AIEgen-sensitized lanthanide nanocrystals as luminescent probes for intracellular Fe3+ monitoring

The abnormal Fe3+ level is known to cause various diseases, such as heart failure, liver damage and neurodegeneration. In situ probing Fe3+ in living cells or organisms is highly desired for both biological research and medical diagnostics. Herein, hybrid nanocomposites NaEuF4@TCPP were constructed by the assembly of an aggregation-induced emission luminogen (AIEgen) TCPP and NaEuF4 nanocrystals (NCs). The anchored TCPP on the surface of NaEuF4 NCs can reduce rotational relaxation of the excited state and efficiently transfer the energy to the Eu3+ ions with minimized nonradiative energy loss. Consequently, the prepared NaEuF4@TCPP nanoparticles (NPs) exhibited an intense red emission with a 103-fold enhancement relative to that in NaEuF4 NCs under 365 nm excitation. A selectively quenching response to Fe3+ ions for the NaEuF4@TCPP NPs makes them luminescent probes for sensitive detection of Fe3+ ions with a low detection limit of 340 nM. Moreover, the luminescence of NaEuF4@TCPP NPs could be recovered by the addition of iron chelators. Benefiting from their good biocompatibility and stability in living cells, together with the characteristic of the reversible luminescence response, the lipo-coated NaEuF4@TCPP probes were successfully applied for real-time monitoring of Fe3+ ions in living HeLa cells. These results are expected to motivate the exploration of AIE-based lanthanide probes for sensing and biomedical applications.