Development and Applications of a Modifiable Aerosol Platform

Abstract

Pathogen-containing droplets expelled into the air as infected individuals speak, cough, sneeze, or laugh may infect proximal secondary hosts. Facemasks are an effective, low-cost method to help prevent airborne transmission mediated by pathogen-laden droplets in the environment. To understand the testing of facemask materials to protect against airborne pathogens, we followed the American Society for Testing and Materials (ASTM) standard F2101-12 and built an in-house test platform. However, the standard lacks clear guidelines. To address this, we built an aerosol platform at McMaster University to generate and test droplets containing viable bacteria, allowing us to assess the filtration performance of different facemask materials. We created optimized procedures to ensure the generation and sampling of infectious aerosols are consistent and reliable. The operation, maintenance, and sterilization of the platform were also detailed. Airborne disease transmission is a complex phenomenon influenced by multiple factors. Conditions such as muco-obstructive airway disorders can increase the viscosity and solute content of airway lining fluid. Therefore, individual variability in airway mucus composition and initial droplet size may influence transmission dynamics. Thirdly, environmental conditions such as temperature and humidity can change the aerosol microenvironment and alter encapsulated pathogen viability. Evidence suggests infectious aerosols originate from the breakup of the airway lining fluid, and the site of origin within the airways can affect the size of pathogen-laden droplets. Using the bacteriophage Phi6 as a stand-in for the SARS-CoV-2 virus, we examined how droplet size, mucus composition, pathogen load, and environmental conditions (temperature and humidity) affect pathogen survival. Our findings may provide insight into the dynamics of airborne transmission and can help improve strategies to reduce the spread of respiratory infections. Lastly, we adapted the platform to conduct in vitro lung exposure studies of deposition, safety, and efficacy of bactericidal agents. The human airway epithelial cell line, Calu-3, cultured in an air-liquid interface system, was used to recapitulate the physiological characteristics of the respiratory mucosa. Pseudomonas aeruginosa biofilms cultured for 24 hours were placed within the impactor and exposed to aerosolized bactericidal agents. Preliminary results show that our cell-integrated exposure platform can assess in vitro safety, efficacy, and dosage of inhaled therapeutics. This setup can potentially help gather pre-clinical data to support in vivo studies of treatments for respiratory diseases. This platform has significant potential for expanding aerosol research at McMaster University to evaluate the effectiveness of personal protective equipment, study how infectious aerosols spread, and explore inhaled delivery of therapeutic agents to the lungs. These findings contribute to our understanding of airborne transmission and may inform strategies to reduce the spread of infections.