EFFECTS OF LIPID COMPOSITION ON SIZE AND POLYDISPERSITY OF SELF-ASSEMBLED UNILAM

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In basic research, unilamellar lipid vesicles often serve as models for cell membranes. More recently they are also extensively used as nanoscale vehicles for reagents in a wide variety of applications, including for example drug delivery and targeting. In most of these applications the vesicle size and polydispersity are key parameters and are intimately linked to the vesicle composition due to the self assembled nature of the system. In this project we set out to study the effects of lipid chain length and amount of charged lipids on these parameters. The unilamellar vesicles were prepared using multiple extrusions of a lipid suspension through 50-nm polycarbonate filter membranes. The subsequent x-ray scattering measurements and analysis showed that a reliable determination of the vesicle size and size distribution was difficult for most of these vesicles. This was due to the fact that the mean size of the vesicles produced is about 20%-30% larger than the size of the pores in the extrusion filter and thus exceeded the current capabilities of the instrument. The experiment will be repeated in the future with a smaller extrusion filter (30 nm) and slightly different lipid compositions that should more readily form smaller vesicles.