Developing a lung-on-chip device for studying the impact of micro- and nanoplastics on human lung tissue

Following the slow degradation of abundant plastics, micro- and nanoplastics (MNPs) are accumulating in the environment. MNPs have been found in various food sources and in the air; as such, they can be consumed and/or inhaled by humans [1]. Yet, the potential health risks associated with MNPs are still unknown. Existing data are conflicting and, importantly, accurate models to evaluate MNP impact are lacking [2]. Altogether, there is a need for reliable humanized models to study the effects of MNPs on human health [3].
In this context, we are developing a lung-on-chip (LOC) model to study the translocation of MNPs across the lung epithelium and interactions between MNPs and this essential physiological barrier. Our lung-on-chip model incorporates a gelatin methacrylate (GelMA) hydrogel that is much akin the native lung extracellular matrix. The hydrogel concentration and UV exposure time have been optimized to match the stiffness of the lung extracellular matrix, as verified with rheology. In the LOC, epithelial cells are cultured on top of the hydrogel, which is molded with trenches to mimic the curvature of the smallest bronchiole in the lung. Cells are cultured under air-liquid interface (ALI) conditions, which is necessary to reach full differentiation and polarization. CaLu-3 cells (human lung epithelial cells) have successfully been cultured on our molded GelMA hydrogels, with the formation of a tight monolayer, as revealed by immunostaining and confocal microscopy. In current work, we are quantifying the monolayer tightness using TEER measurements, and extending our model to primary human lung epithelial cells (normal human bronchial epithelial cells, NHBE). Taking advantage of our open design, we are now exposing our models to MNPs in suspension in a first instance, and studying MNP translocation across the differentiated epithelium.
As a next step, we are incorporating dynamic stretching in the model to replicate breathing motion, which is known to play a critical role in cell behavior and interactions with (nano) particles. For this, two vertical and flexible PDMS membranes are placed on both sides of the molded hydrogel, which is covalently attached to the PDMS. Upon actuation of these two membranes, we aim at mimicking the breathing motion.
We are currently working on the integration of these different elements to yield a biomimetic human LOC model that incorporates essential environmental and mechanical cues of the lung epithelium. Our platform opens new avenues to reliably study effects of MNPs of various sizes, compositions, and shapes, on the lung physiological barrier.
Research funded by ZonMw and Health-Holland (MOMENTUM project).

References
1. Gruber et al. Exposure and Health 15, 33-51 (2023).
2. Parker et al. Microplastics and Nanoplastics 3(1), 10 (2023).
3. Lu et al. Bioactive Materials 6(9), 2801-2819 (2021).
4. Paggi et al. Sensors and Actuators B: Chemical 315, 127917 (2020).