Fluorescent Carbon Dots for Sensitive and Rapid Monitoring of Intracellular Ferrous Ion

Although iron is an essential constituent for almost all living organisms, iron dyshomeostasis at a cellular level may trigger oxidative stress and neuronal damage. Hence, there are numerous reported carbon dots (CDs) that have been synthesized and applied to determine intracellular iron ions. However, among reported CDs focused to detect Fe(3+) ions, only a few CDs have been designed to specifically determine Fe(2+) ions over Fe(3+) ions for monitoring of intracellular Fe(2+) ions. We have developed the nitrogen-doped CDs (NCDs) for fluorescence turn-off detection of Fe(2+) at cellular level. The as-synthesized NCDs exhibit a strong blue fluorescence and low cytotoxicity, acting as fluorescence probes to detect Fe(2+) as low as 0.702 µM in aqueous solution within 2 min and visualize intracellular Fe(2+) in the concentration range from 0 to 500 µM within 20 min. The as-prepared NCDs possess some advantages such as high biocompatibility, strong fluorescence properties, selectivity, and rapidity for intracellular Fe(2+) monitoring, making NCDs an excellent nanoprobe for biosensing of intracellular ferrous ions.