this invention concerns a manufacturing process for nanoparticles composted of biodegradable polymers and active ingredients with therapeutic , cosmetic , veterinary , and alimentary applications , and a composition which contains said nanoparticles , which are used in products for animals , including humans . the process consists of emulsifying the hydrosoluble substances to form a w / o emulsion ; dissolving the non - emulsionable substances , liposoluble polymer or polymer / compounds in organic solvents ; mixing the w / o emulsion and the organic solution of the hydrophobics to form a pre - emulsioned mixture ; adding the pre - emulsioned mixture , with the assistance of an injector system , to an aqueous emulsifier solution under ultradispersion to form the final emulsion ; leading the final emulsion to evaporation , then centrifuge , freeze , and lyophilize . one variation of the method takes place when the hydrosoluble emulsioned compounds and the liposoluble polymer or polymer / compounds solution are injected separately over the aqueous emulsifying solution . the process of the invention allows nanoparticles of active ingredients to be obtained with a rigorous control over the size of the particle , preserving the active characteristics of the encapsulated compounds .