Orthogonal Functionalization of Ferritin via Supramolecular Re-Assembly

To investigate if the degree of functionalization of ferritin could be controlled using a supramolecular self‐assembly process, two photophysical separable batches of ferritin were created by functionalizing ferritin capsids with either Cy3‐ or Cy5‐dye (loading rate of about 50 %). After dis‐assembly, Cy3‐, Cy5‐ as well as non‐functionalized ferritin subunits were mixed in variable ratios. Photophysical measurements revealed that the ratio in which the subunits were mixed was indeed indicative for the ratios in which the functionalized subunits were observed in the re‐assembled capsids. During re‐assembly, however, a slight preference for the inclusion of non‐functionalized subunits was observed, indicating the reactivity decreased following functionalization. The iron biomineralization properties of ferritin were retained by the multi‐functionalized capsids as FeII diffused rapidly inside making it visible by transmission electron microscopy (TEM). These combined data indicate that it is possible to functionalize ferritin in an orthogonal manner using the supramolecular interaction between ferritin subunits. To investigate the control on ferritin functionalization by supramolecular re‐assembly, ferritin with modular functionality and still capable of iron mineralization was created. The ratio in which Cy3‐, Cy5‐, and non‐functionalized subunits were mixed, was indicative for the ratio in which the variable subunits were observed in the re‐assembled capsids.