A composition and method of fabrication are presented with which nanoparticles may be used as a tool to deliver drugs to a specific target within or on a mammalian body. Specifically, by using stabilizers other than Dextran 70.000 during the polymerization process, according to the present invention, surfactants, which were deemed necessary coating material in the prior art, are no longer required. This is a significant simplification of the fabrication procedure. Many substances are useful as stabilizers, but the preferred stabilizers comprise Dextran 12.000 or polysorbate 85. In the present invention a drug is either incorporated into or adsorbed onto the stabilized nanoparticles. This drug/nanoparticle complex is then administered to the organism on any route such as by oral application, injection or inhalation, whereupon the drug exerts its effect at the desired site of pharmacological action. In a novel medical treatment process, the drug/nanoparticle complex may be administered preferably either by intravenous injection or by oral application. The resulting drug action, which does not occur or which occurs only to an insufficient extent when the drug is administered alone, shows that when linked to said nanoparticles drugs can reach a specific target within or on the mammalian body. The usefulness of the present invention as a universal approach to deliver any drug or diagnostic agent to a specific target within or on the mammalian body was demonstrated by experiments showing an unexpected transfer of the drug across the blood brain barrier.