Fabrication of vesicles with the diameter of 4-30 m was achieved by mixing of a hydrophobic nonionic surfactant (Span 65) with a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (Pluronic P123) in aqueous solutions at room temperature. Ring-shaped structure of the Pluronic P123/Span 65 mixture assemblies was confirmed by fluorescence microscopy. The presence of internal aqueous phase in the Pluronic P123/Span 65 mixture assemblies was determined by measuring the entrapment efficiency of calcein using fluorescence spectroscopy. On the other hand, Pluronic P123/Span 60 mixture system formed wire-like assemblies but not vesicles.

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