Optimizing rapid solvent exchange preparation of multilamellar vesicles.

We have enhanced the rapid solvent exchange (RSE) apparatus by adding controls in temperature, evacuation speed and vortex velocity. Following published protocols yielded vesicles of diverse size and lamellarity as detected by differential scanning calorimetry, photon correlation spectroscopy and X-ray experiments. To optimize the net production of multilamellar vesicles (MLVs) we varied in addition to vortex and evacuation speed lipid and organic solvent concentration, as well as composition of the aqueous medium. Reducing vortexing frequencies and speed of degassing were most beneficial for the yield in MLVs. Additionally also high lipid concentrations and organic solvent/buffer ratios supported MLV formation. To explain our findings we hypothesize on the role of microscopic instabilities on the aqueous phase, which may act as molds for vesicle formation.