Bioelectric Changes in Primary Rat Alveolar Epithelial Cell Monolayers Exposed to Various Nanoplastics

Introduction: About 0.25 megatons of plastic waste from consumer and industrial sources found in waterways, including sub-millimetric plastic particles generated from environmental degradation, may pose significant health risks. The biological and ecological impacts of materials <1 μm (nanoplastics) are of particular concern because they are generally too small for most conventional filtration processes and challenging to collect, detect and identify. Furthermore, their high surface area-to-volume ratio makes them efficient carriers for toxic substances. Despite this, most of the studies in recent literature reviews employed manufactured nanoplastics of uniform size and shape, which do not reflect actual environmental plastic waste. A systematic analysis of environmental nanoplastic impacts on biota would be vital in understanding the full life cycle of plastic pollution. In this study, we investigated how different nanoplastics affect the ion transport properties of lung alveolar epithelium. Methods: We crushed and pulverized cuvettes (polystyrene (PS)), droppers (polyethylene (PE)), centrifuge tubes (polypropylene (PP)), and containers (polyethylene terephthalate (PET)) prior to irradiation and ozone treatment. These nanoplastics in water were twice-filtered with 800 nm polyethersulfone filters and concentrated by evaporation. The resulting nanoplastic solids were weighed and re-suspended in 1 mL mQ water. They were then ultrasonicated for 15 minutes to break up any aggregates. We measured size distribution, surface charge and shape of the nanoplastics using a zeta sizer/DLS and electron and/or confocal microscopy. For ease of detection, these nanoplastics were also stained with Rhodamine B by heat swelling at 70°C for several hours, followed by dialysis or size-exclusion chromatography to remove unbound dye. Commercial 20 nm spherical polystyrene nanoparticles (PNP) with -10 mV zeta potential were used for comparison purposes. Effects of nanoplastics and PNP on primary cultured rat alveolar epithelial cell monolayers were studied by measuring transepithelial resistance (Rt) and spontaneous potential difference (PD) for up to 48 hours after adding nanomaterials to the apical fluid of the monolayers, while control monolayers received only culture fluid apically. Active ion transport rate (Ieq) was estimated as the ratio PD/Rt. Results: Typical size, polydispersity (%PD), morphology and absolute value of zeta potential for our nanoplastics are 120-350 nm, 11-25%, dendritic and 10-13 (±8) mV. PNP exposure led to a rapid decrease in Rt by ~70% at 30 minutes and a slow return to control level thereafter, whereas Ieq decreased by ~50% at 30 minutes and returned to control level very slowly. PP exposure also led to rapid fall in Rt by ~60% with very slow return to control level, but without an effect on Ieq. PS resulted in a slower decrease in Rt by ~40% at 8 hours, followed by return to control level by 48 hours, without affecting Ieq. The other nanoplastics (PE and PET) tested did not cause significant changes in either Rt or Ieq following apical exposure. Conclusions: These observations are consistent with the hypothesis that the material, size, shape and surface charge of nanomaterials influence their effects on the bioelectric properties of the alveolar epithelium. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.