Recent advances in luminescent lanthanides and transition metal complex-based probes for imaging reactive oxygen, nitrogen, and sulfur species in living cells

Reactive oxygen, nitrogen, and sulfur species (RONSS) regulate several pathological activities in biological systems. These RONSS can be seriously harmful to the human body when their production is unbalanced or their concentrations increase owing to external circumstances. In order to investigate the impact of RONSS and prevent diseases, unique probes that can detect RONSS in cells and tissue in a selective and sensitive manner are necessary. The development of luminescent metal complex-based probes has drawn considerable attention for intracellular imaging and real-time sensing of several RONSS. Specifically, luminescent molecular probes containing lanthanide complexes (LnCs) and transition metal complexes (TMCs) are recognized as appealing systems for cellular imaging owing to their background-signal-free luminescence, long emission lifespan, substantial Stokes shift, and multiphoton excitation. Thus, this review aims to examine publications on luminescent LnCs and TMCs for imaging RONSS in living cells, spanning the period of 2015–2023. The first part of this review briefly explains the necessity for intracellular RONSS imaging, as well as several modalities involved in imaging. Thereafter, the design of luminescent lanthanide probes, photophysical properties of TMCs, and sources of RONSS generation in living cells are systematically explained. In the fifth and sixth sections, LnCs and TMCs for imaging RONSS in complex biological samples are well-documented. Finally, conclusions and future directions are presented for further advancing the design of next-generation molecular luminescent responsive probes for in vitro and in vivo RONSS imaging.