Monoolein Cubic Phase Containing Stevioside and its pH-dependent Release Property

초록

Introduction The monoolein (MO)-based cubic phase, composed of lipid bilayers and water channels, can encapsulate both hydrophilic and hydrophobic active ingredients. Its responsiveness to external stimuli can be modulated by incorporating polymers and functional materials into the water channels. In this study, a pH-responsive MO cubic phase was developed by incorporating hydrophobically modified gelatin (HmGel) and pectin (HmPec), enabling the controlled release of steviol glycoside (SG).Methods SG was loaded into the MO cubic phase containing HmGel and HmPec. The physicochemical properties of the cubic phase were characterized using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Structural and chemical stability was evaluated over 12 weeks at 27 degrees C and 37 degrees C, and SG release behavior was assessed under various pH conditions.Results The maximum SG loading capacity was approximately 1.98%. As the SG content increased, the phase transition temperature of the cubic phase rose from 62.2 degrees C to 84.2 degrees C, as confirmed by POM and DSC. TEM images showed no significant structural disruption. The cubic phase retained chemical stability against double bond oxidation during storage. Release studies revealed that stevioside (a major component of SG) was suppressed under acidic conditions (pH 3.0 and pH 4.5) but promoted at neutral to basic pH (pH 6, 7.4, and 8).Discussion The suppressed release at low pH was attributed to the formation of a coacervate between HmGel and HmPec, which increased the diffusion resistance within the water channels. These results suggest that the system can serve as an effective pH-responsive drug delivery vehicle. However, further investigations, including in vivo studies, may be necessary to validate its practical applicability.Conclusion The developed pH-responsive MO cubic phase can act as an enteric delivery system that suppresses release in the stomach and promotes release in the intestine. Moreover, it is applicable as a dermal carrier for cosmetics or topical drugs, ensuring storage stability under acidic conditions and triggering rapid release under near-neutral pH upon skin application.

키워드