Energy-Free, Singlet Oxygen-Based Chemodynamic Therapy for Selective Tumor Treatment without Dark Toxicity

A cancer-targeted glutathione-gated probe for self-sufficient ST/CDT combination therapy and FRET-based miRNA imaging

A cancer-targeted glutathione (GSH)-gated theranostic probe (CGT probe) for intracellular miRNA imaging and combined treatment of self-sufficient starvation therapy (ST) and chemodynamic therapy (CDT) was developed. The CGT probe is constructed using MnO2 nanosheet (MS) as carrier material to adsorb the elaborately designed functional DNAs. It can be internalized by cancer cells via specific recognition between the AS1411 aptamer and nucleolin. After CGT probe entering the cancer cells, the overexpressed GSH, as gate-control, can degrade MS to Mn2+ which can be used for CDT by Fenton-like reaction. Simultaneously, Mn2+-mediated CDT can further cascade with the enzyme-like activities (catalase-like activity and glucose oxidase-like activity) of CGT probe, achieving self-sufficient ST/CDT synergistic therapy. Meanwhile, the anchored DNAs are released, achieving in situ signal amplification via disubstituted-catalytic hairpin assembly (DCHA) and FRET (fluorescence resonance energy transfer) imaging of miR-21. The in vitro and in vivo experiments demonstrated that accurate and sensitive miRNA detection can be achieved using the CGT probe. Overall, the ingenious CGT probe opens a new avenue for the development of early clinical diagnosis and cancer therapy.

Nanomaterials-Induced Redox Imbalance: Challenged and Opportunities for Nanomaterials in Cancer Therapy

Cancer cells typically display redox imbalance compared with normal cells due to increased metabolic rate, accumulated mitochondrial dysfunction, elevated cell signaling, and accelerated peroxisomal activities. This redox imbalance may regulate gene expression, alter protein stability, and modulate existing cellular programs, resulting in inefficient treatment modalities. Therapeutic strategies targeting intra- or extracellular redox states of cancer cells at varying state of progression may trigger programmed cell death if exceeded a certain threshold, enabling therapeutic selectivity and overcoming cancer resistance to radiotherapy and chemotherapy. Nanotechnology provides new opportunities for modulating redox state in cancer cells due to their excellent designability and high reactivity. Various nanomaterials are widely researched to enhance highly reactive substances (free radicals) production, disrupt the endogenous antioxidant defense systems, or both. Here, the physiological features of redox imbalance in cancer cells are described and the challenges in modulating redox state in cancer cells are illustrated. Then, nanomaterials that regulate redox imbalance are classified and elaborated upon based on their ability to target redox regulations. Finally, the future perspectives in this field are proposed. It is hoped this review provides guidance for the design of nanomaterials-based approaches involving modulating intra- or extracellular redox states for cancer therapy, especially for cancers resistant to radiotherapy or chemotherapy, etc.

Boosting the synergism between cancer ferroptosis and immunotherapy via targeted stimuli-responsive liposomes

Both ferroptotic therapy and immunotherapy have been widely employed in cancer treatment. However, ferroptotic cell death fails to induce dendritic cells maturation, which limits the therapeutic outcome of ferroptotic cancer therapy. To address this, the current work reports a tailored liposome to establish a positive loop between ferroptotic therapy and immunotherapy. As the key component of liposome, a unique phospholipid is designed to bear two arachidonic acid tails. The liposome is further surface-engineered with fucose ligand and physically encapsulates immunostimulatory CpG oligodeoxynucleotides (ODNs). The tailored liposome shows enhanced cellular uptake in a model 4T1 cell line. Meanwhile, the high level of reactive oxygen species in cancer cells can induce ferroptosis-specific peroxidation of DAPC and trigger the release CpG ODNs. The CpG ODNs further enable the maturation of dendritic cells and enhance the effector function of CD8+ T cells. IFN-γ released from CD8+ T cells promotes cancer cell ferroptosis via inhibiting SLC7A11 and suppressing the biosynthesis of glutathione. The tailored liposome can also act in synergism with PD-L1 antibody, resulting in enhanced anti-cancer efficacy in a 4T1 tumor-bearing mice model. This work provides a promising strategy for cancer treatment through orchestrating ferroptotic therapy and immunotherapy.

Recent advances and prospects of metal-organic frameworks in cancer therapies

Metal-organic frameworks (MOFs) have been broadly applied in biomedical and other fields. MOFs have high porosity, a large comparative area, and good biostability and have attracted significant attention, especially in cancer therapies. This paper presents the latest applications of MOFs in chemodynamic therapy (CDT), sonodynamic therapy (SDT), photodynamic therapy (PDT), photothermal therapy (PTT), immunotherapy (IT), and combination therapy for breast cancer. A combination therapy is the combination of two different treatment modalities, such as CDT and PDT combination therapy, and is considered more effective than separate therapies. Herein, we have also discussed the advantages and disadvantages of combination therapy in the treatment of breast cancer. This paper aims to illustrate the potential of MOFs in new cancer therapeutic approaches, discuss their potential advantages, and provide some reflections on the latest research results.

A laser free self-luminous nanosystem for photodynamic therapy of cervical cancer cells

Photodynamic therapy is a tumor treatment strategy. However, most of the photodynamic therapies rely on laser irradiation triggering, which limits their application in deep tissues. This study designed a self-luminescent nano system, hybrid protein oxygen nanocarrier coated graphene quantum dots (GQDs@HPOC) and mesoporous silica nanoparticles coated Luminol (L@MSNs), which self-assembled into GQDs@HPOC/L@MSNs without laser irradiation. The system utilized the weak acidic environment of tumors to trigger the release of Luminol and the chemiluminescence was catalyzed by HPOC. Next CRET occurred between Luminol and GQDs, producing 1O2, which could generate photodynamic damage to cervical cancer cells without the need for external laser irradiation. The system achieved the peak uptake in primary cervical cancer cells in 3 h, and had good biosafety before self-assembly. The system could significantly kill cells at a concentration of 16 μg/ml. The system will be further applied in in vivo experiments to investigate its therapeutic ability, providing a new strategy for the clinical treatment of cervical cancer.

Biocompatible Polymer-Modified Nanoplatform for Ferroptosis-Enhanced Combination Cancer Therapy

Ferroptosis is a novel type of iron-dependent non-apoptotic pathway that regulates cell death and shows unique mechanisms including causing lipid peroxide accumulation, sensitizing drug-resistant cancers, priming immunity by immunogenic cell death, and cooperatively acting with other anticancer modalities for eradicating aggressive malignancies and tumor relapse. Recently, there has been a great deal of effort to design and develop anticancer biocompatible polymeric nanoplatforms including polypeptide and PEGylated ones to achieve effective ferroptosis therapy (FT) and synergistic combination therapies including chemotherapy (CT), photodynamic therapy (PDT), sonodynamic therapy (SDT), photothermal therapy (PTT), gas therapy (GT) including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2 S), and immunotherapy (IT). To be noted, the combo therapies such as FT-CT, FT-PTT, FT-GT, and FT-IT are attracting much efforts to fight against intractable and metastatic tumors as they can generate synergistic antitumor effects and immunogenic cell death (ICD) effects or modulate immunosuppressive tumor microenvironments to initiate strong antitumor immunity and memory effects. The polymeric Fenton nano-agents with good biosafety and high anticancer efficacy will provide a guarantee for their applications. In this review, various biocompatible polymer-modified nanoplatforms designed for FT and combo treatments are summarized for anticancer therapies and discussed for potential clinical transitions.

DNAzyme-Mediated Cascade Nanoreactor for Cuproptosis-Promoted Pancreatic Cancer Synergistic Therapy

Cuproptosis, a kind of newly recognized cell death modality, shows enormous prospect in cancer treatment. The inducer of cuproptosis has more advantages in tumor therapy, especially that can trigger cuproptosis and chemodynamic therapy (CDT) simultaneously. However, cuproptosis is restricted to the deficiency of intracellular copper ions and the nonspecific delivery of copper-based ionophores. Therefore, high level delivery, responsive release, and utilizing synergistic-function of inducer become the key on cuproptosis-based oncotherapy. In this work, a cascade nanosystem is constructed for enhanced cuproptosis and CDT. In the weak acidic environment of tumor cells, DNA, zinc ions, and Cu+ can release from the nanosystem. Since Cu+ having superior performance in mediating both Fenton-like reaction and cuproptosis, the released Cu+ induces cuproptosis and CDT efficiently, accompanied by Cu2+ generation. Then Cu2+ can be converted into Cu+ partially by glutathione (GSH) to from a Cu+ supply loop and ensure the synergistic action. Meanwhile, the consumption of GSH also contributes to cuproptosis and CDT in return. Finally, DNA and Zn2+ form DNAzyme to shear catalase-related RNA, resulting in the accumulation of hydrogen peroxide and further enhancing combination therapy. These results provide a promising nanotherapeutic platform and may inspire the design for potential cancer treatment based on cuproptosis.

Stimuli-responsive cancer nanomedicines inhibit glycolysis and impair redox homeostasis

The solid tumors are characterized with oxidative stress and metabolic reprogramming, which has been independently used for targeted tumor monotherapy. However, the potential of targeting metabolism-redox circuit in tumor therapy has long been neglected. Herein, we report a hybrid nanocarrier for concurrent targeting of glycolysis and redox balance in the current work. The nanocarriers are made of pH- and ATP-responsive zeolitic imidazolate framework (ZIF-8) as the porous core that was further coated with poloxamer 407 as the steric stabilizer. Two active cargos, glucose oxidase (GOx) and 3-bromopyruvate (3-BrPA) were co-loaded in the core of nanocarrier. GOx is well-known for its ability of producing hydrogen peroxide at the expense of glucose and oxygen. 3-BrPA can reduce oxygen and glucose consumption through glycolysis, which sensitized cancer cells to GOx-induced apoptosis. At the cellular level, the hybrid nanocarrier significantly impaired the redox balance in the liver hepatocellular carcinoma cell line (HepG2), as evidenced by the depletion of glutathione and boost of reactive oxygen species. The potency of hybrid nanocarrier in terms of suppressing HepG2 cell energy metabolism was proven by the exhaustion of ATP. As a consequence, cell viability was greatly reduced. The in vivo efficacy of hybrid nanocarriers was demonstrated in HepG2 tumor-bearing mice. The current work presents an approach of targeting metabolism-redox circuit for tumor treatment, which may enrich the available anti-tumor strategies. STATEMENT OF SIGNIFICANCE: Metabolic alterations and elevated reactive oxygen species (ROS) are two characteristics of cancer. The metabolic patterns of cancer cells are elaborately reprogrammed to enable the rapid propagation of cancer cells. However, the potential of targeting the metabolism-redox circuit in anti-tumor therapy has long been neglected. As a proof-of-concept, we report an engineered stimuli-responsive nanomedicine that can eradicate cancer cells via cooperative glycolysis inhibition and redox impairment. The current work presents an approach of targeting the metabolism-redox circuit for tumor treatment, which may enrich the available anti-tumor strategies.

Nano-baicalein facilitates chemotherapy in breast cancer by targeting tumor microenvironment

Cancer-associated fibroblasts constitute a significant component in the tumor microenvironment, playing a pivotal role in tumor proliferation, invasion, migration, and metastasis. Consequently, therapy combining chemotherapeutic agents with tumor microenvironment (TME) modulators appears to be a promising avenue for cancer treatment. In this paper, a tumor microenvironment-based mPEG-PLGA nanoparticle loaded with baicalein (PMs-Ba) was constructed for the purpose of improving the tumor microenvironment in cases of triple-negative breast cancer. The results demonstrate that, on the one hand, PMs-Ba was able to inhibit the transforming growth factor β(TGF-β) signaling pathway to avoid the activation of cancer-associated fibroblasts (CAFs), thereby influencing the interstitial microenvironment of the tumor. On the other hand, the agent led to an increase in the infiltration of cytotoxic T cells, activating the tumor immune microenvironment. Meanwhile, in the murine breast cancer model, an intravenous injection of PMs-Ba combined with doxorubicin nanoparticles (PMs-ADM) significantly improved the antitumor effectiveness. These results suggest that baicalein encapsulated in nanoparticles may be a promising strategy for modulating the TME and for adjuvant chemotherapy, signifying a potential TME-remodeling nanoformulation that could enhance the antitumor efficacy of nanotherapeutics.

Coenzyme-depleting nanocarriers for enhanced redox cancer therapy under hypoxia

Cancer cells show unique redox homeostasis. Glutathione (GSH) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) play essential roles as coenzymes of multiple key antioxidant enzymes. Coenzyme depletion offers a unique opportunity for cancer treatment by inducing oxidative stress. Here, we report an innovative hybrid nanocarrier for cancer redox therapy via selective depletion of GSH and NADPH. The nanocarrier core is a sorafenib-loaded porous zeolitic imidazole framework (ZIF-65), and the shell is epigallocatechin gallate (EGCG)-Fe³⁺ complex (EF). The nitroimidazole ligand in ZIF-65 could selectively deplete NADPH under hypoxia. Sorafenib diminished GSH by inhibiting cystine import and GSH biosynthesis. EGCG can reduce Fe³⁺ to Fe²⁺, which aids the generation of hydroxyl radicals via the Fenton reaction. The reversible coordination between nitroimidazole and Zn²⁺, EGCG, and Fe³⁺ enables triggered cargo release in acidic lysosomes. Tailored nanocarriers induced the depletion of both coenzymes (GSH and NADPH) and boosted reactive oxygen species in a 4T1 murine cancer cell line. The altered redox balance eventually resulted in efficient apoptotic cell death. The current work offers a novel means of redox cancer therapy via the selective depletion of key antioxidant enzymes in hypoxic cells.

NIR-II Luminescent and Multi-Responsive Rare Earth Nanocrystals for Improved Chemodynamic Therapy

Chemodynamic therapy (CDT) based on the Fe²⁺-mediated Fenton reaction can amplify intracellular oxidative stress by producing toxic •OH. However, the high-dose need for Fe²⁺ delivery in tumors and its significant cytotoxicity to normal tissues set a challenge. Therefore, a controllable delivery to activate the Fenton reaction and enhance Fe²⁺ tumor accumulation has become an approach to solve this conflict. Herein, we report a rare-earth-nanocrystal (RENC)-based Fe²⁺ delivery system using light-control techniques and DNA nanotechnology to realize programmable Fe²⁺ delivery. Ferrocenes, the source of Fe²⁺, are modified on the surface of RENCs through pH-responsive DNAs, which are further shielded by a PEG layer to elongate blood circulation and "turn off" the cytotoxicity of ferrocene. The up-/down-conversion dual-mode emissions of RENCs endow the delivery system with both capabilities of diagnosis and delivery control. The down-conversion NIR-II fluorescence can locate tumors. Consequently, up-conversion UV light spatiotemporally activates the catalytic activity of Fe²⁺ by shedding off the protective PEG layer. The exposed ferrocene-DNAs not only can "turn on" Fenton catalytic activity but also respond to tumor acidity, driving cross-linking and enhanced Fe²⁺ enrichment in tumors by 4.5-fold. Accordingly, this novel design concept will be inspiring for developing CDT nanomedicines in the future.

WZ35 inhibits gastric cancer cell metastasis by depleting glutathione to promote cellular metabolic remodeling

This study aimed at elucidating the crosstalk between redox reaction and metabolic remodeling through uncovering the mechanism underlying WZ35-mediated reactive oxygen species (ROS) production and regulation of amino acid metabolism to inhibit gastric cancer (GC) cell metastasis. The activity and biosafety of curcumin analog, WZ35, were verified in vitro and in vivo. The potential molecular mechanism underlying WZ35-mediated enhanced radiotherapeutic sensitivity by reduced Glutathione (GSH) depletion was elucidated by RNA sequencing, single-cell sequencing (scRNA-seq), metabolic mass spectrometry, and other molecular experiments. Compared to curcumin, WZ35 proved more potent anti-proliferative and anti-metastasis properties. Importantly, we demonstrated that WZ35 could consume GSH in multiple ways, including by reduction of raw materials and consumption reserves, inhibition of reformation, and enhanced decomposition. Mechanistically, we identify that WZ35 maintains the GSH depletion phenotype through the ROS-YAP-AXL-ALKBH5-GLS2 loop, further backing the relevance of metabolic remodeling in the tumor microenvironment with tumor metastasis and the role of m⁶A in tumor metastasis. Collectively, our study identified WZ35 as a novel GSH depletion agent and a previously undiscovered GSH depletion loop mechanism in GC cell metastasis.

Reactive oxygen species-upregulating nanomedicines towards enhanced cancer therapy

Reactive oxygen species (ROS) play a crucial role in physiological and pathological processes, emerging as a therapeutic target in cancer. Owing to the high concentration of ROS in solid tumor tissues, ROS-based treatments, such as photodynamic therapy and chemodynamic therapy, and ROS-responsive drug delivery systems have been widely explored to powerfully and specifically suppress tumors. However, their anticancer efficacy is still hampered by the heterogeneous ROS levels, and thus comprehensively upregulating the ROS levels in tumor tissues can ensure an enhanced therapeutic effect, which can further sensitize and/or synergize with other therapies to inhibit tumor growth and metastasis. Herein, we review the recently emerging drug delivery strategies and technologies for increasing the H₂O₂, ˙OH, ¹O₂, and ˙O₂^- concentrations in cancer cells, including the efficient delivery of natural enzymes, nanozymes, small molecular biological molecules, and nanoscale Fenton-reagents and semiconductors and neutralization of intracellular antioxidant substances and localized input of mechanical and electromagnetic waves (such as ultrasound, near infrared light, microwaves, and X-rays). The applications of these ROS-upregulating nanosystems in enhancing and synergizing cancer therapies including chemotherapy, chemodynamic therapy, phototherapy, and immunotherapy are surveyed. In addition, we discuss the challenges of ROS-upregulating systems and the prospects for future studies.

Silencing the Catalase Gene with SiRNA for Enhanced Chemodynamic Therapy

Chemodynamic therapy (CDT) has been emerging as a promising strategy for cancer treatment. But the CDT efficiency is restricted by the insufficient intracellular hydrogen peroxide (H2O2) level. Herein, we present a method for H2O2 accumulation in tumor cells by silencing the catalase (CAT) gene with siRNA to achieve enhanced CDT. Cu-siRNA nanocomposites are fabricated by self-assembly of Cu2+ and CAT siRNA and then modified with hyaluronic acid (HA) for active tumor targeting. After tumor cell uptake, the released Cu2+ is reduced by highly expressed glutathione (GSH) to Cu+, which then catalyzes H2O2 to produce toxic hydroxyl radicals (•OH) to kill tumor cells. CAT siRNA can efficiently silence the CAT mRNA to inhibit the consumption of H2O2, resulting in H2O2 accumulation. The Cu2+-mediated GSH elimination and siRNA-induced endogenous H2O2 enrichment both potentiate CDT. Cu-siRNA@HA exhibits good biocompatibility and therapeutic efficiency. This work thus paves a new way to supply H2O2 in CDT and may hold potential for clinical application.

A Cascade Nanoreactor of Metal-Protein-Polyphenol Capsule for Oxygen-Mediated Synergistic Tumor Starvation and Chemodynamic Therapy

Starvation therapy kills tumor cells via consuming glucose to cut off their energy supply. However, since glucose oxidase (GOx)-mediated glycolysis is oxygen-dependent, the cascade reaction based on GOx faces the challenge of a hypoxic tumor microenvironment. By decomposition of glycolysis production of H₂ O₂ into O₂ , starvation therapy can be enhanced, but chemodynamic therapy is limited. Here, a close-loop strategy for on demand H₂ O₂ and O₂ delivery, release, and recycling is proposed. The nanoreactor (metal-protein-polyphenol capsule) is designed by incorporating two native proteins, GOx and hemoglobin (Hb), in polyphenol networks with zeolitic imidazolate framework as sacrificial templates. Glycolysis occurs in the presence of GOx with O₂ consumption and the produced H₂ O₂ reacts with Hb to produce highly cytotoxic hydroxyl radicals (•OH) and methemoglobin (MHb) (Fenton reaction). Benefiting from the different oxygen carrying capacities of Hb and MHb, oxygen on Hb is rapidly released to supplement its consumption during glycolysis. Glycolysis and Fenton reactions are mutually reinforced by oxygen supply, consuming more glucose and producing more hydroxyl radicals and ultimately enhancing both starvation therapy and chemodynamic therapy. This cascade nanoreactor exhibits high efficiency for tumor suppression and provides an effective strategy for oxygen-mediated synergistic starvation therapy and chemodynamic therapy.

Reactive species conversion into 1O2 promotes substantial inhibition of chlorinated byproduct formation during electrooxidation of phenols in Cl--laden wastewater

The generation of chlorinated byproducts during the electrochemical oxidation (EO) of Cl^--laden wastewater is a significant concern. We aim to propose a concept of converting reactive species (e.g., reactive chlorines and HO^• resulting from electrolysis) into ¹O₂ via the addition of H₂O₂, which substantially alleviates chlorinated organic formation. When phenol was used as a model organic compound, the results showed that the H₂O₂-involving EO system outperformed the H₂O₂-absent system in terms of higher rate constants (5.95 × 10^-2 min^-1vs. 2.97 × 10^-2 min^-1) and a much lower accumulation of total organic chlorinated products (1.42 mg L^-1vs. 8.18 mg L^-1) during a 60 min operation. The rate constants of disappearance of a variety of phenolic compounds were positively correlated with the Hammett constants (σ), suggesting that the reactive species preferred oxidizing phenols with electron-rich groups. After the identification of ¹O₂ that was abundant in the bulk solution with the use of electron paramagnetic resonance and computational kinetic simulation, the routes of ¹O₂ generation were revealed. Despite the consensus as to the contribution of reaction between H₂O₂ and ClO^- to ¹O₂ formation, we conclude that the predominant pathway is through H₂O₂ reaction with electrogenerated HO^• or chlorine radicals (Cl^• and Cl₂^•-) to produce O₂^•-, followed by self-combination. Density functional theory calculations theoretically showed the difficulty in forming chlorinated byproducts for the ¹O₂-initiated phenol oxidation in the presence of Cl^-, which, by contrast, easily occurred for the Cl^•-or HO^•-initiated phenol reaction. The experiments run with real coking wastewater containing high-concentration phenols further demonstrated the superiority of the H₂O₂-involving EO system. The findings imply that this unique method for treating Cl^--laden organic wastewater is expected to be widely adopted for generalizing EO technology for environmental applications.

Recent advances of the core-shell MOFs in tumour therapy

Coordination chemistry has always been vital to explore the material prominence of metal-organic systems. The metal-organic chemistry plays a fundamental role in decisive structural features, which are accountable for tuning the properties of materials. Tumour therapy has become an important research field of medical treatment in the world. Metal-organic frameworks (MOFs) have attracted extensive interest in medical science research due to their large effective surface area, clear pore network, and critical catalytic performance. Compared with traditional MOF materials, MOF materials with core-shell structures have a higher loading rate and better stability, which can overcome a single function. They have been successfully used in tumour medical research and have excellent prospects for diagnosing and treating various tumours. The current review article thoroughly describes the various synthetic approaches for engineering core-shell MOF materials, the structural types, and the potential functional applications. We also discussed core-shell MOF materials for the various treatment of tumours, such as tumour chemotherapy, tumour phototherapy and tumour microenvironment anti-hypoxia therapy. In this paper, the synthesized procedures of core-shell MOFs and their applications for tumour treatment have been discussed, and their future research has prospected. The current improved strategies, challenges, and prospects are also presented because of the metal-organic chemistry governing the structural modification of core-shell MOFs for tumour therapy applications. Therefore, the present review article opens a new door for medicinal chemists to tune the structural features of the core-shell MOF materials to modulate tumour therapy with simple, low-cost materials for better human lives.

Enhancing Tumor Therapy of Fe(III)-Shikonin Supramolecular Nanomedicine via Triple Ferroptosis Amplification

Ferroptosis has been considered as a promising pathway to overcome apoptosis-induced tumor chemoresistance. However, the antitumor efficacy of ferroptosis-inducing agents is still limited because of the complexity and diversity of tumor microenvironments. Herein, we demonstrate a triple ferroptosis amplification strategy for tumor therapy by associating iron-based nanocarriers, ferroptosis molecular drugs, and H₂O₂-producing enzymes. Fe(III)-Shikonin (FeShik) metal-polyphenol-coordinated networks are employed to load a ferroptosis inducer of sorafenib (SRF) inside and glucose oxidase (GOx) outside, thus producing SRF@FeShik-GOx supramolecular nanomedicines (SNs). After delivering into glutathione (GSH)-overexpressed tumor cells, FeShik will disassemble and release Fe²⁺ to induce cell death via ferroptosis. At the same time, GOx executes its catalytic activity to produce an acid environment and plenty of H₂O₂ for stimulating ^•OH generation via the Fenton reaction. Moreover, SRF will suppress the biosynthesis of GSH by inhibiting system Xc^-, further deactivating the enzymatic activity of glutathione peroxidase 4 (GPX4). Up-regulation of the oxidative stress level and down-regulation of GPX4 expression can dramatically accelerate the accumulation of lethal lipid peroxides, leading to ferroptosis amplification of tumor cells. The current strategy that utilizes ferroptosis-inducing agents as both nanocarriers and cargoes provides a pathway to enhance the efficacy of ferroptosis-based tumor therapy.

Hypoxia-responsive nanocarriers for chemotherapy sensitization via dual-mode inhibition of hypoxia-inducible factor-1 alpha

The overexpression of hypoxia-inducible factor-1 alpha (HIF-1α) in solid tumor compromises the potency of chemotherapy under hypoxia. The high level of HIF-1α arises from the stabilization effect of reduced nicotinamideadeninedinucleotide(phosphate) NAD(P)H: quinone oxidoreductase 1 (NQO1). It was postulated that the inhibition of NQO1 could degrade HIF-1α and sensitize hypoxic cancer cells to antineoplastic agents. In the current work, we report hypoxia-responsive polymer micelles, i.e. methoxyl poly(ethylene glycol)-co-poly(aspartate-nitroimidazole) orchestrate with a NQO1 inhibitor (dicoumarol) to sensitize the ovarian cancer cell line (SKOV3) to a model anticancer agent (sorafenib) at low oxygen conditions. Both cargos were physically encapsulated in the nanoscale micelles. The placebo micelles transiently induced the depletion of reduced nicotinamideadeninedinucleotidephosphate (NADPH) as well as glutathione and thioredoxin under hypoxia, which further inactivated NQO1 because NADPH was the cofactor of NQO1. As a consequence, the expression of HIF-1α was repressed due to the dual action of dicoumarol and polymer. The degradation of HIF-1α significantly increased the vulnerability of SKOV3 cells to sorafenib-induced apoptosis, as indicated by the enhancement of cytotoxicity, and increase of caspase 3 and cytochrome C. The current work opens new avenues of addressing hypoxia-induced drug resistance in chemotherapy.

Remote drug loading into liposomes via click reaction

The development of liposome-based drugs was severely limited due to inefficient loading strategies. Herein, we developed a click reaction-mediated loading procedure by designing an enzyme-sensitive maleimide (MAL) tag for ferrying chemotherapeutics into preformed liposomes containing glutathione (GSH). Based on this strategy, various hydrophobic drugs could be encapsulated into liposomes within 5-30 min with encapsulation efficiency >95% and loading capacity of 10-30% (w/w). The entrapped cargo could be slowly released from the liposomes, followed by rapid enzyme-mediated conversion into active drugs to exert antitumor activity under physiological conditions. The resulting drug-loaded liposomes significantly prolonged the blood circulation of cargos and displayed more potent in vivo antitumor efficacy than free drugs at the equitoxic dose. More importantly, this method is a remote drug loading strategy in nature, which is suitable for industrial production. This is the first demonstration of active loading of MAL-tagged chemotherapeutics in liposomes for improved antitumor efficacies, which has the potential to serve as a universal drug loading strategy for the development of liposomal formulations of chemotherapeutics.

A triphenylphosphine coordinated cinnamaldehyde-derived copper(I) Fenton-like agent with mitochondrial aggregation damage for chemodynamic therapy

Chemodynamic therapy (CDT), which uses agents to induce cell death by decomposing endogenous hydrogen peroxide (H₂O₂) into highly toxic hydroxyl radicals (˙OH), has been recognized as a promising approach to treat cancer. However, improving the efficiency of ˙OH production is considered one of the biggest challenges that limits the therapeutic efficacy of CDT. Herein, to controllably and efficiently induce oxidative damage through the production of ˙OH, we developed a new metal complex CDT agent with atomically precise structural characteristics as a deviation from traditional nanomaterial-CDT agents. The obtained CDT agent, a cinnamaldehyde derived copper(I) complex (denoted Cin-OD-Cu), was found to be continuously enriched in the mitochondria of A2780 ovarian carcinoma cells, which was accompanied by the generation of large amounts of ˙OH via Cu(I)-mediated Fenton-like reactions of H₂O₂, thereby stimulating oxidative stress in the mitochondria and eventually leading to cell death. Moreover, in vivo experiments showed that Cin-OD-Cu was capable of effectively inhibiting tumor growth with excellent biocompatibility. We believe this research enriches the limited selection of atomically precise metal complex CDT agents in particular for reactive oxygen species-mediated treatments aimed at inducing mitochondria oxidative damage; we anticipate that it will provide new insights into the development of novel, atomically precise agents for CDT.

Size Changeable Nanomedicines Assembled by Noncovalent Interactions of Responsive Small Molecules for Enhancing Tumor Therapy

The size of nanocarriers strongly affects their performance in biological systems, especially the capacity to overcome various barriers before delivering the payloads to destinations. However, the optimum size varies at different delivery stages in cancer therapy due to the complicated tumor microenvironment. Relatively large particles are favored for long-term circulation in vivo, while smaller particles contribute to deep penetration into tumor tissues. This dilemma in the size of particles stimulates the development of stimuli-responsive size-shrinking nanocarriers. Herein, we report a facile strategy to construct a tumor-triggered tannic acid (TA) nanoassembly with improved drug delivery efficiency. Cystamine (CA), a small molecule with a disulfide bond, is thus used to mediate TA assembling via cooperative noncovalent interactions, which endows the nanoassembly with intrinsic pH/GSH dual-responsiveness. The obtained TA nanoassemblies were systematically investigated. DOX encapsulated nanoassembly labeled TCFD NP shows high drug loading efficiency, pH/GSH-responsiveness and significant size shrinkage from 122 to 10 nm with simultaneous drug release. The in vitro and in vivo experimental results demonstrate the excellent biocompatibility, sufficient intracellular delivery, enhanced tumor retention/penetration, and superior anticancer efficacy of the small-molecule-mediated nanoassembly. This noncovalent strategy provides a simple method to fabricate a tumor-triggered size-changeable delivery platform to overcome biological barriers.

Ferroptosis-Driven Nanotherapeutics to Reverse Drug Resistance in Tumor Microenvironment

Ferroptosis, characterized by iron-dependent lipid reactive oxygen species (ROS) accumulation, is non-apoptotic programmed cell death highly relevant to tumor development. It was found to manipulate oncogenes and resistant mutations of cancer cells via lipid metabolism pathways converging on phospholipid glutathione peroxidase (GPX4) that squanders lipid peroxides (L-OOH) to block the iron-mediated reactions of peroxides, thus rendering resistant cancer cells vulnerable to ferroptotic cell death. By accumulating ROS and lipid peroxidation (LPO) products to lethal levels in tumor microenvironment (TME), ferroptosis-driven nanotherapeutics show a superior ability of eradicating aggressive malignancies than traditional therapeutic modalities, especially for the drug-resistant tumors with high metastasis tendency. Moreover, Fenton reaction, inhibition of GPX-4, and exogenous regulation of LPO are three major therapeutic strategies to induce ferroptosis in cancer cells, which were generally applied in ferroptosis-driven nanotherapeutics. In this review, we elaborate current trends of ferroptosis-driven nanotherapeutics to reverse drug resistance of tumors in anticancer fields at the intersection of cancer biology, materials science, and chemistry. Finally, their challenges and perspectives toward feasible translational studies are spotlighted, which would ignite the hope of anti-resistant cancer treatment.

Oxidative stress-amplified nanomedicine for intensified ferroptosis-apoptosis combined tumor therapy

Ferroptosis, as an effective sensitizer for apoptosis-based cancer treatments, has been elucidated to rely on high levels of intracellular oxidative stress mediated by the accumulation of reactive oxygen species (ROS). However, ferroptosis-related oxidation effect is largely counteracted by the endogenous reductive glutathione (GSH). Here, we constructed a self-assembled metal-organic nanomedicine p53/Ce6@ZF-T, which was composed of p53 plasmid-complexed chlorin e6 (Ce6)-poly(amidoamine), Fe²⁺-containing mesoporous zeolitic imidazolate framework-8 and naturally derived tannic acid (TA). The highly cytotoxic ROS was continuously produced via Fe²⁺-mediated and TA-assisted enhanced Fenton reaction as well as Ce6-induced photosensitive reaction, and meanwhile, the intratumoral upregulated p53 expression inactivated glutathione peroxidase 4 (GPX4) to suppress lipid peroxidation (LPO) resistance, thus resulting in amplified oxidative stress and intensified ferroptosis-apoptosis therapy. The notable anticancer efficacy of p53/Ce6@ZF-T both in vitro and in vivo substantially evidenced the high feasibility of oxidative stress-amplified therapeutic modality for enhanced ferroptosis-apoptosis combined therapy, which would be a promising approach in the field of cancer treatment in the future.

An Energy-Storing DNA-Based Nanocomplex for Laser-Free Photodynamic Therapy

Photodynamic therapy (PDT) is a therapeutic strategy that is dependent on external light irradiation that faces a major challenge in cancer treatment due to the poor tissue-penetration depths of light irradiation. Herein, a DNA nanocomplex that integrates persistent-luminescence nanoparticles (PLNPs) is developed, which realizes tumor-site glutathione-activated PDT for breast cancer without exogenous laser excitation. The scaffold of the nanocomplex is AS1411-aptamer-encoded ultralong single-stranded DNA chain with two functions: i) providing sufficient intercalation sites for the photosensitizer, and ii) recognizing nucleolin that specifically overexpresses on the surface of cancer cells. The PLNPs in the nanocomplex are energy-charged to act as a self-illuminant and coated with a shell of MnO₂ for blocking energy degradation. In response to the overexpressed glutathione in cancer cells, the MnO₂ shell decomposes to provide Mn²⁺ to catalytically produce O₂ , which is essential to PDT. Meanwhile, PLNPs are released and act as a self-illuminant to activate the photosensitizer to convert O₂ into cytotoxic ¹ O₂ . Significant tumor inhibition effects are demonstrated in breast tumor xenograft models without exogenous laser excitation. It is envisioned that a laser-excitation-free PDT strategy enabled by the PLNP-DNA nanocomplex promotes the development of PDT and provides a new local therapeutic approach.

Triggered azobenzene-based prodrugs and drug delivery systems

Azobenzene-based molecules show unique trans-cis isomerization upon ultraviolet light irradiation, which induce the change of polarity, crystallinity, stability, and binding affinity with pharmacological target. Moreover, azobenzene is the substrate of azoreductase that is often overexpressed in many pathological sites, e.g. hypoxic solid tumor. Therefore, azobenzene can be a multifunctional molecule in material science, pharmaceutical science and biomedicine because of its sensitivity to light, hypoxia and certain enzymes, hence showing potential application in site-specific smart therapy. Herein we focus on the employment of azobenzene and its derivatives for engineering triggered prodrug and drug delivery systems, and provide an overview of photoswitchable azo-based prodrugs, the associated problems regarding ultraviolet light and reversible isomerization, as well as the potential solutions. We also present the advance of azo-bearing delivery vehicles wherein azobenzene act as the linker, capping agent, and building block, and discuss the corresponding mechanisms for controlled cargo release, endocytosis enhancement and sensitization of free radical cancer therapy.

Anti-VEGFR2-labeled enzyme-immobilized metal-organic frameworks for tumor vasculature targeted catalytic therapy

Tumor vasculature-targeting therapy either using angiogenesis inhibitors or vascular disrupting agents offers an important new avenue for cancer therapy. In this work, a tumor-specific catalytic nanomedicine for enhanced tumor ablation accompanied with tumor vasculature disruption and angiogenesis inhibition was developed through a cascade reaction with enzyme glucose oxidase (GOD) modified on Fe-based metal organic framework (Fe-MOF) coupled with anti-VEGFR2.The GOD enzyme could catalyze the intratumoral glucose decomposition to trigger tumor starvation and yet provide abundant hydrogen peroxide as the substrate for Fenton-like reaction catalyzed by Fe-MOF to produce sufficient highly toxic hydroxyl radicals for enhanced chemodynamic therapy and instantly attacked tumor vascular endothelial cells to destroy the existing vasculature, while the anti-VEGFR2 antibody guided the nanohybrids to target blood vessels and block the VEGF-VEGFR2 connection to prevent angiogenesis. Both in vitro and in vivo results demonstrated the smart nanohybrids could cause the tumor cell apoptosis and vasculature disruption, and exhibited enhanced tumor regression in A549 xenograft tumor-bearing mice model. This study suggested that synergistic targeting tumor growth and its vasculature network would be more promising for curing solid tumors. STATEMENT OF SIGNIFICANCE: Cooperative destruction of tumor cells and tumor vasculature offers a potential avenue for cancer therapy. Under this premise, a tumor-specific catalytic nanomedicine for enhanced tumor ablation accompanied with tumor vasculature disruption and new angiogenesis inhibition was developed through a cascade reaction with glucose oxidase modified on the surface of iron-based metal organic framework coupled with VEGFR2 antibody. The resulting data demonstrated that a therapeutic regimen targeting tumor growth as well as its vasculature with both existing vasculature disruption and neovasculature inhibition would be more potential for complete eradication of tumors.

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.

Novel carrier-free, charge-reversal and DNA-affinity nanodrugs for synergistic cascade cancer chemo-chemodynamic therapy

The combination of chemotherapy (CT) and chemodynamic therapy (CDT) is an emerging therapeutic strategy for tumors; however, its therapeutic efficacy is usually impaired by the shortage of high-efficiency intracellular catalysts for CDT and the poor tumor selectivity of CT. To address this concern, novel carrier-free nanodrugs (CMC-DD2) self-assembled from the natural melanin complex (CMC) with a superior CDT performance, and dehydroabietic acid hexamer (DD2) displaying a potent antitumor activity were proposed for the synergistic combination of CT and CDT. CMC-DD2 preferred to enter tumor cells and localize in the nucleus after lysosome escape due to its pH-dependent charge-reversal properties. Nanodrugs internalized by the nucleus directly bound the DNA and altered its conformation. Then, the dissociation of CMC-DD2 was efficiently triggered by intracellular hydrogen peroxide (H₂O₂) with the release of DNA damaging agents, including nitrate anions, hydroxyl radicals (●OH) and DD2. Finally, severe DNA damage induced mitochondrial apoptosis in HepG2 cells. An in vivo assessment further demonstrated the superior tumor selectivity and suppressor capacity and no/low toxicity of the nanodrugs. Overall, novel carrier-free, charge-reversal, nucleus-targeting, biodegradable, and DNA-affinity nanodrugs represent safe and effective platforms for the combination of CT and CDT.

Recent advances in MOF-based nanoplatforms generating reactive species for chemodynamic therapy

Still today, cancer remains a threat to human health. Possible common treatments to cure this disease include chemotherapy (CT), radiotherapy (RT), photothermal therapy (PTT), and surgical resection, which give unreasonable results because of their limited efficiency and also lead to side-effects. Hence, different strategies are now being exploited to not only enhance the efficiency of these traditional therapeutic methods or treat the tumor cells but also curtail the side effects. A latest method with authentic proof of chemodynamic therapy (CDT) utilizing the Fenton reaction is now gaining importance. This approach, which is developed based on the high level of hydrogen peroxide (H2O2) in a tumor microenvironment (TME), can be used to catalyze the Fenton reaction to generate cancer cell-killing reactive oxygen species (ROS). The selection of materials is extremely important and nanomaterials offer the most likely method to facilitate CDT. Among various materials, metal-organic frameworks (MOFs) which have been extensively applied in medical areas are regarded as a promising material and possess potential for the next generation of nanotechnology. This review focuses on summarizing the use of MOFs in CDT and their synergetic therapeutics as well as the challenges, obstacles, and development.

Synthesis, modification and bioapplications of nanoscale copper chalcogenides

Copper chalcogenides have a simple general formula, variable atomic ratios, and complicated crystal structures, which lead to their wealth of optical, electrical, and magnetic properties with great potential for wide applications ranging from energy conversion to the biomedical field. Herein, we summarize the recent advances in (1) the synthesis of size- and morphology tunable nanostructures by different methods; (2) surface modification and functionalization for different purposes; and (3) bioapplications for diagnosis and treatment of tumors by different imaging and therapy methods, as well as antibacterial applications. We also briefly discuss the future directions and challenges of copper chalcogenide nanoparticles in the biomedical field.

Mn-DNA coordination of nanoparticles for efficient chemodynamic therapy

A kind of nanoparticle is developed for highly efficient chemodynamic therapy that only relies on the endogenous H2O2 of cancer cells. For this nanoparticle, high-molecular-weight DNA is used as the biocompatible carrier to load abundant Mn2+ ions. Therefore, the resultant Mn-DNA coordination nanoparticles can efficiently deliver and sensitively release Mn2+ in cancer cells, resulting in high toxicity through the Fenton-like reaction.

Redox-Responsive Self-Assembled Nanoparticles for Cancer Therapy

Chemotherapy, combined with other treatments, is widely applied in the clinical treatment of cancer. However, deficiencies inherited from the traditional route of administration limit its successful application. With the development of nanotechnology, a series of smart nanodelivery systems have been developed to utilize the unique tumor environment (pH changes, different enzymes, and redox potential gradients) and exogenous stimuli (thermal changes, magnetic fields, and light) to improve the curative effect of anticancer drugs. In this review, endogenous and exogenous stimuli are briefly introduced. Among these stimuli, various redox-sensitive linkages are primarily described in detail, and their application with self-assembled nanoparticles is recounted. Finally, the application of redox-responsive self-assembled nanoparticles in cancer therapy is summarized.

Upconverting Nanocarriers Enable Triggered Microtubule Inhibition and Concurrent Ferroptosis Induction for Selective Treatment of Triple-Negative Breast Cancer

Despite the resistance of triple-negative breast cancer (TNBC) to targeted hormone therapy, the discovery of azobenzene combretastatin A4 (Azo-CA4) provides therapeutic opportunities for TNBC. Here, Azo-CA4 was loaded in upconverting nanocarriers that could convert near-infrared (NIR) light to UV light to activate Azo-CA4. Upon irradiation, Azo-CA4-loaded nanocarriers significantly reduced the viability of TNBC cells via both apoptosis and ferroptosis. The former was induced by photoisomerization of Azo-CA4, accompanied by microtubule breakdown and cell cycle arrest at G₂/M phase. The latter was caused by the UV light-induced reduction of Fe³⁺ to Fe²⁺ that facilitates the peroxidation of tailored lipids. The cooperation between apoptosis and ferroptosis in eliminating TNBC was demonstrated in a xenograft mice model in terms of histological staining, tumor growth inhibition, and animal survival. Since the NIR light is only applied to the tumor site, the adverse effects of such triggered nanocarriers to the healthy organs are negligible.

The Progress and Prospect of Zeolitic Imidazolate Frameworks in Cancer Therapy, Antibacterial Activity, and Biomineralization

The progressive development of zeolitic imidazolate frameworks (ZIFs), as a subfamily of metal-organic frameworks (MOFs), and their unique features, including tunable pore size, large surface area, high thermal stability, and biodegradability/biocompatibility, have made them attractive in the field of biomedicine, especially for drug delivery and biomineralization applications. The high porosity of ZIFs gives them the opportunity for encapsulating a high amount of therapeutic drugs, proteins, imaging cargos, or a combination of them to construct advanced multifunctional drug delivery systems (DDSs) with combined therapeutic and imaging capabilities. This review summarizes recent strategies on the design and fabrication of ZIF-based nansystems and their exploration in the biomedical field. First, recent developments for the adjustment of particle size, functionality, and morphology of ZIFs are discussed, which are important for achieving optimized therapeutic/theranostic nanosystems. Second, recent trends on the application of ZIF nanocarriers for the loading of diverse cargos, including anticancer medicines, antibiotic drugs, enzymes, proteins, photosensitizers, as well as imaging and photothermal agents, are investigated in order to understand how multifunctional DDSs can be designed based on the ZIF nanoparticles to treat different diseases, such as cancer and infection. Finally, prospects on the future research direction and applications of ZIF-based nanomedicines are discussed.

Dihydroartemisinin-Loaded Magnetic Nanoparticles for Enhanced Chemodynamic Therapy

Recently, chemodynamic therapy (CDT) has represented a new approach for cancer treatment with low toxicity and side effects. Nonetheless, it has been a challenge to improve the therapeutic effect through increasing the amount of reactive oxygen species (ROS). Herein, we increased the amount of ROS agents in the Fenton-like reaction by loading dihydroartemisinin (DHA) which was an artemisinin (ART) derivative containing peroxide groups, into magnetic nanoparticles (MNP), thereby improving the therapeutic effect of CDT. Blank MNP were almost non-cytotoxic, whereas three MNP loading ART-based drugs, MNP-ART, MNP-DHA, and MNP-artesunate (MNP-AS), all showed significant killing effect on breast cancer cells (MCF-7 cells), in which MNP-DHA were the most potent. What's more, the MNP-DHA showed high toxicity to drug-resistant breast cancer cells (MCF-7/ADR cells), demonstrating its ability to overcome multidrug resistance (MDR). The study revealed that MNP could produce ferrous ions under the acidic condition of tumor microenvironment, which catalyzed DHA to produce large amounts of ROS, leading to cell death. Further experiments also showed that the MNP-DHA had significant inhibitory effect on another two aggressive breast cancer cell lines (MDA-MB-231 and MDA-MB-453 cells), which indicated that the great potential of MNP-DHA for the treatment of intractable breast cancers.

Hyaluronic acid hydrophilic surface rehabilitating curcumin nanocrystals for targeted breast cancer treatment with prolonged biodistribution

Due to its high therapeutic efficiency and low systemic toxicity, natural bioactive curcumin has attracted more and more attention as a potential antineoplastic drug.

Nanoscale Covalent Organic Framework for Combinatorial Antitumor Photodynamic and Photothermal Therapy

Despite the excellent photodynamic and photothermal properties of organic molecular photosensitizers (PSs) and photothermal agents (PTAs), such as porphyrin and naphthalocyanine, their poor water solubility severely impedes their biological applications. Covalent organic frameworks (COFs), as an emerging class of organic crystalline porous materials, possess free active end groups (bonding defects) and large inner pores, which make them an ideal type of nanocarriers for loading hydrophobic organic molecular PSs and PTAs by both bonding defect functionalization (BDF) and guest encapsulation approaches to obtain multifunctional nanomedicines for PDT/PTT combination therapy. In this work, we report a nanoscale COF (NCOF) prepared via a facile synthetic approach under ambient conditions. Furthermore, a dual-modal PDT/PTT therapeutic nanoagent, VONc@COF-Por (3), is successfully fabricated by stepwise BDF and guest encapsulation processes. The covalently grafted porphyrinic PS (Por) and the noncovalently loaded naphthalocyanine PTA (VONc) are independently responsible for the PDT and PTT functionalities of the nanoagent. Upon visible (red LED) and NIR (808 nm laser) irradiation, VONc@COF-Por (3) displayed high ¹O₂ generation and photothermal conversion ability (55.9%), consequently providing an excellent combined PDT/PTT therapeutic effect on inhibiting MCF-7 tumor cell proliferation and metastasis, which was well evidenced by in vitro and in vivo experiments. We believe that the results obtained herein can significantly promote the development of NCOF-based multifunctional nanomedicines for biomedical applications.