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Interfacial Interactions between Escherichia coli and Polystyrene Nanoplastics: a Physicochemical Perspective
Summary
When nanoplastic particles encounter bacteria in the environment, the nature of that interaction affects how plastics move through ecosystems and whether they carry pathogens. This study examined how polystyrene nanoparticles (both plain and amine-modified) interact with E. coli at a physicochemical level, finding that attachment depended strongly on particle surface charge, pH, and concentration. The amine-modified particles bound more readily to bacterial surfaces and altered bacterial membranes, suggesting that surface chemistry—which changes as plastics weather in the environment—substantially influences the ecological behavior of nanoplastics and their potential to ferry microorganisms to new locations.
Nanoplastics are increasingly recognized as emerging environmental contaminants, yet the physicochemical mechanisms governing their interactions with bacterial cells remain insufficiently understood. In this study, we investigated the interactions between Gram-negative Escherichia coli and polystyrene nanoparticles (PS and PS-NH2; 100 and 200 nm) using electrophoretic light scattering (ELS), Fourier-transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). Zeta potential measurements revealed concentration-, pH-, and time-dependent shifts in the electrokinetic behavior of bacteria-nanoparticle mixtures, reflecting composite signals arising from nanoparticle attachment and surface-level interactions rather than direct measurements of bacterial surface charge. FTIR and AFM analyses confirmed nanoparticle surface adhesion and localized envelope perturbations; however, evidence for nanoparticle penetration remained indirect and subject to methodological limitations. Microbiological assays showed growth inhibition at nanoparticle concentrations ≥50 μg/mL, but no bactericidal activity was conclusively confirmed under the applied conditions. Overall, the results demonstrate that polystyrene nanoparticles induce measurable physicochemical and sublethal biological effects on E. coli without reaching cytotoxic thresholds, underscoring the importance of cautious interpretation when linking nanoparticle-induced surface perturbations to biological outcomes.