a method of making ultra - small chitosan nanoparticles having a size range of approximately 10 - 20 nm , includes preparing a first microemulsion containing effective amounts of cyclohexane , n - hexanol , chitosan polymer and a nonionic surfactant . a second microemulsion is prepared containing effective amounts of cyclohexane , n - hexanol , tartaric acid , edc , n - hydroxysuccinimide , and a nonionic surfactant . the method continues by reacting the first and second microemulsions for a time sufficient to form the ultra - small chitosan nanoparticles and recovering the nanoparticles from the reacted microemulsion . the chitosan polymer may be crosslinked and may also be tagged with a fluorescent compound , a radio - opaque compound , a paramagnetic ion , a ligand specific for a predetermined biologic target , a drug , and combinations thereof .