Near infrared-assisted Fenton reaction for tumor-specific and mitochondrial DNA-targeted photochemotherapy

Tumor Microenvironment-Responsive Cu2(OH)PO4 Nanocrystals for Selective and Controllable Radiosentization via the X-ray-Triggered Fenton-like Reaction

Traditional radiotherapy can induce injury to the normal tissue around the tumor, so the development of novel radiosensitizer with high selectivity and controllability that can lead to more effective and reliable radiotherapy is highly desirable. Herein, a new smart radiosensitizer based on Cu₂(OH)PO₄ nanocrystals that can simultaneously respond to endogenous stimulus (H₂O₂) and exogenous stimulus (X-ray) is reported. First, Cu₂(OH)PO₄ nanocrystals can generate Cu^I sites under X-ray irradiation through X-ray-induced photoelectron transfer process. Then, X-ray-triggered Cu^I sites serve as a catalyst for efficiently decomposing overexpressed H₂O₂ in the tumor microenvironment into highly toxic hydroxyl radical through the Fenton-like reaction, finally inducing apoptosis and necrosis of cancer cells. Meanwhile, this nonspontaneous Fenton-like reaction is greatly limited within normal tissues because of its oxygen-rich condition and insufficient H₂O₂ relative to tumor tissues. Thus, this strategy can ensure that the process of radiosentization can only be executed within hypoxic tumors but not in normal cells, resulting in the minimum damages to surrounding healthy tissues. As a result, the X-ray-triggered Fenton-like reaction via introducing nontoxic Cu₂(OH)PO₄ nanocrystals under the dual stimuli provides a more controllable and reliable activation approach to simultaneously enhance the radiotherapeutic efficacy and reduce side effects.

The interplay of circulating tumor DNA and chromatin modification, therapeutic resistance, and metastasis

Peripheral circulating free DNA (cfDNA) is DNA that is detected in plasma or serum fluid with a cell-free status. For cancer patients, cfDNA not only originates from apoptotic cells but also from necrotic tumor cells and disseminated tumor cells that have escaped into the blood during epithelial-mesenchymal transition. Additionally, cfDNA derived from tumors, also known as circulating tumor DNA (ctDNA), carries tumor-associated genetic and epigenetic changes in cancer patients, which makes ctDNA a potential biomarker for the early diagnosis of tumors, monitory and therapeutic evaluations, and prognostic assessments, among others, for various kinds of cancer. Moreover, analyses of cfDNA chromatin modifications can reflect the heterogeneity of tumors and have potential for predicting tumor drug resistance.

Nanocatalysts-Augmented and Photothermal-Enhanced Tumor-Specific Sequential Nanocatalytic Therapy in Both NIR-I and NIR-II Biowindows

The tumor microenvironment (TME) has been increasingly recognized as a crucial contributor to tumorigenesis. Based on the unique TME for achieving tumor-specific therapy, here a novel concept of photothermal-enhanced sequential nanocatalytic therapy in both NIR-I and NIR-II biowindows is proposed, which innovatively changes the condition of nanocatalytic Fenton reaction for production of highly efficient hydroxyl radicals (•OH) and consequently suppressing the tumor growth. Evidence suggests that glucose plays a vital role in powering cancer progression. Encouraged by the oxidation of glucose to gluconic acid and H₂ O₂ by glucose oxidase (GOD), an Fe₃ O₄ /GOD-functionalized polypyrrole (PPy)-based composite nanocatalyst is constructed to achieve diagnostic imaging-guided, photothermal-enhanced, and TME-specific sequential nanocatalytic tumor therapy. The consumption of intratumoral glucose by GOD leads to the in situ elevation of the H₂ O₂ level, and the integrated Fe₃ O₄ component then catalyzes H₂ O₂ into highly toxic •OH to efficiently induce cancer-cell death. Importantly, the high photothermal-conversion efficiency (66.4% in NIR-II biowindow) of the PPy component elevates the local tumor temperature in both NIR-I and NIR-II biowindows to substaintially accelerate and improve the nanocatalytic disproportionation degree of H₂ O₂ for enhancing the nanocatalytic-therapeutic efficacy, which successfully achieves a remarkable synergistic anticancer outcome with minimal side effects.

Pretreatment of Tribulus terrestris L. causes anti-ischemic cardioprotection through MAPK mediated anti-apoptotic pathway in rat

The aim of the present investigation is the evaluation and elucidation of the mechanisms by which Tribulus terrestris L. methanol extract (TTM) devoid of fruit exhibits protection against cardiac ischemia in in vitro (H9c2 cell line) and in vivo (Wistar rat) model. Tribulus terrestris L. (TT) was used in this study to evaluate the efficacy against cardiac ischemia employing in vitro and in vivo models of myocardial ischemia. H9c2 cells were used for the in vitro induction of ischemia. Male Wistar rats (10 weeks old) weighing 180-220 g were used for the in vivo experiments. ECG and clinically relevant cardiac biomarkers like serum lactate dehydrogenase, serum creatinine kinase, serum creatinine kinase myocardial B fraction, serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase were analysed to evaluate efficacy in the rat. For elucidation of molecular mechanisms of its beneficial activity in vitro, expression of apoptotic markers like Bax, Bad, Bcl-2 and signalling pathways involving mitogen-activated protein kinases like p38α, JNK, and Akt were studied. Tribulus terrestris L. was found effective against cardiac ischemia in the rat which was evident from ECG and various cardiac biomarkers analysis. Tribulus terrestris L. was found to act through the mitogen-activated signalling pathway leading to prevention of apoptosis during ischemic insult. The beneficial effect of Tribulus terrestris L. against cardiac ischemia was seen both in in vitro and in vivo models via its anti-apoptotic potential.

Ascorbyl and hydroxyl radical generation mediated by a copper complex adsorbed on gold

Electrochemistry, nuclease assays, and EPR were used to detect ascorbyl and hydroxyl radical generation by a copper complex adsorbed on gold.

Poly(norepinephrine)-coated FeOOH nanoparticles as carriers of artemisinin for cancer photothermal-chemical combination therapy

The photothermal-chemical combination therapy is a promising approach for cancer treatment, however, chemotherapy often causes severe toxic and side effects on normal tissues. Herein, tumor-specific FeOOH@PNE-Art nanoparticles were fabricated via coating poly(norepinephrine) (PNE) on FeOOH nanoparticles, followed by loading of artemisinin (Art). The as-prepared nanoparticles exhibited excellent biocompatibility, strong near-infrared (NIR) absorbance and pH-responsive synchronous release of Art and iron ions. The released iron ions could not only supply iron ions in cancer cells which mediate endoperoxide bridge cleavage of Art and generate reactive oxygen species (ROS), but also react with H₂O₂ at tumour sites via the Fenton reaction and produce hydroxyl radicals, inducing a tumour-specific killing. Moreover, owing to the synchronous release of Art and iron ions as well as the low leakage of iron ions, FeOOH@PNE-Art nanoparticles showed extremely low toxicity to normal tissue. Under NIR light irradiation, the tumours in FeOOH@PNE-Art injected mice were thoroughly eliminated after 7 days of treatment and no tumour recurrence was found 30 days after treatment, manifesting very high efficacy of combination therapy.

Tumor-specific FeOOH@PNE-Art nanoparticles were fabricated that showed high efficacy of photothermal-chemical combination therapy and low toxicity to normal tissue.

Iron-sulfur clusters in nucleic acid metabolism: Varying roles of ancient cofactors

Despite their relative simplicity, iron-sulfur clusters have been omnipresent as cofactors in myriad cellular processes such as oxidative phosphorylation and other respiratory pathways. Recent research advances confirm the presence of different clusters in enzymes involved in nucleic acid metabolism. Iron-sulfur clusters can therefore be considered hallmarks of cellular metabolism. Helicases, nucleases, glycosylases, DNA polymerases and transcription factors, among others, incorporate various types of clusters that serve differing roles. In this chapter, we review our current understanding of the identity and functions of iron-sulfur clusters in DNA and RNA metabolizing enzymes, highlighting their importance as regulators of cellular function.

Integrated block copolymer prodrug nanoparticles for combination of tumor oxidative stress amplification and ROS-responsive drug release

In tumor tissues, reactive oxygen species (ROS) level is significantly higher than that in normal tissues, which has been frequently explored as the specific stimulus to trigger drug release. However, the low intrinsic ROS concentration and heterogeneous distribution in tumor tissues hinder the applications as the stimulus for drug delivery. Herein, we developed integrated nanoparticles to remold tumor microenvironment via specific amplification of the tumor oxidative stress and simultaneously realize ROS-responsive drug release. The amphiphilic block copolymer prodrugs composed of poly(ethylene glycol) and polymerized methacrylate monomer containing thioketal-linked camptothecin (CPT) were synthesized and self-assembled to form core-shell micelles for encapsulation of β-lapachone (Lapa@NPs). After tumor accumulation and internalization into tumor cells post systemic administration of Lapa@NPs, Lapa can selectively induce remarkable ROS level increase via the catalysis of NAD(P)H: quinone oxidoreductase-1 (NQO1) enzyme overexpressed in cancer cells. Subsequently, enhanced ROS concentration would trigger the cleavage of thioketal linkers to release drug. The released CPT together with high ROS level achieved a synergistic therapy to suppress tumor growth. Moreover, Lapa@NPs exhibited superior biosafety due to the tumor-specific activation of the cascade reaction. Accordingly, Lapa@NPs represent a novel polymer prodrug design and drug release strategy via tumor-specific oxidative stress amplification and subsequent ROS-responsive drug release.

A mitochondria-targeting photothermogenic nanozyme for MRI-guided mild photothermal therapy

Iridium complexes were used as a mitochondria-targeting agent to modify the surface of a photothermogenic nanozyme Fe3O4 nanoparticles (Ir@Fe3O4 NPs). Upon NIR irradiation, Ir@Fe3O4 NPs increase the localized temperature to 42 °C which accelerates the catalysis of ˙OH production from H2O2 resulting in excellent mild photothermal therapy.

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.

An Adenosine Triphosphate-Responsive Autocatalytic Fenton Nanoparticle for Tumor Ablation with Self-Supplied H2O2 and Acceleration of Fe(III)/Fe(II) Conversion

Chemodynamic therapy (CDT) can efficiently destroy tumor cells via Fenton reaction in the presence of H₂O₂ and a robust catalyst. However, it has faced severe challenges including the limited amounts of H₂O₂ and inefficiency of catalysts. Here, an adenosine triphosphate (ATP)-responsive autocatalytic Fenton nanosystem (GOx@ZIF@MPN), incorporated with glucose oxidase (GOx) in zeolitic imidazolate framework (ZIF) and then coated with metal polyphenol network (MPN), was designed and synthesized for tumor ablation with self-supplied H₂O₂ and TA-mediated acceleration of Fe(III)/Fe(II) conversion. In the ATP-overexpressed tumor cells, the outer shell MPN of GOx@ZIF@MPN was degraded into Fe(III) and tannic acid (TA) and the internal GOx was exposed. Then, GOx reacted with the endogenous glucose to produce plenty of H₂O₂, and TA reduced Fe(III) to Fe(II), which is a much more vigorous catalyst for the Fenton reaction. Subsequently, self-produced H₂O₂ was catalyzed by Fe(II) to generate highly toxic hydroxyl radical (•OH) and Fe(III). The produced Fe(III) with low catalytic activity was quickly reduced to reactive Fe(II) mediated by TA, forming an accelerated Fe(III)/Fe(II) conversion to guarantee efficient Fenton reaction-mediated CDT. This autocatalytic Fenton nanosystem might provide a good paradigm for effective tumor treatment.

Magnetic Targeting, Tumor Microenvironment-Responsive Intelligent Nanocatalysts for Enhanced Tumor Ablation

Therapeutic nanosystems which can be triggered by the distinctive tumor microenvironment possess great selectivity and safety to treat cancers via in situ transformation of nontoxic prodrugs into toxic therapeutic agents. Here, we constructed intelligent, magnetic targeting, and tumor microenvironment-responsive nanocatalysts that can acquire oxidation therapy of cancer via specific reaction at tumor site. The magnetic nanoparticle core of iron carbide-glucose oxidase (Fe₅C₂-GOD) achieved by physical absorption has a high enzyme payload, and the manganese dioxide (MnO₂) nanoshell as an intelligent "gatekeeper" shields GOD from premature leaking until reaching tumor tissue. Fe₅C₂-GOD@MnO₂ nanocatalysts maintained inactive in normal cells upon systemic administration. On the contrary, after endocytosis by tumor cells, tumor acidic microenvironment induced decomposition of MnO₂ nanoshell into Mn²⁺ and O₂, meanwhile releasing GOD. Mn²⁺ could serve as a magnetic resonance imaging (MRI) contrast agent for real-time monitoring treatment process. Then the generated O₂ and released GOD in nanocatalysts could effectively exhaust glucose in tumor cells, simultaneously generating plenty of H₂O₂ which may accelerate the subsequent Fenton reaction catalyzed by the Fe₅C₂ magnetic core in mildly acidic tumor microenvironments. Finally, we demonstrated the tumor site-specific production of highly toxic hydroxyl radicals for enhanced anticancer therapeutic efficacy while minimizing systemic toxicity in mice.

A tumor treatment strategy based on biodegradable BSA@ZIF-8 for simultaneously ablating tumors and inhibiting infection

Studies have shown a clear correlation between cancer incidence and infection, and cancer treatment can also trigger infection so as to lead to an inflammatory response. In this case, we have designed a new tumor treatment strategy based on biodegradable BSA@ZIF-8 for simultaneously ablating tumors and inhibiting infection. This biodegradable ZIF contains abundant porous structures, showing increased absorption of ions and inelastic collisions. A large amount of frictional heat produced by the collisions results in increased tumor cell death under microwave irradiation. This can effectively inhibit tumor growth in mice by microwave ablation with a good anti-tumor effect (95.4%). Intriguingly, the Zn²⁺ released from the degradation of BSA@ZIF-8 causes damage to bacterial cell walls, and destruction of the metabolism and structure of the membrane, leading to bacterial cell death, and ultimately achieving good antibacterial properties. Moreover, BSA@ZIF-8 is biodegradable without long-term toxicity in vivo. The in vivo experimental results show that BSA@ZIF-8 can protect 80% of the mice from lethal challenge with tumors and the accompanying infection. Overall, we present a novel strategy using biodegradable ZIFs for microwave ablation therapy with simultaneous antibacterial and anti-infection effects for the first time, which has achieved good tumor treatment outcomes.

Non-peptidic guanidinium-functionalized silica nanoparticles as selective mitochondria-targeting drug nanocarriers

We report on the design and fabrication of a Fe3O4 core-mesoporous silica nanoparticle shell (Fe3O4@MSNs)-based mitochondria-targeting drug nanocarrier. A guanidinium derivative (GA) was conjugated onto the Fe3O4@MSNs as the mitochondria-targeting ligand. The fabrication of the Fe3O4@MSNs and their functionalization with GA were carried out by the sol-gel polymerization of alkoxysilane groups. Doxorubicin (DOX), an anti-cancer drug, was loaded into the pores of a GA-attached Fe3O4@MSNs due to both its anti-cancer properties and to allow for the fluorescent visualization of the nanocarriers. The selective and efficient mitochondria-targeting ability of a DOX-loaded GA-Fe3O4@MSNs (DOX/GA-Fe3O4@MSNs) was demonstrated by a co-localization study, transmission electron microscopy, and a fluorometric analysis on isolated mitochondria. It was found that the DOX/GA-Fe3O4@MSNs selectively accumulated into mitochondria within only five minutes; to the best of our knowledge, this is the shortest accumulation time reported for mitochondria targeting systems. Moreover, 2.6 times higher amount of DOX was accumulated in mitochondria by DOX/GA-Fe3O4@MSNs than by DOX/TPP-Fe3O4@MSNs. A cell viability assay indicated that the DOX/GA-Fe3O4@MSNs have high cytotoxicity to cancer cells, whereas the GA-Fe3O4@MSNs without DOX are non-cytotoxic; this indicates that the DOX/GA-Fe3O4@MSNs have great potential for use as biocompatible and effective mitochondria-targeting nanocarriers for cancer therapy.

All-in-One Theranostic Nanoagent with Enhanced Reactive Oxygen Species Generation and Modulating Tumor Microenvironment Ability for Effective Tumor Eradication

Despite regulation of the reactive oxygen species (ROS) level is an intelligent strategy for cancer therapy, the therapeutic effects of ROS-mediated therapy (including photodynamic therapy (PDT) and chemodynamic therapy (CDT)) are limited by oxygen reliance, inherent flaws of traditional photosensitizers, and strict reaction conditions of effective Fenton reaction. Herein, we reported biocompatible copper ferrite nanospheres (CFNs) with enhanced ROS production under irradiation with a 650 nm laser through direct electron transfer and photoenhanced Fenton reaction and high photothermal conversion efficiency upon exposure to an 808 nm laser, exhibiting a considerable improved synergistic treatment effect. Importantly, by exploiting the properties of O₂ generation and glutathione (GSH) depletion of CFNs, CFNs relieve the hypoxia and antioxidant capability of the tumor, achieving photoenhanced CDT and improved PDT. The high relaxivity of 468.06 mM^-1 s^-1 enables CFNs to act as an outstanding contrast agent for MRI in vitro and in vivo. These findings certify the potential of such "all in one" nanotheranostic agent integrated PDT, photoenhanced CDT, photothermal therapy (PTT), and MRI imaging capabilities along with modulating the tumor microenvironment function in theranostics of cancer.

Tumor Microenvironment-Enabled Nanotherapy

Cancer is now one of the world's leading threats to human health. With the development of oncology in both biology and biomedicine, it has been demonstrated that abnormal physiochemical conditions and dysregulated biosynthetic intermediates in tumor microenvironment (TME) play a pivotal role in enabling tumor cells to defend or evade the damage by traditional clinical tumor therapeutics including surgery, chemotherapy, radiotherapy, etc. The fast advances of TME-enabled theranostic nanomedicine have offered promising perspectives, strategies, and approaches for combating cancer based on the novel concept of TME-enabled nanotherapy. In this comprehensive review, the origins of TME (e.g., enhanced permeability and retention effect, overexpressed biosynthetic intermediates, mild acidic nature, redox potentials, hypoxia) are initially introduced and discussed, followed by detailed discussion and overview on the state-of-the-art progresses in TME-enabled antitumor nanotherapies (e.g., chemo/chemodynamic therapy, photodynamic therapy, radiotherapy). Finally, the obstacles and challenges of future development on TME-enabled nanotherapies for further clinical translation are outlooked.

Artemisinin-Loaded Mesoporous Nanoplatform for pH-Responsive Radical Generation Synergistic Tumor Theranostics

The development of novel and effective cancer treatments will greatly contribute to prolonging and improving patient lives. In this study, a multifunctional nanoplatform was designed and developed based on mesoporous NiO (mNiO) nanoparticles and terbium complexes as an artemisinin (ART) vehicle, a T₂-weighted contrast agent, and a luminescence imaging probe. mNiO is a novel pH-responsive material that can degrade and release nickel ions (Ni²⁺) in an acidic tumor microenvironment. The endoperoxide bridge bond in the structure of ART tends to react with Ni²⁺ to produce radicals that can kill tumor cells. On the basis of its excellent near-infrared absorbance, mNiO can also be considered as a novel photothermal conversion agent for cancer photothermal therapy (PTT). Compared with free ART or PTT only, this novel agent showed remarkably enhanced antitumor activity in cultured cells and in tumor mice models, owing to the hypoxic tumor microenvironment impelling synergistic therapeutic action. These results provide a novel way of using a promising natural drug-based nanoplatform for synergistic therapy of tumors.

Localized Fe(II)-Induced Cytotoxic Reactive Oxygen Species Generating Nanosystem for Enhanced Anticancer Therapy

The anticancer therapy on the basis of reactive oxygen species (ROS)-mediated cellular apoptosis has achieved great progress. However, this kind of theraputic strategy still faces some challenges such as light, photosensitizer and oxygen (O₂) dependence. In this article, a ROS-mediated anticancer therapy independent of light, photosensitizer and oxygen was established based on a Fe²⁺-induced ROS-generating nanosystem. First, artemisinin (ART) was loaded in porous magnetic supraparticles (MSP) by a nanodeposition method. Then, the poly(aspartic acid)-based polymer, which consisted of dopamine, indocyanine green, and polyethylene glycol side chain, was coated onto the surface of ART-loaded MSP. When the nanoparticles entered into cancer cells, a reaction of Fe²⁺-mediated cleavage of the endoperoxide bridge contained in ART occurred and subsequent a large amount of ROS was generated. Moreover, a NIR light was used to effectively increase the local temperature of tumor in virtue of the superior photothermal effects of MSP, which enabled us to accelerate the ROS generation and achieved an enhanced ROS yield. The newly developed nanodrug system displayed a high level of intracellular ROS generation, leading to the desired killing efficacy against malignant cells and solid tumor. This smart nanosystem holds great potential to overcome the existing barrier in PDT and opens a promising avenue for anticancer therapy.

Cancer cell nucleus-targeting nanocomposites for advanced tumor therapeutics

Recent advances in the chemical design and synthesis of nuclear-targeted nanotherapeutics for combating tumors are summarized and highlighted.

Nanoparticle-triggered in situ catalytic chemical reactions for tumour-specific therapy

This tutorial review highlights the progress and future development of nanoparticle-triggered in situ catalytic chemical reactions for tumour-specific therapy.

Visualization of mitochondrial DNA in living cells with super-resolution microscopy using thiophene-based terpyridine Zn(ii) complexes

The thiophene-based terpyridine Zn(ii) complex LC targeted mitochondria by intercalative binding with mtDNA. STED super-resolution micrographs visualized mitochondrial cristae/inner matrix mtDNA.