Aggregation-induced emission-active iridium (III)-based mitochondria-targeting nanoparticle for two-photon imaging-guided photodynamic therapy

Synergistic photoinduction of ferroptosis and apoptosis by a mitochondria-targeted iridium complex for bladder cancer therapy

Bladder cancer (BC) is one of the most common malignant tumors of the urinary system, and has a high recurrence rate and treatment resistance. Recent results indicate that mitochondrial metabolism influences the therapeutic outcomes of BC. Mitochondria-targeted photosensitizer (PS) is a promising anticancer therapeutic approach that may overcome the limitations of conventional BC treatments. Herein, two mitochondria-targeted iridium(III) PSs, Ir-Mito1 and Ir-Mito2, have been designed for BC treatment. Mechanically, Ir-Mito2 induced a decrease in mitochondrial membrane potential via white light activation, further triggering a reduction of the B-cell lymphoma 2 protein (Bcl-2)/Bcl-associated X protein (Bax) ratio and increment of cleaved caspase3. Meanwhile, the reduction of glutathione, deactivation of glutathione peroxidase 4 (GPX4), increase of acyl-CoA synthetase long chain family member 4 (ACSL4), and accumulation of lipid peroxide resulted in synergistically activating of ferroptosis and apoptosis. The results demonstrated that Ir-Mito2 exhibited excellent antitumor efficacy with superior biosafety in vivo. This work on light-activated and mitochondrial-targeted PS provides an innovative therapeutic platform for BC.

Recent advances in nanomedicine design strategies for targeting subcellular structures

The current state of cancer treatment has encountered limitations, with each method having its own drawbacks. The emergence of nanotechnology in recent years has highlighted its potential in overcoming these limitations. Nanomedicine offers various drug delivery mechanisms, including passive, active, and endogenous targeting, with the advantage of modifiability and shapability. This flexibility enables researchers to develop tailored treatments for different types of tumors and populations. As nanodrug technology evolves from first to third generation, the focus is now on achieving precise drug delivery by targeting subcellular structures within tumors. This review summarizes the progress made in subcellular structure-targeted nanodrugs over the past 5 years, highlighting design strategies for targeting mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus, and cytoskeleton. The review also addresses the current status, limitations, and future directions about the research of nanodrugs.

Significant enhancement of anticancer effect of iridium (III) complexes encapsulated in liposomes

In this study, the ligand EIPP (5-ethoxy-2-(1H-imidazo[4,5-f] [1,10] phenanthrolin-2-yl)phenol) and [Ir(ppy)2(EIPP)](PF6)] (5a, ppy = 2-phenylpyridine) and [Ir(piq)2(EIPP)](PF6)] (5b, piq = 1-phenylisoquinoline) were synthesized and they were entrapped into liposomes to produce 5alipo and 5blipo. 5a and 5b were characterized via HRMS, NMR, UV-vis and IR. The cytotoxicity of 5a, 5b, 5alipo and 5blipo on cancer and non-cancer cells was estimated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). MTT assay demonstrated that 5a and 5b did not show any significant cellular activity but their liposome-encapsulated 5alipo and 5blipo had significant toxic effects. The mechanism of 5alipo, 5blipo-inducing apoptosis was explored by studying cellular uptake, mitochondrial localization, mitochondrial membrane potential, cytochrome C, glutathione (GSH), malondialdehyde (MDA) and protein immunoblotting. The results demonstrated that 5alipo and 5blipo caused a release of cytochrome C, downregulated the expression of Bcl-2, upregulated the expression of BAX, activated caspase 3, and downregulated PARP expression. It was shown that 5alipo and 5blipo could inhibit cancer cell proliferation in G2/M phase by regulating p53 and p21 proteins. Additionally, 5alipo and 5blipo induced autophagy through an adjustment from LC3-I to LC3-II and caused ferroptosis. The in vivo antitumor activity of 5alipo was examined in detail.

Leveraging the Photofunctions of Transition Metal Complexes for the Design of Innovative Phototherapeutics

Despite the advent of various medical interventions for cancer treatment, the disease continues to pose a formidable global health challenge, necessitating the development of new therapeutic approaches for more effective treatment outcomes. Photodynamic therapy (PDT), which utilizes light to activate a photosensitizer to produce cytotoxic reactive oxygen species (ROS) for eradicating cancer cells, has emerged as a promising approach for cancer treatment due to its high spatiotemporal precision and minimal invasiveness. However, the widespread clinical use of PDT faces several challenges, including the inefficient production of ROS in the hypoxic tumor microenvironment, the limited penetration depth of light in biological tissues, and the inadequate accumulation of photosensitizers at the tumor site. Over the past decade, there has been increasing interest in the utilization of photofunctional transition metal complexes as photosensitizers for PDT applications due to their intriguing photophysical and photochemical properties. This review provides an overview of the current design strategies used in the development of transition metal complexes as innovative phototherapeutics, aiming to address the limitations associated with PDT and achieve more effective treatment outcomes. The current challenges and future perspectives on the clinical translation of transition metal complexes are also discussed.

Protein corona dynamicity contributes to biological destiny disparities of nanoparticles

Extracellular protein coronas (exPCs), which have been identified in various biofluids, are recognized for their pivotal role in mediating the interaction between nanoparticles and the cytomembrane. However, it is still unclear whether various exPCs can induce different levels of intracellular proteostasis, which is of utmost importance in preserving cellular function, and eliciting distinct intracellular biological behaviors. To investigate this, two types of exPC-coated iron oxide nanoparticles (IONPs) are prepared and used to investigate the influence of exPCs on extracellular and intracellular biological outcomes. The results demonstrate that the formation of exPCs promotes the colloidal stability of IONPs, and the discrepancies in the components of the two exPCs, including opsonin, dysopsonin, and lipoprotein, are responsible for the disparities in cellular uptake and endocytic pathways. Moreover, the differential evolution of the two exPCs during cellular internalization leads to distinct autophagy and glycolysis activities, which can be attributed to the altered depletion of angiopoietin 1 during the formation of intracellular protein coronas, which ultimately impacts the PI3K/AKT-mTOR signaling. These findings offer valuable insights into the dynamic characteristics of exPCs during cellular internalization, and their consequential implications for cellular internalization and intracellular metabolism activity, which may facilitate the comprehension of PCs on biological effects of NPs and expedite the design and application of biomedical nanoparticles.

Lactic acid responsive sequential production of hydrogen peroxide and consumption of glutathione for enhanced ferroptosis tumor therapy

Ferroptosis is characterized by the lethal accumulation of lipid reactive oxygen species (ROS), which has great potential for tumor therapy. However, developing new ferroptosis-inducing strategies by combining nanomaterials with small molecule inducers is important. In this study, an enzyme-gated biodegradable natural-product delivery system based on lactate oxidase (LOD)-gated biodegradable iridium (Ir)-doped hollow mesoporous organosilica nanoparticles (HMONs) loaded with honokiol (HNK) (HNK@Ir-HMONs-LOD, HIHL) is designed to enhance ferroptosis in colon tumor therapy. After reaching the tumor microenvironment, the outer LOD dissociates and releases the HNK to induce ferroptosis. Moreover, the released dopant Ir4+ and disulfide-bridged organosilica frameworks deplete intracellular glutathione (GSH), which is followed by GSH-mediated Ir(IV)/Ir(III) conversion. This leads to the repression of glutathione peroxidase 4 (GPX4) activity and decomposition of intratumoral hydrogen peroxide (H2O2) into hydroxyl radicals (•OH) by Ir3+-mediated Fenton-like reactions. Moreover, LOD efficiently depletes lactic acid to facilitate the generation of H2O2 and boost the Fenton reaction, which in turn enhances ROS generation. With the synergistic effects of these cascade reactions and the release of HNK, notable ferroptosis efficacy was observed both in vitro and in vivo. This combination of natural product-induced and lactic acid-responsive sequential production of H2O2 as well as the consumption of glutathione may provide a new paradigm for achieving effective ferroptosis-based cancer therapy.

Iridium(III) complexes conjugated with naproxen exhibit potent anti-tumor activities by inducing mitochondrial damage, modulating inflammation, and enhancing immunity

A series of Ir(III)-naproxen (NPX) conjugates with the molecular formula [Ir(C^N)2bpy(4-CH2ONPX-4'-CH2ONPX)](PF6) (Ir-NPX-1-3) were designed and synthesized, including C^N = 2-phenylpyridine (ppy, Ir-NPX-1), 2-(2-thienyl)pyridine (thpy, Ir-NPX-2) and 2-(2,4-difluorophenyl)pyridine (dfppy, Ir-NPX-3). Cytotoxicity tests showed that Ir-NPX-1-3 exhibited excellent antitumor activity, especially in A549R cells. The cellular uptake experiment showed that the complexes were mainly localized in mitochondria, and induced apoptosis in A549R cells by damaging the structure and function of mitochondria. The main manifestations are a decrease in the mitochondrial membrane potential (MMP), an increase in reactive oxygen species (ROS) levels, and cell cycle arrest. Furthermore, Ir-NPX-1-3 could inhibit the migration and colony formation of cancer cells, demonstrating potential anti-metastatic ability. Finally, the anti-inflammatory and immunological applications of Ir-NPX-1-3 were verified. The downregulation of cyclooxygenase-2 (COX-2) and programmed death-ligand 1 (PD-L1) expression levels and the release of immunogenic cell death (ICD) related signaling molecules such as damage-associated molecular patterns (DAMPs) (cell surface calreticulin (CRT), high mobility group box 1 (HMGB1), and adenosine triphosphate (ATP)) indicate that these Ir(III) -NPX conjugates are novel ICD inducers with synergistic effects in multiple anti-tumor pathways.