A Probe Based on a Soft Salt Complex for Ratiometric and Lifetime Imaging of Variations in Intracellular Oxygen Content

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

Luminescence imaging is a powerful and versatile technique for investigating cell physiology and pathology in living systems, making significant contributions to life science research and clinical diagnosis. In recent years, luminescent transition metal complexes have gained significant attention for diagnostic and therapeutic applications due to their unique photophysical and photochemical properties. In this Review, we provide a comprehensive overview of the recent development of luminescent transition metal complexes for bioimaging and biosensing applications, with a focus on transition metal centers with a d6, d8, and d10 electronic configuration. We elucidate the structure-property relationships of luminescent transition metal complexes, exploring how their structural characteristics can be manipulated to control their biological behavior such as cellular uptake, localization, biocompatibility, pharmacokinetics, and biodistribution. Furthermore, we introduce the various design strategies that leverage the interesting photophysical properties of luminescent transition metal complexes for a wide variety of biological applications, including autofluorescence-free imaging, multimodal imaging, organelle imaging, biological sensing, microenvironment monitoring, bioorthogonal labeling, bacterial imaging, and cell viability assessment. Finally, we provide insights into the challenges and perspectives of luminescent transition metal complexes for bioimaging and biosensing applications, as well as their use in disease diagnosis and treatment evaluation.

An ALP-responsive, anionic iridium complex for specific recognition of osteosarcoma cells

Poor cellular permeability greatly hampers the utilization of anionic Ir(III) complexes, though efficiently emissive and remarkably stable, in cell-based diagnosis. To overcome this barrier, we present the development of an alkaline phosphatase (ALP)-responsive, anionic, and aggregation-induced emission (AIE)-active Ir(III) complex (Ir1) for specific recognition of osteosarcoma cells. Containing phosphate moieties, Ir1 exhibits a net -1 charge, enabling charge repulsion from the cell membrane and resulting in low cellular uptake and good biocompatibility in normal osteoblast cells. Upon ALP-mediated hydrolysis of phosphate groups, the resulting dephosphorylated product, Ir2, demonstrates a positive charge and increased lipophilicity, promoting cellular uptake and activating its AIE properties for specific recognition of osteosarcoma cells that express elevated levels of ALP. This study elucidates the role of ALP as an ideal trigger for enhancing the cellular permeability of phosphate ester-containing Ir(III) complexes, thus expanding the potential of anionic Ir(III) complexes for biomedical applications.

Soft salts based on platinum(II) complexes with high emission quantum efficiencies in the near infrared region for in vivo imaging

Two soft salts (S1 and S2) based on platinum(ii) complexes with a near-infrared emission have been designed and synthesized. It has been demonstrated that S2 has a high photostability and a low cytotoxicity, and it has been successfully applied to in vivo imaging for the first time.

An anionic iridium(iii) complex as a visible-light absorbing photosensitizer

A new anionic Ir(iii) photosensitizer bearing coumarin dyes has been developed and applied to the visible-light-driven hydrogen generation.