A Mesh-Hopper System for Delivering Microplastic Fibers to Cells at the Air-Liquid Interface for Toxicity Assessment

Sripriya Nannu Shankar, Amber O'Connor, AMIN SHIRKHANI, Anna Lewis, Alex Theodore, Lee Ferguson, Tara Sabo-Attwood, Chang-Yu Wu, University of Florida

     Abstract Number: 707
     Working Group: Aerosol Exposure

Abstract
Inhalation of microplastic fibers (MPFs) has been reported to cause respiratory lesions, chronic bronchitis, pulmonary fibrosis, lung cancer and chronic obstructive pulmonary disease. Existing in vitro exposure systems assessing the toxicity of MPFs rely on suspending the fibers within the medium prior to cell exposures, which is not physiologically relevant. To our knowledge, there is no system that can deliver the fibers directly to cells cultured at the air-liquid interface (ALI). In this study, a custom designed mesh system comprising of a hollow rod (6 mm×50 mm) mounted on a support was developed for the delivery of dyed (19.5 µm×<3 mm) and undyed (14 µm×45 µm) polyethylene terephthalate MPFs. Based on ImageJ analysis of the fibers, the number of fibers/mg of the material were 2,900±824 and 9,010±289 for the dyed and undyed fibers, respectively. Through gravimetric analysis, efficiencies of at least 85% were achieved through the mesh-hopper system, for delivering ~250-2500 and 500-2500 of dyed and undyed fibers respectively, corresponding to doses of 261.2-2612 µg/cm² and 168.18-839.39 µg/cm². A 6-day repeated dosing of 500 fibers to primary normal human bronchial epithelial (NHBE) cells cultured at the ALI resulted in a cell viability of ~73% for the dyed and ~90% for the undyed fibers, as assessed by trypan blue assay. The cell viability when exposed to the leachate was ~84% and ~98% for the dyed, and undyed fibers, respectively. This suggests that both MPFs and components that leach from MPFs may negatively impact cells in vitro, specifically for dyed MPFs that are colored with azobenzene disperse dyes. The study demonstrates the applicability of the mesh-hopper system as a simple, straightforward, and efficient tool to deliver MPFs directly to cells at the ALI, to study the impacts of MPFs on lung cells under in vitro conditions.