Impact of Engineered Carbon Nanodiamonds on Model Lung Surfactant Monolayers

By understanding the effects that Engineered Carbon Nanodiamonds (ECN) have on lung surfactants and other phospholipid membranes, we hope to better understand the toxicity of these particles. Lung surfactant is found at the air-liquid interface in the lungs, and its presence helps to reduce surface tension, making it easier to breathe. The ECNs may come into contact with this surfactant through intentional (targeted drug delivery), or unintentional exposure. This project specifically examined how ECNs impact the reversible collapse of these at the air-liquid interface. Four different lipid compositions were studied with each representing a major composition of lung surfactant. A Langmuir Ribbon Barrier Trough was used to perform compression-expansion cycles. The contraction and expansion of this barrier is useful to mimic the act of breathing. Area versus surface pressure isotherms were generated for five consecutive cycles. The experiments were performed on a PBS buffer with a pH of 7.4 to represent the human body. Phospholipid samples were made in chloroform with a concentration of 1 mg/mL with some lipid samples containing 1 wt % ECNs. The isotherms were then analyzed to find the area between the curves for each cycle, which is a good indicator of material retention. It was ultimately found that while the mechanism of collapse remains the same, the addition of nanoparticles did impact the retention of material at the interface. The effect that ECNs had on this retention was dependent upon phospholipid composition, specifically factors such as charge and tail saturation.