Preparing Nanoparticles…

Emulsion cross-linking method:-

In this method, water-in-oil (w/o) emulsion is prepared by emulsifying the chitosan solution in the oil phase. Aqueous droplets are stabilized using a suitable surfactant, the stable emulsion is cross-linked by appropriate cross-linking agent such as glutaraldehyde to harden the droplets, and the particles are filtered and washed repeatedly. By this method particle size can be controlled by controlling the size of the aqueous droplets. However, the particle size of the final product depends upon the extent of the cross-linking agent used while hardening in addition to the speed of stirring during the formation of emulsion. The drawback of this method involves tedious procedure as well as use of harsh cross-linking agents, which might possibly induce chemical reaction with agents, however complete removal of the un-reacted cross-linking agent may be difficult in this process.

Nanoprecipitation:-

The nanoparticles formation as shown in Figure 1.5 is instantaneous and the entire procedure is carried out in only one step. Briefly, it requires two solvents that are miscible. Ideally, both the polymer and the drug must dissolve in the first one (the solvent), but not in the second system (the non-solvent). Nanoprecipitation occurs by a rapid desolvation of the polymer when the polymer solution is added to the nonsolvent.

Schematic representation of nanoprecipitation technique

 

Advantages of nanoprecipitation:-

1.  This method is efficient one for lipophilic drugs.

2.  It involves the use of any type of synthetic polymers like poly lactic acid, poly lactic co - glycolic acid.

Disadvantages of nanoprecipitation:-

1. The usefulness of this technique is limited to water-miscible solvents.

2. This is not an efficient means to encapsulate water soluble drugs.