Transferrin-directed preparation of red-emitting copper nanoclusters for targeted imaging of transferrin receptor over-expressed cancer cells

Transferrin (Trf)-functionalized copper nanoclusters (Trf-Cu NCs) were fabricated as a novel red-emitting fluorescent probe for the targeted bioimaging of cancer cells. A one-pot approach was developed to prepare stable, water-soluble and red-emitting Trf-Cu NCs at room temperature via a biomineralization process with Trf as the template and ascorbic acid as a green reducing agent. Trf acted not only as a stabilizer and reducer, but also as a functional ligand for targeting the transferrin receptor. The as-prepared Trf-Cu NCs showed an intense red fluorescence with a red emission peak at 670 nm (quantum yield about 6.2%), suggesting that the probe could potentially be used for bioimaging in vivo. The developed Trf-Cu NCs had excellent photostability and water solubility and exhibited a high specificity to transferrin receptor with negligible cytotoxicity. The probe was successfully applied to the targeted bioimaging of HeLa cells.