Monoolein Cubic Phase Including Hydrophobized Modified Gelatin and Poly(ethyleneimine) and Its Effect on the Stability of Retinyl Palmitate.

Retinyl palmitate (RP) was added in monoolein (MO) cubic phase including decanoyl poly(ethyleneimine) (DePEI) and decanoyl gelatin (DeGel) in its water channel. RP, DePEI, and DeGel was incorporated In the cubic phase without structural disintegration, as confirmed by transmission electron microscopy. Differential scanning calorimetric and polarized optical microscopic analysis showed that adding the additives reduces phase transition temperature of cubic phase by 2 °C to 3 °C. The time-dependent chemical stability of RP added in the cubic phase was analyzed for 4 weeks at 5 °C, 20 °C, 30 °C, and 40 °C, using RP loaded in o/w emulsion as a control. The chemical stability of RP added in cubic phase containing DePEI and DeGel was somewhat higher as compared to the RP added in the cubic phase without DeGel/DePEI, possibly because DeGel/DePEI complex might shield RP from its environment by blocking the water channels inside the cubic phase. Moreover, the chemical stability of RP added in the cubic phase was comparatively higher than RP added in o/w emulsion.