Gelation, multiple emulsions

One of the main drawbacks to the commercial development of multiple emulsions is their inherent instability. The intention of this paper is to review studies on the stability and mechanism of breakdown of multiple systems and attempts to minimise such instability, for example, by appropriate choice of surfactant, polymerisable surfactants or gelation of the aqueous or oily phases. 

Hosseini, S. M., Hosseini, H., Mohammadifar, M.A., Mortazavian, A. M., Mohammadi, A., Khosravi-Darani, K., Shojaee-Aliabadi, S., Dehghan, S., and Khaksar, R. (2013). Incorporation of essential oil in alginate microparticles by multiple emulsion/ionic gelation process. International Journal of Biological Macromolecules, 62, 582-588. 

Use of High Viscosity Oii Recently Weiss et al. (2005) investigated the possibility of using a semicrystalline oil phase in W/O/gel to control the release of encapsulated hydrophilic compounds from polysaccharide gels with multiple emulsions. Various lipid phases prevent the diffusion of water/surfactant/ active material from the inner phase and also gelation of the oily or aqueous phase. For example, MCT-oil and various vegetable fats were investigated for... 

Gelation of the Outer Aqueous Phase (W/O/Gel) Most of the additives inserted in the multiple emulsions under study are not permitted in foods. Viscosities were found to be enhanced by cellulose derivatives such as hydro-xypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), hydro-xyethyl cellulose (HEC), and the natural hydrocolloids, such as xanthan, guar gum, and carrageenan. The viscosity or gelling agents can affect some of the multiple emulsion properties such as entrapping yields, stability, droplet size, consistency, and skin feel (Ozer et al., 2000). 

For instance, Yadav and Ahuja prepared nanoparticles using gum cordia as the polymer and to evaluate them for ophthalmic delivery of fluconazole. A w/o/w emulsion containing fluconazole and gum cordia in aqueous phase, methylene chloride as the oily phase, and dioctyl sodium sulfosuccinate and polyvinyl alcohol as the primary and secondary emulsifiers, respectively, were cross-linked by the ionic gelation technique to produce a fluconazole-loaded nanoreservoir system. The formulation of nanoparticles was optimized using response surface methodology. Multiple response simultaneous optimizations using the desirability approach were used to find optimal experimental conditions. The optimal conditions were found to be concentrations of gum cordia (0.85%, w/v), di-octyl sodium sulfosuccinate (9.07%, w/v), and fluconazole (6.06%, w/v). On comparison of the optimized nanosuspension formulation with commercial formulation, it was found to provide comparable in vitro corneal permeability of... 

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