2025 AIChE Annual Meeting

Nanomembrane Based Sensing of Environmental Microplastics and Their Cytotoxic Footprint

Microplastics (MPs) are persistent environmental contaminants measuring between 5 millimeters and 1 micron in length. In the environment, they fragment into nanoscale pieces, increasing their surface area to volume ratio, and allowing them to more readily uptake toxic organic compounds and heavy metal pollutants. They pervade all ecosystems and organisms, raising significant concern for human health. Research to this point has been primarily focused on the effects of MP inhalation and ingestion, however the skin has also been shown to be permeable to nanoparticles, making it a critical area for research. Despite their growing presence, the cytotoxic effects of MP-pollutant interactions and reliable methods to detect and isolate environmental MPs under 20 microns are not well developed. This work aims to investigate the cytotoxicity of zinc chloride (ZnCl₂, a commonly found compound in dermatology and some industrial products) and the adsorption of ZnCl₂ to pristine MPs. Also, a method for detecting MPs under 20 microns was optimized for environmental water samples collected from Lake Ontario in Rochester, NY, USA.

An immortalized human keratinocyte cell line (HaCaT), modeling human skin cells, was exposed to ZnCl₂ without MPs. Cell viability assays revealed dose-dependent cytotoxicity of ZnCl₂, providing baseline data for future exposure to both MPs and ZnCl₂. Secondly, adsorption of ZnCl₂ to pristine 5-micron polystyrene beads was analyzed using dynamic light scattering (DLS) to measure size and zeta-potential. The measurements collected are consistent with zinc adsorption to MP surfaces, providing insight into the concentrations at which pristine MPs tend to uptake heavy metals.

Lastly, a method for detecting environmental MPs under 20 microns was optimized using 8- and 1-micron slit size nanoporous membrane chips. The filtrate was stained with Nile Red to detect MP presence, imaged with fluorescence microscopy, and analyzed using Fiji ImageJ to measure the percent area of stained particle coverage. Contamination reduction and steps for troubleshooting were assessed to establish a reproducible process for MP detection. Some points of interest were in controlling laboratory equipment contamination and troubleshooting the staining of MPs with Nile Red. An additional oxidation step to remove the organic matter matrix could improve this process, further revealing MPs.

Altogether, the combined approaches advance the understanding of the risk associated with both environmental and pristine MPs, laying the groundwork for more comprehensive exposure and monitoring of environmental MPs.