NANOPARTICLES: AN OVERVIEW OF THE PREPARATION METHODS FROM PREFORMED POLYMERS

Polymer nanoparticles have many potential applications in biomedical field, since they can be used as drug delivery systems and/or for diagnostic purposes. The encapsulation into polymer nanoparticles may prevent drug degradation, control the rate and extent of release, and deliver a higher concentration of the active molecule to a desired organ/tissue. Nevertheless, the physicochemical characteristics of nanoparticles may greatly influence the activity of the encapsulated molecule. To obtain a suitable drug delivery system the choice of the nanoparticle preparation method is a crucial key. The selection of a specific technique is generally determined by the physicochemical characteristics of both polymer and drug, the delivery route, regulatory restrictions, and the desired physicochemical and morphological parameters of the nanoparticles. Two main strategies are employed for the preparation of polymer nanoparticles: the dispersion of preformed polymers and the polymerization of monomers. This review focuses on most commonly used methods that start from preformed polymers, and, in particular, on five techniques: nanoprecipitation, salting- out, emulsification diffusion, emulsification evaporation, and double emulsion solvent evaporation.