High-Resolution Investigation of Nanoparticle Interaction with a Model Pulmonary Surfactant Monolayer

Abstract

The pulmonary surfactant film spanning the inner alveolar surface prevents alveolar collapse during the end-exhalation and reduces the work of breathing. Nanoparticles (NPs) present in the atmosphere or nanocarriers targeted through the pulmonary route for medical purposes challenge this biological barrier. During interaction with or passage of NPs through the alveolar surfactant, the biophysical functioning of the film may be altered. However, experimental evidence showing detailed biophysical interaction of NPs with the pulmonary surfactant film are scant. In this study, we have investigated the impact of a hydrophobic polyorganosiloxane (AmOrSil20) NPs on the integrity as well as on the structural organization of the model pulmonary surfactant film. Primarily, scanning force microscopic techniques and electron microscopy have been used to visualize the topology as well as to characterize the localization of nanoparticles within the compressed pulmonary surfactant film. We could show that the NPs partition in the fluid phase of the compressed film at lower surface pressure, and at higher surface pressure, such NPs interact extensively with the surface-associated structures. Major amounts of NPs are retained at the interface and are released slowly into the aqueous subphase during repeated compression/expansion cycles. Further, the process of vesicle insertion into the interfacial film was observed to slow down with increasing NP concentrations. The hydrophobic AmOrSil20 NPs up to a given concentration do not substantially affect the structural organization and functioning of pulmonary surfactant film; however, such NPs do show drastic impacts at higher concentrations.

Shape affects the interactions of nanoparticles with pulmonary surfactant

“…It was found that the hydrophobic NPs immerse themselves in the hydrophobic tails of the interfacial DPPC molecules, while hydrophilic NPs adsorb onto the hydrophilic head-groups of the interfacial DPPC molecules. This finding is in good agreement with previous in-vitro , in-vivo and in-silico translocation results [39,46,54–58]. …”

“…Both in-vitro experiments [35–39] and computer simulations [40–46] have confirmed that the phospholipids of PS undergo surface phase transition during the compression-expansion cycles. During film compression, phospholipid monolayers undergo surface phase transitions from a “fluid-like” LE phase to a “solid-like” LC phase, which is opposite to the direction of phase transition during film expansion.…”

“…The PS consists of approximately 10% proteins and 90% lipids, with dipalmitoyl-phosphatidylcholine (DPPC) being the most abundant single lipid component for most mammalian species. Being the primary surface active component in the PS, the DPPC monolayer at the air-water interface has been widely used as a model PS system both in in-vitro experiments [30–39] and in molecular dynamics simulations [40–46]. …”

Biophysical Influence of Airborne Carbon Nanomaterials on Natural Pulmonary Surfactant

“…These results are in good agreement with previous in vitro and in silico studies that show hydrophobic NP adsorb to the surfactant film where the nano-bio interactions govern the surfactant inhibition. 11,12,14,20 …”

Chemical Basis of Interactions Between Engineered Nanoparticles and Biological Systems

“…Hydrophobic polyorganosiloxane nanoparticles do not substantially affect the structural organization of a model pulmonary surfactant film at low concentrations (e.g., 10 μg/mL) but significantly affect such properties at high concentrations (e.g., 3000 μg/mL). 82 Polystyrene nanoparticles with a diameter of 20 nm demonstrate greater interactions with the endothelial model membrane than those with a diameter of > 60 nm. 64 Perturbations from nanoparticles may cause pore formation in lipid bilayers.…”