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Non-photoaging and eco-corona reinforce nanoplastics-root engagement via root exudates in the rhizosphere.
Summary
Tiny plastic particles (nanoplastics) that break down in soil don't just disappear, they get coated with chemicals from plant roots that actually make them stick to roots more easily, especially after the plastic has been chemically "aged" by environmental exposure. This matters because it suggests weathered plastic fragments in soil could be taken up by crops more readily than fresh plastic, potentially creating a pathway for these particles to enter our food supply. More research is needed to confirm whether this uptake translates into measurable amounts in the edible parts of plants we eat.
How non-photoaging alters the binding of rhizosphere nanoplastics to root exudates (eco-corona) and subsequent root surface interactions remains unclear. Here, polystyrene nanoplastics (PSNPs) were subjected to Fenton and sulfidation aging. Spectroscopic analyses showed that root exudates formed distinct eco-coronas on pristine and aged PSNPs via non-covalent interactions. Aging shifted the binding mode from weak hydrophobic adsorption on pristine PS to hydrogen-bonding interactions with organic acids on aged PS. Consequently, colloidal behaviors differed, with hydrodynamic sizes increasing to 400 nm (pristine), > 600 nm (Fenton-aged), or fluctuating markedly (sulfide-aged). Confocal imaging showed that aging reduced PSNP adsorption on root protoplasts, whereas eco-corona formation decreased adsorption of pristine PS but markedly enhanced that of aged PS. Mechanistically, the corona masked hydrophobic sites on pristine PS, while carboxyl groups with residual Fe²⁺/Fe³⁺ promoted electrostatic/cation bridging on Fenton-aged PS, and carboxyl-rich exudates together with surface radicals enhanced punctate clustering and endocytosis on sulfide-aged PS. Root exposure experiments further showed that sulfide-aged PS exhibited an "easy adsorption, easy elution" pattern, mainly accumulating in the root elongation zone with a thin mucus layer. These findings demonstrate that aging reshapes nanoplastic surface chemistry, thereby regulating eco-corona formation and reprogramming interactions with the root surface and plasma membrane.