Control of Physicochemical Properties of Liposomes Using a Supercritical Reverse Phase Evaporation Method

Abstract

L-R-Dipalmitoylphosphatidylcholine (DPPC) and L-R-dioleoylphosphatidylcholine (DOPC) liposomes were prepared using the previously developed supercritical reverse phase evaporation (scRPE) method. The effects of phospholipid structure, preparation pressure, and amount of ethanol on their physicochemical properties were examined using measurements of trapping efficiency, cloud point, dynamic light scattering, and osmotic water transport. The trapping efficiencies of DOPC liposomes were higher than those of DPPC due to their bulky structure. The maximum trapping efficiency of DOPC liposomes prepared by the scRPE method was as high as 40%. The phase behavior of the phospholipid/ethanol/CO2 mixture before introducing water strongly influenced the physicochemical properties of the liposomes. The sizes of liposomes prepared at pressures below 200 bar seem to be larger than those of liposomes prepared at >200 bar. The variability of size caused the difference in the trapping efficiencies of the liposomes prepared from both states. The minimum ethanol concentration to obtain water in a CO 2 emulsion at 200 bar is 6.8 wt %, which corresponds well to the optimum ethanol concentration to obtain large unilamellar vesicles with the highest trapping efficiency. On the other hand, multilamellar vesicles seem to be formed when the ethanol concentration added to the system is less than 6.8 wt % since the trapping efficiency and osmotic shrinkage velocity are low. These results show that the scRPE method makes it possible to control the physicochemical properties of liposomes such as particle size, size distribution, trapping efficiency, and lamellarity in a single step.

Drastic Improvements in Trapping Efficiency and Dispersibility for Phosphatidylcholine Liposomes in the Presence of Divalent Metal Ions

“…In contrast to their results, the particle size of DPPC liposomes observed in Fig. 2 was bigger than that of those observed by Magome et al The difference in the liposome preparation method and lipid seem to be the reason of these differences (12). However, the number of layers became much smaller in the presence of divalent ions, as the trapping efficiency and the number of liposomes were much higher than those of the control.…”

Conventional and Dense Gas Techniques for the Production of Liposomes: A Review

“…The oilsoluble substance was present with the lipid and the watersoluble substance introduced with the aqueous phase. The product from the scRPE method was compared to MLVs, LUVs and giant unilamellar vesicles (GUVs) formed using conventional methods (29,39). The scRPE method achieved a trapping efficiency comparable to the conventional LUVs, lower than the GUVs and higher than the MLVs.…”

Preparation and Characteristics of Polyethylene Films Containing Superfine Particles (Part 2)

“…Ultraviolet light-preventive white zinc oxide was taken up first as the nucleus substance in this work and superfine particles (nanocapsular polymer filler) containing the extremely tiny nucleus substance particles uniformly dispersed in liposomes were prepared by the reverse phase evaporation method [2][3][4][5][6] . The prepared nanocapsular polymer filler was added to colorless transparent PE to obtain ultraviolet light-preventive PE film that allows to cut off UV light of wavelengths below 400 nm.…”