Emulsifiers microemulsions

Disperse systems The hydrophobic drug is dissolved in an organic solvent and in addition may also contain an emulsifier. On contact with the intestinal fluids, the drug is emulsified (microemulsions) by bile salts and is absorbed through the intestine. 

Yaghmur, A., de Campo, L., Sagalowicz, L., Leser, M.E., and Glatter, O. (2005). Emulsified microemulsions and oil-containing liquid crystalline phases. Langmuir. 21, 569-577. 

Micelle Formulations A micelle system can be either water-based or oil-based. The use of a micelle formulation for poorly water-soluble drugs for systemic delivery has been well recognized. In recent years, the effective development of self-emulsifying microemulsions or mixed micelle-based lipid formulations products, such as Sandimmun Neoral (cyclosporin), Norvir (ritonavir), and Fortovase (saquinavir), has substantially increased interest in the application of lipid-based micelle formulation to improve oral delivery of poorly water-soluble drugs as well as protein and peptide drugs.51... 

Grossiord et al. (21) diseuss an additional method termed, by them, the oily isotropic dispersion process. We prefer a more accurate terminology of emulsified microemulsions. The idea is to disperse an oil phase within water by smfactant and to form an L2 phase. This phase is... 

Figure 4 Preparation of W/O/W multiple emulsion by oily isotropic dispersion (emulsified microemulsion). (From Ref 21.)...

The main goals remaining are to obtain submic-rometer double-emulsion droplets with long-term stability (possibly with emulsified microemulsions) and to trigger and control the release at will. 

N Garti, H Houminer. Emulsified Microemulsions for Sustained Release of Drugs. PhD irrtemal report. The Hebrew University of Jerusalem, 1996. 

Hydrogenated tallow acid emulsifier, microcryst. wax Hydrogenated tallowamide DEA emulsifier, microemulsions Polyglyceryl-6 isostearate Sodium cocaminopropionate emulsifier, milk/dairy prods. 

The freeze fracture method has been used to study the structure of colloidal particles in water-oil mixtures stabilized by polymer emulsifiers. Microemulsions consisting of water, toluene and graft copolymer composed of a polystyrene backbone and a poly(ethylene oxide) graft were deposited onto a small gold plate, quenched in liquid nitrogen in equilibrium with its own solid phase [436]. Replicas of the fractured surfaces were washed with tetrahydrofuran, which showed the micellar structure of the copolymers. A similar method was used for the preparation of polystyrene polymer latexes for TEM study of the size distribution [437]. In this case, the frozen droplet was microtomed, with a cold knife at -100 to -120°C, etched for up to 90 s and then a platinum-carbon replica was prepared. Etching was found to be unnecessary and a potential cause of error. The remaining latex was dissolved away before examination of the replica. Such replicas can reveal the size distribution and structure of the latex particles. 

Zhang, X. N., Tang, L. H., Gong, J. H., Yan, X. Y., and Zhang, Q. 2006. An alternative paclitaxel self-emulsifying microemulsion formulation Preparation, pharmacokinetic profile, and hypersensitivity evaluation. PDA Journal of Pharmaceutical Science and Technology, 60, 89-94. 

Regarding the long-standing issue of the confusion of treating microemulsions as one type of emulsion. Chapter 7 by Otto Clatter and coauthors, dealing with emulsified microemulsions, is particularly enlightening as it clearly hints to this misconception. 

The best multiple emulsions are likely to be prepared by the separation membrane technique, with polymeric amphiphilic, viscosity-enhancing agents, emulsified microemulsions, and proper selection of the amphiphilic blends of biomacromolecules (proteins and hydrocolloids) in each of the interfaces. The main goal remains to obtain submicron multiple emulsion droplets with longterm stability, possibly by replacing the inner emulsion with a microemulsion that is thermodynamically stable (emulsified microemulsions). Better control of the release pattern from the inner phase is stiU far from being achieved. 

The same concept of emulsified microemulsion was earlier reported by Pilman et al. (Pilman et al, 1980) and also patented (Gaonkar, 1994a). If one can prove that the internal compartmentalization is of stable microemulsion, it might bring a breakthrough to this field, since the sizes of the external droplets could be reduced to values below one micrometer. Such formulations will... 

Last, the results of a very recent investigation concerning a novel type of multiple emulsion, dubbed emulsified microemulsion (EME), are herewith... 

Lutz R, Aserin A, Wachtel EJ, Ben Shoshan E, Danino D, Garti N. 2007. A study of emulsified microemulsion by SAXS, cryo-TEM, SD-NMR and electrical conductivity. / Dispersion Sci Technol 28(8) forthcoming. 

Few fonnulations based on double emulsions (in which droplets of the dispersed phase further contain smaller dispersed droplets) are on the market as these consist of large, polydispersed droplets (10-100 (xm) that are thermodynamically unstable. ControUmg the release of compounds incorporated in double emulsions is normally achieved by stabilizing the interface of the inner emulsion, careful composition of the oil and aqueous phases, and/or stabilization of the secondary interface (Davis et al, 1985 Garti, 1997). However, most double emulsions tend to release entrapped compounds in an uncontrolled manner. A novel possibility for the stabilization of the inner emulsion is to use microemulsions. Pilman and co-workers (1980) reported the use of microemulsions dispersed within the inner phase of water-in-oil-in-water (w/o/w) duplex emulsions, and stabilized in a sodium caseinate solution resulting in emulsified microemulsions. In principle, these emulsified microemulsions may be used as controlled delivery system for nutraceuticals and pharmaceuticals. 

Lutz and co-workers (2007) formulated a w/o/w emulsified microemulsions based on a two-step emulsification process whereby the w/o microemulsion was dispersed in a continuous aqueous phase containing a steric stabilization amphiphile - graft copolymer Pluronic F127. Water up to 15 wt-% in the inner microemulsion and 30 wt-% of miCToemulsion in the double emulsion was entrapped, in comparison to only 5 wt-% obtained in previous studies carried out by Yaghmur and co-workers (2005), which suggested the possibility of enhanced solubilization of entrapped nutrients. 

Yaghmur A, de Campo L, Sagalowicz L, Leser M and Glatter O. 2005. Emulsified microemulsions and oU-containing liquid crystalline phases. Langmuir 569-577. 

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