Tumor Microenvironment-"AND" Near-Infrared Light-Activated Coordination Polymer Nanoprodrug for On-Demand CO-Sensitized Synergistic Cancer Therapy

LD and ER targeted cysteine fluorescence sensing driven A/B-ring-naphthalene/indole simultaneously substituted water hypersensitive flavonol: simultaneous dual-colour visualization of LDs and ER, and precisely controlled linear CO delivery

The first cysteine (Cys) fluorescence sensing-driven flavonol, HIBC (3-hydroxy-2-(1-methyl-1H-indol-3-yl)-4H-benzo[g]chromen-4-one), has been developed as a single fluorescent probe (SFprobe) and a photoCORM. This compound is characterized by the simultaneous substitutions at both the A- and B-rings with naphthalene and indole, respectively. Notably, HIBC exhibits remarkable hypersensitivity to minor variations in water fractions (fw, vol% in acetonitrile) ranging from 0% to 15%, enabling in situ real-time visualization of lipid droplets (LDs) and the endoplasmic reticulum (ER) with high spatial resolution through distinct dual-colour fluorescence without any crosstalk. Under O2, HIBC facilitates the delivery of precisely controlled amounts of CO gas within a therapeutic and safe dosage range to living systems via visible light irradiation. This control is achieved by modulating either the intensity or the duration of the irradiated light or by adjusting the dosage of the photoCORM. Its fluorescence allows for in situ real-time imaging and tracking of intracellular distribution while monitoring CO delivery progress. HIBC is generated from the sensing reaction between the precursor IBCA (2-(1-methyl-1H-indol-3-yl)-4-oxo-4H-benzo[g]chromen-3-yl acrylate) and the Cys. In PBS buffer containing only 30% of DMSO, IBCA can rapidly detect and image both endogenous and exogenous Cys within just 250 seconds. It demonstrates high selectivity-particularly against homocysteine (Hcy) and glutathione (GSH)-and sensitivity, achieving detection limits as low as 87 nM in live HeLa cells and zebrafish across a wide linear concentration range of 0-10 μM (0-2 equiv.). Importantly, IBCA also targets LDs and ER while monitoring fluctuations in Cys levels during periods of ER stress. Both IBCA and HIBC, along with all photoreaction products, exhibit negligible toxicity while demonstrating good permeability in live HeLa cells and zebrafish. The HIBC we developed represents a pioneering instance of a flavonol driven by Cys fluorescence sensing that features simultaneous substitutions at both the A-and B-rings with naphthalene and indole moieties, respectively. Compared to the unsubstituted flavonol, these structural improvements not only lead to a substantial red shift of 88 nm in the absorption peak but also significantly enhance the overall performance. It serves not only as an exceptionally water hypersensitive SFprobe for simultaneous dual-colour fluorescence visualization of LDs and ER but also functions effectively as a photoCORM. This work not only provides a method for precise control over CO release but also facilitates the development of user-friendly molecular tools for further investigation into the roles played by LDs, ER, Cys and CO in biological processes, their interactions and relationships among them, along with their potential applications in clinical diagnosis.

Localized Light-Triggered CO Delivery: Comparing the Amount of CO Delivered and Cellular Toxicity

Molecules that enable the controlled delivery of carbon monoxide (CO) in biological environments are of significant current interest to probe the beneficial roles of CO for humans. Assumptions regarding the ability of molecules to reliably deliver CO continue to impact the field, including in work involving non-metal CO delivery motifs. Flavonols are drawing increasing interest as light-triggered CO release motifs due to their ease of synthesis, functionalization, and fluorescence trackability. Importantly, the light-driven CO release properties of flavonols depend on their structure and must be fully evaluated under various conditions to understand the relationship between the amount of CO delivered and the induced biological effects. Herein, we use a family of amine-functionalized π-extended flavonols to demonstrate that structural differences result in differing interactions with biomolecules, cellular uptake, and changes in subcellular localization, which can affect the amount of CO delivered intracellularly. This results in differences in the CO-induced cellular toxicity.

Hypoxia-Targeted-Therapy: Mussel-inspired hollow polydopamine nanocarrier containing MoS2 nanozyme and tirapazamine with anti-angiogenesis property for synergistic tumor therapy

Photothermal therapy (PTT) using thermal and tumor microenvironment-responsive reagents is promising for cancer treatment. This study demonstrates an effective PTT nanodrug consisting of hollow-structured, thermally sensitive polydopamine nanobowls (HPDA NB), molybdenum sulfide (MoS2) nanozyme, and tirapazamine (TPZ; a hypoxia-responsive drug), with a structure of HPDA@TPZ/MoS NBs, which is hereafter denoted as HPTZMoS NBs. With the Fenton-like activity, the HPTZMoS NBs in the presence of H2O2 catalyze the formation of hydroxyl radicals, providing chemodynamic therapy (CDT) effect and deactivating glutathione. Under acidic conditions, HPTZMoS NBs facilitate the release of sulfide ions (S2-) and TPZ, providing a combination of chemotherapy (CT) and hydrogen sulfide (H2S) gas therapy (GT). Under an 808-nm NIR laser irradiation, the HPTZMoS NBs efficiently convert photo energy to thermal energy, providing PTT and improved CDT, CT, and GT effects. Upon treatment with an NIR laser and H2O2, a synergistic effect leads to substantial tumor cell eradication. Additionally, HPTZMoS NBs disrupt vascular endothelial growth factor (VEGF-A165)-induced cell migration in human umbilical vein endothelial cells through its strong interaction with VEGF-A165. In vivo studies in 4T1-tumor-bearing mice confirm that HPTZMoS NBs induces significant tumor destruction through a combination of PTT, hyperthermia-induced CDT, GT, and CT pathways. This study presents a multifaceted, highly selective nanotherapy platform with potent anti-angiogenesis properties, holding significant promise for future clinical applications.

Benzimidazole scaffold as a potent anticancer agent with different mechanisms of action (2016-2023)

Benzimidazole scaffolds have potent anticancer activity due to their structure similarity to nucleoside. In addition, benzimidazoles could function as hydrogen donors or acceptors and bind to different drug targets that participate in cancer progression. The literature had many anticancer agents containing benzimidazole cores that gained much interest. Provoked by our endless interest in benzimidazoles as anticancer agents, we summarized the successful trials of the benzimidazole scaffolds in this concern. Moreover, we discuss the substantial opportunities in cancer treatment using benzimidazole-based drugs that may direct medicinal chemists for a compelling future design of more active chemotherapeutic agents with potential clinical applications. The uniqueness of this work lies in the highlighted benzimidazole scaffold hybridization with different molecules and benzimidazole-metal complexes, detailed mechanisms of action, and the IC50 of the developed compounds determined by different laboratories after 2015.

Thermal CO Release Reactivity of a π-Extended Flavonol Anion

The π-extended flavonol Flav-1 (1) undergoes reaction with KOH or KO2 to form 1-, which reacts with O2 at ambient temperature, resulting in CO release and depside formation. Mechanistic and DFT studies support a reaction pathway involving reaction of 1- with O2 on the triplet energy surface in the rate-determining step. Formation of a cyclic peroxide leads to CO extrusion. These studies indicate that if formed in biological environments, 1- will release CO in the absence of light illumination.

An encounter between metal ions and natural products: natural products-coordinated metal ions for the diagnosis and treatment of tumors

Natural products-coordinated metal ions to form the nanomedicines are in the spotlight for cancer therapy. Some natural products could be coordinated with metal ions forming nanomedicines via simple and green environmental self-assembly, which not only improved the bioavailability of natural products, but also conferred multiple therapeutic modalities and multimodal imaging. On the one hand, in the weak acidity, glutathione (GSH) and hydrogen peroxide (H2O2) overexpression of tumor microenvironment (TME), such carrier-free nanomedicines could be further enhanced the therapeutic effect via optimizing the species of metal ions. On the other hand, nanomedicines could exert the precise treatment of tumor under the guidance of multiple imaging. Hence, this review summarized the research progress in recent years on the application of natural product-coordinated metal ions in cancer therapy. In addition, the prospects and challenges for the application of natural product-coordinated metal ions were discussed, especially how to improve targeting ability and stability and assess the safety of metal ions, so as to facilitate the clinical translation and application of natural product-coordinated metal ions nanomedicines.

Investigating the Combined Toxicity of Cu(II) and Carbon Monoxide (CO); Cellular CO Delivery Using a Cu(II) Flavonolato Complex

Carbon monoxide (CO) delivery molecules are of significant current interest as potential therapeutics, including for anticancer applications. A recent approach toward generating new types of materials-based anticancer agents involves combining the Fenton reactivity of a redox active metal ion with CO delivery. However, small molecule examples of these types of entities have not been systematically studied to evaluate the combined effect on cellular toxicity. Herein we describe a Cu(II) flavonolato complex which produces anticancer effects through a combination of copper-mediated reactive oxygen species (ROS) generation and light-induced flavonol CO release. Confocal microscopy studies provide evidence of enhanced flavonol uptake in the copper flavonolato system relative to the free flavonol, which leads to an increased amount of CO delivery within cells. Importantly, this work demonstrates that a metal flavonolato species can be used to produce enhanced toxicity effects resulting from both metal ion-induced Fenton reactivity and increased cellular uptake of a flavonol CO donor.

Glutathione-triggered release of SO2 gas to augment oxidative stress for enhanced chemodynamic and sonodynamic therapy

Recently, gas therapy has emerged as a promising alternative treatment for deep-seated tumors. However, some challenges regarding insufficient or uncontrolled gas generation as well as unclear therapeutic mechanisms restrict its further clinical application. Herein, a well-designed nanoreactor based on intracellular glutathione (GSH)-triggered generation of sulfur dioxide (SO2) gas to augment oxidative stress has been developed for synergistic chemodynamic therapy (CDT)/sonodynamic therapy (SDT)/SO2 gas therapy. The nanoreactor (designed as CCM@FH-DNs) is constructed by employing iron-doped hollow mesoporous silica nanoparticles as carriers, the surface of which was modified with the SO2 prodrug 2,4-dinitrobenzenesulfonyl (DNs) and further coated with cancer cell membranes for homologous targeting. The CCM@FH-DNs can not only serve as a Fenton-like agent for CDT, but also as a sonosensitizer for SDT. Importantly, CCM@FH-DNs can release SO2 for SO2-mediated gas therapy. Both in vitro and in vivo evaluations demonstrate that the CCM@FH-DNs nanoreactor performs well in augmenting oxidative stress for SO2 gas therapy-enhanced CDT/SDT via GSH depletion and glutathione peroxidase-4 enzyme deactivation as well as superoxide dismutase inhibition. Moreover, the doped iron ions ensure that the CCM@FH-DNs nanoreactors enable magnetic resonance imaging-guided therapy. Such a GSH-triggered SO2 gas therapy-enhanced CDT/SDT strategy provides an intelligent paradigm for developing efficient tumor microenvironment-responsive treatments.

Strategies to engineer various nanocarrier-based hybrid catalysts for enhanced chemodynamic cancer therapy

Chemodynamic therapy (CDT) is a newly developed cancer-therapeutic modality that kills cancer cells by the highly toxic hydroxyl radical (˙OH) generated from the in situ triggered Fenton/Fenton-like reactions in an acidic and H2O2-overproduced tumor microenvironment (TME). By taking the advantage of the TME-activated catalytic reaction, CDT enables a highly specific and minimally-invasive cancer treatment without external energy input, whose efficiency mainly depends on the reactant concentrations of both the catalytic ions and H2O2, and the reaction conditions (including pH, temperature, and amount of glutathione). Unfortunately, it suffers from unsatisfactory therapy efficiency for clinical application because of the limited activators (i.e., mild acid pH and insufficient H2O2 content) and overexpressed reducing substance in TME. Currently, various synergistic strategies have been elaborately developed to increase the CDT efficiency by regulating the TME, enhancing the catalytic efficiency of catalysts, or combining with other therapeutic modalities. To realize these strategies, the construction of diverse nanocarriers to deliver Fenton catalysts and cooperatively therapeutic agents to tumors is the key prerequisite, which is now being studied but has not been thoroughly summarized. In particular, nanocarriers that can not only serve as carriers but are also active themselves for therapy are recently attracting increasing attention because of their less risk of toxicity and metabolic burden compared to nanocarriers without therapeutic capabilities. These therapy-active nanocarriers well meet the requirements of an ideal therapy system with maximum multifunctionality but minimal components. From this new perspective, in this review, we comprehensively summarize the very recent research progress on nanocarrier-based systems for enhanced CDT and the strategies of how to integrate various Fenton agents into the nanocarriers, with particular focus on the studies of therapy-active nanocarriers for the construction of CDT catalysts, aiming to guide the design of nanosystems with less components and more functionalities for enhanced CDT. Finally, the challenges and prospects of such a burgeoning cancer-theranostic modality are outlooked to provide inspirations for the further development and clinical translation of CDT.

Copper indium selenium nanomaterials for photo-amplified immunotherapy through simultaneously enhancing cytotoxic T lymphocyte recruitment and M1 polarization of macrophages

Photoactivated immunotherapy has promising therapeutic efficacy for treating malignancies, especially metastatic tumors. In this study, an erythrocyte membrane-encapsulated copper indium selenium (RCIS) semiconductor nanomaterial was developed to eliminate primary and metastatic tumors, in which copper ions can induce chemodynamic performance, and the narrow band gap endows RCIS with the properties of near-infrared (NIR) light-activated photothermal and photodynamic amplified immunotherapy. Furthermore, RCIS can be used as a nanocarrier to form RNCIS nanoparticles (NPs) by loading NLG919, which blocks the indoleamine 2,3-dioxygenase-1. Under NIR light irradiation, RNCIS NPs release NLG919 at tumor sites via photothermal properties, thereby promoting the recruitment of cytotoxic T lymphocytes and M1 polarization of macrophages, targeting the activation and amplification of immune responses. Herein, in vitro and in vivo studies showed that RNCIS NPs effectively kill cancer cells and eliminate primary and metastatic tumors. Therefore, this study suggests that semiconductor nanomaterials with narrow bandgaps have great potential as photoimmunotherapy agents and NIR light-responsive nanocarriers for controlled release, providing a great paradigm for synergetic tumor photoimmunotherapy. STATEMENT OF SIGNIFICANCE: The Erythrocyte membrane-coated, NLG919-loaded copper indium selenium (RNCIS) semiconductor was designed for eliminating primary and metastatic tumors. RNCIS exhibits chemodynamic, photodynamic, and photothermal activated immunotherapy by inhibiting indoleamine 2,3-dioxygenase-1. This can enhance the recruitment of cytotoxic T lymphocyte and M1 polarization of macrophage, leading to higher synergetic photo-immune therapeutic efficacy.

Targeting endothelial permeability in the EPR effect

The characteristics of the primary tumor blood vessels and the tumor microenvironment drive the enhanced permeability and retention (EPR) effect, which confers an advantage towards enhanced delivery of anti-cancer nanomedicine and has shown beneficial effects in preclinical models. Increased vascular permeability is a landmark feature of the tumor vessels and an important driver of the EPR. The main focus of this review is the endothelial regulation of vascular permeability. We discuss current challenges of targeting vascular permeability towards clinical translation and summarize the structural components and mechanisms of endothelial permeability, the principal mediators and signaling players, the targeted approaches that have been used and their outcomes to date. We also critically discuss the effects of the tumor-infiltrating immune cells, their interplay with the tumor vessels and the impact of immune responses on nanomedicine delivery, the impact of anti-angiogenic and tumor-stroma targeting approaches, and desirable nanoparticle design approaches for greater translational benefit.

Carbon monoxide therapy: a promising strategy for cancer

Cancer is one of the acute life-threatening diseases endangering the whole of humanity. The treatment modalities for cancer are various. However, in most cases, a single treatment choice provides multiple side effects, poor targeting, and ineffective treatment. In recent years, the physiological regulatory function of carbon monoxide (CO) in the cancer process has been reported gradually, and CO-related nano-drugs have been explored. It shows better application prospects in cancer treatment and provides new ideas for treatment. The present review introduces the pathophysiological role of CO. The recent advances in cancer therapy, such as CO-mediated gas therapy, combined application of CO chemotherapy, photodynamic therapy (PDT), photothermal therapy (PTT), and immunotherapy, are described. Current challenges and future developments in CO-based treatment are also discussed. This review provides comprehensive information on recent advances in CO therapy and also some valuable guidance for promoting the progress of gas therapy nanomedicine.

2D Cu-Bipyridine MOF Nanosheet as an Agent for Colon Cancer Therapy: A Three-in-One Approach for Enhancing Chemodynamic Therapy

Chemodynamic therapy (CDT) is a highly tumor-specific and minimally invasive treatment that is widely used in cancer therapy. However, its therapeutic effect is limited by the poor efficiency of hydroxyl radical generation. In colon cancer in particular, the high expression of hydrogen sulfide (H₂S), which has strong reducibility, results in the consumption of generated hydroxyl radicals, further weakening the efficacy of CDT. To overcome this problem, we developed a novel two-dimensional (2D) Cu-bipyridine metal-organic framework (MOF) nanosheet [Cu(bpy)₂(OTf)₂] for colon cancer CDT. The therapeutic effect of Cu(bpy)₂(OTf)₂ is enhanced based on three factors. First, the developed 2D Cu-MOF rapidly consumes H₂S to inhibit the consumption of generated hydroxyl radicals. Second, the ultrasmall CuS generated after H₂S depletion facilitates Fenton-like reactions. Third, the generated CuS exhibits good photothermal performance in the second near-infrared window, allowing for photothermal-enhanced CDT. The ability of Cu(bpy)₂(OTf)₂ to improve the CDT effect was demonstrated through both in vitro and in vivo experiments. This work demonstrates the applicability of 2D Cu-MOF in the CDT of colon cancer and provides a novel strategy for constructing CDT agents for colon cancer.

A multifunctional nanoplatform delivering carbon monoxide and a cysteine protease inhibitor to mitochondria under NIR light shows enhanced synergistic anticancer efficacy

Photoactivated chemotherapy has attracted widespread attention due to its ability to circumvent the shortcomings of hypoxia in tumor tissues compared with traditional photodynamic therapy. In this work, novel multifunctional nanoplatform (1), Ru-inhibitor@TPPMnCO@N-GQDs, was designed and prepared, which was capable of mitochondria-targeted co-delivery of the cysteine protease inhibitor and carbon monoxide (CO) stimulated with an 808 nm near infrared (NIR) laser. Nanoplatform (1) was prepared by covalent attachment of a mitochondria-targeted CO donor (TPPMnCO) and a Ru(II)-caged cysteine protease inhibitor (Ru-inhibitor) on the surface of fluorescent N-doped graphene quantum dots (N-GQDs). Nanoplatform (1) preferentially accumulated in the mitochondria of cancer cells and instantly delivered CO and the cysteine protease inhibitor upon 808 nm NIR light irradiation, thus damaging mitochondria and leading to significant in vitro and in vivo anticancer efficacy. In addition, nanoplatform (1) has good biocompatibility and did not exert any toxic side effects on mice during the period of treatment. The targeted subcellular mitochondrial co-delivery of CO and the cysteine protease inhibitor may provide new insights into CO and enzyme inhibitor combined therapies for cancer treatment.

Flavonol-Based Carbon Monoxide Delivery Molecule with Endoplasmic Reticulum, Mitochondria, And Lysosome Localization

Light-triggered carbon monoxide (CO) delivery molecules are of significant current interest for evaluating the role of CO in biology and as potential therapeutics. Herein we report the first example of a metal free CO delivery molecule that can be tracked via confocal microscopy at low micromolar concentrations in cells prior to CO release. The NEt₂-appended extended flavonol (4) localizes to the endoplasmic reticulum, mitochondria, and lysosomes. Subcellular localization of 4 results in CO-induced toxicity effects that are distinct as compared to a nonlocalized analog. Anti-inflammatory effects of 4, as measured by TNF-α suppression, occur at the nanomolar level in the absence of CO release, and are enhanced with visible-light-induced CO release. Overall, the highly trackable nature of 4 enables studies of the biological effects of both a localized flavonol and CO release at low micromolar to nanomolar concentrations.

Chemodynamic Therapy via Fenton and Fenton-Like Nanomaterials: Strategies and Recent Advances

Chemodynamic therapy (CDT), a novel cancer therapeutic strategy defined as the treatment using Fenton or Fenton-like reaction to produce •OH in the tumor region, was first proposed by Bu, Shi, and co-workers in 2016. Recently, with the rapid development of Fenton and Fenton-like nanomaterials, CDT has attracted tremendous attention because of its unique advantages: 1) It is tumor-selective with low side effects; 2) the CDT process does not depend on external field stimulation; 3) it can modulate the hypoxic and immunosuppressive tumor microenvironment; 4) the treatment cost of CDT is low. In addition to the Fe-involved CDT strategies, the Fenton-like reaction-mediated CDT strategies have also been proposed, which are based on many other metal elements including copper, manganese, cobalt, titanium, vanadium, palladium, silver, molybdenum, ruthenium, tungsten, cerium, and zinc. Moreover, CDT has been combined with other therapies like chemotherapy, radiotherapy, phototherapy, sonodynamic therapy, and immunotherapy for achieving enhanced anticancer effects. Besides, there have also been studies that extend the application of CDT to the antibacterial field. This review introduces the latest advancements in the nanomaterials-involved CDT from 2018 to the present and proposes the current limitations as well as future research directions in the related field.

Near-infrared light-triggered nano-prodrug for cancer gas therapy

Gas therapy (GT) has attracted increasing attention in recent years as a new cancer treatment method with favorable therapeutic efficacy and reduced side effects. Several gas molecules, such as nitric oxide (NO), carbon monoxide (CO), hydrogen (H2), hydrogen sulfide (H2S) and sulfur dioxide (SO2), have been employed to treat cancers by directly killing tumor cells, enhancing drug accumulation in tumors or sensitizing tumor cells to chemotherapy, photodynamic therapy or radiotherapy. Despite the great progress of gas therapy, most gas molecules are prone to nonspecific distribution when administered systemically, resulting in strong toxicity to normal tissues. Therefore, how to deliver and release gas molecules to targeted tissues on demand is the main issue to be considered before clinical applications of gas therapy. As a specific and noninvasive stimulus with deep penetration, near-infrared (NIR) light has been widely used to trigger the cleavage and release of gas from nano-prodrugs via photothermal or photodynamic effects, achieving the on-demand release of gas molecules with high controllability. In this review, we will summarize the recent progress in cancer gas therapy triggered by NIR light. Furthermore, the prospects and challenges in this field are presented, with the hope for ongoing development.