(J-381) Validation and Characterization of Aerosolized Bead Deposition for a Novel Airway-on-Chip

The air we breathe is packed with particle matter pollution from both natural and man-made sources, such as pollen, mold spores, inorganic compounds, metals, dust, and soot (1). In this project, we are specifically investigating PM_2.5 ; particles with a diameter equal to or less than 2.5µm. Specialized epithelial cells in the nasal passageway produce mucous to trap inhaled particles and have cilia that beat rhythmically to clear the mucous (and its contents) from the airway (2). Researchers at the MSML will expose these cells to aerosolized florescent carboxylated polystyrene latex beads (later referred to as particles, or beads), which will imitate PM_2.5 inside a novel nasal-airway-on-chip platform. There is no current method to validate the generation of particles and their deposition pattern inside the novel airway-chip platform. Therefore, this study aimed to develop a bead capture chamber to validate aerosol size and concentration, as well as optimize the parameters for aerosol generation.

Tests on the flow rates output by the atomizer were performed with the goal of achieving at least 5 minutes of steady aerosol production. The setup of these experiments is shown in Figure 1. Flow rate was measured in two places, and the pressure in the atomizer was also measured. Four atomizer water volumes were tested, and the location for evaluating aerosol generation was changed in later tests. The goal output flow rates tested were 5.0 and 6.0 SLPM.

The next experiment will involve using an air compressor instead of the compressed air source built into the lab. A pressure regulator will also be added to the system. The methods of this experiment will be identical to that of previous experiments apart from a more well-defined method for evaluating aerosol.

Once a stable aerosol generating system is achieved, tests to capture and evaluate aerosolized beads will be performed. Solidworks was used to design a capture chamber for aerosolized beads. The chamber is composed of CNC cut acrylic, laser cut polystyrene, and 3D printed PLA, shown in Figure 2. The presence of beads in the aerosol will be validated and the particle characteristics from deposition at four different flow rates will be compared. The deposited particles will be counted and particle sizes will be measured, giving the average concentration of particles deposited, size range, and average particle size for each flow rate.

Initial experiments determined that with the aerosol system used, a flow rate of 6.0 SLPM at Flowmeter 2 was not achievable, but a flow rate of 5.0 SLPM with steady aerosol generation was achievable. Aerosol was produced during all trials and the water volume for optimal aerosol production was determined.

It is expected that the culmination of future experiments will provide results that show a stable aerosol generating system that is capable of aerosolizing polystyrene beads which deposit on microscope slides both perpendicular and parallel to airflow. They will also determine whether Poly-D Lysine is necessary for bead deposition and whether 2.0 µm or 0.2 µm beads should be used.

The final experiment will provide data showing average concentration of particles deposited, size range, and average particle size for each flow rate. Then, a graph will be created of average particle count and size versus aerosol flow rate, which will quantify the characterizations of particles that are produced by the atomizer at different flow rates. This data will be used to determine the optimal flow rate that will achieve the desired PM exposure for the cells inside the nasal chip.

¹ What is Particle Pollution? EPA. United States Environmental Protection Agency. Available at: https://www.epa.gov/pmcourse/what-particle-pollution. (Accessed: 8th October 2022)

² Xing, Y., Xu, Y., Shi, M., Lian, Y. The impact of PM2.5 on the human respiratory system. Journal of Thoracic Disease 8, 1:E69–E74 (2016). DOI: 10.3978/j.issn.2072-1439.2016.01.19