Preparing Nanoparticles by Emulsification Diffusion Method

In this method, polymer is dissolved in measured amount of solvent (ethyl acetate, benzyl alcohol, propylene carbonate, methyl ethyl ketone. Organic phase is added into required amount of aqueous phase containing the stabiliser. After mutual saturation of organic and continuous phase, the mixture is emulsified with a high speed homogenizer. For full diffusion into the water phase, excess amount of water is added to the oil in water emulsion under magnetic stirring, leading to the nanoprecipitation of the polymer.

                Schematic illustration of the Emulsion Diffusion Method

Advantages of emulsion diffusion method:-

It offers high encapsulation efficiency, no need for homogenization, high batch to batch reproductibility, ease of scaling up, simplicity and narrow size distribution. 

Limitations of emulsion diffusion method:-

High volumes of water have to be eliminated from suspension, leakage of water soluble drug into saturated aqueous external phase during emulsification reducing encapsulation efficiency.

Arranged by Div.

 

Preparing nanoparticles by Salting –out Method

In this method as shown in Figure; acetone is chosen as the water-miscible organic solvent because of its pharmaceutical acceptance with regard to toxicity. The method consists of the addition of water soluble polyvinyl alcohol in a highly concentrated salt solution in water (aqueous phase) to a polymer solution in acetone (organic phase). Although acetone is miscible with pure water in all ratios, the high salt concentration of the aqueous phase prevents mixing of the phase. After emulsification, the addition of pure water in a sufficient quantity causes acetone to diffuse into the aqueous phase, resulting in the formation of nanoparticles.

 

Schematic representation of Salting out technique

Advantages of salting out technique

The main advantage of this technique is that it minimizes stress to protein encapsulants, it doesn’t require an increase of temperature and therefore maybe useful when heat sensitive material has to be processed.

Disadvantages of salting out technique

It is exclusively applicable to lipophilic drugs and extensive nanoparticle washing steps.