Over the last decade, biodegradable polymers have been of increasing interest due to their many benefits. These benefits include the ability to deliver a combination of varying therapeutic ingredients, the capability to include targeting moieties, and to protect APIs from degradation, as well as controlled release and terminal sterilization via filtration. The Microfluidizer™ has been widely accepted as an ideal technology for the generation of polymer nanoparticles.
The water phase generally contains a surfactant, such as the widely used polyvinyl alcohol (PVA). Recently, several researchers have had success with polymeric surfactants such as polysorbate or polyoxyethane, and phospholipids like 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). The oil phase consists of a solvent, usually ethyl acetate or methylene chloride. It is important that the chosen solvent have very low miscibility with water. When using ethyl acetate—which has some miscibility with water—researchers will often saturate the water phase with ethyl acetate. The most commonly used polymer is poly(lactide-co-glycolide) (PLGA) of which there are several types which can be used to manipulate the critical features of the nanoparticles, such as dissolution rate and compatibility with active ingredients. Contrast enhancers can also be encapsulated in the particles to allow researchers to verify that the active ingredient is delivered to the desired location.
To produce the nanoparticles, the oil phase is added at the appropriate concentration to the water phase and pre-mixed using a rotor-stator mixer or other similar technology. This crude emulsion is then introduced to the MicrofluidizerTM. Critical processing parameters are the interaction chamber type, the processing pressure, the temperature of both the machine and the formulation, and the number of passes. Once the desired particle size is verified, the solvent can be removed via solvent-exchange techniques or evaporation in a hood while mixing.
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