Surface Activity of Poly(ethylene glycol)-Coated Silver Nanoparticles in the Presence of a Lipid Monolayer

Mechanistic Pathway of Lipid Phase-Dependent Lipid Corona Formation on Phenylalanine-Functionalized Gold Nanoparticles: A Combined Experimental and Molecular Dynamics Simulation Study

In recent years, the underlying mechanism of formation of the lipid corona and its stability have begun to garner interest in the nanoscience community. However, until now, very little is known about the role of different properties of nanoparticles (NPs) (surface charge density, hydrophobicity, and size) in lipid corona formation. Apart from the physicochemical properties of NPs, the different properties of lipids remain elusive in lipid corona formation. In the present contribution, we have investigated the interaction of phenylalanine-functionalized gold NPs (Au-Phe NPs) with different zwitterionic lipid vesicles of different phase states (sol-gel and liquid crystalline at room temperature) as a function of lipid concentration. The main objective of the present work is to understand how the lipid phase affects lipid corona formation and lipid-induced aggregation in various media. Our results establish that the lipid phase state, area per lipid head group, and the buffer medium play important roles in lipid-induced aggregation. The lipid corona occurs for NPs at high lipid concentration, irrespective of the phase states and area per lipid head group of the lipid bilayer. Notably, the lipid corona also forms at a low concentration of lipid vesicles in the liquid crystalline phase (1,2-dioleoyl-sn-glycero-3-phosphocholine). The corona formation brings in remarkable stability to NPs against freeze-thaw cycles. Based on the stability, for the first time, we classify lipid corona as "hard lipid corona" and "soft lipid corona". This distinct classification will help to develop suitable nanomaterials for various biomedical applications.

Extraction of Bionanomaterials from the Aqueous Bulk by Using Surface Active and Water-Soluble Magnetic Nanoparticles

Surface active and water-soluble magnetic nanoparticles (NPs) were used to demonstrate the extraction of bionanomaterials from the aqueous bulk. Au NPs conjugated with different water-insoluble and water-soluble proteins were used as model bionanomaterials. UV-visible studies, zeta potential, and microscopic analyses were performed to quantify the extraction. Sodium dodecyl sulfate and dimethylene bis(dodecyldimethylammonium bromide) (12-2-12) stabilized surface active magnetic NPs were fully capable of extracting Au NPs conjugated with predominantly hydrophobic proteins from the aqueous bulk when placed at the aqueous-air interface. However, they were poor in extracting Au NPs from the aqueous bulk which were coated with predominantly hydrophilic water-soluble protein. On the other hand, water-soluble dodecyldimethyl-3-ammonio-1-propanesulfonate stabilized magnetic NPs proved to be fully capable of extracting all kinds of Au NPs conjugated with either water-soluble or water-insoluble proteins. The results highlight the remarkable ability of magnetic NPs in the extraction of bionanomaterials when placed at either biointerfaces or in the aqueous bulk of biological systems.

Computational Studies of Lipid-Wrapped Gold Nanoparticle Transport Through Model Lung Surfactant Monolayers

Colloidal nanoparticles, such as gold nanoparticles (AuNPs), are promising materials for the delivery of hydrophilic drugs via the pulmonary route. The inhaled nanoparticle drug carriers primarily deposit in lung alveoli and interact with the alveolar surface known as lung surfactants. Therefore, it is vital to understand the interactions of nanocarriers with the surfactant layer. To understand the interactions at the molecular level, here we simulated model lung surfactant monolayers with phospholipid (PL)-wrapped AuNPs at the vacuum-water interface using coarse-grained molecular dynamics simulations. The PL-wrapped AuNPs quickly adsorbed into the surfactant layer, altered the structural properties of the monolayer, and at high concentrations initiated the compressed monolayer to collapse/buckle. Among the surfactant monolayer lipid components, cholesterol adsorbed to the AuNPs preferentially over PL species. The position of the adsorbed PL-AuNPs within the monolayer, and subsequent monolayer perturbation, vary depending on the monolayer phase, monolayer composition, and species of PL used as a ligand. Information provided by these molecular dynamic simulations helps to rationalize why some colloidal nanoparticles work better as nanocarriers than others and aid the design of new ones, to avoid biological toxicity and improve efficacy for pulmonary drug delivery.