Monoglyceride-based cubosomes stabilized by Laponite: Separating the effects of stabilizer, pH and temperature

The use of colloidal stabilizers for liquid crystalline phases broadens the possible applications of cubosomes. However, in the case of Laponite XLG as the stabilizer, the pH is increased. This can lead to changes in the system. In this paper the effects of high pH and type of stabilizer on the liquid crystal structure of monoglyceride/water phases are separated and examined. Specifically, a comparison between the synthetic hectorite platelet (Laponite XLG) and Pluronic F127 triblock copolymer as the stabilizer of the dispersions is presented. At neutral pH a pure Pn3m phase is observed in the bulk phase, which transforms into a two-phase coexistence (Pn3m and Im3m) with high pH. In the dispersion the F127 triblock copolymer as stabilizer also promotes the coexistence of these two cubic phases, where Im3m phase dominates. Dispersions with Laponite exhibit only one cubic phase of type Pn3m in the same pH regime. The disruptive role of F127 on the internal structure of the particles is evidenced in lower melting temperatures than found in the bulk phase, whilst Laponite is found to be undisruptive and the phase behaviour is directly dictated by the bulk phase. Finally, the effect of temperature on Laponite-stabilized hexosomes, formed in-situ from cubosomes due to hydrolysis of the monoglyceride, was investigated. (C) 2010 Elsevier B.V. All rights reserved.