A method for preparing polymeric nanoparticles having entrapped active ingredients or drugs, the method includes the step of preparing a reaction by mixturing water, a surfactant, and a water-soluble radical initiator polymerizing a polymerizable monomer in the reaction to obtain a dispersion of polymeric nanoparticles having a controlled size with average diameters smaller than 50 nm dissolving one or more active ingredients in a suitable solvent adding the solution of active ingredients to the dispersion of polymeric nanoparticles and allowing that the active ingredients to become entrapped within polymeric nanoparticles and evaporating the dispersion of polymeric nanoparticles having entrapped active ingredients to evaporate the residual monomer and the solvent used as a vehicle for loading the active ingredient.
