Imaging mitochondrial palladium species in living cells with a NIR iridium(III) complex

Dual-color and specific luminescence detection of Pd2+ ions using iridium(III) complex-based probes in food samples

The toxicity of palladium (Pd) is highly associated with its oxidative states, thus it is important to develop specific detection methods for Pd2+ ions in food and environmental systems. However, the reliable and selective detection of Pd2+ ions remains challenging. Here, we report two iridium(III) complexes with dual colors (717 nm and 637 nm) for the specific detection of Pd2+ ions, with the 3,3'-diamino group being used as a specific recognition unit for Pd2+ ions for the first time. The dual-color probes showed a luminescence quenching response to Pd2+ ions in aqueous solution within 1 min, along with an obvious color change under UV irradiation. Moreover, complexes 1-2 allow sensitive and selective detection of Pd2+ ions with a limit of detection (LOD) of 0.69 μM and 0.26 μM, respectively, showing a good linear response for Pd2+ ions in the range of 1-13 μM (R2 = 0.985) and 1-9 μM (R2 = 0.996). Finally, the probes were successfully applied for the detection of Pd2+ ions in food and environmental samples with good recoveries ranging from 85.4 to 118.7 %, providing a robust analytical tool for Pd2+ ions quantification for onsite setting.

Inhibiting Glycolysis and Disrupting the Mitochondrial HK2-VDAC1 Protein-Protein Interaction Using a Bifunctional Lonidamine-Conjugated Metal Probe for Combating Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) relies primarily on aerobic glycolysis for energy and rapid cancer cell proliferation. Hexokinase 2 (HK2), a key enzyme regulating glycolysis, is overexpressed in TNBC, promoting tumor cell proliferation and apoptosis resistance by interacting with the mitochondrial membrane's voltage-dependent anion channel 1 (VDAC1). However, the development of bioactive molecules for effectively disrupting the HK2-VDAC1 interaction remains challenging. Herein, we have modified londamine (LND) with an iridium(III) complex to create bifunctional far-red probe 1. This complex not only has the ability to distinguish TNBC cells from normal cells by probing HK2 in mitochondria, but also significantly enhances antitumor activity by inhibiting mitochondrial glycolysis and effectively disrupting the HK2-VDAC1 interaction. This led to increased Bax-VDAC1 interaction, opening of the mitochondrial permeability transition pores (MPTPs), and generation of ROS, ultimately leading to mitochondrial dysfunction and enhanced cancer cell apoptosis. Probe 1 also demonstrated stronger antiproliferative activity than LND alone in a TNBC mouse model by targeting the HK2-VDAC1 interaction without causing overt toxicity. This work showcases the potential of probe 1 as an effective therapeutic agent for TNBC by inhibiting the mitochondrial HK2-VDAC1 interaction.

Selective detection of mitochondrial Cu2+ in living cells by a near-infrared iridium(III) complex

The widespread use of copper (Cu) has raised concerns about environmental pollution and adverse effects on human health, highlighting the need to develop copper detection methods. Developing near-infrared (NIR) luminescent probes for imaging subcellular Cu2+ is still a challenge. In this work, we have developed a luminescence probe based on a NIR iridium(III) complex, which rapidly detects Cu2+ by combining salicylaldehyde and amine groups through a simple Schiff base reaction on the N^N ligand. The probe exhibits strong luminescence with a quantum yield of 0.66 and is able to detect Cu2+ with a limit of detection (LOD) of 0.31 μM, without interference from other metal ions. Mechanistic studies showed that the probe coordinated Cu2+ ions with a molar ratio of 1:1 and binding constant as low as 4.02 × 10-2 μM, and operated through photoinduced electron transfer (PeT) for luminescence quenching. Importantly, the photostability experiments confirmed the desirable photostability of the probe in aqueous solution and in cellulo compared with a commercial organic dye. Furthermore, cellular imaging experiments demonstrated its capability for the visualization of Cu2+ in the mitochondria of living cells, which paves the way for the study of the subcellular distribution of Cu2+ and related toxicity analysis.

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.

Development of a NIR Iridium(III) Complex-Based Probe for the Selective Detection of Iron(II) Ions

As a commonly used metal ion, iron(II) (Fe2+) ions pose a potential threat to ecosystems and human health. Therefore, it is particularly important to develop analytical techniques for the rapid and accurate detection of Fe2+ ions. However, the development of near-infrared (NIR) luminescence probes with good photostability for Fe2+ ions remain challenging. In this work, we report a novel iridium(III) complex-based luminescence probe for the sensitive and rapid detection of Fe2+ ions in a solution based on an Fe2+-mediated reduction reaction. This probe is capable of sensitively detecting Fe2+ ions with a limit of detection (LOD) of 0.26 μM. Furthermore, this probe shows high photostability, and its luminescence remains stable under 365 nm irradiation over a time period of 30 min. To our knowledge, this is first iridium(III) complex-based NIR probe for the detection of Fe2+ ions. We believe that this work provides a new method for the detection of Fe2+ ions and has great potential for future applications in water quality testing and human monitoring.

Recent Advances in Organometallic NIR Iridium(III) Complexes for Detection and Therapy

Iridium(III) complexes are emerging as a promising tool in the area of detection and therapy due to their prominent photophysical properties, including higher photostability, tunable phosphorescence emission, long-lasting phosphorescence, and high quantum yields. In recent years, much effort has been devoted to develop novel near-infrared (NIR) iridium(III) complexes to improve signal-to-noise ratio and enhance tissue penetration. In this review, we summarize different classes of organometallic NIR iridium(III) complexes for detection and therapy, including cyclometalated ligand-enabled NIR iridium(III) complexes and NIR-dye-conjugated iridium(III) complexes. Moreover, the prospects and challenges for organometallic NIR iridium(III) complexes for targeted detection and therapy are discussed.