Interaction of soybean oil with phosphatidylcholine and their formation of small dispersed particles.
Stable aqueous dispersions of soybean oil (SO) were obtained by cosonication with dipalmitoylphosphatidylcholine (DPPC) in the SO mole fraction range 0.1-0.8. To clarify the dispersal mechanism, the dispersed particles were characterized, and the interaction between SO and DPPC was investigated using several physicochemical techniques. Dynamic light scattering (DLS) measurements showed that the diameter of the dispersed particles was 40-60 nm. The trapped aqueous volume inside the particles was determined fluorometrically using the aqueous space marker calcein. The trapped volume in the SO/DPPC particles decreased remarkably with the addition of SO into small unilamellar vesicles of DPPC. The decline in fraction of vesicular particles was also confirmed by fluorescence quenching of N-dansylhexadecylamine in the DPPC membrane by the addition of the quencher CuSO4. These results indicate that the excess SO separated from the DPPC bilayers is stabilized as emulsion particles by the DPPC surface monolayer. Monolayer-bilayer equilibrium of SO/DPPC mixtures was estimated by measurement of spreading and collapse pressures. The results showed that the coexistence of emulsion particles (surface monolayer of DPPC + core of SO) with vesicular particles (bilayer) was critically important for the formation of stably dispersed particles of the lipid mixture.
Asai
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Y
Formulation Research Laboratory, Kawashima, Eisai Company, Limited, Gifu, Japan.
Watanabe
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S
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D005217:Fat Emulsions, Intravenous; D005453:Fluorescence; D012995:Solubility; D013024:Soybean Oil / Q000737:chemistry*
D005217:Fat Emulsions, Intravenous; D015060:1,2-Dipalmitoylphosphatidylcholine; D013024:Soybean Oil