An osmium-peroxo complex for photoactive therapy of hypoxic tumors

Engineering copper (II) in situ reduction and delivery by a novel amphiphilic diacylhydrazone for chemodynamic therapy

Chemodynamic treatment (CDT) possesses the ability to disturb intracellular redox equilibrium, thus inhibiting tumor development. The copper-induced CDT generally needs the delivery of copper (II) ions to tumor cells and reacting with local GSH, to produce Cu+, and thus generating toxic hydroxyl radicals (·OH) via a Fenton-like reaction. Due to an insufficient amount of endogenous GSH, it remains a great challenge to achieve satisfactory anticancer efficacy and the development of a receptor with the capability of both binding and reducing Cu (II) ions is valuable. In this study, we synthesized a novel amphiphilic diacylhydrazone (compound 1) by a brief chemical reaction. Compound 1 was not only capable of complexation with copper(II) ions but able to reduce the divalent copper ions partially to the monovalent ones. The generated assembly (complex 1) containing mixed Cu (I)/Cu (II) presents a spherical-like nanoparticle, which could easily enter the HCT-116 cells and release both Cu+ and Cu2+ in a mildly acidic environment. The complex 1 therefore inhibited the growth of HCT-116 cells due to the mitochondrial damage initiated by the enhanced Fenton-like effect and the growth inhibition rate of in vivo colon cancer proliferation reached 85.12 %, significantly higher than that of its components of either compound 1 or Cu(ClO4)2, as well as paclitaxel (the positive control). Meanwhile, complex 1 had relatively low toxicity. This work provided a reference for transit Cu (I/II)-mediated precision-targeted CDT therapeutic regimen.

Gold(I) N-Heterocyclic Carbene Complexes as Ferroptosis Inducing Anticancer Agents

This study presents the chemical synthesis and biological evaluation of a series of gold(I)-N-heterocyclic carbene complexes as potential anticancer agents. The compounds demonstrated broad activity against various cancer cell lines, exhibiting cytotoxicity in the low micromolar range. Mechanistic investigations revealed that these complexes preferentially accumulate in the mitochondria of cancer cells, where they induce the generation of reactive oxygen species and lipid peroxides, ultimately triggering ferroptosis. Further studies in multicellular tumor spheroids confirmed the compounds' ability to penetrate three-dimensional cellular structures and effectively eradicate them at low micromolar concentrations. This work represents the first known example of a gold(I)-N-heterocyclic carbene complex inducing ferroptosis, expanding the therapeutic potential of gold(I)-based metallodrugs.

Ultrafast excited-state dynamics and "three-in-one" phototheranostic properties of a phenanthroline-carbolong photosensitizer

The favorable excited-state dynamics, nonlinear optics, and extraordinary phototheranostic capabilities of conjugated metallaaromatics are attractive topics of research. A promising and multifunctional photosensitizer, double-phenanthroline-carbolong DPC, was investigated comparatively. It featured strong two-photon absorption (2PA) properties within the near-infrared (NIR) range, with a maximum 2PA cross-section of ∼7417 GM at 770 nm in MeOH. Time-dependent density functional theory and ultrafast excited-state dynamics illustrated that fast charge transfer coupled with intersystem crossing to the stable triplet state outcompeted radiative decays. The "three-in-one" phototherapeutic effect included NIR-wavelength 2PA excitation, photodynamic therapy, and photothermal therapy in DPC, as illustrated subsequently. The significant contribution from the intrinsic intramolecular charge communication along the DPC skeleton provided the possibility for moderate photothermal conversion (η = 36.8%) and photodynamic synergistic therapy (Φ Δ = 8.4%). Interestingly, singlet oxygen generation from DPC was also observed when irradiated at two-photon excitation wavelengths. In vitro experiments demonstrated the synergistic phototoxicity of DPC in 4T1 cancer cells. This work offers insights into extraordinary carbolong metallaaromatics and highlights their potential applications in the fields of nonlinear optics and multifunctional phototheranostics.

Ferrocene conjugated Os(II) complex for photo-catalytic cancer therapy of triple-negative breast cancer cells

A novel ferrocene-conjugated bimetallic Os(II) photocatalyst (OsFe) showed micromolar photocatalytic anticancer activity against triple-negative breast cancer cells via NADH oxidation and caspase 3 activation under visible light.

Aggregation-Induced Photosensitization of Long-Chain-Substituted Osmium Complexes for Lysosomes Targeting Photodynamic Therapy

Photodynamic therapy (PDT) has been demonstrated to be an effective tool for cancer treatment. Seeking organelle-targeting photosensitizers (PSs) with robust reactive oxygen species (ROS) production is extremely in demand. Herein, we propose an aggregation-induced photosensitization strategy for effective PDT with osmium complexes. We designed and synthesized three osmium complexes (Os-Me, Os-tBu, and Os-Nonly) with ligands of different alkyl chains. In phosphate-buffered saline solution, the complex Os-Nonly formed a spherical aggregate with diameters of around 220 nm. The results from ROS assays indicate that Os-Nonly showed the highest efficiency in generating superoxide anions and singlet oxygen, demonstrating its role as a type I/II photosensitizer. Additionally, Os-Nonly specifically targeted lysosomes in 4T1 and MCF-7 cells, producing ROS in a sustained and efficient manner with high phototoxicity (IC50 = 6.999 μM in MCF-7 cells), thereby inducing cancer cell death. In 4T1-tumor-bearing mice models, Os-Nonly effectively inhibited tumor growth with a minimal impact on normal organs.

Intracellular Photocatalytic NADH/NAD(P)H Oxidation for Cancer Drug Development

Photocatalytic cancer therapy (PCT) has emerged as a cutting-edge anticancer mechanism of action, harnessing light energy to mediate the catalytic oxidation of intracellular substrates. PCT is of significant current importance due to its potential to address the limitations of conventional chemotherapy, particularly drug resistance and side effects. This approach offers a noninvasive, targeted cancer treatment option by utilizing metal-based photocatalysts to induce redox and metabolic disorders within cancer cells. The photocatalysts disrupt the cancer cell metabolism by converting NADH/NAD(P)H to NAD+/NAD(P)+ via catalytic photoredox processes, altering intracellular NAD+/NADH or NAD(P)+/NAD(P)H ratios, which are crucial for cellular metabolism. Ir(III), Ru(II), Re(I), and Os(II) photocatalysts demonstrated promising PCT efficacy. Despite these developments, gaps remain in the literature for translating this new anticancer mechanism into clinical trials. This Perspective critically examines the developments in this research area and provides future directions for designing efficient photocatalysts for PCT.

Advances in the Design of Photoactivatable Metallodrugs: Excited State Metallomics

Photoactivatable metal complexes offer the prospect of novel drugs with low side effects and new mechanisms of action to combat resistance to current therapy. We highlight recent progress in the design of platinum, ruthenium, iridium, gold and other transition metal complexes, especially for applications as anticancer and anti-infective agents. In particular, understanding excited state chemistry related to identification of the bioactive species (excited state metallomics/pharmacophores) is important. Photoactivatable metallodrugs are classified here as photocatalysts, photorelease agents and ligand-activated agents. Their activation wavelengths, cellular mechanisms of action, experimental and theoretical metallomics of excited states and photoproducts are discussed to explore new strategies for the design and investigation of photoactivatable metallodrugs. These photoactivatable metallodrugs have potential in clinical applications of Photodynamic Therapy (PDT), Photoactivated Chemotherapy (PACT) and Photothermal Therapy (PTT).

Photoredox-Mediated Immunotherapy Utilizing Rhenium(I) Photocatalysts with Electron Donor-Acceptor-Donor Configuration

The hypoxic environment of solid tumors significantly diminishes the therapeutic efficacy of oxygen-dependent photodynamic therapy. Developing efficient photosensitizers that operate via photoredox catalysis presents a promising strategy to overcome this challenge. Herein, we report the rational design of two rhenium(I) tricarbonyl complexes (Re-TPO and Re-TP) with electron donor-acceptor-donor configuration. Notably, Re-TP exhibits aggregation-induced emission properties and enhanced spin-orbit coupling compared to Re-TPO, thus exhibiting promoted photosensitizing capability. In addition to generating type I and II reactive oxygen species, the excited Re-TP facilitates the photocatalytic oxidation of NADH to NAD+ and the photoreduction of pyruvic acid to lactic acid. This metabolic intervention triggers PD-L1-linked immune responses and disrupts tumor redox balance, leading to ferroptosis and immunogenic cell death. The combined ferroptosis and immunotherapy effects significantly suppress both primary and distant B16 tumors. This investigation provides a compelling model for designing efficient metal-based PSs for photoredox-mediated photoimmunotherapy against hypoxic tumors.

A novel cyanine photosensitizer for sequential dual-site GSH depletion and ROS-potentiated cancer photodynamic therapy

The efficacy of photodynamic therapy (PDT) is often limited by the reductive microenvironment in tumor cells due to the high level of glutathione (GSH) and glutathione peroxidase 4 (GPX4), which maintain redox homeostasis. Therefore, designing a GSH-responsive photosensitizer that depletes intracellular GSH is a promising strategy to enhance PDT selectivity and efficacy. Herein, we present a GSH-selective sequentially responsive theranostic photosensitizer, Cy-Res. This cyanine agent targeting mitochondria effectively depletes two GSH molecules, leading to the generation of abundant ROS and exacerbating oxidative stress. Additionally, it achieves an 80-fold fluorescence enhancement upon response to GSH, enabling selective imaging of tumor cells. By mitigating GSH's impact on PDT, Cy-ResNPs achieves synergistic and efficient PDT treatment of invasive melanoma under low-power irradiation (808 nm, 80 mW/cm2). The inhibitory processes downregulate GPX4, increase apoptotic proteins like Bax, and promote mixed cell death involving both ferroptosis and apoptosis. Overall, this study offers new insights and strategies for the development of GSH-responsive theranostic agents, highlighting their potential for application in tumor diagnosis and therapy.

The Aromaticity of Osmapentalenes Derivatives - An Analysis Based on Electron-Delocalization Indices

A systematic investigation of the aromatic features of the electronic structures of a family of recently synthesized osmapentalene derivatives has been carried by means of indices derived from the calculated one-electron density matrix of the corresponding geometry optimized compounds, and complemented by the analysis of the valence molecular orbitals and the delocalized bonding units emerging from the adaptive natural density partitioning method. The calculated delocalization indices between consecutive atom pairs, and normalized multicenter indices are very suggestive of the aromatic character of the equatorial fused carbon rings (except triangular ones) for all the members of the family. Since the electron-delocalization based indices allow precise quantification of the aromaticity, differences of the aromatic character among the various members have also been highlighted, and have been found to be consistent with the magnetic based criteria indices reported earlier. Finally, the valence molecular orbitals along with the delocalized bonding units of the adaptive natural density partitioning indicate that the aromaticity of these compounds is sustained by either 10 or 14 π electrons, which satisfy the Hückel aromatic electron counting rule.

Multifunctional Ru(III)/Fe3O4/DNA nanoplatform for photothermal-enhanced photodynamic and chemodynamic cancer therapy

Among the many cancer treatment methods, there have been many reports on the use of nanoplatforms with single treatment methods such as photothermal, photodynamic or chemodynamic for cancer treatment. In this study, Ru(III) with photodynamic effect and Fe3O4 nanoparticles with photothermal and chemodynamic effects are connected through long DNA chains with efficient active targeting rolling circle amplification to construct Ru(III)/Fe3O4/DNA nano-platform realizes the combination of photothermal, photodynamic and chemodynamic treatment, which significantly improves the therapeutic effect of the nano-platform. Its multiple active targeting capabilities reduce the damage to normal cells. Ru(III) has excellent photodynamic effect and can catalyze the respiration product NADH (Nicotinamide adenine dinucleotide)to produce highly oxidizing H2O2. Fe3O4 NPs has weak absorption at 808 nm indicates that it can perform mild photothermal treatment, and the Fe2+ in it can react with H2O2 to produce ·OH and participate in chemodynamic treatment. Each repeating unit on the rolling circle amplified DNA long chain is connected to the AS1411 aptamer that can actively target cancer cells. Unlike the passive targeting of other nanomedicines, active and efficient targeting is achieved, and a small amount of drugs can achieve high efficacy. The therapeutic effect also reduces the damage to normal cells. The comprehensive killing effect of Ru(III)/Fe3O4/DNA can reach 85.1 %. Its high targeting of cancer cells can also be used for imaging detection of cancer cells. This new nanoplatform provides an idea for the synergy of multiple cancer treatments.

Exploring Excited-State Intramolecular Proton-Coupled Electron Transfer in Dinuclear Ir(III)-Complex via Covalently Tagged Hydroquinone: Phototherapy Through Futile Redox Cycling

Anticipating intramolecular excited-state proton-coupled electron transfer (PCET) process within dinuclear Ir2-photocatalytic system via the covalent linkage is seminal, yet challenging. Indeed, the development of various dinuclear complexes is also promising for studying integral photophysics and facilitating applications in catalysis or biology. Herein, this study reports dinuclear [Ir2(bis{imidazo-phenanthrolin-2-yl}-hydroquinone)(ppy)4]2+ (12+) complex by leveraging both ligand-centered redox property and intramolecular H-bonding for exploring dual excited-state proton-transfer assisted PCET process. The vital role of covalently placed hydroquinone in bridged ligand is investigated as electron-proton transfer (ET-PT) mediator in intramolecular PCET and validated from triplet spin density plot. Moreover, bimolecular photoinduced ET reaction is studied in acetonitrile/water medium, forging the lowest energy triplet charge separated (3CSPhen-Im) state of 12+ with methyl viologen via favorably concerted-PCET pathway. The result indicates strong donor-acceptors coupling, which limits charge recombination and enhances catalytic efficiency. To showcase the potential application, this bioinspired PCET-based photocatalytic platform is studied for phototherapeutics, indicating significant mitochondrial localization and leading to programmed cell death (apoptosis) through futile redox cycling. Indeed, the consequences of effective internalization (via energy-dependent endocytosis), better safety profile, and higher photoinduced antiproliferative activity of 12+ compared to Cisplatin, as explored in 3D tumor spheroids, this study anticipates it to be a potential lead compound.

Synthesis and Spectroscopic Study of a Homogenous Bimetallic Os(II) Complex as a New Gastric Cancer Photosensitizer

A homogenous dinuclear Os(II) complex bisOs was synthesized and fully characterized. The electrochemical cyclic voltammetry study, and density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were performed to investigate the electronic property. bisOs showed an obvious interaction with lipase and BSA, and can generate singlet oxygen under blue and red LED light irradiation, with a singlet oxygen quantum yield (ΦΔ) of 0.36 in comparison to that of [Ru(bpy)3]Cl2 in acetonitrile. bisOs exhibited moderate to great photocytotoxicity against HGC-27 human gastric cancer cells under blue LED light irradiation, giving the IC50 value as low as 1.83 μM (PI value is 9.7), while was almost non-cytotoxic in the dark. The cellular singlet oxygen detection in HGC-27 cancer cells exhibited a concentration-dependent manner, and cell uptake of bisOs in A549 cells was as high as 120 ng/106 cells, subcellular colocalization study indicated that bisOs was not accumulated in nucleus, and less likely to target mitochondria. This work provides a new example of dinuclear osmium complex as potential photosensitizer candidate for gastric treatment.

Osmapentalenofurans Constructed by Reacting Os≡C1 of Osmapentalyne with Phenols

Over the past decade, significant research efforts have focused on osmapentalyne, characterized by the more reactive Os≡C7 (Carbon atoms numbered in a clockwise direction on the osmapentalyne skeleton), across areas encompassing electrophilic, nucleophilic, and addition reactions. Nevertheless, the reactivity of osmapentalyne featuring Os≡C1 remains ripe for further exploration. In this investigation, we effectively synthesized a lineage of osmapentalenofurans through the nucleophilic reaction of osmapentalyne incorporating Os≡C1 with phenols. These resulting complexes demonstrate near-infrared luminescence traits in both solid and liquid states. Particularly noteworthy is the osmapentalenofuran derived from tetraphenylethane (TPE) unit, which showcases remarkable aggregation-induced emission (AIE) property in the aggregated state. These osmapentalenofurans are also able to further extend their range of reactions, including reactions with base and isonitrile. This study not only broadens the scope of applications for metal aromatics but also furnishes valuable insights into the realm of specialized functional materials.

Ferroptosis Inducing Co(III) Polypyridine Sulfasalazine Complex for Therapeutically Enhanced Anticancer Therapy

Despite significant improvements in the treatment of cancerous tumors in the last decades, cancer remains one of the deadliest diseases worldwide. To overcome the shortcomings of currently applied chemotherapeutic treatments, much research efforts have been devoted towards the development of ferroptosis inducing anticancer agents. Ferroptosis is a newly described form of regulated, non-apoptotic cell death that is associated with high potential inside the clinics. Herein, the chemical synthesis and biological evaluation of a Co(III) polypyridine sulfasalazine complex as a ferroptosis inducer is reported. Upon entering the cancerous cells, the metal complex primarily accumulated in the mitochondria, triggering the production of hydroxy radicals and lipid peroxides, ultimately causing cell death by ferroptosis. The compound demonstrated to eradicate various monolayer cancer cells as well as colon carcinoma multicellular tumor spheroids. To the best of our knowledge this study reports on the first example of a Co(III) complex that is capable of inducing ferroptosis.

Synthesis and antitumor activity of copper(II) complexes of imidazole derivatives

Complexes [Cu(PI)2(H2O)](NO3)2 (1), [Cu(PBI)2(NO3)]NO3 (2), [Cu(TBI)2(NO3)]NO3 (3), [Cu(BBIP)2](ClO4)2 (4) and [Cu(BBIP)(CH3OH)(ClO4)2] (5) were synthesized from the reactions of Cu(II) salts with 2-(2'-pyridyl)imidazole (PI), (2-(2'-pyridyl)benzimidazole (PBI), 2-(4'-thiazolyl)-benzimidazole (TBI), 2,6-bis(benzimidazol-2-yl)-pyridine (BBIP), respectively. Their compositions and crystal structures were determined. Their in-vitro antitumor activities were screened on four cancer cell lines and one normal cell line (HL-7702) using cisplatin as the positive control. Complexes 2 and 4 show higher cytotoxicity than the other three complexes. The cytotoxicity of complex 2 are comparable to those for cisplatin, and the cytotoxicity for 4 are much higher than those for cisplatin. From a viewpoint of antitumor, 2 might be a nice choice on the tumor cell line of T24 because its IC50 values on T24 and HL-7702 are 15.03 ± 1.10 and 21.34 ± 0.35, respectively. Thus, a mechanistic study for complexes 2 and 4 on T24 cells was conducted. It revealed that they can reduce mitochondrial membrane potential and increase mitochondrial membrane permeability, resulting in increased intracellular ROS levels, Ca2+ inward flow, dysfunctional mitochondria and the eventual cell apoptosis. In conclusion, they can induce cell apoptosis through mitochondrial dysfunction. These findings could be useful in the development of new antitumor agents.

Enhanced Sonodynamic Therapy for Deep Tumors Using a Self-Assembled Organoplatinum(II) Sonosensitizer

Despite the promising advances in photodynamic therapy (PDT), it remains challenging to target and treat deep-seated solid tumors effectively. Herein, we developed an organoplatinum(II) complex (Pt-TPE) with self-assembly properties for sonodynamic therapy (SDT). Pt-TPE forms a nanofiber network structure through Pt-Pt and π-π stacking interactions. Notably, under ultrasound (US), Pt-TPE demonstrates unique self-assembly-induced singlet oxygen (1O2) generation due to a significantly enhanced singlet-triplet intersystem crossing (ISC). This generation of 1O2 occurs exclusively in the self-assembled state of Pt-TPE. Additionally, Pt-TPE exhibits sono-cytotoxicity against cancer cells by impairing mitochondrial membrane potential (MMP), inhibiting glucose uptake, and aerobic glycolysis. Furthermore, US-activated Pt-TPE significantly inhibits deep solid tumors in mice, achieving remarkable therapeutic efficacy even at penetration depths greater than 10 cm. This study highlights the potential of self-assembled metal complexes to enhance the efficacy of SDT for treating deep tumors.

Piezoelectric Bilayer Nickel-Iron Layered Double Hydroxide Nanosheets with Tumor Microenvironment Responsiveness for Intensive Piezocatalytic Therapy

Piezocatalytic therapy (PCT) based on 2D layered materials has emerged as a promising non-invasive tumor treatment modality, offering superior advantages. However, a systematic investigation of PCT, particularly the mechanisms underlying the reactive oxygen species (ROS) generation by 2D nanomaterials, is still in its infancy. Here, for the first time, biodegradable piezoelectric 2D bilayer nickel-iron layered double hydroxide (NiFe-LDH) nanosheets (thickness of ≈1.86 nm) are reported for enhanced PCT and ferroptosis. Under ultrasound irradiation, the piezoelectric semiconducting NiFe-LDH exhibits a remarkable ability to generate superoxide anion radicals, due to the formation of a built-in electric field that facilitates the separation of electrons and holes. Notably, the significant excitonic effect in the ultrathin NiFe-LDH system enables long-lived excited triplet excitons (lifetime of ≈5.04 µs) to effectively convert triplet O2 molecules into singlet oxygen. Moreover, NiFe-LDH exhibited tumor microenvironment (TME)-responsive peroxidase (POD)-like and glutathione (GSH)-depleting capabilities, further enhancing oxidative stress in tumor cells and inducing ferroptosis. To the best of knowledge, this is the first report on piezoelectric semiconducting sonosensitizers based on LDHs for PCT and ferroptosis, providing a comprehensive understanding of the piezocatalysis mechanism and valuable references for the application of LDHs and other 2D materials in cancer therapy.

Sonoinduced Tumor Therapy and Metastasis Inhibition by a Ruthenium Complex with Dual Action: Superoxide Anion Sensitization and Ligand Fracture

Photoresponsive ruthenium(II) complexes have recently emerged as a promising tool for synergistic photodynamic therapy and chemotherapy in oncology, as well as for antimicrobial applications. However, the limited penetration power of photons prevents the treatment of deep-seated lesions. In this study, we introduce a sonoresponsive ruthenium complex capable of generating superoxide anion (O2•-) via type I process and initiating a ligand fracture process upon ultrasound triggering. Attaching hydroxyflavone (HF) as an "electron reservoir" to the octahedral-polypyridyl-ruthenium complex resulted in decreased highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps and triplet-state metal to ligand charge transfer (3MLCT) state energy (0.89 eV). This modification enhanced the generation of O2•- under therapeutic ultrasound irradiation at a frequency of 1 MHz. The produced O2•- rapidly induced an intramolecular cascade reaction and HF ligand fracture. As a proof-of-concept, we engineered the Ru complex into a metallopolymer platform (PolyRuHF), which could be activated by low-power ultrasound (1.5 W cm-2, 1.0 MHz, 50% duty cycle) within a centimeter range of tissue. This activation led to O2•- generation and the release of cytotoxic ruthenium complexes. Consequently, PolyRuHF induced cellular apoptosis and ferroptosis by causing mitochondrial dysfunction and excessive toxic lipid peroxidation. Furthermore, PolyRuHF effectively inhibited subcutaneous and orthotopic breast tumors and prevented lung metastasis by downregulating metastasis-related proteins in mice. This study introduces the first sonoresponsive ruthenium complex for sonodynamic therapy/sonoactivated chemotherapy, offering new avenues for deep tumor treatment.

Near infra-red luminescent osmium labelled gold nanoparticles for cellular imaging and singlet oxygen generation

Osmium(II) complexes have attractive properties for potential theranostic agents given their anticancer activitiy, their redox potentials favourable for biological transformations within cancer cells and their luminescence in the near infrared (NIR) region. To achieve localised detection and delivery, gold nanoparticles (AuNP) provide an attractive scaffold to attach multiple luminescent agents on a single particle and provide a multimodal platform for detection and loaclaised delivery. We have developed 13 nm and 25 nm AuNP decorated with an osmium complex based on 1,10-phenantholine and surface active bipyridine ligands, OsPhenSS for live cell imaging and singlet oxygen generation, notated as OsPhenSS·AuNP13 and OsPhenSS·AuNP25. The AuNP designs not only allow versatile modalities for localisation of the probe but also water solubility for the osmium metal complex. The osmium decorated nanoparticles OsPhenSS·AuNP13 and OsPhenSS·AuNP25 display characteristic NIR luminescence from the osmium(II) 3MLCT at 785 nm in aqueous solutions with visible excitation. Upon incubation of the nanoparticles in lung cancer and breast carcinoma the luminescence signature of osmium and the gold reflectance reveal localisation in the cytoplasmic and perinuclear compartments. Excitation of the nanoparticles at 552 nm in the presence of a ROS indicator revealed a marked increase in the green fluorescence from the indicator, consistent with photo-induced ROS generation. The detection of singlet oxygen by time-resolved luminescence studies of the osmium and the nanoparticle probes further demonstrates the dual activity of the osmium-based nanoprobes for imaging and therapy. The introduction of gold nanoparticles for carrying osmium imaging probes allows a novel versatile strategy combining detection and localised therapies at the nanoscale.

Platinum Group Metals Nanoparticles in Breast Cancer Therapy

Despite various methods currently used in cancer therapy, breast cancer remains the leading cause of morbidity and mortality worldwide. Current therapeutics face limitations such as multidrug resistance, drug toxicity and off-target effects, poor drug bioavailability and biocompatibility, and inefficient drug delivery. Nanotechnology has emerged as a promising approach to cancer diagnosis, imaging, and therapy. Several preclinical studies have demonstrated that compounds and nanoparticles formulated from platinum group metals (PGMs) effectively treat breast cancer. PGMs are chemically stable, easy to functionalise, versatile, and tunable. They can target hypoxic microenvironments, catalyse the production of reactive oxygen species, and offer the potential for combination therapy. PGM nanoparticles can be incorporated with anticancer drugs to improve efficacy and can be attached to targeting moieties to enhance tumour-targeting efficiency. This review focuses on the therapeutic outcomes of platinum group metal nanoparticles (PGMNs) against various breast cancer cells and briefly discusses clinical trials of these nanoparticles in breast cancer treatment. It further illustrates the potential applications of PGMNs in breast cancer and presents opportunities for future PGM-based nanomaterial applications in combatting breast cancer.

Recent advances for enhanced photodynamic therapy: from new mechanisms to innovative strategies

Photodynamic therapy (PDT) has been developed as a potential cancer treatment approach owing to its non-invasiveness, spatiotemporal control and limited side effects. Currently, great efforts have been made to improve the PDT effect in terms of safety and efficiency. In this review, we highlight recent advances in innovative strategies for enhanced PDT, including (1) the development of novel radicals, (2) design of activatable photosensitizers based on the TME and light, and (3) photocatalytic NADH oxidation to damage the mitochondrial electron transport chain. Additionally, the new mechanisms for PDT are also presented as an inspiration for the design of novel PSs. Finally, we discuss the current challenges and future prospects in the clinical practice of these innovative strategies. It is hoped that this review will provide a new angle for understanding the relationship between the intratumoural redox environment and PDT mechanisms, and new ideas for the future development of smart PDT systems.

Efficient hydroxyl radical generation of an activatable phthalocyanine photosensitizer: oligomer higher than monomer and nanoaggregate

It remains a challenge to develop a single-component organic photosensitizer that efficiently produces hydroxyl radicals (˙OH) without oxygen involvement, especially while maintaining tumor-targeting capability. Herein, we propose an intelligent molecular design strategy whereby a tumor-targeted phthalocyanine is initially ˙OH-free and can be activated by overexpressed β-nicotinamide adenine dinucleotide sodium salt hydrate (NAD(P)H) in hypoxic tumors to efficiently produce ˙OH under light irradiation. Furthermore, the oligomer models based on the phthalocyanine molecules were constructed by a supramolecular regulation strategy, which were in an intermediate state between monomer and nanoaggregate, to achieve enhanced ˙OH generation. The level of NAD(P)H in cancer cells can be exhausted through two pathways, including spontaneous redox and the photocatalytic redox of phthalocyanines. As a result, the in vivo and in vitro assays illustrated that the oligomeric phthalocyanine containing N-O units (OligPcNOB) can specifically target cancer cells and tumor tissue with overexpressing biotin receptors. OligPcNOB exhibited significant photocytotoxicity even in an extremely low oxygen environment and successfully inhibited tumor progression.

Promising G-Quadruplex-Targeted Dibenzoquinoxaline Type-1 Photosensitizer Triggers DNA Damage in Triple-Negative Breast Cancer Cells

G-quadruplexes (G4s) are potential drug targets in cancer treatment. However, the G4-targeted ligands seem to lack sufficient selectivity between tumors and normal tissues, appealing for a new modified anticancer strategy on the basis of them. Type-1 photodynamic therapy (PDT) is a promising strategy possessing excellent spatiotemporal precision for solid tumors with a hypoxic microenvironment. However, type-1 photosensitizers that target G4s and induce in situ photodamage have never been previously reported. In this study, we reported a promising type-1 photosensitizer based on a G4-targeted, high-contrast fluorescent ligand (TR2). The subsequent studies demonstrated that TR2 could transfer from lysosomes to nuclei and induce elevated G4 formation as well as DNA damage upon irradiation. Notably, it was observed that TR2 may not activate DNA damage repair machinery upon irradiation, suggesting a durable, strong effect on inducing DNA damage. Consequently, light-irradiated TR2 exhibited excellent photocytotoxicity on triple-negative breast cancer cell proliferation (at nanomolar concentration) and showed obvious inhibition on the growth of three-dimensional (3D) tumor spheroids. Finally, RNA-seq analysis demonstrated that TR2-mediated PDT may have a negative impact on enhancing the DNA damage repair machinery and may activate the antitumor immunity pathways. Overall, this study provided a promising chemical tool for image-guided PDT.

Facile synthesis of a hydrazone-based zinc(ii) complex for ferroptosis-augmented sonodynamic therapy

Sonodynamic therapy (SDT), as a novel non-invasive cancer treatment modality derived from photodynamic therapy (PDT), has drawn much attention due to its unique advantages for the treatment of deep tumors. Zinc-based complexes have shown great clinical prospect in PDT due to their excellent photodynamic activity and biosafety. However, their application in SDT has lagged seriously behind. Exploring efficient zinc-based complexes as sono-sensitizers remains an appealing but significantly challenging task. Herein, we develop a hydrazone ligand-based zinc complex (ZnAMTC) for SDT of tumors in vitro and in vivo. ZnAMTC was facilely synthesized via a two-step reaction from low-cost raw materials without tedious purification. It shows negligible dark toxicity and can produce singlet oxygen (1O2) under ultrasound (US) irradiation, exhibiting high sono-cytotoxicity to various cancer cells. Mechanism studies show that ZnAMTC can effectively reduce the levels of glutathione (GSH) and glutathione peroxidase 4 (GPX4) under US irradiation and later cause ferroptosis of cancer cells. In vivo studies further demonstrate that ZnAMTC exhibits efficient tumor growth inhibition under US irradiation and has good biosafety. This work provides useful insights into the design of first-row transition metal complexes for SDT application.

An Electron Donor-Acceptor Structured Rhenium(I) Complex Photo-Sensitizer Evokes Mutually Reinforcing "Closed-Loop" Ferroptosis and Immunotherapy

The hypoxic microenvironment of solid tumors severely lowers the efficacy of oxygen-dependent photodynamic therapy (PDT). The development of hypoxia-tolerant photosensitizers for PDT is an urgent requirement. In this study, a novel rhenium complex (Re-TTPY) to develop a "closed-loop" therapy based on PDT-induced ferroptosis and immune therapy is reported. Due to its electron donor-acceptor (D-A) structure, Re-TTPY undergoes energy transfer and electron transfer processes under 550 nm light irradiation and displays hypoxia-tolerant type I/II combined PDT capability, which can generate 1O2, O2 -, and ·OH simultaneously. Further, the reactive oxygen species (ROSs) leads to the depletion of 1,4-dihydronicotinamide adenine dinucleotide (NADH), glutathione peroxidase 4 (GPX4), and glutathione (GSH). As a result, ferroptosis occurs in cells, simultaneously triggers immunogenic cell death (ICD), and promotes the maturation of dendritic cells (DCs) and infiltration of T cells. The release of interferon-γ (IFN-γ) by CD8+ T cells downregulates the expression of GPX4, further enhancing the occurrence of ferroptosis, and thereby, forming a mutually reinforcing "closed-loop" therapeutic approach.

Progress and Challenges in Tumor Ferroptosis Treatment Strategies: A Comprehensive Review of Metal Complexes and Nanomedicine

Ferroptosis is a new form of regulated cell death featuring iron-dependent lipid peroxides accumulation to kill tumor cells. A growing body of evidence has shown the potential of ferroptosis-based cancer therapy in eradicating refractory malignancies that are resistant to apoptosis-based conventional therapies. In recent years, studies have reported a number of ferroptosis inducers that can increase the vulnerability of tumor cells to ferroptosis by regulating ferroptosis-related signaling pathways. Encouraged by the rapid development of ferroptosis-driven cancer therapies, interdisciplinary fields that combine ferroptosis, pharmaceutical chemistry, and nanotechnology are focused. First, the prerequisites and metabolic pathways for ferroptosis are briefly introduced. Then, in detail emerging ferroptosis inducers designed to boost ferroptosis-induced tumor therapy, including metal complexes, metal-based nanoparticles, and metal-free nanoparticles are summarized. Subsequently, the application of synergistic strategies that combine ferroptosis with apoptosis and other regulated cell death for cancer therapy, with emphasis on the use of both cuproptosis and ferroptosis to induce redox dysregulation in tumor and intracellular bimetallic copper/iron metabolism disorders during tumor treatment is discussed. Finally, challenges associated with clinical translation and potential future directions for potentiating cancer ferroptosis therapies are highlighted.

Self-Assembly of 2D Polyphthalocyanine in Lysosome Enables Multienzyme Activity Enhancement to Induce Tumor Ferroptosis

Nanozymes show great potential in facilitating tumor ferroptosis by upregulation of reactive oxygen species (ROS) and downregulation of glutathione (GSH). However, mild acidity (pH 6.5-6.9) of tumor microenvironment severely restricts the activity of nanozymes. Although lysosomes as acidic organelles (pH = 3.5-5.5) are hopeful for improving enzyme-like activity, most reported nanozymes are not capable of effectively accumulating in the lysosomes. Herein, an acid-responsive self-assembly strategy based on iron phthalocyanine-rich covalent organic framework nanosheets (COFFePc NSs) is developed, which enables lysosomal targeting aggregation of COFFePc NSs due to the existence of abundant negative hydroxyl groups and rigid structure. Meanwhile, COFFePc NSs display exceptional multienzyme-mimic performance at lower pH to efficiently generate ROS to cause lysosome damage and apoptosis by synergistic photothermal effect. Subsequently, the released COFFePc with GSH oxidase-mimicking activity can consume GSH to promote ferroptosis. This is the first report of a 2D COF using its own properties to achieve lysosomal self-assembly. Overall, the work provides a new paradigm for the development of lysosome-targeted nanosystems.

A type I and type II chemical biology toolbox to overcome the hypoxic tumour microenvironment for photodynamic therapy

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality employed for the treatment of various types of cancers, localized infections, and other diseases. Upon illumination, the photo-excited photosensitizer generates singlet oxygen and other reactive species, thereby inducing cytotoxicity in the target cells. The hypoxic tumour microenvironment (TME), however, poses a limitation on the supply of oxygen in tumour tissues. Moreover, under such conditions, tumour metastasis and drug resistance frequently occur, further compromising the efficacy of PDT in combating tumours. Traditionally, type I photosensitizers with lower oxygen consumption demonstrate significant potential in overcoming hypoxic environments and play a crucial role in determining the therapeutic efficacy of PDT because type I photosensitizers can generate highly cytotoxic free radicals. In comparison, type II photosensitizers exhibit high oxygen dependence. The rate of reactive oxygen species (ROS) generation in the type II process is significantly higher than that in the type I process. Thus, the efficiency and selectivity of PDT depend on the properties of the photosensitizer. Here, the recent development and application of type I and type II photosensitizers, mainly in the past year, are summarized. The design methods, electronic structures, photophysical properties, lipophilic properties, electric charge, and other molecular characteristics of these photosensitizers are discussed in detail. These modifications alter the microstructure of photosensitizers and directly impact the results of PDT. The main content of this paper will have a positive promoting and inspiring effect on the future development of PDT.

[FeIIICl(TMPPH2)][FeIIICl4]2: A Stand-Alone Molecular Nanomedicine That Induces High Cytotoxicity by Ferroptosis

Developing clinically meaningful nanomedicines for cancer therapy requires the drugs to be effective, safe, simple, cheap, and easy to store. In the present work, we report that a simple cationic Fe(III)-rich salt of [FeIIICl(TMPPH2)][FeIIICl4]2 (Fe-TMPP) exhibits a superior anticancer performance on a broad spectrum of cancer cell lines, including breast, colorectal cancer, liver, pancreatic, prostate, and gastric cancers, with half maximal inhibitory concentration (IC50) values in the range of 0.098-3.97 μM (0.066-2.68 μg mL-1), comparable to the best-reported medicines. Fe-TMPP can form stand-alone nanoparticles in water without the need for extra surface modification or organic-solvent-assisted antisolvent precipitation. Critically, Fe-TMPP is TME-responsive (TME = tumor microenvironment), and can only elicit its function in the TME with overexpressed H2O2, converting H2O2 to the cytotoxic •OH to oxidize the phospholipid of the cancer cell membrane, causing ferroptosis, a programmed cell death process of cancer cells.

A review on ferroptosis and photodynamic therapy synergism: Enhancing anticancer treatment

Ferroptosis is an iron-dependent programmed cell death modality, which has showed great potential in anticancer treatment. Photodynamic therapy (PDT) is widely used in clinic as an anticancer therapy. PDT combined with ferroptosis-promoting therapy has been found to be a promising strategy to improve anti-cancer therapy efficacy. Fenton reaction in ferroptosis can provide oxygen for PDT, and PDT can produce reactive oxygen species for Fenton reaction to enhance ferroptosis. In this review, we briefly present the importance of ferroptosis in anticancer treatment, mechanism of ferroptosis, researches on PDT induced ferroptosis, and the mechanism of the synergistic effect of PDT and ferroptosis on cancer killing.

Functional Upgrading of an Organo-Ir(III) Complex to an Organo-Ir(III) Prodrug as a DNA Damage-Responsive Autophagic Inducer for Hypoxic Lung Cancer Therapy

The efficiency of nitrogen mustards (NMs), among the first chemotherapeutic agents against cancer, is limited by their monotonous mechanism of action (MoA). And tumor hypoxia is a significant obstacle in the attenuation of the chemotherapeutic efficacy. To repurpose the drug and combat hypoxia, herein, we constructed an organo-Ir(III) prodrug, IrCpNM, with the composition of a reactive oxygen species (ROS)-inducing moiety (Ir-arene fragment)-a hypoxic responsive moiety (azo linker)-a DNA-alkylating moiety (nitrogen mustard), and realized DNA damage response (DDR)-mediated autophagy for hypoxic lung cancer therapy for the first time. Prodrug IrCpNM could upregulate the level of catalase (CAT) to catalyze the decomposition of excessive H2O2 to O2 and downregulate the expression of the hypoxia-inducible factor (HIF-1α) to relieve hypoxia. Subsequently, IrCpNM initiates the quadruple synergetic actions under hypoxia, as simultaneous ROS promotion and glutathione (GSH) depletion to enhance the redox disbalance and severe oxidative and cross-linking DNA damages to trigger the occurrence of DDR-mediated autophagy via the ATM/Chk2 cascade and the PIK3CA/PI3K-AKT1-mTOR-RPS6KB1 signaling pathway. In vitro and in vivo experiments have confirmed the greatly antiproliferative capacity of IrCpNM against the hypoxic solid tumor. This work demonstrated the effectiveness of the DNA damage-responsive organometallic prodrug strategy with the microenvironment targeting system and the rebirth of traditional chemotherapeutic agents with a new anticancer mechanism.

Recent Progress in Ferroptosis Induced Tumor Cell Death by Anti-tumor Metallic complexes

Metal complexes represented by platinum complexes play a very important role in cancer treatment due to their diverse chemical structures and anti-tumor activities. Recently, ferroptosis has emerged as a newly occurring cell death form in the anti-tumor process. It has been reported that metal complexes could inhibit the proliferation and metastasis of tumors and combat chemotherapy resistance by targeting ferroptosis. In this review, we briefly describe ferroptosis as a fundamental process for tumor suppression and triggering anti-tumor immune responses. We summarize recent developments on metal complexes that induce ferroptosis. Finally, we outline the prospects for the application of metal complexes to the treatment of tumors based on ferroptosis and the associated problems that need to be solved, and discussed other potential research directions of metal complexes.

Metallaaromatic Complexes as Candidates for Future Molecular Materials and Electronic Devices: Recent Advancements

In recent years, the field of organometallic chemistry has made a great progress and diverse types of metallaaromatics have successively been reported. In those studies, incorporation of ligated osmium centers into metallaaromatic systems played a prominent role. The reviewed literature documents that certain metallaaromatics with unconventional photophysical properties, redox and electronic transport properties and magnetism, have potential to be widely used in diverse practical applications, with selected examples of amino acid and fluoride anion identification, photothermal effects, functional materials, photodynamic therapy (PDT) in biomedicine, single-molecule junction conductors, and electron-transport layer materials (ETLs) in solar cells.

Iron-Based Nanovehicle Delivering Fin56 for Hyperthermia-Boosted Ferroptosis Therapy Against Osteosarcoma

Background

Although systemic chemotherapy is a standard approach for osteosarcoma (OS) treatment, its efficacy is limited by the inherent or acquired resistance to apoptosis of tumor cells. Ferroptosis is considered as an effective strategy capable of stimulating alternative pathways of cancer cell demise. The purpose of this study is to develop a novel strategy boosting ferroptotic cascade for synergistic cancer therapy.

Methods and Results

A novel nanovehicle composed of arginine-glycine-aspartate (RGD) modified mesoporous silica-coated iron oxide loading Fin56 was rationally prepared (FSR-Fin56). With the RGD-mediated targeting affinity, FSR-Fin56 could achieve selective accumulation and accurate delivery of cargos into cancer cells. Upon exposure to NIR light, the nanovehicle could generate localized hyperthermia and disintegrate to liberate the therapeutic payload. The released Fin56 triggered the degradation of GPX4, while Fe3+ depleted the intracellular GSH pool, producing Fe2+ as a Fenton agent. The local rise in temperature, in conjunction with Fe2+-mediated Fenton reaction, led to a rapid and significant accumulation of ROS, culminating in LPOs and ferroptotic death. The outstanding therapeutic efficacy and safety of the nanovehicle were validated both in vitro and in vivo.

Conclusion

The Fin56-loaded FSR nanovehicle could effectively disturb the redox balance in cancer cells. Coupled with NIR laser irradiation, the cooperative CDT and PTT achieved a boosted ferroptosis-inducing therapy. Taken together, this study offers a compelling strategy for cancer treatment, particularly for ferroptosis-sensitive tumors like osteosarcoma.

Exploring the Use of Intracellular Chelation and Non-Iron Metals to Program Ferroptosis for Anticancer Application

The discovery of regulated cell death (RCD) revolutionized chemotherapy. With caspase-dependent apoptosis initially being thought to be the only form of RCD, many drug development strategies aimed to synthesize compounds that turn on this kind of cell death. While yielding a variety of drugs, this approach is limited, given the acquired resistance of cancers to these drugs and the lack of specificity of the drugs for targeting cancer cells alone. The discovery of non-apoptotic forms of RCD is leading to new avenues for drug design. Evidence shows that ferroptosis, a relatively recently discovered iron-based cell death pathway, has therapeutic potential for anticancer application. Recent studies point to the interrelationship between iron and other essential metals, copper and zinc, and the disturbance of their respective homeostasis as critical to the onset of ferroptosis. Other studies reveal that several coordination complexes of non-iron metals have the capacity to induce ferroptosis. This collective knowledge will be assessed to determine how chelation approaches and coordination chemistry can be engineered to program ferroptosis in chemotherapy.

Recent Development of Copper-Based Nanozymes for Biomedical Applications

Copper (Cu), an indispensable trace element within the human body, serving as an intrinsic constituent of numerous natural enzymes, carrying out vital biological functions. Furthermore, nanomaterials exhibiting enzyme-mimicking properties, commonly known as nanozymes, possess distinct advantages over their natural enzyme counterparts, including cost-effectiveness, enhanced stability, and adjustable performance. These advantageous attributes have captivated the attention of researchers, inspiring them to devise various Cu-based nanomaterials, such as copper oxide, Cu metal-organic framework, and CuS, and explore their potential in enzymatic catalysis. This comprehensive review encapsulates the most recent advancements in Cu-based nanozymes, illuminating their applications in the realm of biochemistry. Initially, it is delved into the emulation of typical enzyme types achieved by Cu-based nanomaterials. Subsequently, the latest breakthroughs concerning Cu-based nanozymes in biochemical sensing, bacterial inhibition, cancer therapy, and neurodegenerative diseases treatment is discussed. Within this segment, it is also explored the modulation of Cu-based nanozyme activity. Finally, a visionary outlook for the future development of Cu-based nanozymes is presented.

Experimental and theoretical evidences for the formation of transition metal complexes with five coplanar metal-carbon σ bonds

The σ bond is an important concept in chemistry, and the metal-carbon (M-C) σ bond in particular is a central feature in organometallic chemistry. Synthesis of stable complexes with five coplanar M-C σ bonds is challenging. Here, we describe the synthesis of two different types of stable complexes with five coplanar M-C σ bonds, and examine the stability of such complexes which use rigid conjugated carbon chains to chelate with the metal center. Density functional theory (DFT) calculations show that the M-C σ bonds in these complexes have primarily a covalent character. Besides the σ nature, there are also a π conjugation component among the metal center and carbons, which causes delocalization. This work expanded the coplanar M-C σ bonds to five.

An Activatable Prodrug Nanosystem for Ultrasound-Driven Multimodal Tumor Therapy and Metastasis Inhibition

Ultrasound, featuring deep tissue penetration and noninvasiveness, offers a new opportunity to activate functional materials in a tumor-selective manner. However, very few direct ultrasound-responsive redox systems are applicable under therapeutic ultrasound (1 MHz). Herein, the investigations on nanoprodrug of DHE@PEG-SS-DSPE are reported, which exhibit glutathione-activated release of dihydroethidium (DHE) in tumor cells. DHE is stable with good biosafety and is transformed into cytotoxic ethidium to induce DNA damage under medical ultrasound irradiation, accompanied by the generation of reactive oxygen species. Further, DHE@PEG-SS-DSPE could effectively induce ferroptosis through glutathione depletion, lipid peroxide accumulation, and downregulation of glutathione peroxidase 4. In vivo studies confirmed that DHE@PEG-SS-DSPE nanoparticles effectively inhibit both the growth of solid tumors and the expression of metastasis-related proteins in mice, thus effectively inhibiting lung metastasis. This DHE-based prodrug nanosystem could lay a foundation for the design of ultrasound-driven therapeutic agents.

Near-Infrared Self-Assembled Hydroxyl Radical Generator Based on Photoinduced Cascade Electron Transfer for Hypoxic Tumor Phototherapy

The hydroxyl radical (•OH) is an extremely potent reactive oxygen species that plays a crucial role in photooxidations within the realm of hypoxic tumor therapy. However, the current methods for •OH photogeneration typically rely on inorganic materials that require UV/vis light excitation. Consequently, photogenerators based on organic molecules, especially those utilizing near-infrared (NIR) light excitation, are rare. In this study, the concept of photoinduced cascade charge transfer (PICET), which utilizes NIR heavy-atom-free photosensitizers (ANOR-Cy5) to generate •OH is introduced. The ANOR-Cy5 photosensitizer, with its flexible hydrophobic structure, enables the formation of nanoparticles in aqueous solutions through molecular assembly. PICET involves a symmetry-breaking charge separation-induced localized charge-separated state, transitioning to a delocalized charge-separated state, which governs the efficiency of •OH generation. Thanks to the oxygen-independent nature of •OH generation and its robust oxidative properties, the ANOR-Cy5-based photosensitizer demonstrates highly effective photoinduced anti-cancer effects, even under severely hypoxic conditions. This discovery emphasizes the potential for achieving •OH photogeneration using a single organic molecule through the engineering of molecular self-assembly, thereby opening up new possibilities for phototherapy and beyond.

Photodynamic Therapy Combined with Ferroptosis Is a Synergistic Antitumor Therapy Strategy

Ferroptosis is a programmed death mode that regulates redox homeostasis in cells, and recent studies suggest that it is a promising mode of tumor cell death. Ferroptosis is regulated by iron metabolism, lipid metabolism, and intracellular reducing substances, which is the mechanism basis of its combination with photodynamic therapy (PDT). PDT generates reactive oxygen species (ROS) and 1O2 through type I and type II photochemical reactions, and subsequently induces ferroptosis through the Fenton reaction and the peroxidation of cell membrane lipids. PDT kills tumor cells by generating excessive cytotoxic ROS. Due to the limited laser depth and photosensitizer enrichment, the systemic treatment effect of PDT is not good. Combining PDT with ferroptosis can compensate for these shortcomings. Nanoparticles constructed by photosensitizers and ferroptosis agonists are widely used in the field of combination therapy, and their targeting and biological safety can be improved through modification. These nanoparticles not only directly kill tumor cells but also further exert the synergistic effect of PDT and ferroptosis by activating antitumor immunity, improving the hypoxia microenvironment, and inhibiting the tumor angiogenesis. Ferroptosis-agonist-induced chemotherapy and PDT-induced ablation also have good clinical application prospects. In this review, we summarize the current research progress on PDT and ferroptosis and how PDT and ferroptosis promote each other.

Reactive X (where X = O, N, S, C, Cl, Br, and I) species nanomedicine

Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, where X = O, N, S, C, Cl, Br, and I) have important roles in various normal physiological processes and act as essential regulators of cell metabolism; their inherent biological activities govern cell signaling, immune balance, and tissue homeostasis. However, an imbalance between RXS production and consumption will induce the occurrence and development of various diseases. Due to the considerable progress of nanomedicine, a variety of nanosystems that can regulate RXS has been rationally designed and engineered for restoring RXS balance to halt the pathological processes of different diseases. The invention of radical-regulating nanomaterials creates the possibility of intriguing projects for disease treatment and promotes advances in nanomedicine. In this comprehensive review, we summarize, discuss, and highlight very-recent advances in RXS-based nanomedicine for versatile disease treatments. This review particularly focuses on the types and pathological effects of these reactive species and explores the biological effects of RXS-based nanomaterials, accompanied by a discussion and the outlook of the challenges faced and future clinical translations of RXS nanomedicines.

A Multifunctional Nanozyme with NADH Dehydrogenase-Like Activity and Nitric Oxide Release under Near-Infrared Light Irradiation as an Efficient Therapeutic for Antimicrobial Resistance Infection and Wound Healing

In recent years, antimicrobial resistance (AMR) has become one of the greatest threats to human health. There is an urgent need to develop new antibacterial agents to effectively treat AMR infection. Herein, a novel nanozyme platform (Cu,N-GQDs@Ru-NO) is prepared, where Cu,N-doped graphene quantum dots (Cu,N-GQDs) are covalently functionalized with a nitric oxide (NO) donor, ruthenium nitrosyl (Ru-NO). Under 808 nm near-infrared (NIR) light irradiation, Cu,N-GQDs@Ru-NO demonstrates nicotinamide adenine dinucleotide (NADH) dehydrogenase-like activity for photo-oxidizing NADH to NAD+ , thus disrupting the redox balance in bacterial cells and resulting in bacterial death; meanwhile, the onsite NIR light-delivered NO effectively eradicates the methicillin-resistant Staphylococcus aureus (MRSA) bacterial and biofilms, and promotes wound healing; furthermore, the nanozyme shows excellent photothermal effect that enhances the antibacterial efficacy as well. With the combination of NADH dehydrogenase activity, photothermal therapy, and NO gas therapy, the Cu,N-GQDs@Ru-NO nanozyme displays both in vitro and in vivo excellent efficacy for MRSA infection and biofilm eradication, which provides a new therapeutic modality for effectively treating MRSA inflammatory wounds.

Interrogating bioinspired ESIPT/PCET-based Ir(iii)-complexes as organelle-targeted phototherapeutics: a redox-catalysis under hypoxia to evoke synergistic ferroptosis/apoptosis

Installing proton-coupled electron transfer (PCET) in Ir-complexes is indeed a newly explored phenomenon, offering high quantum efficiency and tunable photophysics; however, the prospects for its application in various fields, including interrogating biological systems, are quite open and exciting. Herein, we developed various organelle-targeted Ir(iii)-complexes by leveraging the photoinduced PCET process to see the opportunities in phototherapeutic application and investigate the underlying mechanisms of action (MOAs). We diversified the ligands' nature and also incorporated a H-bonded benzimidazole-phenol (BIP) moiety with π-conjugated ancillary ligands in Ir(iii) to study the excited-state intramolecular proton transfer (ESIPT) process for tuning dual emission bands and to tempt excited-state PCET. These visible or two-photon-NIR light activatable Ir-catalysts generate reactive hydroxyl radicals (˙OH) and simultaneously oxidize electron donating biomolecules (1,4-dihydronicotinamide adenine dinucleotide or glutathione) to disrupt redox homeostasis, downregulate the GPX4 enzyme, and amplify oxidative stress and lipid peroxide (LPO) accumulation. Our homogeneous photocatalytic platform efficiently triggers organelle dysfunction mediated by a Fenton-like pathway with spatiotemporal control upon illumination to evoke ferroptosis poised with the synergistic action of apoptosis in a hypoxic environment leading to cell death. Ir2 is the most efficient photochemotherapy agent among others, which provided profound cytophototoxicity to 4T1 and MCF-7 cancerous cells and inhibited solid hypoxic tumor growth in vitro and in vivo.

Metallodrugs in the battle against non-small cell lung cancer: unlocking the potential for improved therapeutic outcomes

Non-small cell lung cancer (NSCLC) remains a leading cause of cancer mortality worldwide. Platinum-based chemotherapy is standard-of-care but has limitations including toxicity and resistance. Metal complexes of gold, ruthenium, and other metals have emerged as promising alternatives. This review provides a comprehensive analysis of metallodrugs for NSCLC. Bibliometric analysis reveals growing interest in elucidating mechanisms, developing targeted therapies, and synergistic combinations. Classification of metallodrugs highlights platinum, gold, and ruthenium compounds, as well as emerging metals. Diverse mechanisms include DNA damage, redox modulation, and immunomodulation. Preclinical studies demonstrate cytotoxicity and antitumor effects in vitro and in vivo, providing proof-of-concept. Clinical trials indicate platinums have utility but resistance remains problematic. Non-platinum metallodrugs exhibit favorable safety but modest single agent efficacy to date. Drug delivery approaches like nanoparticles show potential to enhance therapeutic index. Future directions include optimization of metal-based complexes, elucidation of resistance mechanisms, biomarker development, and combination therapies to fully realize the promise of metallodrugs for NSCLC.

Metal-Based Photosensitizers as Inducers of Regulated Cell Death Mechanisms

Over the last few decades, various forms of regulated cell death (RCD) have been discovered and were found to improve cancer treatment. Although there are several reviews on RCD induced by photodynamic therapy (PDT), a comprehensive summary covering metal-based photosensitizers (PSs) as RCD inducers has not yet been presented. In this review, we systematically summarize the works on metal-based PSs that induce different types of RCD, including ferroptosis, immunogenic cell death (ICD), and pyroptosis. The characteristics and mechanisms of each RCD are explained. At the end of each section, a summary of the reported commonalities between different metal-based PSs inducing the same RCD is emphasized, and future perspectives on metal-based PSs inducing novel forms of RCD are discussed at the end of the review. Considering the essential roles of metal-based PSs and RCD in cancer therapy, we hope that this review will provide the stage for future advances in metal-based PSs as RCD inducers.

A near-infrared light-activatable Ru(ii)-coumarin photosensitizer active under hypoxic conditions

Photodynamic therapy (PDT) represents a promising approach for cancer treatment. However, the oxygen dependency of PDT to generate reactive oxygen species (ROS) hampers its therapeutic efficacy, especially against hypoxic solid tumors. In addition, some photosensitizers (PSs) have dark toxicity and are only activatable with short wavelengths such as blue or UV-light, which suffer from poor tissue penetration. Herein, we developed a novel hypoxia-active PS with operability in the near-infrared (NIR) region based on the conjugation of a cyclometalated Ru(ii) polypyridyl complex of the type [Ru(C^N)(N^N)₂] to a NIR-emitting COUPY dye. The novel Ru(ii)-coumarin conjugate exhibits water-solubility, dark stability in biological media and high photostability along with advantageous luminescent properties that facilitate both bioimaging and phototherapy. Spectroscopic and photobiological studies revealed that this conjugate efficiently generates singlet oxygen and superoxide radical anions, thereby achieving high photoactivity toward cancer cells upon highly-penetrating 740 nm light irradiation even under hypoxic environments (2% O₂). The induction of ROS-mediated cancer cell death upon low-energy wavelength irradiation along with the low dark toxicity exerted by this Ru(ii)-coumarin conjugate could circumvent tissue penetration issues while alleviating the hypoxia limitation of PDT. As such, this strategy could pave the way to the development of novel NIR- and hypoxia-active Ru(ii)-based theragnostic PSs fuelled by the conjugation of tunable, low molecular-weight COUPY fluorophores.

Metal complexes induced ferroptosis for anticancer therapy

Metal complexes for anti-tumor treatment have been developed rapidly in recent decades since the application of cisplatin in clinics. However, some tumor cells are resistant to apoptosis and not sensitive to metallodrugs that function through the apoptotic pathway. Recently, metal complexes have been reported to cause ferroptosis against tumor cells, which offers new opportunities for anticancer therapy. In this perspective, ferroptosis-inducing metal complexes and their working mechanisms are introduced, while the challenges and opportunities are also discussed.

Naphthalene Diimide-Functionalized Half-Sandwich Ru(II) Complexes as Mitochondria-Targeted Anticancer and Antimetastatic Agents

In this work, four naphthalene diimide (NDI)-functionalized half-sandwich Ru(II) complexes Ru1-Ru4 bearing the general formula [(η⁶-arene)Ru^II(N^N)Cl]PF₆, where arene = benzene (bn), p-cymene (p-cym), 1,3,5-trimethylbenzene (tmb), and hexamethylbenzene (hmb), have been synthesized and characterized. By introducing the NDI unit into the N,N-chelating ligand of these half-sandwich complexes, the poor luminescent half-sandwich complexes are endowed with excellent emission performance. Besides, modification on the arene ligand of arene-Ru(II) complexes can influence the electron density of the metal center, resulting in great changes in the kinetic properties, catalytic activities in the oxidative conversion of NADH to NAD⁺, and biological activities of these compounds. Particularly, Ru4 exhibits the highest reactivity and the strongest inhibitory activity against the growth of three tested cancer cell lines. Further study revealed that Ru4 can enter cells quickly in an energy-dependent manner and preferentially accumulate in the mitochondria of MDA-MB-231 cells, inducing cell apoptosis via reactive oxygen species overproduction and mitochondrial dysfunction. Significantly, Ru4 can effectively inhibit the cell migration and invasion. Overall, the complexation with NDI and modification on the arene ligand endowed the half-sandwich Ru(II) complexes with improved spectroscopic properties and anticancer activities, highlighting their potential applications for cancer treatment.