19F NMR as a tool to probe drug binding and structural dynamics in ferritin-based nanocarriers

Ferritin-based nanocarriers offer a promising platform for targeted drug delivery due to their biocompatibility, stability, and ability to cross biological barriers. In this study, we used human heavy chain ferritin (HuHf) nanocage incorporating 5-fluorotryptophan to investigate the binding and structural dynamics of three gold(i)-based cytotoxic compounds: auranofin (AF), aurothiomalate (AuTM), and a gold(i)-N-heterocyclic carbene complex (AuNHC). Using 19F NMR spectroscopy, we monitored site-specific interactions at the cysteine dyad (C90/C102) near the fluorinated tryptophan residue (W93), revealing distinct chemical shift signatures for each compound. Molecular dynamics simulations complemented the spectroscopic data, elucidating how conformational rearrangements of W93 correlate with the NMR shifts. Such rearrangements can change significantly the local environment of W93, affecting its solvent exposure as well as the distance from the gold(i) ion. These findings provide atomistic insight into the structural behavior of metallated ferritin nanocages and establish 19F NMR as a powerful tool for probing protein-metal interactions in drug delivery systems also of nanoscale dimension.