(322h) Interfacial Dynamics of Phospholipids Membranes and Their Interactions with Nanoparticles

Phospholipids are major components in lipid membranes in living cells which serve important biological functions. Because of their amphiphilic nature, phospholipids can, in aqueous environment, self-assemble into the bilayer structures present in cell membranes such as lung alveoli and myelin sheath. Interactions of such cell membranes with nano-objects have been important topics in the fields of colloids and biophysics, as well as biomedical fields in past decades. Given that nanoparticles (NPs) can serve as not only drug delivery carriers but also toxic foreign objects in contact with cell membranes, this work seeks to answer questions pertaining to fundamental understanding of the complex molecular interactions in NPs-phospholipid systems at different length scales, in particular, focusing on lung surfactant system.

In this study, pristine and hydrophobically modified silica NPs were selected to model various types of engineered nanoparticles (ENPs). Monodisperse ~50 nm silica NPs were synthesized via a modified Stöber method and surface of silica NPs were modified with alkyl silanes of varying chain length and polarity. 1,2-Dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), one of the major components of lung surfactant layers, was chosen as our model phospholipid molecule. The extent of surface modification was determined using transmission Fourier transform infrared spectroscopic measurements and contact angle studies. It was found that the presence of nanoparticles strongly influences the fluidity, rigidity, and pressure-area isotherms of phospholipid layers. In addition, surface hydrophobicity of nanoparticles was shown to strongly control the interfacial dynamics of such phospholipidic layers.

We anticipate fundamental knowledge gained through this study would provide new insights into not only understanding the subsequent retention, translocation, and clearance of inhaled ENPs and the sequential processes associated with the nanoparticle toxicity but also designing effective drug delivery carriers systems.