Engineered PS and PAN Microplastic Fibers Elicit Stronger A549 Epithelial Responses than Spherical Polystyrene Particles.

Polymeric fibers are a prevalent form of airborne micro- and nanoplastics (MNPs), yet their inhalation hazards remain poorly constrained because toxicological studies have largely relied on spherical particles or heterogeneous fiber materials. Here, polystyrene (PS) and polyacrylonitrile (PAN) fiber MNPs were fabricated by electrospinning followed by cryomilling, probe sonication, and filtration, yielding discrete fibers with comparable diameters and lengths. FTIR confirmed preservation of polymer identity and showed no detectable residual solvent signal in the isolated fibers. Using A549 lung epithelial cells as an inhalation-relevant in vitro model, we found that PS and PAN fiber MNPs induced dose-dependent reductions in viability together with increased membrane damage, oxidative stress, and IL-8 release, whereas spherical PS particles elicited comparatively limited responses at the tested mass concentrations. Scanning electron microscopy further showed abnormal cell-fiber interactions, including membrane deformation and apparent partial membrane wrapping around fibers, consistent with morphology-dependent cellular injury. Together, these results show that engineered polymeric fiber MNPs elicit stronger epithelial stress and inflammatory responses than spherical particle controls under the tested conditions, supporting morphology-aware evaluation of airborne MNP hazards.