Native-state monitoring of nanoplastic corona dynamics and their mitigating role in ecotoxicity using an integrated hollow fiber flow field-flow fractionation platform.

Upon entering environmental systems, nanoplastics (NPs) adsorb natural organic matter, forming eco-coronas that dictate their ecotoxicological fate. However, conventional isolation alters fragile corona structures, and unseparated free biomolecules confound toxicity assessments, making native-state characterization challenging. To overcome this, we developed an integrated platform coupling hollow fiber flow field-flow fractionation with UV-Vis and point-discharge optical emission spectrometry (HF5-UV/PD-OES). This gentle separation isolated intact corona-coated polystyrene NPs (PSNPs) while eliminating free-molecule interference. Tracking native-state temporal dynamics of bovine serum albumin (BSA) and fulvic acid (FA) coronas revealed a three-stage evolution: rapid adsorption, structural reorganization, and dynamic equilibrium. Governed by surface curvature, 100 nm PSNPs accommodated significantly thicker coronas than highly curved 50 nm counterparts. A hybrid CNN-BiLSTM deep-learning model decoded PD-OES spectral fingerprints, accurately discriminating pristine, BSA-coated, and FA-coated PSNPs (98.67% accuracy). Using these highly purified fractions, ecotoxicological assays on Tetrahymena thermophila provided unconfounded evidence that the corona acts as a protective interfacial shield. While effectively mitigating acute oxidative stress and lethality, internalized particles continue to impose a persistent sub-lethal physical burden on cells. This study offers a robust tool for probing NP surface transformations and proves the corona decisively modulates toxicity in ecological risk assessments.