Review: emulsion techniques for producing polymer based drug delivery systems

Emulsification method is one of the popular methods for producing materials used inbiosensing, bioimaging and others, especially, drug delivery polymer systems in microsize andnanosize. The concrete techniques related to this method are emulsification, self-emulsification,in a combination with solvent evaporation process, homogenization, or ultranosication. Thestructure of emulsion formulation consists of two phases: an internal phase and an externalphase. Based on the structure and nature of the phases, emulsions can be classified into differenttypes such as two-phase systems (oil in water emulsion (O/W) or water in oil emulsion (W/O))or three-phase systems (water in oil in water triple emulsion (W/O/W) or oil in water in oil tripleemulsion (O/W/O)). The droplet sizes in micro-emulsion systems are often higher than 1 mwhile those in nano-emulsions or mini-emulsions are in the range of 100-500 nm. Some specialnano-emulsion systems can contain droplets with a size of few nanometers. Factors includingsolvents, oil/water phase ratio, droplet oil size, composition ratio, nature of raw materials,emulsifiers, etc. can affect the morphology, properties, and size of the obtained products. Thispaper reviews emulsion techniques which have been applied for producing polymeric drugdelivery systems. The components, properties, characteristics, encapsulation efficiency as wellas drug release rate, water solubility, toxicity and administration efficacy of drug emulsionformulations will be mentioned. Advantages and limitations of emulsion techniques are alsodiscussed.