Fabrication of microplastic and nanoplastic particles and fibres for use in pulmonary toxicity studies

BACKGROUND: Micro/nanoplastics (MNPs) are a commonly detected environmental contaminant in indoor and outdoor environments. Airborne MNPs are of various shapes and sizes, some of which are small enough to reach the deep lung if inhaled. Current research into the toxicity of airborne MNPs in the lung has only involved a small number of polymers and shapes due to their limited availability. The most commonly available are polystyrene spheres and to date, these have been used in the majority of studies, though their relevance to environmental MNPs is limited. To address this gap, we aimed to develop a method to fabricate MNPs of three environmentally relevant polymers, producing both micro- and nano-sized particles as well as fibres. Enhancing the consistency and accessibility of test materials will enable researchers to better investigate how size, shape, and polymer type influence lung toxicity, while also reducing variability introduced during fabrication. RESULTS: We successfully developed methods to fabricate MNPs of polyamide, polystyrene, and polyethylene terephthalate, as microplastics, nanoplastics, and fibres. MNPs were characterized for their chemical purity and size. The size of the fabricated MNPs were found to be of a respirable dimension. As a solvent-based method of preparation was used, leachates from the MNPs were analysed to check for contamination that could cause non-specific toxicity. These were found to have no effect on the metabolic activity of either THP-1 macrophages or transformed type-1 (TT1) epithelial cells. CONCLUSIONS: This work provides pulmonary toxicologists with a method for the fabrication of MNPs and their physical and chemical characteristics. Their characteristics indicate they are a representative test material for experimental systems.