Cationic liposomes in double emulsions for controlled release.

Liposomes containing a model active component were entrapped within the internal aqueous phase (W(1)) of W(1)/O/W(2) double emulsions, thus providing a double-encapsulation system. Our motivation for the development of this system is to prevent liposomes from interacting with unfavorable physicochemical conditions and to optimize this system for dermal vaccine delivery. The choice of cationic liposomes is based on the fact that they have high penetration ability across the skin and hair follicles, and an adjuvant effect on the activation of antigen-presenting cells.

Temperature-induced protein release from water-in-oil-in-water double emulsions.

A model water-in-oil-in-water (W1/O/W2) double emulsion was prepared by a two-step emulsification procedure and subsequently subjected to temperature changes that caused the oil phase to freeze and thaw while the two aqueous phases remained liquid. Our previous work on individual double-emulsion globules1 demonstrated that crystallizing the oil phase (O) preserves stability, while subsequent thawing triggers coalescence of the droplets of the internal aqueous phase (W1) with the external aqueous phase (W2), termed external coalescence. Activation of this instability mechanism led to instant release of fluorescently tagged bovine serum albumin (fluorescein isothiocyanate (FITC)-BSA) from the W 1 droplets and into W2.

Induction of instability in water-in-oil-in-water double emulsions by freeze-thaw cycling.

Individual water-in-oil-in-water (W1/O/W2) double-emulsion globules loaded with fluorescently labeled bovine serum albumin (FITC-BSA) were optically monitored within cylindrical capillaries during freeze-thaw cycling. Coalescence of internal aqueous droplets (W1) and external aqueous phase (W2), termed external coalescence, was not observed before or during freezing of the oil phase (O). On the other hand, this instability mechanism was readily promoted during thawing.

Controlled release from a nanocarrier entrapped within a microcarrier.

This study illustrates the entrapment of the dye molecule fluorescein sodium salt (FSS) by hydrogel nanoparticles, which are in turn confined inside a water-in-oil-in-water double-emulsion globule, and its subsequent release by the action of the competing agent hydrochloric acid (HCl). Thus, a "double carrier" concept is being introduced in which a nanoscale delivery vehicle is being transported by a microscale delivery vehicle in order to simultaneously take advantage of both systems. This may facilitate storage and handling while protecting the active substance and improving its action upon application.