Monoolein cubic phases containing hydrogen peroxide

Monoolein (MO) cubic phases were prepared by hydrating MO using distilled water or 12 wt.% H₂O₂ solution so that the content of aqueous phase in the cubic phase is 30 wt.%. The thermal transition of the isotropic cubic phase to reversed hexagonal phase was observed on a polarizing photomicroscope and the transition temperature was found to be around 65 °C on a differential scanning calorimeter (DSC). Small-angle X-ray scattering (SAXS) patterns indicated the cubic phases had diamond surfaces. The cubic phase released H₂O₂ into an aqueous phase in a saturation manner so that approx. 50% of total loaded H₂O₂ release in the first 10 h and thereafter relatively slow was observed over 40 h. The cubic phase was stable at 45 °C for 56 days before it broke down into an oily phase and an aqueous phase in 70 days. According to ¹H NMR spectrum, glycerol moiety and ---CH₂=CH₂--- of the oily phase were detected less in number than those of intact MO. Therefore, the hydrolysis and the oxidation of MO would be responsible for the breakdown of the cubic phase. The tensile adhesive forces of the cubic phases were higher than a skin-adhesive patch prepared using polyacrylate. The cubic phase containing H₂O₂ could be used as a topical disinfected gel for a wounded skin.