Complex dispersions of multilamellar vesicles: a promising new carrier for controlled release and protection of encapsulated molecules

Multilamellar vesicles called Spherulites(R) have recently been discovered and are being developed for encapsulation applications. In this study, we present new systems of Spherulites called complex dispersions. These are prepared by dispersing Spherulites within an oily medium, and then emulsifying this oily dispersion of Spherulites within an aqueous solvent. The ability of complex dispersions to reduce the release of encapsulated ions under variable osmotic dilutions was evaluated and compared with Spherulites directly dispersible in an aqueous medium, and with multiple emulsions. An advantage of complex dispersions over Spheruilites is to present an additional oily barrier. Indeed, this barrier retarded the release of encapsulated ions. Complex dispersions also proved to be less sensitive to osmotic pressure than multiple emulsions. It appeared that the dilution of a complex dispersion formulated with no external aqueous phase containing a hydrophilic surfactant provided the slowest release of encapsulated ions. Furthermore, this formulation maintained a difference of pH between the internal and external aqueous phases for a few hours. In conclusion, these new systems of Spherulites known as complex dispersions show great potential for pharmaceutical applications such as controlled release and protection of encapsulated substances. (C) 2003 Published by Elsevier Science B.V.