Ferritin: Versatile Host, Nanoreactor, and Delivery Agent

The ferritin family of proteins can be thought of as natural, nano‐sized containers. Their native function is to oxidize and store iron as a hydrated ferric oxide mineral, which can be removed to give apoferritin. The hollow interior ( D =5–8 nm) provides an excellent template for inorganic nanoparticle (NP) synthesis. In addition to preparing new cores in situ , apoferritins can be disassembled and reassembled around a NP of interest. Ferritin encapsulation increases NP biocompatibility and allows site‐specific functionalization. We and others have prepared many NP‐filled ferritins, as well as ferritins loaded with small molecules of interest. Uniquely, apoferritin serves as a model for a general anesthetic‐protein binding site, which has led to the discovery of the first fluorescent general anesthetic and improved understanding of anesthetic mechanisms. Finally, ferritin conjugates have exciting applications for targeted delivery, which we have explored in the vascular endothelium.