Fine Control of the Release and Encapsulation of Fe Ions in Dendrimers through Ferritin-like Redox Switching

摘要

Dendrimers having a uniform sphere-like structure are expected to have novel properties using the innervoids as "reaction flasks" or "metal-storage capsules" for nanoreaction chemistry. Recently, numerous dendrimers incorporating metal ions or clusters have received much attention as nanocatalysts and drug delivery materials. We have already reported that tin ions, Sn~(2+) ions, are coordinated to the imine groups of a spherical phenylazomethine dendrimer (DPA) in a stepwise radial fashion, which should make it possible to control the number and location of the Sn ions incorporated into the dendrimers. We would like to expand the variety of metal ions that can be incorporated into DPA in a stepwise radial fashion to create novel organic-inorganic hybrid materials. As one of the most common and significant iron ions, Fe~(3+) was used for the incorporation into DPA. Iron possesses very interesting properties such as magnetism redox chemistry, and catalysis and is also one of the essential elements of our body. There are some iron storage proteins called ferritins in the liver. The mechanism of encapsulation and release of iron is caused by the redox of the iron in the protein shell. Here, we show a successful attempt to control the "encapsulation/release" of iron ions in the dendrimer through the redox switching driven by the Fe~(2+)/Fe~(3+) couple. This ferritin-like dendrimer is the first material that should prove to be useful for creating a drug delivery system.