Manipulation of Lipid Bilayer Structure and Phase Behavior Through Embedded Hydrophobic Nanoparticles

The potential application of hybrid lipid vesicles containing hydrophobic nanoparticles embedded in the bilayer is dependent upon lipid phase behavior, which controls structure and stability.  The effect of nanoparticle intercalation on bilayer thickness and phase transition behavior was studied with stearylamine-stabilized nanoparticles enclosed within the bilayer of dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylglycerol vesicles of varying lipid to nanoparticle ratios.  Differential Scanning Calorimetry results show that at higher nanoparticle loadings the lipid melting temperature is significantly affected and phase separation begins to occur.  It is further demonstrated that hysteric losses are present upon the cooling of these vesicles.  Increased hydrophobic mismatch caused by high nanoparticle loadings prolong the rigid gel phase, and the minimization of mismatch upon aggregation of nanoparticles in the fluid phase leads to a likewise persistence of the fluid phase during cooling.  These alterations in phase behavior due to nanoparticle inclusion can be compared to the impact of hydrophobic proteins and may lead to the application of protein models to help tune potential drug delivery therapies.