(329e) Preparation and Properties of Niosomes Prepared with Polyglycerol Fatty Acid Esters Using the Supercritical Carbon Dioxide Reverse Phase Evaporation Method

Liposomes have phospholipid bilayers with an aqueous phase at their core. They have been used in drug delivery systems, cosmetics, as biomembrane models, and as microcapsules for chemical reactions. One of the most interesting properties of liposomes is that they retain water-soluble substances in the inner aqueous phase and oil-soluble substances in the surrounding bilayer.

Although liposomes are expected to have a wide range of uses in industry, they have several problems concerning their physical and chemical stabilities. One useful approach to reduce these problems is to use nonionic surfactants, instead of phospholipids, to form vesicles. Compared to liposomes, vesicles made of nonionic surfactants are more suitable for industrial applications because of their high physicochemical stabilities and low cost. Furthermore, there are a large number of nonionic surfactants available for the design of nonionic vesicles, known as niosomes, because many combinations of hydrophilic and lipophilic groups can be made. For example, niosomes prepared using polyoxyethylene alkyl ethers, sucrose fatty acid esters, polyglycerol fatty acid esters, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters have been reported. However, the preparation of liposomes or niosomes requires the use of harmful organic solvents such as chloroform and acetone. These organic solvents are necessary to dissolve the phospholipids or nonionic surfactants. When vesicles are used as drug carriers and in cosmetics, the use of organic solvents must be minimized. Recently, Otake et al. reported a new, environmentally friendly method, the supercritical carbon dioxide reverse phase evaporation method (scRPE method), for the preparation of liposomes or niosomes in a single step using supercritical CO₂ (scCO₂)^1,2). However, niosome formation by the scRPE method has been demonstrated only for nonionic surfactants with polyoxyethylene as the hydrophilic group^3,4). In pharmaceuticals, cosmetics, and food products, consumers prefer to use products made from safer materials, especially plant-derived materials. Thus, petroleum-derived materials such as polyoxyethylene-type nonionic surfactants should be avoided. However, there are few reports of niosomes prepared with non-polyoxyethylene-type nonionic surfactants.

 In this study, the scRPE method was used to prepare niosomes with polyglycerol fatty acid ester (PG ester)-type nonionic surfactants. PG ester-type nonionic surfactants are widely used as food additives because they are safe to be used for such purposes. In this paper, we report the effects of the molecular structures of nonionic surfactants on niosome formation. In addition, we investigated their physicochemical properties, including trapping efficiency, by cryogenic transmission electron microscopy (cryo-TEM), fluorescence anisotropy (FA), differential scanning calorimeter (DSC), and dynamic light scattering (DLS).

Through this method, decaglycerol distearate (DG2S) and decaglycerol diisostearate (DG2IS) formed niosomes. On the other hand, decaglycerol monostearate (DG1S), which has a high hydrophilic-lipophilic balance (HLB) value, yielded a solution of spherical micelles, and decaglycerol tristearate (DG3S), which has a low HLB value, yielded a gel-like solution. Niosomes of DG2IS had higher trapping efficiencies and dispersion stabilities than those of DG2S because the membrane fluidity of the DG2IS niosomes was greater than that of the DG2S niosomes. The niosomes obtained in the present study are candidates for cosmetic and pharmaceutical applications because they are formed from nonionic surfactants derived from natural sources, and prepared using the scRPE method, which avoids the use of harmful organic solvents.

The findings obtained in this study give useful information on the preparation of niosomes using nonionic surfactants derived from natural sources using an environmentally friendly method.

References

1) Otake K.; Imura T.; Sakai H.; Abe M. Development of a New Preparation Method of Liposomes Using Supercritical Carbon Dioxide, Langmuir, 17, 3898-3901 (2001).

2) Otake K.; Shimomura T.; Goto T.; Imura T.; Furuya T.; Yoda S.; Takebayashi Y.; Sakai H.; Abe M., Preparation of Liposomes Using an Improved Supercritical Reverse Phase Evaporation Method, Langmuir, 22(6), 2543-2550 (2006)

3) Ri K.; Yamaguchi S.; Wongtrakul P.; Hashimoto S.; Otake K.; Ohkubo T.; Sakai H.; Abe M., Preparation and Characterization of Nonionic Surfactant Vesicles Using Supercritical Carbon Dioxide, Mater. Technol., 23(5), 340-347 (2005)

4) Yamaguchi S.; Tsuchiya K.; Sakai K.; Abe M.; Sakai H., Preparation of Nonionic Vesicles Using the Supercritical Carbon Dioxide Reverse Phase Evaporation Method and Analysis of Their Solution Properties, J. Oleo Sci., 65(1), 21-26 (2016)