A highly sensitive and selective fluorescein-based fluorescence probe for Au³⁺ and its application in living cell imaging

A new fluorescein-based fluorescent probe for the detection of Au³⁺ has been developed. This probe was derived from 4′,5′-fluoresceindicarboxaldehyde and exhibited highly selective and sensitive response toward gold(III) ions in aqueous solution. There is a good linear relationship between the fluorescence intensity at 523 nm and the concentrations of Au³⁺ ranging from 0 μM to 60 μM, which makes it effective for the detection of Au³⁺. The limit of detection (LOD) was evaluated to be 0.07 μM based on S/N = 3. The fluorescence enhancement was attributed to the irreversible CN bond hydrolysis that occurred to this probe in the presence of Au³⁺, generating the fluorescent 4′,5′-fluoresceindicarboxaldehyde. Furthermore, the imaging experiments indicated that this probe is cell-permeable and can be used to detect Au³⁺ within living cell.