Multicomponent metal-organic framework nanocomposites for tumor-responsive synergistic therapy

Targeted tumor therapy through tumor microenvironment (TME)-responsive nanoplatforms is an emerging treatment strategy used to enhance tumor-specificity to selectively kill cancer cells. Here, we introduce a nanosized zeolitic imidazolate framework-8 (ZIF-8) that simultaneously contains natural glucose oxidase (GOx) and Prussian blue nanoparticles (PBNPs) to construct multi-component metal-organic framework nanocomposites (denoted as ZIF@GOx@PBNPs), which possess cascade catalytic activity selectively within the TME. Once reaching a tumor site, GOx and PBNPs inside the nanocomposites are sequentially released and participate in the cascade catalytic reaction. In weak acidic TME, GOx, which effectively catalyzes the oxidation of intratumoral glucose to hydrogen peroxide (H₂O₂) and gluconic acid, not only initiates starvation therapy by cutting off the nutrition source for cancer cells but also produces the reactant for sequential Fenton reaction for chemodynamic therapy. Meanwhile, PBNPs, which are released from the ZIF-8 framework dissociated by acidified pH due to the produced gluconic acid, convert the generated H₂O₂ into harmful radicals to melanomas. In this way, the cascade catalytic reactions of ZIF@GOx@PBNPs enhance reactive oxygen species production and cause oxidative damage to DNA in cancer cells, resulting in remarkable inhibition of tumor growth. The tumor specificity is endowed by using the biomolecules overexpressed in TME as a "switch" to initiate the first catalytic reaction by GOx. Given the significant antitumor efficiency both in vitro and in vivo, ZIF@GOx@PBNPs could be applied as a promising therapeutic platform enabling starvation/chemodynamic synergism, high therapeutic efficiency, and minimal side effects.

Complexes of hydrogen peroxide molecules with DNA nucleic bases

The analysis of complexes formation of hydrogen peroxide molecule with DNA nucleic bases is carried out using methods of quantum chemistry. Optimized geometries of complexes are determined and the interaction energies that lead to complex formation are calculated. Comparison with the same calculations for water molecule is made. It is shown that complexes with hydrogen peroxide molecule are energetically more stable than the same complexes with water molecule. Such energetic advantage is achieved particularly due to geometrical properties of hydrogen peroxide molecule, especially presence of dihedral angle. Position of hydrogen peroxide molecule in close vicinity to DNA could lead to blocking of its recognition by proteins or direct damage via hydroxyl radical formation. These results can have significant impact in understanding of mechanisms of cancer therapy.Communicated by Ramaswamy H. Sarma.

Free radicals: Relationship to Human Diseases and Potential Therapeutic applications

Reactive species are highly-reactive enzymatically, or non-enzymatically produced compounds with important roles in physiological and pathophysiological cellular processes. Although reactive species represent an extensively researched topic in biomedical sciences, many aspects of their roles and functions remain unclear. This review aims to systematically summarize findings regarding the biochemical characteristics of various types of reactive species and specify the localization and mechanisms of their production in cells. In addition, we discuss the specific roles of free radicals in cellular physiology, focusing on the current lines of research that aim to identify the reactive oxygen species-initiated cascades of reactions resulting in adaptive or pathological cellular responses. Finally, we present recent findings regarding the therapeutic modulations of intracellular levels of reactive oxygen species, which may have substantial significance in developing novel agents for treating several diseases.

Insight into a Fenton-like Reaction Using Nanodiamond Based Relaxometry

Copper has several biological functions, but also some toxicity, as it can act as a catalyst for oxidative damage to tissues. This is especially relevant in the presence of H2O2, a by-product of oxygen metabolism. In this study, the reactions of copper with H2O2 have been investigated with spectroscopic techniques. These results were complemented by a new quantum sensing technique (relaxometry), which allows nanoscale magnetic resonance measurements at room temperature, and at nanomolar concentrations. For this purpose, we used fluorescent nanodiamonds (FNDs) containing ensembles of specific defects called nitrogen-vacancy (NV) centers. More specifically, we performed so-called T1 measurements. We use this method to provide real-time measurements of copper during a Fenton-like reaction. Unlike with other chemical fluorescent probes, we can determine both the increase and decrease in copper formed in real time.

One-Pot Approach to Fe2+ /Fe3+ -Based MOFs with Enhanced Catalytic Activity for Fenton Reaction

Smart theragnostic nanoplatforms exhibit great promise in clinical tumor treatment. The Fe-based Fenton reaction in tumor sites may generate reactive oxygen species to kill cancer cells with negligible side effects on normal tissues. However, its efficiency and duration are limited by the low intracellular concentration of H₂ O₂ , weak acidicity of tumor tissue, and low catalytic activity of conventional Fenton reagents. Herein, a facile strategy is proposed to efficiently overcome these obstacles. An efficient enzymatic/Fenton-starvation nanoreactor PMs loaded with glucose oxidase and perfluoropentane (PGPMs) is constructed through synthesizing methoxy-PEG-carboxymethy-modified iron (Fe²⁺ /Fe³⁺ )-based metal-organic frameworks (PMs), followed by loading glucose oxidase (GOx) and perfluoropentane (PFP). PGPMs accumulating in the tumor tissue exhibit tumor microenvironment-responsive biodegradable behavior and unusual catalytic activity for Fenton reaction advantageous over Fe³⁺ -based MOFs. Meanwhile, encapsulation of GOx into PGPMs further significantly increases the catalytic activity for Fenton reaction and also induces starvation therapy. PGPMs also exhibit considerable capabilities of ultrasound and tumor microenvironment-responsive T2 MR imaging applicable for contrast-enhanced diagnosis. Both in vitro and in vivo studies demonstrate the great diagnostic and therapeutic potentials of this nanoreactor in tumor.

Metal-organic complex-based chemodynamic therapy agents for cancer therapy

In recent years, many inorganic nanoparticle-based chemodynamic therapy (CDT) agents have been employed in cancer therapy; however, the relatively lower catalytic activity compared to that of other CDT agents and long-term toxicity owing to low biodegradability present significant challenges for their future clinical application. In light of this, metal-organic complex-based agents have been attracting attention as potential alternatives/complements to traditional CDT agents. During the past few years, many reports of agents with improved therapeutic potential have been published; however, no comprehensive review regarding metal-organic complex-based CDT agents has appeared to date. In this feature article, we present the different types and characteristics of metal-organic CDT agents and the potential future therapeutic applications associated with each of these. Representative agents that have been used in the field of CDT over the past 5 years are summarized, and recent advances aimed at improving the therapeutic efficacy in various tumors are highlighted. This framework allows us to discuss recent trends in the field of CDT. We also provide views as to where the field is moving and discuss how the potential of CDT agents can be broadened to include a range of clinical applications that go beyond standard CDT-based treatment strategies.

Therapeutic Potential of Reactive Oxygen Species: State of the Art and Recent Advances

In the last decade, several studies have proven that when at low concentration reactive oxygen species (ROS) show an adaptive beneficial effect and posited the idea that they can be utilized as inexpensive and convenient inducers of tissue regeneration. On the other hand, the recent discovery that cancer cells are more sensitive to oxidative damage paved the way for their use in the selective killing of tumor cells, and sensors to monitor ROS production during cancer treatment are under extensive investigation. Nevertheless, although ROS-activated signaling pathways are well established, less is known about the mechanisms underlying the switch from an anabolic to a cytotoxic response. Furthermore, a high variability in biological response is observed between different modalities of administration, cell types, donor ages, eventual concomitant diseases, and external microenvironment. On the other hand, available preclinical studies are scarce, whereas the quest for the most suitable systems for in vivo delivery is still elusive. Furthermore, new strategies to control the temporal pattern of ROS release need to be developed, if considering their tumorigenic potential. This review initially discusses ROS mechanisms of action and their potential application in stem cell biology, tissue engineering, and cancer therapy. It then outlines the state of art of ROS-based drugs and identifies challenges faced in translating ROS research into clinical practice.

Tailored core‒shell dual metal-organic frameworks as a versatile nanomotor for effective synergistic antitumor therapy

Malignant tumor has become an urgent threat to global public healthcare. Because of the heterogeneity of tumor, single therapy presents great limitations while synergistic therapy is arousing much attention, which shows desperate need of intelligent carrier for co-delivery. A core‒shell dual metal–organic frameworks (MOFs) system was delicately designed in this study, which not only possessed the unique properties of both materials, but also provided two individual specific functional zones for co-drug delivery. Photosensitizer indocyanine green (ICG) and chemotherapeutic agent doxorubicin (DOX) were stepwisely encapsulated into the nanopores of MIL-88 core and ZIF-8 shell to construct a synergistic photothermal/photodynamic/chemotherapy nanoplatform. Except for efficient drug delivery, the MIL-88 could be functioned as a nanomotor to convert the excessive hydrogen peroxide at tumor microenvironment into adequate oxygen for photodynamic therapy. The DOX release from MIL-88-ICG@ZIF-8-DOX nanoparticles was triggered at tumor acidic microenvironment and further accelerated by near-infrared (NIR) light irradiation. The in vivo antitumor study showed superior synergistic antitumor effect by concentrating the nanoparticles into dissolving microneedles as compared to intravenous and intratumoral injection of nanoparticles, with a significantly higher inhibition rate. It is anticipated that the multi-model synergistic system based on dual-MOFs was promising for further biomedical application.

Combined Fenton and starvation therapies using hemoglobin and glucose oxidase

Separately, Fenton and starvation cancer therapies have been recently reported as impressive methods for tumor destruction. Here, we introduce natural hemoglobin and glucose oxidase (GOx) for efficient cancer treatment following combined Fenton and starvation therapies. GOx and hemoglobin were encapsulated in zeolitic imidazolate frameworks 8 (ZIF-8) to fabricate a pH-sensitive MOF activated by tumor acidity. In the slightly acidic environment of cancer cells, GOx is released and it consumes d-glucose and molecular oxygen, nutrients essential for the survival of cancer cells, and produces gluconic acid and hydrogen peroxide, respectively. The produced gluconic acid increases the acidity of the tumor microenvironment leading to complete MOF destruction and enhances hemoglobin and GOx release. The Fe ions from the heme groups of hemoglobin also release in the presence of both endogenous and produced H2O2 and generate hydroxyl radicals. The produced OH˙ radical can rapidly oxidize the surrounding biomacromolecules in the biological system and treat the cancer cells. In vitro experiments demonstrate that this novel nanoparticle is cytotoxic to cancer cells HeLa and MCF-7, at very low concentrations (<2 μg mL-1). In addition, the selectivity index values are 5.52 and 11.04 for HeLa and MCF-7 cells, respectively, which are much higher than those of commercial drugs and those of similar studies reported by other research groups. This work thus demonstrates a novel pH-sensitive system containing hemoglobin and GOx for effective and selective cancer treatment using both radical generation and nutrient starvation.

Cancer Treatment through Nanoparticle-Facilitated Fenton Reaction

Currently, cancer is the second largest cause of death worldwide and has reached critical levels. In spite of all the efforts, common treatments including chemotherapy, photodynamic therapy, and photothermal therapy suffer from various problems which limit their efficiency and performance. For this reason, different strategies are being explored which improve the efficiency of these traditional therapeutic methods or treat the tumor cells directly. One such strategy utilizing the Fenton reaction has been investigated by many groups for the possible treatment of cancer cells. This approach is based on the knowledge that high levels of hydrogen peroxide exist within cancer cells and can be used to catalyze the Fenton reaction, leading to cancer-killing reactive oxygen species. Analysis of the current literature has shown that, due to the diverse morphologies, different sizes, various chemical properties, and the tunable structure of nanoparticles, nanotechnology offers the most promising method to facilitate the Fenton reaction with cancer therapy. This review aims to highlight the use of the Fenton reaction using different nanoparticles to improve traditional cancer therapies and the emerging Fenton-based therapy, highlighting the obstacles, challenges, and promising developments in each of these areas.