Liposomes are spherical vesicles formed by phospholipid bilayers and comprise the foremost structure of any biological membrane. Applications of liposomes span from drug delivery to cosmetics. Recently, tremendous attention has been focused on studying the interactions of inorganic nanoparticles with liposomes which is an ideal model system for investigating nanoparticle/membrane interactions and designing novel self-assemblies. It is hypothesized that the size and surface chemistry of the metallic nanoparticles can be tailored to substantially impact the rigidity of the phospholipid vesicle assemblies. For hydrophilic surface-modified nanoparticles, the nanoparticles attached to the charged headgroups of the phospholipid membrane, which can impact the structure and rigidity of the vesicle assembly. Hydrophobic surface modified small nanoparticles are preferentially encapsulated within the phospholipid membrane bilayer. Scanning calorimetry (DSC) results for dodecanethiol capped silver nanoparticles (AgNPs) and oleic acid capped Fe3O4 nanoparticles (5 nm diameter) encapsulated within the phospholipid membrane bilayers indicate the impact of encapsulated nanoparticles on the phase behavior of liposomes. The dipalmitoylphosphosphatidylcholine (DPPC, zwitterionic) / dipalmitoylphosphatidylglycerol (DPPG, anionic) 85/15 vesicles have a gel to fluid transition at 41 °C and the phase transition temperature for AgNPs encapsulated liposomes decreased significantly. However, the phase transition temperature for oleic acid capped Fe3O4 nanoparticle encapsulated liposomes increased. The nanoparticle-lipid bilayer interactions that are reflected by lipid bilayer permeability, were studied using spectrofluorometry by measuring the efflux of encapsulated fluorescein the probe dye from the small unilamellar vesicles in the presence of the surface functionalized AuNPs and AgNPs. The extent of change in fluorescence signal in the form of relative fluorescence of the fluorescein dye was used to determine the change in membrane permeability. Fluorescein leakage results have indicated that11-mercaptoundecanoic acid and citrate functionalized hydrophilic AuNPs significantly impact the lipid bilayer permeability. The nanoparticle size effect on the lipid bilayer permeability has been studied with citrate functionalized 5, 13, and 30 nm diameter AuNPs.

Modifying lipid bilayer permeability with inorganic nanoparticles

251st National Meeting (2016)

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