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Hydrogel Transformation Reveals a Conventionally Inaccessible Sub-Micrometer Microplastic Fraction in Intact Human Tissues
Summary
Scientists developed a new way to detect the tiniest microplastics, smaller than a speck of dust, inside human tissue without the usual risk of contamination that plagues older methods. Testing it on human placenta, they found that most of these plastic particles (73%) are so small they've been invisible to standard detection methods used until now. This matters because it suggests we've been dramatically undercounting the plastic in our bodies, especially the smallest particles, which may be the ones most able to slip into cells and organs and potentially cause harm.
Abstract Reliable detection of micro- and nanoplastics (MNPs) in human tissues remains analytically challenging due to complex biological matrices, contamination risks, and limited sensitivity of existing spectroscopic and mass-based techniques toward submicrometer particles. Here, we present a histology-compatible analytical approach that enables in situ, volumetric detection and quantification of MNPs in biological tissues with submicrometer sensitivity. The method combines hydrogel-based tissue transformation and optical clearing with fluorescence staining and three-dimensional optical imaging, preserving the spatial architecture of the tissue while removing interfering biological components. This approach effectively minimizes external contamination and enables Nile Red-based identification of MNPs embedded within intact tissue volumes. Analytical performance was validated using spiked biological models and reference polymers, demonstrating reliable retention, detection, and classification of MNPs down to a conservatively defined limit of approximately 0.4 μm. False positives from endogenous hydrophobic structures are suppressed by enzymatic delipidation and are benchmarked using orthogonal fluorescence lifetime signatures against lipid artifacts and plastic reference materials. Applied to human placental tissue, the workflow resolves a particle population dominated by submicrometer MNPs (73% below 1 μm). This size fraction is systematically excluded by filtration-based workflows and, because its cumulative mass is negligible, falls below the detection limits of bulk pyrolysis-based methods. Consequently, the number-dominant MNP fraction in human tissue has remained largely inaccessible to existing analytical approaches. By enabling sensitive, structurally (rather than procedurally) contamination-resistant, and spatially resolved detection of MNPs directly within intact tissues, this approach bridges a critical gap between nanomaterials characterization and exposure biology. It provides a broadly applicable platform for future biomonitoring, exposure assessment, and hypothesis-driven studies on the biological fate of MNPs.