Emulsion multiple

The term multiple emulsion describes a w/o emulsion ia an o/w emulsion. Eor example, when a w/o emulsion is added to water, no dispersion is expected unless the aqueous phase is fortified with a suitable emulsifier. The resultiag dispersioa may thea be a blead of a w/o and an o/w emulsion, or it may be a multiple emulsion of the w/o/w type. In this latter case, the initial w/o emulsion becomes the internal phase of the final product. Generally, these preparations are not very stable unless they are produced under rigidly controlled conditions (32,39,40). 

The multiple emulsion technique includes three steps 1) preparation of a primary oil-in-water emulsion in which the oil dispersed phase is constituted of CH2CI2 and the aqueous continuous phase is a mixture of 2% v/v acetic acid solution methanol (4/1, v/v) containing chitosan (1.6%) and Tween (1.6, w/v) 2) multiple emulsion formation with mineral oil (oily outer phase) containing Span 20 (2%, w/v) 3) evaporation of aqueous solvents under reduced pressure. Details can be found in various publications [208,209]. Chemical cross-linking is an option of this method enzymatic cross-linking can also be performed [210]. Physical cross-linking may take place to a certain extent if chitosan is exposed to high temperature. 

The number of the constituent phases of a disperse system can be higher than two. Many commercial multiphase pharmaceutical products cannot be categorized easily and should be classified as complex disperse systems. Examples include various types of multiple emulsions and suspensions in which solid particles are dispersed within an emulsion base. These complexities influence the physicochemical properties of the system, which, in turn, determine the overall characteristics of the dosage forms with which the formulators are concerned. 

Multiple emulsions are more complex systems. If a simple emulsion is further dispersed within another continuous phase, these systems are called... 

P Couvreur, MJ Blanco-Prieto, F Puisieux, B Roques, E Fattal. Multiple emulsion technology for the design of microspheres containing peptides and olegopep-tides. Adv Drug Del Rev 28 85-96, 1997. 

By first dispersing the EUP in water containing the base for neutralization of the carboxyl acid groups of the EUP and then adding the comonomer with intensive stirring, normal emulsions are obtained. They are favorable because, with multiple emulsions, insoluble polymers are formed, which decrease the yield of microgels. 

The most widely studied deformable systems are emulsions. These can come in many forms, with oil in water (O/W) and water in oil (W/O) the most commonly encountered. However, there are multiple emulsions where oil or water droplets become trapped inside another drop such that they are W/O/W or O/W/O. Silicone oils can become incompatible at certain molecular weights and with different chemical substitutions and this can lead to oil in oil emulsions O/O. At high concentrations, typical of some pharmaceutical creams, cosmetics and foodstuffs the droplets are in contact and deform. Volume fractions in excess of 0.90 can be achieved. The drops are separated by thin surfactant films. Selfbodied systems are multicomponent systems in which the dispersion is a mixture of droplets and precipitated organic species such as a long chain alcohol. The solids can form part of the stabilising layer - these are called Pickering emulsions. 

Y. Mine, M. Shimizu, and T. Nakashima Preparation and Stabilization of Simple and Multiple Emulsions Using Microporous Glass Membrane. Colloid Surfaces B Biointerfaces 6, 261 (1996). 

S. Sugiura, M. Nakajima, K. Yamamoto, S. Iwamoto, T. Oda, M. Satake, and M. Seki Prepartion Characteristics of Water-in-Oil-in-Water Multiple Emulsions Using MicroChannel Emulsification. J. Colloid Interface Sci. 270, 221 (2004). 

Slow release rates and remarkable long shelf-life (months) were obtained compared to typical multiple emulsions stabilized by two short surfactants (SMO and polyoxyethylene (20) sorbitan monolaurate). Finally, the long lifetime of the emulsions allowed study via diffusing wave spectroscopy (DWS) of the interactions between the droplets and the globule surface [37],... 

N. Garti, M. Frenkel, and R. Schwartz Multiple Emulsions II. Proposed Technique to Overcome Unpleasant Taste of Drugs. J. Dispersion Sci. Technol. 4, 237 (1983). 

S. Magdassi and N. Garti Release of Electrolytes in Multiple Emulsions Coalescence and Breakdown or Diffusion Through Oil Phase Collois Surf. 12, 367 (1984). 

S. Magdassi andN. Garti A KineticModelforReleaseof Electrolytes from W/OAV Multiple Emulsions. J. Controlled Release 3,273 (1986). 

N. Garti, S. Magdassi, and D. WhitehUl Transfer Phenomena Across the Oil Phase in Water-Oil-Water Multiple Emulsions Evaluated hy Coulter Counter 1. Effect of Emulsifier 1 on Water Permeahihty. J. CoUoid Interface Sci. 104,587 (1985). 

N. Jager-Lezer, I. Terrisse, E. Bruneau, S. Tokgoz, L. Eerreira, D. Clausse, M. SeiUer,d and J.L. Grossiord Influence of Lipophihc Surfactant on the Release Kinetics of Water-Soluble Molecules Entrapped in a W/O/W Multiple Emulsion. J. Controlled Release 45, 1 (1997). 

Y. Sela, Y. Magdassi, and N. Garti Polymeric Surfactants Based on PolysUoxanes-Graft-Poly(Oxyethylene) for Stabilization of Multiple Emulsions. Colloids Surfaces 83, 143 (1993). 

R Michaut, P. Perrin, and P. Hebraud Interface Composition of Multiple Emulsions Rheology as a Probe. Langmuir 20, 8576 (2004). 

B.P. Binks, A.K.R. Dyab, and P.D.I. Rletcher Multiple Emulsions Stabilised Solely by Nanoparticles. In Proceedings of the 3rd World Congress on Emulsions, Lyon, Prance (2002). 

Multiple colloids involve the coexistence of three phases, of which two are finely divided, such as multiple emulsions (mayonnaise, milk) of water-in-oil-in-water (w/o/w) or oil-in-water-in-oil (o/w/o). 

Electrostatic and non-electrostatic biopolymer complexes can also be used as effective steric stabilizers of double (multiple) emulsions. In this type of emulsion, the droplets of one liquid are dispersed within larger droplets of a second immiscible liquid (the dispersion medium for the smaller droplets of the first liquid). In practice, it is found that the so-called direct water-in-oil-in-water (W/O/W) double emulsions are more common than inverse oil-in-water-in-oil (O/W/O) emulsions (Grigoriev and Miller, 2009). In a specific example, some W/O/W double emulsions with polyglycerol polyricinoleate (PGPR) as the primary emulsifier and WPI-polysaccharide complexes as the secondary emulsifying agent were found to be efficient storage carriers for sustained release of entrapped vitamin Bi (Benichou et al., 2002). 

Kim, H.-J., Decker, E.A., McClements, D.J. (2006). Preparation of multiple emulsions based on thermodynamic incompatibility of heat-denatured whey protein and pectin solutions. Food Hydrocolloids, 20, 586-595. 

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