An Overview on Microemulsion

An Overview on Microemulsion

Author Name : Bhushan Dhangar, Vishal Gurumukhi, Nilesh Patil

ABSTRACT

Microemulsions are thermodynamically stable isotopically clear dispersion of two immiscible liquids, such as oil and water, stabilized by an interfacial film of surfactants along with co-surfactants. Microemulsions are having the advantages over both colloidal systems under investigation and conventional emulsions, suspensions and micellar solutions. Microemulsions provide alternative drug carriers. Microemulsions offer the advantages of spontaneous formation, easy of manufacturing and scale-up, thermodynamic stable, improved drug solubilization of hydrophobic drugs and bioavailability.

 The term of micro emulsion applies to a mixture with at least three components; an oily phase, an aqueous phase and a surface active species, so called surfactants. Sometimes the forth component i.e., co-surfactant can/must be present. Depending on the ratios between the components, in the two extremes the microstructure of the micro emulsions vary from a very tiny water droplets dispersed in oil phase (w/o micro emulsion) to an oil droplets dispersed in water phase (o/w micro emulsion). The microstructure of the mixture changes continuously from one to another extreme, namely, from a spherical to cylindrical, tubular and interconnected continuous oil and water phases separated with a very thin layer of surfactant molecules, in the middle, which is defined as discontinues micro emulsion. The micro emulsions of each kind are thermodynamically stable and transparent solutions. There are main differences between emulsions and micro emulsions in terms of structure and stability.

Microemulsions are one of the best candidates as sustained drug delivery system because of their long shelf life, improved drug solubilization with ease of preparation and administration. A microemulsion is considered to be a thermodynamically or kinetically stable liquid dispersion of oil and a water phases, in combination with a surfactant. The dispersed phase typically comprises small particles or droplets, with a size range of 5 nm-200 nm and has very low oil/water interfacial tension. Because the droplet size is less than 25% of the wavelength of visible light, microemulsions are transparent. These are formed readily and sometimes spontaneously, generally without high-energy input. In many cases a co-surfactant or co-solvent is used in addition to the surfactant, the oil phase and the water phase. The main objective of this review paper is to discuss microemulsions asdrug carrier system with other possible applications

Keywords: Microemulsions, thermodynamically stable,Interfacial tension,Solubilization.