Citrate-based fluorophore-modified cellulose nanocrystals as a biocompatible fluorescent probe for detecting ferric ions and intracellular imaging.

In this contribution, citrate-based fluorophore (CF)-modified cellulose nanocrystals (CNCs) were prepared in a facile manner using sulfuric acid hydrolysis of citric acid/cysteine-treated microcrystalline celluloses. These rod-like CNCs have an average length of 156 nm and an average width of 7.9 nm. Because of conjugated CFs, these CNCs exhibit typical fluorescence characteristics, including a maximum excitation wavelength at 350 nm, maximum emission wavelength at 435 nm, high quantum yield of 83%, and good photostability. More importantly, these fluorescent CNCs exhibit a selective quenching effect toward Fe ions; meanwhile, these CNCs exhibit negligible cytotoxicity and were internalized by cells. Therefore, these CNCs can be used as a fluorescence probe for detecting Fe ions in living cells.