9.6.3.6　Dendrimers

Dendrimers are highly branched，unimolecular，globular，micellar nanostructure，and multivalent NPs.Their diameters range from 2 nm to 20 nm.A dendrimer is typically built from a core on which series of branches are engrafted in an arborescent way and often adopts a spherical three-dimensional morphology.Its properties（e.g.，monodispersity，polyvalence，and stability）make it an ideal carrier with precision and selectivity.Dendrimers provide controlled release from the inner core and drugs are incorporated in interior as well as being attached on the surface.

Due to the definite 3D structure and several surface functional groups，dendrimers can act by encapsulation of drugs within the dendritic structure or by forming electrostatic/covalent bonds between drugs with terminal functional groups of dendrimers.Two mechanisms of the drug delivery from drug-dendrimer conjugate have been reported in the literature.The first mechanism is owed to in vivo cleavage of covalent bonds between drug and dendrimer in existence of enzymes or an environment required for bond breaking.The second mode of drug release is the alteration in physical conditions，temperature and pH which are not dependent on external factors.(https://www.daowen.com)