Multitechnique characterization of eco-corona formation on airborne nanoplastics

The increasing presence of micro- and nanoplastics in natural environments raises concerns about their interactions with biological particles such as pollen, that may act as carriers but could also undergo subtle chemical or structural changes, potentially influencing their ecological role. At the same time, the analytical and technological approaches used to investigate nanoplastic pollution mechanism can themselves raise concerns regarding their greenness. In this interdisciplinary study, we explored the interactions between multifloral bee pollen and polyethylene terephthalate nanoparticles (NanoPET) under environmentally relevant conditions using a multimodal analytical strategy combining AF4 (Asymmetrical Flow Field-Flow Fractionation) multidetection, Pyrolysis-GC-MS (py-GC-MS), Field Emission Scanning Electron Microscopy (FESEM), and dielectrophoresis-Raman spectroscopy (DEP-Raman). This approach aims to clarify nanoplastics exposure profiles and the associated potential health risk, as well as to promote more sustainable laboratory workflows. Pollen and NanoPET were first characterized individually by AF4, FESEM, and DEP-Raman, which provided their size distributions, morphology, and characteristic spectral signatures. Py-GC-MS offered detailed molecular fingerprints, especially for bee pollen, which had not been previously analysed with this technique. To assess the interaction between pollen and NanoPET, mixed samples were analysed using a "profilomic" approach based on changes in AF4 fractograms, UV/Vis and Raman spectra. Two distinct interaction mechanisms have emerged: the formation of a corona of soluble pollen-derived macromolecules around NanoPET, and the coating of pollen grains by NanoPET particles, as confirmed by FESEM imaging. DEP-Raman further confirmed the presence of interactions by separating non-interacting NanoPET particles and revealing spectra that included characteristic peaks of both pollen and NanoPET. Py-GC-MS analysis of fractions collected from AF4 processing of mixed samples also confirmed the presence of characteristic ions deriving from both components. Together, these findings highlight the formation of hybrid bio-nano structures and suggest potential ecological implications. Moreover, they demonstrate how multidimensional, low-impact analytical workflow can offer detailed insight into nanoplastics behaviour in complex biological matrices, paving the way for greener and more comprehensive environmental nanotoxicology studies.