Structural and thermal analysis of lipid vesicles encapsulating hydrophobic gold nanoparticles.
The structure and stability of hybrid lipid vesicles containing bilayer-encapsulated hydrophobic nanoparticles is dependent upon lipid phase behavior. By embedding stearylamine-stabilized gold nanoparticles in dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylglycerol vesicles, we show that encapsulation at lipid to nanoparticle ratios from 10,000:1 to 5000:1 leads to bilayer thickening and hydrophobic mismatch, favoring nanoparticle inclusion in gel phase vesicles. High loadings lead to large increases in the gel to fluid melting temperature upon heating and significant hysteresis on cooling, which cannot be attributed solely to excess free ligand. This behavior is due to a cooperative effect of excess free SA ligand and nanoparticle embedment. Nanoparticle clustering was observed during lipid melting and could be reversed upon lipid freezing owing to lateral capillary forces within the bilayer. The impact of nanoparticle embedment on vesicle structure and properties at such low concentrations is reminiscent of hydrophobic proteins, suggesting that the underlying lipid biophysics between proteins and nanoparticle are similar and may provide a predictive design tool for therapeutic applications.
Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, South Carolina 29634, USA.
Gregory
G
Von White
Yanjing
Y
Chen
Julia
J
Roder-Hanna
Geoffrey D
GD
Bothun
Christopher L
CL
Kitchens
D000327:Adsorption; D000588:Amines / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008081:Liposomes / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature
D000588:Amines; D008081:Liposomes; D046911:Macromolecular Substances; D006046:Gold; C009317:stearylamine