FerriIridium: A Lysosome‐Targeting Iron(III)‐Activated Iridium(III) Prodrug for Chemotherapy in Gastric Cancer Cells

Combinatorial Synthesis toward the Discovery of Highly Cytotoxic Fe(III) Complexes

Cancer remains one of the deadliest diseases worldwide, with some tumors proving difficult to treat and increasingly resistant to current therapies. Capitalizing on this, there is a need for new therapeutic agents with novel mechanisms of action. Among promising candidates, Fe(III) complexes have gained significant attention as potential chemotherapeutic agents. However, research on these compounds has been limited to a small number, leading to inefficiencies in drug discovery. This study addresses these limitations by developing a combinatorial library of 495 new Fe(III) complexes synthesized from aminophenol, hydroxybenzaldehyde, and pyridine derivatives. The compounds were screened for cytotoxicity against human breast adenocarcinoma and noncancerous fibroblasts, identifying a novel class of Fe(III) complexes with modest cancer cell selectivity. The lead compound effectively eradicated breast cancer tumor spheroids at low micromolar concentrations, highlighting the potential of this approach for rapid drug discovery.

Theranostic Rhenium(I)-Based ER-Phagy Retardant Promotes Immunogenic Cell Death

ER-phagy is a double-edged sword in the occurrence, development, and treatment of cancer; especially, its functions in immunotherapy are still unknown. In this work, we designed a theranostic Re complex (Re1) containing a BODIPY-derived ligand and a β-carboline ligand to target the endoplasmic reticulum (ER) and block ER-phagy at the late stages. Interestingly, as validated both in vitro and in vivo, ER-phagy blockage greatly enhances the capability of Re1 to induce immunogenic cell death (ICD). In summary, we dexterously fused two molecular modules for ER targeting and ER-phagy blockage into a coordination complex to afford a highly effective ICD inducer, which provides clues for designing new cancer immunotherapeutics.

A Near-Infrared-II Fluorescent Nanoprobe Offering Real-Time Tracking of Fenton-Like Reaction for Cancer Chemodynamic Theranostics

Chemodynamic therapy (CDT) utilizing Fenton or Fenton-like reactions to generate cytotoxic hydroxyl radicals by metal ions has become a compelling strategy for cancer treatment. Visualizing intratumoral Fenton or Fenton-like reactions especially at a cellular level in real-time can directly monitor the process of CDT, which is not yet feasible. Here, we present a molecule BADA chelating Cu2+ to form Cu-BADA nanoparticles, exhibiting fluorescence quenching properties through intermolecular electron transfer. The nanoparticles are lit up owing to glutathione and acid dual activatable Fenton-like reaction and generation of near-infrared-II fluorescent o-quinones. Moreover, fluorescence vanishing correlated with the decreased intratumoral Cu concentration, thus enabling to track the "on-off" process of Fenton-like reaction specifically in the tumor. Compared to 660 nm-excitation, the o-quinones excited at 830 nm offer deeper tissue near-infrared-II fluorescence imaging with higher resolution. Our results demonstrate a fluorescence nanotheranostic agent for CDT capable of monitoring the spatiotemporal dynamics of Fenton-like reaction.

Rational Design of Biocompatible Ir(III) Photosensitizer to Overcome Drug-Resistant Cancer via Oxidative Autophagy Inhibition

Autophagy is a crucial quality control mechanism that degrades damaged cellular components through lysosomal fusion with autophagosomes. However, elevated autophagy levels can promote drug resistance in cancer cells, enhancing their survival. Downregulation of autophagy through oxidative stress is a clinically promising strategy to counteract drug resistance, yet precise control of oxidative stress in autophagic proteins remains challenging. Here, a molecular design strategy of biocompatible neutral Ir(III) photosensitizers is demonstrated, B2 and B4, for precise reactive oxygen species (ROS) control at lysosomes to inhibit autophagy. The underlying molecular mechanisms for the biocompatibility and lysosome selectivity of Ir(III) complexes are explored by comparing B2 with the cationic or the non-lysosome-targeting analogs. Also, the biological mechanisms for autophagy inhibition via lysosomal oxidation are explored. Proteome analyses reveal significant oxidation of proteins essential for autophagy, including lysosomal and fusion-mediator proteins. These findings are verified in vitro, using mass spectrometry, live cell imaging, and a model SNARE complex. The anti-tumor efficacy of the precise lysosomal oxidation strategy is further validated in vivo with B4, engineered for red light absorbance. This study is expected to inspire the therapeutic use of spatiotemporal ROS control for sophisticated modulation of autophagy.

Mitochondria Localized Anticancer Iridium(III) Prodrugs for Targeted Delivery of Myeloid Cell Leukemia-1 (Mcl-1) Inhibitors and Cytotoxic Iridium(III) Complex

Myeloid cell leukemia-1 (Mcl-1) is an antiapoptotic oncoprotein overexpressed in several malignancies and acts as one of the promising therapeutic targets for cancer. Even though there are several small molecule based Mcl-1 inhibitors reported, the delivery of Mcl-1 inhibitor at the target site is quite challenging. In this regard, we developed a series of mitochondria targeting luminescent cyclometalated iridium(III) prodrugs bearing Mcl-1 inhibitors via ester linkage due to the presence of Mcl-1 protein in the outer mitochondrial membrane. Among the synthesized prodrugs, IrThpy@L2 was found to exhibit the potent cytotoxicity (IC50 = 30.93 nM) against HCT116 cell line when compared with bare Mcl-1 inhibitors (IC50 > 100 μM). Mechanistic studies further revealed that IrThpy@L2 quickly gets internalized inside the mitochondria of HCT116 cells and undergoes activation in the presence of overexpressed esterase which leads to the release of two cytotoxic species i.e. Mcl-1 inhibitors (I-2) and cytotoxic iridium(III) complex (IrThpy@OH). The improved cytotoxicity of IrThpy@L2 is due to the mitochondria targeting ability of iridium(III) prodrug, subsequent esterase activated release of I-2 to inhibit Mcl-1 protein and IrThpy@OH to generate reactive oxygen species (ROS). After prodrug activation, the released cytotoxic species cause mitochondrial membrane depolarization, activate a cascade of mitochondria-mediated cell death events, and arrest the cell cycle in S-phase which leads to apoptosis. The potent anticancer activity of IrThpy@L2 was further evident from the drastic morphological changes, size reduction in the solid tumor mimicking 3D multicellular tumor spheroids (MCTS) of HCT116.

Endoplasmic reticulum-targeted iridium(III) photosensitizer induces pyroptosis for augmented tumor immunotherapy

An ideal tumor treatment strategy involves therapeutic approaches that can enhance the immunogenicity of the tumor microenvironment while simultaneously eliminating the primary tumor. A cholic acid-modified iridium(III) (Ir3) photosensitizer, targeted to the endoplasmic reticulum (ER), has been reported to exhibit potent type I and type II photodynamic therapeutic effects against triple-negative breast cancer (MDA-MB-231). This photosensitizer induces pyroptotic cell death mediated by gasdermin E (GSDME) through photodynamic means and enhances tumor immunotherapy. Mechanistic studies have revealed that complex Ir3 induces characteristics of damage-related molecular patterns (DAMPs) in MDA-MB-231 breast cancer cells under light conditions. These include cell-surface calreticulin (CRT) eversion, extracellular high mobility group box 1 (HMGB1) and ATP release, accompanied by ER stress and increased reactive oxygen species (ROS). Consequently, complex Ir3 promotes dendritic cell maturation and antigen presentation under light conditions, fully activates T cell-dependent immune response in vivo, and ultimately eliminates distant tumors while destroying primary tumors. In conclusion, immune regulation and targeted intervention mediated by metal complexes represent a new and promising approach to tumor therapy. This provides an effective strategy for the development of combined targeted therapy and immunotherapy.

Photoinduction of Ferroptosis and cGAS-STING Activation by a H2S-Responsive Iridium(III) Complex for Cancer-Specific Therapy

Triggering ferroptosis represents a promising anticancer therapeutic strategy, but the development of a selective ferroptosis inducer for cancer-specific therapy remains a great challenge. Herein, a H2S-responsive iridium(III) complex NA-Ir has been well-designed as a ferroptosis inducer. NA-Ir could selectively light up H2S-rich cancer cells, primarily localize in mitochondria, intercalate into mitochondrial DNA (mtDNA), and induce mtDNA damage, exhibiting higher anticancer activity under light irradiation. Mechanistic studies showed that NA-Ir-mediated PDT triggered lipid peroxidation and glutathione peroxidase 4 downregulation through ROS production and GSH depletion, resulting in ferroptosis through multiple pathways. Moreover, the intense mtDNA damage can activate the cyclic GMP-AMP synthase-stimulator of the interferon gene (cGAS-STING) pathway, leading to ferritinophagy and further ferroptosis. RNA-sequencing analysis showed that NA-Ir-mediated PDT mainly affects the expression of genes related to ferroptosis, autophagy, and cancer immunity. This study demonstrates the first cancer-specific example with ferroptosis and cGAS-STING activation, which provides a new strategy for multimodal synergistic therapy.

A Cyclometalated Iridium(III) Complex Exerts High Anticancer Efficacy via Fatty Acid Beta-Oxidation Inhibition and Sphingolipid Metabolism Reprogramming

Given the extensive role of lipids in cancer development, there is substantial clinical interest in developing therapies that target lipid metabolism. In this study, we identified one cyclometalated iridium complex (Ir2) that exhibits potent antiproliferation activity in MIA PaCa-2 cells by regulating fatty acid metabolism and sphingolipid metabolism simultaneously. Ir2 also efficiently overcomes cisplatin resistance in vitro. Satisfyingly, the generated Ir2@F127 carriers, as a temperature-sensitive in situ gelling system of Ir2, showed effective cancer treatment with minimal side effects in an in vivo xenograft study. To the best of our knowledge, Ir2 is the first reported cyclometalated iridium complex that exerts anticancer activity in MIA PaCa-2 cells by intervening in lipid metabolism, which provides an alternative pathway for the anticancer mechanism of cyclometalated iridium complexes.

Subcellular targeting strategies for protein and peptide delivery

Cytosolic delivery of proteins and peptides provides opportunities for effective disease treatment, as they can specifically modulate intracellular processes. However, most of protein-based therapeutics only have extracellular targets and are cell-membrane impermeable due to relatively large size and hydrophilicity. The use of organelle-targeting strategy offers great potential to overcome extracellular and cell membrane barriers, and enables localization of protein and peptide therapeutics in the organelles. Although progresses have been made in the recent years, organelle-targeted protein and peptide delivery is still challenging and under exploration. We reviewed recent advances in subcellular targeted delivery of proteins/peptides with a focus on targeting mechanisms and strategies, and highlight recent examples of active and passive organelle-specific protein and peptide delivery systems. This emerging platform could open a new avenue to develop more effective protein and peptide therapeutics.

Near Infrared-Fluorescent Dinuclear Iridium(III) Nanoparticles for Immunogenic Sonodynamic Therapy

Dinuclear iridium(III) complexes activated by light-inducible spatiotemporal control are emerging as promising candidates for cancer therapy. However, broader applications of current light-activated dinuclear iridium(III) complexes are limited by the ineffective tissue penetration and undesirable feedback on guidance activation. Here, an ultrasound (US) triggered near infrared-fluorescent dinuclear iridium(III) nanoparticle, NanoIr, is first reported to precisely and spatiotemporally inhibit tumor growth. It is demonstrated that reactive oxygen species can be generated by NanoIr upon exposure to US irradiation (NanoIr + US), thereby inducing immunogenic cell death. When combined with cisplatin, NanoIr + US elicits synergistic effects in patient-derived tumor xenograft mice models of ovarian cancer. This work first provides a design of dinuclear iridium(III) nanoparticles for immunogenic sonodynamic therapy.

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.

IrCytoToxDB: a dataset of iridium(III) complexes cytotoxicities against various cell lines

Iridium(III) complexes nowadays became rising stars in various health-related applications. Thus, there is a necessity to assess cytotoxicity of the synthesized molecules against cancer/normal cell lines. In this report, we present a dataset of 2694 experimental cytotoxicity values of 803 iridium complexes against 127 different cell lines. We specify the experimental conditions and provide representation of the complexes molecules in machine-readable format. The dataset provides a starting point for exploration of new iridium-based cellular probes and opens new possibilities for predictions of toxicities and data-driven generation of new organometallic anticancer agents.

Design, synthesis, and antitumor mechanism investigation of iridium(III) complexes conjugated with ibuprofen

The design and synthesis of a series of metal complexes formed by non-steroidal anti-inflammatory drugs (NSAIDs) ibuprofen (IBP) and iridium(III), with the molecular formula [Ir(C^N)2bpy(4-CH2OIBP-4'-CH2OIBP)](PF6) (Ir-IBP-1, Ir-IBP-2) (C^N = 2-phenylpyridine (ppy, Ir-IBP-1), 2-(2-thienyl)pyridine (thpy, Ir-IBP-2)) was introduced in this article. Firstly, it was found that the anti-proliferative activity of these complexes was more effective than that of cisplatin. Further research showed that Ir-IBP-1 and Ir-IBP-2 can accumulate in intracellular mitochondria, thereby disrupting mitochondrial membrane potential (MMP), increasing intracellular reactive oxygen species (ROS), blocking the G2/M phase of the cell cycle, and inducing cell apoptosis. In terms of protein expression, the expression of COX-2, MMP-9, NLRP3 and Caspase-1 proteins can be downregulated, indicating their ability to anti-inflammatory and overcome immune evasion. Furthermore, Ir-IBP-1 and Ir-IBP-2 can induce immunogenic cell death (ICD) by triggering the release of cell surface calreticulin (CRT), high mobility group box 1 (HMGB1) and adenosine triphosphate (ATP). Overall, iridium(III)-IBP conjugates exhibit various anti-tumor mechanisms, including mitochondrial damage, cell cycle arrest, inflammatory suppression, and induction of ICD.

Mitochondrial-targeted cyclometalated Ir(III)-5,7-dibromo/dichloro-2-methyl-8-hydroxyquinoline complexes and their anticancer efficacy evaluation in Hep-G2 cells

Both 8-hydroxyquinoline compounds and iridium (Ir) complexes have emerged as potential novel agents for tumor therapy. In this study, we synthesized and characterized two new Ir(III) complexes, [Ir(L1)(bppy)2] (Br-Ir) and [Ir(L2)(bppy)2] (Cl-Ir), with 5,7-dibromo-2-methyl-8-hydroxyquinoline (HL-1) or 5,7-dichloro-2-methyl-8-hydroxyquinoline as the primary ligand. Complexes Br-Ir and Cl-Ir successfully inhibited antitumor activity in Hep-G2 cells. In addition, complexes Br-Ir and Cl-Ir were localized in the mitochondrial membrane and caused mitochondrial damage, autophagy, and cellular immunity in Hep-G2 cells. We tested the proteins related to mitochondrial and mitophagy by western blot analysis, which showed that they triggered mitophagy-mediated apoptotic cell death. Remarkably, complex Br-Ir showed high in vivo antitumor activity, and the tumor growth inhibition rate was 63.0% (P < 0.05). In summary, our study on complex Br-Ir revealed promising results in in vitro and in vivo antitumor activity assays.

Designing a Mitochondria-Targeted Theranostic Cyclometalated Iridium(III) Complex: Overcoming Cisplatin Resistance and Inhibiting Tumor Metastasis through Necroptosis and Immune Response

To develop a potential theranostic metal agent to reverse the resistance of cancer cells to cisplatin and effectively inhibit tumor growth and metastasis, we proposed to design a cyclometalated iridium (Ir) complex based on the properties of the tumor environment (TME). To the end, we designed and synthesized a series of Ir(III) 2-hydroxy-1-naphthaldehyde thiosemicarbazone complexes by modifying the hydrogen atom(s) of the N-3 position of 2-hydroxy-1-naphthaldehyde thiosemicarbazone compounds and the structure of cyclometalated Ir(III) dimers and then investigated their structure-activity and structure-fluorescence relationships to obtain an Ir(III) complex (Ir5) with remarkable fluorescence and cytotoxicity to cancer cells. Ir5 not only possesses mitochondria-targeted properties but also overcomes cisplatin resistance and effectively inhibits tumor growth and metastasis in vivo. Besides, we confirmed the anticancer mechanisms of Ir5 acting on different components in the TME: directly killing liver cancer cells by inducing necroptosis and activating the necroptosis-related immune response.

Novel tetranuclear grid-like Zn(II) complexes derived from dihydrazone pyrimidine derivatives as antitumor agents

Due to the antitumor properties, Zn(II) complexes have attracted more and more attention. Herein, three novel tetranuclear Zn(II) complexes 1-3 based on dihydrazone pyrimidine derivatives H2L1-H2L3 were synthesized and characterized using IR spectroscopy, 1H NMR spectroscopy, single crystal X-ray diffraction analysis, XRD, TG and elemental analysis. Single crystal X-ray diffraction analysis revealed that 1-3 all displayed a [2 × 2] grid-like topology. The stability in solution, lipophilicity, confocal imaging and antitumor activities were investigated. Complexes 1-3 displayed high structural stability, membrane permeability and different lipophilicities. They can target mitochondria due to the cation charge. The MTT assay indicated that all of them exhibited stronger antiproliferative activity than the corresponding derivatives H2L1-H2L3 and the well-known cisplatin against all the selected tumor cells (BGC-823, BEL-7402, MCF-7 and A549), with IC50 values ranging from 2.83 μM to 7.97 μM. AO/EB double staining, flow cytometry and ROS detection suggested that complexes 1 and 2 could induce BGC-823 apoptosis in a dose-dependent manner. UV-Vis spectra, CD spectra, viscosity analysis and molecular docking revealed that complexes 1 and 2 interact with DNA mainly via partial intercalation and groove binding. Tetranuclear [2 × 2] grid-like Zn(II) complexes have the potential to be promising antitumor agents in the future.

FRET Luminescent Probe for the Ratiometric Imaging of Peroxynitrite in Rat Brain Models of Epilepsy-Based on Organic Dye-Conjugated Iridium(III) Complex

Epilepsy is a chronic neurological disorder characterized by recurrent seizures globally, imposing a substantial burden on patients and their families. The pathological role of peroxynitrite (ONOO-), which can trigger oxidative stress, inflammation, and neuronal hyperexcitability, is critical in epilepsy. However, the development of reliable, in situ, and real-time optical imaging tools to detect ONOO- in the brain encounters some challenges related to the depth of tissue penetration, background interference, optical bleaching, and spectral overlapping. To address these limitations, we present Ir-CBM, a new one-photon and two-photon excitable and long-lived ratiometric luminescent probe designed specifically for precise detection of ONOO- in epilepsy-based on the Förster resonance energy transfer mechanism by combining an iridium(III) complex with an organic fluorophore. Ir-CBM possesses the advantages of rapid response, one-/two-photon excitation, and ratiometric luminescent imaging for monitoring the cellular levels of ONOO- and evaluating the effects of different therapeutic drugs on ONOO- in the brain of an epilepsy model rat. The development and utilization of Ir-CBM offer valuable insights into the design of ratiometric luminescent probes. Furthermore, Ir-CBM serves as a rapid imaging and screening tool for antiepileptic drugs, thereby accelerating the exploration of novel antiepileptic drug screening and improving preventive and therapeutic strategies in epilepsy research.

Ligand Dictated Photosensitization of Iridium(III) Dithiocarbamate Complexes for Photodynamic Therapy

Organelle-targeted photosensitizers (PSs) for photodynamic therapy (PDT) are considered as an effective therapeutic strategy for the development of next generation PSs with the least side effects and high therapeutic efficacy. However, multiorganelle targeted PSs eliciting PDT via both type I and type II mechanisms are scarce. Herein, a series of cyclometalated iridium(III) complexes were formulated [Ir(C∧N)2(S∧S)] (C∧N = 2-phenylpyridine (ppy) and 2-(thiophen-2-yl)pyridine (thpy); S∧S = diethyldithiocarbamate (DEDTC), morpholine-N-dithiocarbamate (MORDTC) and methoxycarbonodithioate (MEDTC)) and the newly designed complexes Ir2@DEDTC and Ir1@MEDTC were characterized by single crystal X-ray crystallography. Complexes containing thpy as C∧N ligand exhibit excellent photophysical properties such as red-shifted emission, high singlet oxygen quantum yield (ϕΔ) and longer photoluminescence lifetime when compared with complexes containing ppy ligands. Ir2@DEDTC exhibits the highest ϕΔ and photoluminescence lifetimes among the synthesized complexes. Therefore, Ir2@DEDTC was chosen to evaluate the photosensitizing ability to produce reactive oxygen species (ROS). Upon blue light irradiation (456 nm), it efficiently produces ROS, i.e., hydroxy radical (•OH) and singlet oxygen (1O2), which was confirmed by electron paramagnetic resonance (EPR) spectroscopy. In vitro photocytotoxicity toward HCT116, HeLa, and PC3 cell lines showed that out of all the synthesized complexes, Ir2@DEDTC has the highest photocytotoxic index (PI > 400) value. Ir2@DEDTC is efficiently taken up by the HCT116 cell line and accumulated mainly in the lysosome and mitochondria of the cells, and after PDT treatment, it elicits cell shrinkage, membrane blebbing, and DNA fragmentation. The phototherapeutic efficacy of Ir2@DEDTC has been investigated against 3D spheroids considering its ability to mimic some of the basic features of solid tumors. The morphology was drastically altered in the Ir2@DEDTC treated 3D spheroid after the light irradiation unleashed the potential of the Ir(III) dithiocarbamate complex as a superior PS for PDT. Hence, mitochondria and lysosome targeted photoactive cyclometalated Ir(III) dithiocarbamate complex exerting oxidative stress via both type I and type II PDT can be regarded as a dual-organelle targeted two-pronged approach for enhanced PDT.

Configurationally regulated half-sandwich iridium(III)-ferrocene heteronuclear metal complexes: Potential anticancer agents

Half-sandwich iridium(III) (IrIII) complexes and ferrocenyl (Fc) derivatives are becoming the research hotspot in the field of anticancer because of their good bioactivity and unique anticancer mechanism different from platinum-based drugs. Then, a series of half-sandwich IrIII-Fc pyridine complexes have been prepared through the structural regulation in this study. The incorporation of half-sandwich IrIII complex with Fc unit successfully improves their anticancer activity, and the optimal performance (IrFc5) is almost 3-fold higher than that of cisplatin against A549 cells, meanwhile, which also shows better anti-proliferative activity against A549/DDP cells. Complexes can aggregate in the intracellular lysosome of A549 cells and induce lysosomal damage, disrupt the cell cycle, increase the level of intracellular reactive oxygen species, and eventually lead to cell apoptosis. Half-sandwich IrIII-Fc heteronuclear metal complexes possess a different anticancer mechanism from cisplatin, which can serve as a potential alternative to platinum-based drugs and show a good application prospect.

Cyclopentadienyl Molybdenum(II) Compounds Bearing Ether and Thioether Functions in the Side Chain: Synthesis, Characterization, and Cytotoxic/Cytostatic Studies

A series of molybdenum(II) compounds [(η5 -Cp')Mo(CO)2 (L2 )][BF4 ] (Cp'=C5 H4 (CH2 )2 SPh, C9 H6 (CH2 )2 OMe, L2= N,N-chelating ligand) have been synthesized and characterized by spectroscopic and analytical methods including X-ray crystallography. The in vitro assay on human leukemia cells MOLT-4 has shown that the substitution in the π-ligand in combination with suitable N,N-chelating ligand can lead to species with cytotoxicity considerably higher than reported to cisplatin. Unusually high activity was observed for compounds bearing phenanthroline ligands [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (3,4,7,8-Me4 phen)][BF4 ] (IC50 =0.7±0.3 μM) and [{η5 -C9 H6 (CH2 )2 OMe}Mo(CO)2 (4,7-Ph2 phen)][BF4 ] (IC50 values 0.8±0.4 μM).

Establishment of a novel lysosomal signature for the diagnosis of gastric cancer with in-vitro and in-situ validation

Background

Gastric cancer (GC) represents a malignancy with a multi-factorial combination of genetic, environmental, and microbial factors. Targeting lysosomes presents significant potential in the treatment of numerous diseases, while lysosome-related genetic markers for early GC detection have not yet been established, despite implementing this process by assembling artificial intelligence algorithms would greatly break through its value in translational medicine, particularly for immunotherapy.

Methods

To this end, this study, by utilizing the transcriptomic as well as single cell data and integrating 20 mainstream machine-learning (ML) algorithms. We optimized an AI-based predictor for GC diagnosis. Then, the reliability of the model was initially confirmed by the results of enrichment analyses currently in use. And the immunological implications of the genes comprising the predictor was explored and response of GC patients were evaluated to immunotherapy and chemotherapy. Further, we performed systematic laboratory work to evaluate the build-up of the central genes, both at the expression stage and at the functional aspect, by which we could also demonstrate the reliability of the model to guide cancer immunotherapy.

Results

Eight lysosomal-related genes were selected for predictive model construction based on the inclusion of RMSE as a reference standard and RF algorithm for ranking, namely ADRB2, KCNE2, MYO7A, IFI30, LAMP3, TPP1, HPS4, and NEU4. Taking into account accuracy, precision, recall, and F1 measurements, a preliminary determination of our study was carried out by means of applying the extra tree and random forest algorithms, incorporating the ROC-AUC value as a consideration, the Extra Tree model seems to be the optimal option with the AUC value of 0.92. The superiority of diagnostic signature is also reflected in the analysis of immune features.

Conclusion

In summary, this study is the first to integrate around 20 mainstream ML algorithms to construct an AI-based diagnostic predictor for gastric cancer based on lysosomal-related genes. This model will facilitate the accurate prediction of early gastric cancer incidence and the subsequent risk assessment or precise individualized immunotherapy, thus improving the survival prognosis of GC patients.

In Response to Precision Medicine: Current Subcellular Targeting Strategies for Cancer Therapy

Emerging as a potent anticancer treatment, subcellular targeted cancer therapy has drawn increasing attention, bringing great opportunities for clinical application. Here, two targeting strategies for four main subcellular organelles (mitochondria, lysosome, endoplasmic reticulum, and nucleus), including molecule- and nanomaterial (inorganic nanoparticles, micelles, organic polymers, and others)-based targeted delivery or therapeutic strategies, are summarized. Phototherapy, chemotherapy, radiotherapy, immunotherapy, and "all-in-one" combination therapy are among the strategies covered in detail. Such materials are constructed based on the specific properties and relevant mechanisms of organelles, enabling the elimination of tumors by inducing dysfunction in the corresponding organelles or destroying specific structures. The challenges faced by organelle-targeting cancer therapies are also summarized. Looking forward, a paradigm for organelle-targeting therapy with enhanced therapeutic efficacy compared to current clinical approaches is envisioned.

N-Heterocyclic Carbene-Iridium Complexes as Photosensitizers for In Vitro Photodynamic Therapy to Trigger Non-Apoptotic Cell Death in Cancer Cells

A series of seven novel iridium complexes were synthetized and characterized as potential photosensitizers for photodynamic therapy (PDT) applications. Among them, four complexes were evaluated in vitro for their anti-proliferative activity with and without irradiation on a panel of five cancer cell lines, namely PC-3 (prostate cancer), T24 (bladder cancer), MCF7 (breast cancer), A549 (lung cancer) and HeLa (cervix cancer), and two non-cancerous cell models (NIH-3T3 fibroblasts and MC3T3 osteoblasts). After irradiation at 458 nm, all tested complexes showed a strong selectivity against cancer cells, with a selectivity index (SI) ranging from 8 to 34 compared with non-cancerous cells. The cytotoxic effect of all these complexes was found to be independent of the anti-apoptotic protein Bcl-xL. The compound exhibiting the best selectivity, complex 4a, was selected for further investigations. Complex 4a was mainly localized in the mitochondria. We found that the loss of cell viability and the decrease in ATP and GSH content induced by complex 4a were independent of both Bcl-xL and caspase activation, leading to a non-apoptotic cell death. By counteracting the intrinsic or acquired resistance to apoptosis associated with cancer, complex 4a could be an interesting therapeutic alternative to be studied in preclinical models.

Anticancer mechanism studies of iridium(III) complexes inhibiting osteosarcoma HOS cells proliferation

Three iridium (III) polypyridine complexes [Ir(bzq)₂(maip)](PF₆) (Ir1，bzq = benzo[h]quinoline, maip = 3-aminophenyl-1H-imidazo[4,5-f][1,10]phenanthroline), [Ir(bzq)₂(apip)](PF₆) (Ir2, apip = 2-aminophenyl-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ir(bzq)₂(paip)](PF₆) (Ir3, paip = 4-aminophenyl-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized. The cytotoxic activities of the three complexes against human osteosarcoma HOS, U2OS, MG63 and normal LO2 cells were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The results showed that Ir1-3 exhibited moderate antitumor activity against HOS with IC₅₀ of 21.8 ± 0. 4 μM,10.5 ± 1.8 μM and 7.4 ± 0.4 μM, respectively. We found that Ir1-3 can effectively inhibit HOS cells growth and blocked the cell cycle at the G0/G1 phase. Further studies revealed that complexes can increase intracellular reactive oxygen species (ROS) and Ca²⁺, which accompanied by mitochondria-mediated intrinsic apoptosis pathway. In addition, autophagy was also investigated. Taken together, the complexes induce HOS apoptosis through a ROS-mediated mitochondrial dysfunction pathway and inhibition of the PI3K (phosphatidylinositol 3-kinase)/AKT (protein kinase B)/mTOR (mammalian target of rapamycin) signaling pathway. This study provides useful help for understanding the anticancer mechanism of iridium (III) complexes toward osteosarcoma treatment.

Organelle-targeted therapies: a comprehensive review on system design for enabling precision oncology

Cancer is a major threat to human health. Among various treatment methods, precision therapy has received significant attention since the inception, due to its ability to efficiently inhibit tumor growth, while curtailing common shortcomings from conventional cancer treatment, leading towards enhanced survival rates. Particularly, organelle-targeted strategies enable precise accumulation of therapeutic agents in organelles, locally triggering organelle-mediated cell death signals which can greatly reduce the therapeutic threshold dosage and minimize side-effects. In this review, we comprehensively discuss history and recent advances in targeted therapies on organelles, specifically including nucleus, mitochondria, lysosomes and endoplasmic reticulum, while focusing on organelle structures, organelle-mediated cell death signal pathways, and design guidelines of organelle-targeted nanomedicines based on intervention mechanisms. Furthermore, a perspective on future research and clinical opportunities and potential challenges in precision oncology is presented. Through demonstrating recent developments in organelle-targeted therapies, we believe this article can further stimulate broader interests in multidisciplinary research and technology development for enabling advanced organelle-targeted nanomedicines and their corresponding clinic translations.

Current status of iridium-based complexes against lung cancer

Lung cancer is one of the most common malignant tumors, with the highest mortality rate in the world, and its incidence is second only to breast cancer. It has posed a serious threat to human health. Cisplatin, a metal-based drug, is one of the most widely used chemotherapeutic agents for the treatment of various cancers. However, its clinical efficacy is seriously limited by numerous side effects and drug resistance. This has led to the exploration and development of other transition metal complexes for the treatment of malignant tumors. In recent years, iridium-based complexes have attracted extensive attention due to their potent anticancer activities, limited side effects, unique antitumor mechanisms, and rich optical properties, and are expected to be potential antitumor drugs. In this review, we summarize the recent progress of iridium complexes against lung cancer and introduce their anti-tumor mechanisms, including apoptosis, cycle arrest, inhibition of lung cancer cell migration, induction of immunogenic cell death, etc.

Phosphorescent Ir(III) Complexes for Biolabeling and Biosensing

Cyclometalated Ir(III) complexes exhibit strong phosphorescence emission with lifetime of submicroseconds to several microseconds at room temperature. Their synthetic versatility enables broad control of physical properties, such as charge and lipophilicity, as well as emission colors. These favorable properties have motivated the use of Ir(III) complexes in luminescent bioimaging applications. This review examines the recent progress in the development of phosphorescent biolabels and sensors based on Ir(III) complexes. It begins with a brief introduction about the basic principles of the syntheses and photophysical processes of cyclometalated Ir(III) complexes. Focus is placed on illustrating the broad imaging utility of Ir(III) complexes. Phosphorescent labels illuminating intracellular organelles, including mitochondria, lysosomes, and cell membranes, are summarized. Ir(III) complexes capable of visualization of tumor spheroids and parasites are also introduced. Facile chemical modification of the cyclometalating ligands endows the Ir(III) complexes with strong sensing ability. Sensors of temperature, pH, CO₂, metal ions, anions, biosulfur species, reactive oxygen species, peptides, and viscosity have recently been added to the molecular imaging tools. This diverse utility demonstrates the potential of phosphorescent Ir(III) complexes toward bioimaging applications.

Linoleic Acid-Glucosamine Hybrid for Endogenous Iron-Activated Ferroptosis Therapy in High-Grade Serous Ovarian Cancer

As the most common subtype in ovarian malignancies, high-grade serous ovarian cancer (HGSOC) made less therapeutic progress in past decades due to the lack of effective drug-able targets. Herein, an effective linoleic acid (LA) and glucosamine (GlcN) hybrid (LA-GlcN) was synthesized for the treatment of HGSOC. The GlcN was introduced to recognize the glucose transporter 1 (GLUT 1) overexpressed in tumor cells to enhance the uptake of LA-GlcN, and the unsaturated LA was employed to trigger ferroptosis by iron-dependent lipid peroxidation. Since the iron content of HGSOC was ∼5 and 2 times, respectively, higher than that of the normal ovarian cells and low-grade serous ovarian cancer cells, these excess irons make them a good target to enhance the ferroptosis of LA-GlcN. The in vitro study demonstrated that LA-GlcN could selectively kill HGSOC cells without affecting normal cells; the in vivo study revealed that LA-GlcN at the dose of 50 mg kg^-1 achieved a comparable tumor inhibition as doxorubicin hydrochloride (4 mg kg^-1) while the overall survival of mice was extended largely due to the low toxicity, and when the dose was increased to 100 mg kg^-1, the therapeutic outcomes could be improved further. This dietary hybrid which targets the excess endogenous iron to activate ferroptosis represents a promising drug for HGSOC treatment.

Synthesis and bioimaging of a BODIPY-based fluorescence quenching probe for Fe3

Iron is the main substance for maintaining life. Real-time determination of ferric ion (Fe3+) in living cells is of great significance for understanding the relationship of Fe3+ concentration changes with various physiological and pathological processes. Fluorescent probes are suitable for the detection of trace metal ions in cells due to their low toxicity and high sensitivity. In this work, a boron-dipyrromethene-based fluorescent probe (BODIPY-CL) for selective detection of Fe3+ was synthesized. The fluorescence emission of BODIPY-CL was determined at 516 nm. In a pH range of 1 to 10, the probe BODIPY-CL exhibits a quenching response to Fe3+. Meanwhile, BODIPY-CL showed a highly selective response to Fe3+ compared with 16 kinds of metal ions. The stoichiometry ratio of BODIPY-CL bound to Fe3+ was nearly 2 : 1. The fluorescence quenching response obtained by the sensor was linear with the Fe3+ concentration in the range of 0-400 μM, and the detection limit was 2.9 μM. BODIPY-CL was successfully applied to image Fe3+ in cells. This study provides a promising fluorescent imaging probe for further research on the physiological and pathological effects of Fe3+.

Controlled Intracellular Polymerization for Cancer Treatment

Numerous prodrugs have been developed and used for cancer treatments to reduce side effects and promote efficacy. In this work, we have developed a new photoactivatable prodrug system based on intracellular photoinduced electron transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization. This unique polymerization process provided a platform for the synthesis of structure-predictable polymers with well-defined structures in living cells. The intracellularly generated poly(N,N-dimethylacrylamide)s were found to induce cell cycle arrest, apoptosis, and necroptosis, inhibit cell proliferation, and reduce cancer cell motilities. This polymerization-based "prodrug" system efficiently inhibits tumor growth and metastasis both in vitro and in vivo and will promote the development of targeted and directed cancer chemotherapy.

Effect of cysteine thiols on the catalytic and anticancer activity of Ru(II) sulfonyl-ethylenediamine complexes

We have synthesized a series of novel substituted sulfonyl ethylenediamine (en) Ru^II arene complexes 1-8 of [(η⁶-arene)Ru(R¹-SO₂-EnBz)X], where the arene is benzene, HO(CH₂)₂O-phenyl or biphenyl (biph), X = Cl or I, and R¹ is phenyl, 4-Me-phenyl, 4-NO₂-phenyl or dansyl. The 'piano-stool' structure of complex 3, [(η⁶-biph)Ru(4-Me-phenyl-SO₂-EnBz)I], was confirmed by X-ray crystallography. The values of their aqua adducts were determined to be high (9.1 to 9.7). Complexes 1-8 have antiproliferative activity against human A2780 ovarian, and A549 lung cancer cells with IC₅₀ values ranging from 4.1 to >50 μM, although, remarkably, complex 7 [(η⁶-biph)Ru(phenyl-SO₂-EnBz)Cl] was inactive towards A2780 cells, but as potent as the clinical drug cisplatin towards A549 cells. All these complexes also showed catalytic activity in transfer hydrogenation (TH) of NAD⁺ to NADH with sodium formate as hydride donor, with TOFs in the range of 2.5-9.7 h^-1. The complexes reacted rapidly with the thiols glutathione (GSH) and N-acetyl-L-cysteine (NAC), forming dinuclear bridged complexes [(η⁶-biph)₂Ru₂(GS)₃]^2- or [(η⁶-biph)₂Ru₂(NAC-H)₃]^2-, with the liberation of the diamine ligand which was detected by LC-MS. In addition, the switching on of fluorescence for complex 8 in aqueous solution confirmed release of the chelated DsEnBz ligand in reactions with these thiols. Reactions with GSH hampered the catalytic TH of NAD⁺ to NADH due to the decomposition of the complexes. Co-administration to cells of complex 2 [(η⁶-biph)Ru(4-Me-phenyl-SO₂-EnBz)Cl] with L-buthionine sulfoximine (L-BSO), an inhibitor of GSH synthesis, partially restored the anticancer activity towards A2780 ovarian cancer cells. Complex 2 caused a concentration-dependent G1 phase cell cycle arrest, and induced a significant level of reactive oxygen species (ROS) in A2780 human ovarian cancer cells. The amount of induced ROS decreased with increase in GSH concentration, perhaps due to the formation of the dinuclear Ru-SG complex.

Photodecaging of a Mitochondria-Localized Iridium(III) Endoperoxide Complex for Two-Photon Photoactivated Therapy under Hypoxia

Despite the clinical success of photodynamic therapy (PDT), the application of this medical technique is intrinsically limited by the low oxygen concentrations found in cancer tumors, hampering the production of therapeutically necessary singlet oxygen (¹O₂). To overcome this limitation, we report on a novel mitochondria-localized iridium(III) endoperoxide prodrug (2-O-IrAn), which, upon two-photon irradiation in NIR, synergistically releases a highly cytotoxic iridium(III) complex (2-IrAn), singlet oxygen, and an alkoxy radical. 2-O-IrAn was found to be highly (photo-)toxic in hypoxic tumor cells and multicellular tumor spheroids (MCTS) in the nanomolar range. To provide cancer selectivity and improve the pharmacological properties of 2-O-IrAn, it was encapsulated into a biotin-functionalized polymer. The generated nanoparticles were found to nearly fully eradicate the tumor inside a mouse model within a single treatment. This study presents, to the best of our knowledge, the first example of an iridium(III)-based endoperoxide prodrug for synergistic photodynamic therapy/photoactivated chemotherapy, opening up new avenues for the treatment of hypoxic tumors.

Biotinylated curcumin as a novel chemosensitizer enhances naphthalimide-induced autophagic cell death in breast cancer cells

Achieving selective release of chemical anticancer agents and improving therapeutic efficacy has always been a hot spot in the field of cancer research, yet how to achieve this remains a great challenge. In this work, we constructed a novel chemical anticancer agent (named MCLOP) by introducing naphthalimide into the skeleton of methylene blue (MB). Under the stimulation by cellular hypochlorous acid (HClO) and visible light, selective release of active naphthalimide can be achieved within breast cancer cell lines, the release process of which can be tracked visually using near-infrared fluorescence of MB (685 nm). More importantly, we developed biotinylated curcumin (Cur-Bio) as a new chemosensitizer, which significantly enhanced the ability of MCLOP to induce autophagic cell death of breast cancer cells. This synergistic treatment strategy exhibited an excellent anti-proliferation effect on breast cancer cells in vitro, three-dimensional (3D) cell sphere model, and mouse tumor model in vivo. This work provides a new strategy for the treatment of breast cancer and also opens new opportunities for the efficient treatment of cancer with curcumin-based chemosensitizer.

Ferroptosis-Enhanced Cancer Immunity by a Ferrocene-Appended Iridium(III) Diphosphine Complex

Ferroptosis is a programmed cell death pathway discovered in recent years, and ferroptosis-inducing agents have great potential as new antitumor candidates. Here, we report a Ir(III) complex (Ir1) containing a ferrocene-modified diphosphine ligand that localizes in lysosomes. Under the acidic environments of lysosomes, Ir1 can effectively catalyze Fenton reaction, produce hydroxyl radicals, induce lipid peroxidation, down-regulate glutathione peroxidase 4, and induce ferroptosis. RNA sequencing analysis shows that Ir1 can significantly affect pathways related to ferroptosis and cancer immunity. Accordingly, Ir1 can induce immunogenic cells death and suppress tumor growth in vitro, regulate T cell activity and immune microenvironments in vivo. In conclusion, we show the potential of small molecules with ferroptosis-inducing capabilities for effective cancer immunotherapy.

Weak-emission iridium(III) complexes as fluorescent turn-on probes for ultrasensitive and selective imaging histidine in living cells and rat tissues

Visualizing endogenous histidine (His) in living systems is an important and challenging work in life science field. Herein, two weak-emission iridium(III) complexes (IrL1 and IrL2) with solvent ligands (CH₃CN) were designed and synthesized. It was found that IrL2 showed a better performance for detecting His with more remarkable fluorescence enhancement and lower limit of detection (LOD = 35 nM). Moreover, the recognitionmechanism was confirmed to be a substitution of solvent ligands by His. Importantly, probe IrL2 was applicable to visualize endogenous His in living cells and rat tissue slices via an energy-dependent endocytotic pathway. We hope that this probe can serve as a useful tool for the diagnosis of His-related diseases.

Supramolecular Self-Assembled DNA Nanosystem for Synergistic Chemical and Gene Regulations on Cancer Cells

Incorporating multiple molecular interactions within a system to realize the metabolic reprogramming of cancer cells is prospected to be of great potential in cancer therapy. Herein, we report a supramolecular self-assembled DNA nanosystem, which reprogrammed the cellular antioxidant system via synergistic chemical and gene regulations. In the nanosystem, amphipathic telluroether was coordinated with Mn^II to self-assemble into micelle, on which a siNrf2 integrated DNA network was assembled. The great electron-donating capability of telluroether was revealed to greatly promote Mn^II -based Fenton-like reaction to generate subversive ^. OH in cancer cells. In response to adenosine triphosphoric acid, the siNrf2 was specially released in cytoplasm for down-regulating expression of detoxification enzymes, which enhanced chemocatalysis-mediated oxidative stress in cancer cells, thus significantly suppressing tumor progression.

Synthesis and biological evaluation of mixed-ligand cyclometalated iridium(III)-quinoline complexes

With the aim of gaining new insight into the underlying apoptosis mechanisms and in vivo efficacy of cyclometalated Ir(III) complexes as metalodrugs, six new cyclometalated Ir(III)-quinoline complexes, [Ir(1a)(2pq)2] (2a), [Ir(1b)(2pq)2] (2b), [Ir(1c)(2pq)2] (2c), [Ir(1d)(2pq)2] (2d), [Ir(1e)(2pq)2] (2e), and [Ir(1f)(2pq)2] (2f) (2pq = 2-phenylisoquinoline), have been synthesized using 5,7-dihalo-8-hydroxylquinoline ligands (1a-1f) and [Ir(2pq)2Cl]2 precursors and characterized. Complexes 2a-2f have shown potent anticancer activity against cisplatin-resistant SK-OV-3/DDP and A549/DDP cells (IC50 = 0.11-1.83 μM), following the order 2e > 2f > 2b > 2c > 2d > 2a. Confocal microscopy images suggest that 2e and 2b could act as red-color probes for specific cell imaging and efficiently initiate apoptosis and autophagy in the mitochondria, cell cytosol, and nucleus. Overexpression of beclin1, caspase-9, cytochrome c, LC3II, and apaf-1; inhibition of p62, cyclin D1, cyclin A2, and CDK2; and a substantial rapid accumulation suggest a paraptotic mode of cell death induced by autophagy, DNA damage, and mitochondrial stress. In addition, the inhibitory rate of 2e on A549/DDP tumor growth was 64.1% at a concentration of 10.0 mg kg-1, which is clearly higher than that of cisplatin. According to the biological assay, the cyclometalated Ir(III)-quinoline complex 2e exhibited a higher anticancer effect than 2b, which may be associated with the electronic effect of the methyl group of the 1e ligand of 2e playing a key role in the mechanism.

A mitochondrion-targeted BODIPY-Ir(III) conjugate as a photoinduced ROS generator for the oxidative destruction of triple-negative breast cancer cells

Photodynamic therapy (PDT) provides an alternative option to root out localized triple-negative breast cancer (TNBC) and has been experiencing a surge of research interest over recent years. In this study, we put forward a paradigm of designing novel transition metal-based PSs with the following characteristics: favorable cell-permeability, significant light-harvesting ability and prominent ROS yield. A novel BODIPY-Ir(III) conjugate has been designed as a photoinduced ROS (¹O₂, ˙OH and ˙O₂^-) generator. BODIPY-Ir is highly photoactive in subduing cancer cells in the PDT regimen with PI values ranging from 172 to 519 and EC₅₀ in the nanomolar regime. Among various cancerous cell lines, TNBC was especially sensitive to BODIPY-Ir-mediated PDT, with a stunning EC₅₀ value of 4.32 nM (PI = 519) under a moderate flux of visible-light irradiation (500 nm, 10.5 mW cm^-2). BODIPY-Ir mainly accumulates in mitochondria and induces cell apoptosis under irradiation. Furthermore, the nanomolar antiproliferative activity of BODIPY-Ir is retained under hypoxia (2.5% O₂). This work sheds light on instilling the O₂-independent type I mechanism and conferring a red-shift absorption to metal-based PSs which fundamentally facilitate the clinical translation of PSs.

Cancer therapeutic strategies based on metal ions

As a necessary substance to maintain the body's normal life activities, metal ions are ubiquitous in organisms and play a major role in various complex physiological and biochemical processes, such as material transportation, energy conversion, information transmission, metabolic regulation, etc. Their abnormal distribution/accumulation in cells can interfere with these processes, causing irreversible physical damage to cells or activating biochemical reactions to induce cell death. Therefore, metal ions can be exploited against a wide spectrum of cancers with high efficiency and without drug resistance, which can effectively inhibit the growth of cancer cells by triggering biocatalysis, breaking the osmotic balance, affecting metabolism, interfering with signal transduction, damaging DNA, etc. This perspective systematically summarizes the latest research progress of metal ion-based anti-tumor therapy, and emphasizes the challenges and development directions of this type of therapeutic strategy, hoping to provide a general implication for future research.

Biomineralized synthesis of a smart O2-regenerating nanoreactor for highly efficient starvation/gas therapy

The emerging starvation therapy holds great promise in cancer treatment, however, its therapeutic effect is heavily reduced by intracellular hypoxia and high glutathione (GSH) conditions. To overcome these limitations, a new concept of starvation therapy pattern that employs biodegradable carriers with special selectivity and exhibits excellent anti-migration and therapy effect without using any invasive chemotherapy drugs was developed. A facile biomineralization method is first chosen to synthesize human serum albumin and folic acid modified MnO2 to guarantee active targeting, long-term stability and responsive degradation in tumor microenvironment. Designed degradation remarkably reduces GSH contents and hugely elevates intracellular O2 levels, both of which significantly improve the catalytic efficiency of GOX. Furthermore, the by-product of H2O2 is intelligently used to oxidize L-arginine and the generated NO results into effective gas therapy. More importantly, the first anti-migration case of starvation therapy has been reported in this work, and detailed molecular mechanism study uncovers that lysosome damage and changes of mitochondria membrane potential contribute to cell apoptosis. This work opens up new ideas to construct novel green yet noninvasive methods to treat cancer and inhibit migration by using degradable carriers and endogenous substances to minimize adverse effect.

Photoresponsive metallopolymer nanoparticles for cancer theranostics

Over the past decades, transition metal complexes have been successfully used in anticancer phototherapies. They have shown promising properties in many different areas including photo-induced ligand exchange or release, rich excited state behavior, and versatile biochemical properties. When encorporated into polymeric frameworks and become part of nanostructures, photoresponsive metallopolymer nanoparticles (MPNs) show enhanced water solubility, extended blood circulation and increased tumor-specific accumulation, which greatly improves the tumor therapeutic effects compared to low-molecule-weight metal complexes. In this review, we aim to present the recent development of photoresponsive MPNs as therapeutic nanomedicines. This review will summarize four major areas separately, namely platinum-containing polymers, zinc-containing polymers, iridium-containing polymers and ruthenium-containing polymers. Representative MPNs of each type are discussed in terms of their design strategies, fabrication methods, and working mechanisms. Current challenges and future perspectives in this field are also highlighted.

Activatable Dual ROS-Producing Probe for Dual Organelle-Engaged Photodynamic Therapy

Photodynamic therapy (PDT) necessitates approaches capable of increasing antitumor effects while decreasing nonspecific photodamage. We herein report an activatable probe (Glu-PyEB) comprising two distinct photosensitizers with mutually suppressed photodynamics. Activation by tumor-associated γ-glutamyltranspeptidase gives rise to a generator of superoxide radical (O₂^-•) accumulated in lysosomes and a producer of singlet oxygen (¹O₂) enriched in mitochondria. This enables light-irradiation-triggered damage of lysosomes and mitochondria, robust cell death, and tumor retardation in vivo, showing the use of paired photosensitizers subjected to reciprocally suppressed photodynamics for activatable PDT.

Rational design of iridium-porphyrin conjugates for novel synergistic photodynamic and photothermal therapy anticancer agents

Near-infrared (NIR) emitters are important probes for biomedical applications. Nanoparticles (NPs) incorporating mono- and tetranuclear iridium(iii) complexes attached to a porphyrin core have been synthesized. They possess deep-red absorbance, long-wavelength excitation (635 nm) and NIR emission (720 nm). TD-DFT calculations demonstrate that the iridium-porphyrin conjugates herein combine the respective advantages of small organic molecules and transition metal complexes as photosensitizers (PSs): (i) the conjugates retain the long-wavelength excitation and NIR emission of porphyrin itself; (ii) the conjugates possess highly effective intersystem crossing (ISC) to obtain a considerably more long-lived triplet photoexcited state. These photoexcited states do not have the usual radiative behavior of phosphorescent Ir(iii) complexes, and they play a very important role in promoting the singlet oxygen (1O2) and heat generation required for photodynamic therapy (PDT) and photothermal therapy (PTT). The tetranuclear 4-Ir NPs exhibit high 1O2 generation ability, outstanding photothermal conversion efficiency (49.5%), good biocompatibility, low half-maximal inhibitory concentration (IC50) (0.057 μM), excellent photothermal imaging and synergistic PDT and PTT under 635 nm laser irradiation. To our knowledge this is the first example of iridium-porphyrin conjugates as PSs for photothermal imaging-guided synergistic PDT and PTT treatment in vivo.

3D CoPt nanostructures hybridized with iridium complexes for multimodal imaging and combined photothermal-chemotherapy

Combined photothermal-chemotherapy has shown great potential in improving the efficiency of tumor treatment. In this article, we have designed a new type of nanocomposite Ir-CoPt-PVP composed of cobalt/platinum alloy nanoparticles (CoPt) and iridium(III) complex (Ir) for combined photothermal therapy (PTT) and chemotherapy. The obtained CoPt was synthesized by a simple solvothermal method and modified by polyvinyl pyrrolidone (PVP), which exhibited excellent photothermal efficiency and stability, and can also be a bimodal bioimaging contrast agent in photothermal imaging (PTI) and photoacoustic imaging (PAI). Furthermore, the combination therapy has shown obvious tumor cell-growth inhibition in vitro. Overall, the results revealed the great potential of Ir-CoPt-PVP nanocomposites in improving therapeutic efficiency by photothermal-chemotherapy and photothermal/photoacoustic imaging.

A Ruthenium(II) complex-based probe for colorimetric and luminescent detection and imaging of hydrogen sulfide in living cells and organisms

The development of reliable bioanalytical probes for sensitive and specific detection of hydrogen sulfide (H₂S) plays important role for better understanding the roles of this biomolecule in living cells and organisms. Taking advantages of unique photophysical properties of ruthenium(II) (Ru(II)) complex, this work presents the development of a responsive Ru(II) complex probe, Ru-PNBD, for colorimetric and luminescent analysis of H₂S in living cells and organisms. In aqueous solution, Ru-PNBD is yellow color and non-luminescent because of the photoinduced electron transfer (PET) process from Ru(II) complex luminophore to NBD moiety. The H₂S-triggered specific nucleophilic substitution reaction with Ru-PNBD cleaves the NBD moiety to form pink NBD-SH and highly luminescent Ru-PH. The color of the solution thus changes from yellow to pink for colorimetric analysis and the emission intensity is about 65-fold increased for luminescent analysis. Ru-PNBD has high sensitivity and selectivity for H₂S detection, low cytotoxicity and good permeability to cell membrane, which allow the application of this probe for H₂S imaging in living cells, Daphnia magna, and larval zebrafish. Collectively, this work provides a useful tool for H₂S analysis and expands the scope of transition metal complex probes.