(540e) Effects of Aerosolized Sub-Micron Particles On The Interfacial Properties of Lung Surfactant Models

Pulmonary surfactant plays an important role in lung stability by reducing the surface tension of the alveolar fluid and avoiding alveolar collapse. Changes to the interfacial properties of this surfactant can lead to potential health implications such as increased work of breathing and impaired gas exchange. Inhaled particles that deposit in the alveolar region of the lung come into contact with the pulmonary surfactant and might alter its interfacial properties. A few recent in vitro studies have reported surfactant dysfunction following exposure to small particles. However, these studies have been focused on colloidal particle suspensions and little is known about particle-surfactant interactions when dry particles are aerosolized onto surfactant films. The present study seeks to improve the current understanding of the effects of inhaled particles on surfactant function by examining particle-surfactant interactions after exposing surfactant films to aerosolized particles.

Langmuir films of dipalmitoyl phosphatidylcholine (DPPC) and Infasurf (calf lung surfactant extract) were used as lung surfactant models and their interactions with carboxyl-modified polystyrene particles (200 nm) were studied. Surfactant films were spread in a Langmuir trough and their dynamic surface tension was probed using a Wilhelmy plate balance. A Dry Powder Insufflator^TM was used to aerosolize dry particles onto surfactant films. Following exposure to particles, surfactant films were subjected to two modes of surface area changes: 1. Surface compression from the surface tension of pure subphase until film collapse and 2. Compression and expansion within the range of physiologically relevant surface tension values to mimic breathing cycles.

Aerosolization of particles on both DPPC and Infasurf films resulted in a shift in the surface area of surfactant collapse and a slight reduction in the minimum surface tension. However, particles induced significant changes (~20 mN/m) in the minimum surface tension of DPPC when aerosolized in the lung relevant surface tension range. In contrast, only minor changes were observed in the maximum surface pressure of Infasurf following aerosolization in the physiologically relevant surface tension range suggesting that Infasurf films are more stable than DPPC in response to particle exposure. Further experiments with different particle-surfactant interaction times showed that particles effects on Infasurf interfacial properties changed as a function of time suggesting that particles affect surfactant function by adsorption of surfactant components. These results provide information on the effects of particles on surfactant function following inhalation, which is of great importance for the fields of pulmonary drug delivery and environmental and occupational health.