microscopic plastic particles smaller than one micrometer – which can enter living organisms through various pathways including air, water, and food. Until now, scientists have struggled to understand exactly how these tiny particles interact with human immune cells and what risks they might pose to human health. The key obstacle has been the difficulty in tracking these particles once they enter the bloodstream and determining their precise effects on different types of immune cells.
Traditional methods for studying nanoplastic interactions with human cells have relied on fluorescent labeling or imaging techniques, but these approaches have significant limitations. Fluorescent markers can detach from the plastic particles, leading to incorrect conclusions, while conventional imaging methods cannot simultaneously track the particles and observe their effects on multiple cell types. Additionally, earlier studies primarily used laboratory cell lines rather than actual human blood cells, limiting their relevance to real-world exposure scenarios.
A new study published in Advanced Materials (“Nanoplastics: Immune Impact, Detection, and Internalization after Human Blood Exposure by Single-Cell Mass Cytometry”) by researchers from the University of Padua and several international collaborators introduces an innovative approach to tracking and studying nanoplastic particles in human blood. The research team used a specialized technique called single-cell mass cytometry (CyTOF) combined with palladium-doped polystyrene nanoparticles to observe how these materials interact with human immune cells at unprecedented detail.
Workflow of the study. Study workflow showing the biological characterization of 50 to 200-nm polystyrene nanoplastics (PS NPs) and metaldoped polystyrene nanoplastics (PS-Pd NPs shell) on peripheral blood mononuclear cells and whole blood. NP impact on up to 30 human blood immune cell types was assessed by single-cell mass cytometry (CyTOF) ex vivo. Evaluation of cell viability, cell functionality, and NP uptake by CyTOF was performed. (Image: Reproduced from DOI:10.1002/adma.202413413, CC BY) (click on image to enlarge)
The researchers developed a method to track plastic particles by incorporating palladium atoms into them, allowing precise detection through mass spectrometry. This technique enabled them to simultaneously monitor the location of the particles and measure their effects on 37 different immune cell subpopulations in human blood – a level of detail previously impossible to achieve.
The study revealed a clear size-dependent effect of nanoplastic particles on immune cells. Larger particles (200 nanometers) demonstrated significantly stronger impacts on cell functionality compared to smaller ones (50-100 nanometers). Classical monocytes showed the highest uptake of the particles, followed by myeloid dendritic cells, plasmacytoid dendritic cells, and memory B cells. The research team also observed substantial particle internalization in various T cell subsets.
Particularly noteworthy was the particles’ ability to trigger specific inflammatory responses. The study documented increased production of several key inflammatory signaling molecules, including interleukin-4 (IL-4), tumor necrosis factor-alpha (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF). These cytokines were elevated across multiple immune cell types, with T helper cells, B cells, natural killer cells, and dendritic cells showing the most pronounced responses.
When tested in mice, the particles accumulated primarily in the liver and spleen, with specific immune cells in these organs showing high levels of particle uptake. In the liver, conventional dendritic cells and macrophages exhibited particularly high levels of particle internalization, with up to 30% of monocytes and granulocytes showing evidence of particle uptake.
The research represents a significant advance in our ability to study the health impacts of plastic pollution. By combining innovative particle tracking methods with sophisticated immune cell analysis, the team has created a powerful new tool for understanding how nanoplastics interact with the human immune system. This approach overcomes many of the technical limitations that have hampered previous studies in this field.
The implications of this work extend beyond just understanding plastic pollution. The methods developed could be applied to studying other types of particles and their effects on human health, potentially advancing our understanding of various environmental exposures and their health impacts. The technique’s ability to simultaneously track particles and measure their effects on multiple cell types provides a more complete picture of potential health impacts than previously possible.
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