Spontaneously Formed Monodisperse Biomimetic Unilamellar Vesicles: The Effect of Charge, Dilution, and Time

Abstract

Using small-angle neutron scattering and dynamic light scattering, we have constructed partial structural phase diagrams of lipid mixtures composed of the phosphatidylcholines dimyristoyl and dihexanoyl doped with calcium ions (Ca 2+) and/or the negatively charged lipid, dimyristoyl phosphatidylglycerol (DMPG). For dilute solutions (lipid concentration ≤1 wt%), spontaneously forming unilamellar vesicles (ULVs) were found, and their polydispersity was determined to be ∼20%. The stability of the Ca 2+- or DMPG-doped ULVs was monitored over a period of 4 days and their structural parameters (e.g., average outer radius, 〈 R o〉) were found to be insensitive to the lipid concentration ( C lp). However, doping the dimyristoyl/dihexanoyl system with both Ca 2+ and DMPG resulted in ULVs whose 〈 R o〉 was found to be C lp dependent. The 〈 R o〉 of DMPG-doped ULVs remained unchanged over an extended period of time (at least 4 days), a good indication of their stability.