Abstract:

This paper describes the formation and characterization of liq. cryst. dispersions based on the hexagonal phase of GMO/tricaprylin/water. As a stabilizer of the soft particles dispersed in the aq. phase, a non-ionic, non-polymeric surfactant-ethoxylated phytosterol with 30 oxyethylene units (PhEO) was utilized. In contrast to Pluronic copolymers, normally utilized in the stabilization of liq. cryst. dispersions with ordered inner structure, use of such non-polymeric surfactant is not a common practice in this field. The authors revealed how properties of these particles, such as internal structure, size, and stability, can be rationally modified by the concn. of the stabilizing agent and processing conditions. The phys. stability of the hexosomes was further examd. by the LUMiFuge technique. Structural effect of PhEO solubilization on the properties of the bulk HII mesophase system showed that phase behavior was greatly influenced following phase transitions: HII → HII + cubic → cubic + L$\alpha$ → L$\alpha$. The decrease of hydrogen bonding of the hydroxyl and carbonyl groups of monoolein with water and simultaneous hydration of EO groups of PhEO appeared to be important for the obsd. behavior. The use of PhEO as a dispersant resulted in a soft matter multi-phase water dispersion with bimodal distribution of the particle population. Effective stabilization of hexosomes was obtained in an extremely narrow concn. range of PhEO (0.1-0.2%), coexisting with small vesicles and disordered particles. At higher PhEO content, particles had disordered inner structure, and unilamellar and multilamellar vesicles, at the expense of hexosomes in consequence of incorporation of the dispersant into the hexosome structure. PhEO was found to induce lamellar phase formation, introducing disorder into the hexagonal LLC and reducing their domain size. Finally, hexosomes were evaluated as delivery vehicles for the therapeutic peptide desmopressin. Sustained release of this drug was obsd. during the first 10 h; however, permeation drastically increased in the 10-24 h range. [on SciFinder(R)]