A Sensitive Ratiometric Thermometer Constructed by AIEgen-Based Mixed Lanthanide MOF for Intracellular Temperature Mapping.

Accurate temperature sensing at the subcellular level is of great significance for gaining insights into a wide range of biological processes. Aggregation-induced emission (AIE) is a promising photophysical phenomenon in which the luminescence intensity is highly related to the degree of restriction of intramolecular motions. By combining AIE luminogen (AIEgen) ligands with mixed lanthanide ions, an AIEgen-based mixed lanthanide MOF (LnMOF) can be synthesized. In this unique MOF matrix, the vibrations of pendant phenyl rings in the AIEgen ligands are particularly sensitive to temperature changes, rendering the mixed LnMOF highly sensitive as a ratiometric thermometer. Within the physiological temperature range (291-321 K), the maximum relative sensitivity (Sm) is ≈7.32% K-1 at 321 K, demonstrating superior performance compared to reported ratiometric luminescent MOFs. With the aim of detecting intracellular temperature, the mixed LnMOF at the nanoscale is synthesized and further modified, enabling the visual detection of intracellular temperature in L929 cells and HeLa cells. This work demonstrates the first example that MOF-based ratio thermometers can be practically used in living cells.