Nanotherapeutics interfere with cellular redox homeostasis for highly improved photodynamic therapy

A TME-enlightened protein-binding photodynamic nanoinhibitor for highly effective oncology treatment

The efficiency of photodynamic therapy (PDT) is greatly dependent on intrinsic features of photosensitizers (PSs), but most PSs suffer from narrow diffusion distances and short life span of singlet oxygen (1O2). Here, to conquer this issue, we propose a strategy for in situ formation of complexes between PSs and proteins to deactivate proteins, leading to highly effective PDT. The tetrafluorophenyl bacteriochlorin (FBC), a strong near-infrared absorbing photosensitizer, can tightly bind to intracellular proteins to form stable complexes, which breaks through the space-time constraints of PSs and proteins. The generated singlet oxygen directly causes the protein dysfunction, leading to high efficiency of PSs. To enable efficient delivery of PSs, a charge-conversional and redox-responsive block copolymer POEGMA-b-(PAEMA/DMMA-co-BMA) (PB) was designed to construct a protein-binding photodynamic nanoinhibitor (FBC@PB), which not only prolongs blood circulation and enhances cellular uptake but also releases FBC on demand in tumor microenvironment (TME). Meanwhile, PDT-induced destruction of cancer cells could produce tumor-associated antigens which were capable to trigger robust antitumor immune responses, facilitating the eradication of residual cancer cells. A series of experiments in vitro and in vivo demonstrated that this multifunctional nanoinhibitor provides a promising strategy to extend photodynamic immunotherapy.

Multifunctional nanogel based on carboxymethyl cellulose interfering with cellular redox homeostasis enhances phycocyanobilin photodynamic therapy

The redox homeostasis defense mechanism of tumor cells is one of the prime reasons for the unsatisfactory effect of photodynamic therapy (PDT). So far, little attention has been paid to this obstacle. In this work, we reported a synthesizing simple yet versatile nanogel (BCPS), synthesized by cystamine dihydrochloride functionalized sodium carboxymethylcellulose (CMC-SS), bovine serum albumin, and Phycocyanobilin self-assembly. The BCPS reduced the levels of glutathione molecules by reacting with glutathione, thereby interfering with intracellular redox homeostasis and enhancing the sensitivity of tumor cells to PDT. The BCPS was shown to possess excellent serum stability, high blood compatibility, low toxic side effects, and higher reactive oxygen species (ROS) utilization. After irradiation, the BCPS could significantly increase intracellular ROS level by approximately 1.6-fold and decrease the IC50 to HeLa cells by approximately 1.5-fold, compared to the pre-functional drugs BCP. This proposed strategy, based on increasing the utilization rate of ROS in tumor cells is promising for application potentials in tumor therapy.

Manganese-Based Redox Homeostasis Disruptor for Inducing Intense Ferroptosis/Apoptosis Through xCT Inhibition And Oxidative Stress Injury

Intracellular redox homeostasis plays an important role in promoting tumor progression, development and even treatment resistance. To this end, redox balance impairment may become a prospective therapeutic target of cancer. Herein, a manganese-based homeostasis modulator (MHS) is developed for inducing severe reactive oxygen species accumulation and glutathione (GSH) deprivation, where such redox dyshomeostasis brings about dramatic ferroptosis/apoptosis. Tumor-specific degradation of manganese oxide nanocarriers contributes to hypoxia alleviation and loaded cargo release, resulting in apoptosis by augmented sonodynamic therapy and chemodynamic therapy. On the other hand, regional oxygenation significantly downregulates the expression of activating transcription factor 4, which can synergize with the released sulfasalazine to inhibit the downstream cystine antiporter xCT. Biosynthesis of GSH is sufficiently interrupted by the xCT suppression, leading to the reduction of glutathione peroxidase 4 (GPx4) level. The resultant excessive lipid peroxides promote intense ferroptosis to motivate cell death. On this basis, splendid treatment outcome by MHS is substantiated both in vitro and in vivo, thanks to the synergy of antitumor immunity elicitation. Taken together, this paradigm provides an insightful strategy to evoke drastic ferroptosis/apoptosis toward therapeutics and may also expand the eligibility of manganese-derived nanoagents for medical applications.

Mineralized Porphyrin Metal-Organic Framework for Improved Tumor Elimination and Combined Immunotherapy

Calcium ion therapy is a potential anticancer treatment. However, the cellular calcium-buffering mechanism limited the effectiveness of calcium ion therapy. Here, we constructed a mineralized porphyrin metal-organic framework (PCa) to produce calcium ions and reactive oxygen species (ROS), which destroyed cell calcium buffering capacity and amplified the cell damage caused by calcium overload. In addition, PCa could induce cell immunogenic death to release tumor-associated antigen (TAA) and be used as an adjuvant. Thus, PCa could increase DC maturation and promote the antitumor activity of CD8⁺ T cells. For mice experiment, PCa not only showed excellent tumor elimination on the subcutaneous breast tumor but also achieved obvious antimetastasis effect in the metastatic tumor model. This nanosystem could eliminate the primary tumor and boost effective antitumor immunotherapy for comprehensive anticancer treatment.

Research development of porphyrin-based metal-organic frameworks: targeting modalities and cancer therapeutic applications

Porphyrins are naturally occurring organic molecules that have attracted widespread attention for their potential in the field of biomedical research. Porphyrin-based metal-organic frameworks (MOFs) that utilize porphyrin molecules as organic ligands have gained attention from researchers due to their excellent results as photosensitizers in tumor photodynamic therapy (PDT). Additionally, MOFs hold significant promise and potential for other tumor therapeutic approaches due to their tunable size and pore size, excellent porosity, and ultra-high specific surface area. Active delivery of nanomaterials via targeted molecules for tumor therapy has demonstrated greater accumulation, lower drug doses, higher therapeutic efficacy, and reduced side effects relative to passive targeting through the enhanced permeation and retention effect (EPR). This paper presents a comprehensive review of the targeting methods employed by porphyrin-based MOFs in tumor targeting therapy over the past few years. It further discusses the applications of porphyrin-based MOFs for targeted cancer therapy through various therapeutic methods. The objective of this paper is to provide a valuable reference and source of ideas for targeted therapy using porphyrin-based MOF materials and to inspire further exploration of their potential in the field of cancer therapy.

NIR-II Light-Activated Gold Nanorods for Synergistic Thermodynamic and Photothermal Therapy of Tumor

There are tricky challenges in tumor therapy due to the hypoxic tumor microenvironment, inevitably inhibiting the treatment efficacy of the traditional photodynamic therapy (PDT), radiation therapy (RT), and sonodynamic therapy (SDT). Herein, to overcome tumor hypoxia limitation, we constructed a near-infrared II (NIR-II) light-triggered thermodynamic therapy (TDT) nanoplatform of Au@mSiO₂-AIPH@PCM/PEG (ASAPP) by integrating the Au nanorods (Au NRs) and thermally activated alkyl free radical-releasing molecules (AIPH). Au NRs@mSiO₂ was used as a photothermally responsive material and AIPH carrier, and the hot-melt phase-change material (PCM) was used as a capping agent to prevent leakage of AIPH during blood circulation. Upon NIR-II light irradiation, heat-triggered free radical release from AIPH was successfully achieved for killing cancer cells in vitro and in vivo without oxygen dependence, leading to synergistically enhanced antitumor therapy.

Recent advances in sonodynamic immunotherapy

Tumor immunotherapy has become an important means of tumor therapy by enhancing the immune response and triggering the activation of immune cells. However, currently, only a small number of patients respond to immunotherapy alone, and patients may experience immune-related adverse events (irAEs) during the course of treatment. Sonodynamic therapy (SDT) can produce cytotoxic substances to tumor tissue, induce apoptosis and enhance immunity. SDT combined with immunotherapy is considered a promising strategy for cancer treatment. In this mini review, we summarize the role of SDT in immunotherapy in recent years, including the application of SDT-triggered immunotherapy and the combination of SDT and immunotherapy.

Redox Imbalance Triggered Intratumoral Cascade Reaction for Tumor "turn on" Imaging and Synergistic Therapy

The redox homeostasis in tumors enhances their antioxidant defense ability, limiting reactive oxygen species mediated tumor therapy efficacy. The development of strategies for specific and continuous disruption of the redox homeostasis in tumor cells facilitates the improvement of the cancer therapeutic effect by promoting the apoptosis of tumor cells. Herein, a responsively biodegradable targeting multifunctional integrated nanosphere (HDMn-QDs/PEG-FA) is designed to enhance the anti-tumor efficacy by triggering intratumoral cascade reactions to effectively disrupt intracellular redox homeostasis. Once HDMn-QDs/PEG-FA enters tumor cells, manganese dioxide (MnO₂ ) shell on the surface of nanosphere consumes glutathione (GSH) to produce Mn²⁺ , enabling enhanced chemodynamic therapy (CDT) via a Fenton-like reaction and T₁ -weighted magnetic resonance imaging. Meanwhile, the degradation of MnO₂ can also cause the fluorescence recovery of quantum dots conjugated on the surface of the shell, realizing "turn-on" fluorescence imaging. In addition, the doxorubicin is released because of the cleavage of the embedded SS bond in the hybrid core framework by GSH. A superior synergistic therapeutic efficiency combined CDT and chemotherapy is shown by HDMn-QDs/PEG-FA in vivo. The tumor-inhibition rate reaches to 94.8% and does not cause normal tissue damage due to the good targeting and tumor microenvironment-specific response.

Mitochondria-targeted iridium-based photosensitizers enhancing photodynamic therapy effect by disturbing cellular redox balance

Photodynamic therapy (PDT) is a non-invasive, light-activated treatment approach that has been broadly employed in cancer. Cyclometallic iridium (Ш) complexes are candidates for ideal photosensitizers due to their unique photophysical and photochemical features, such as high quantum yield, large Stokes shift, strong resistance to photobleaching, and high cellular permeability. We evaluated a panel of iridium complexes and identified PC9 as a powerful photosensitizer to kill cancer cells. PC9 shows an 8-fold increase of cytotoxicity to HeLa cells under light irradiation. Further investigation discloses that PC9 has a strong mitochondrial-targeting ability and can inhibit the antioxidant enzyme thioredoxin reductase, which contributes to improving PDT efficacy. Our data indicate that iridium complexes are efficient photosensitizers with distinct physicochemical properties and cellular actions, and deserve further development as promising agents for PDT.

Biomimetic photosensitizer nanocrystals trigger enhanced ferroptosis for improving cancer treatment

As a novel non-apoptotic cell death pathway, ferroptosis can effectively enhance the antitumor effects of photodynamic therapy (PDT) by disrupting intracellular redox homeostasis. However, the reported nanocomposites that combined the PDT and ferroptosis are cumbersome to prepare, and the unfavorable tumor microenvironment also severely interferes with their tumor suppressive effects. To address this inherent barrier, this study attempted to explore photosensitizers that could activate ferroptosis pathway and found that the photosensitizer aloe-emodin (AE) could induce cellular ferroptosis based on its specific inhibiting activity to Glutathione S-transferase P1(GSTP1), a key protein for ferroptosis. Herein, we prepared AE@RBC/Fe nanocrystals (NCs) with synergistic PDT and ferroptosis therapeutic effects by one-step emulsification to obtain AE NCs cores and further modification of red blood cells (RBC) membranes and ferritin. Benefiting from the involvement of ferritin, the prepared AE@RBC/Fe NCs provide not only sufficient oxygen for oxygen-dependent PDT, but also Fe³⁺ for iron-dependent ferroptosis in tumor cells. Furthermore, the biomimetic surface functionalization facilitated the prolonged circulation and cancer targeting of AE@RBC/Fe NCs in vivo. The in vitro and in vivo results demonstrate that AE@RBC/Fe NCs exhibit significantly enhanced therapeutic effects for the combined two antitumor mechanisms and provide a promising prospect for achieving PDT/ferroptosis synergistic therapy.

Nanomedicine-Enabled/Augmented Cell Pyroptosis for Efficient Tumor Nanotherapy

The terrible morbidity and mortality of malignant tumors urgently require innovative therapeutics, especially for apoptosis-resistant tumors. Pyroptosis, a pro-inflammatory form of programmed cell death (PCD), is featured with pore formation in plasma membrane, cell swelling with giant bubbles, and leakage of cytoplasmic pro-inflammatory cytokines, which can remodel the tumor immune microenvironment by stimulating a "cold" tumor microenvironment to be an immunogenic "hot" tumor microenvironment, and consequently augment the therapeutic efficiency of malignant tumors. Benefiting from current advances in nanotechnology, nanomedicine is extensively applied to potentiate, enable, and augment pyroptosis for enhancing cancer-therapeutic efficacy and specificity. This review provides a concentrated summary and discussion of the most recent progress achieved in this emerging field, highlighting the nanomedicine-enabled/augmented specific pyroptosis strategy for favoring the construction of next-generation nanomedicines to efficiently induce PCD. It is highly expected that the further clinical translation of nanomedicine can be accelerated by inducing pyroptotic cell death based on bioactive nanomedicines.

Melanin Nanoparticle-Actuated Redox-State Perturbation and Temporally Photoactivated Thermal Stress for Synergistic Tumor Therapy

The elevation of antioxidant defense systems by adaptation response to localized reactive oxygen species (ROS) accumulation may confer resistance to excessive oxidative stress and cause therapeutic lethality. Herein, a highly effective tumor therapy is developed through perturbation in cellular redox homeostasis. Specifically, metal-ion-assisted oxidation polymerization of the melanin precursor (l-DOPA) whose carboxyl groups exert a charge-shielding effect leads to the formation of catechol-rich but quinone-deficient nanoparticles (NPs). These NPs possess appreciable ROS-scavenging ability, and particularly the raised quinone group levels in oxidized products can then trigger subsequent depletion of antioxidative species (GSH) and, in turn, the redox-cycle consumption of catechol/quinone groups. After incubating with cells, varying degrees of redox-state and energy metabolism fluctuations with time (∼6 h) are observed, where ROS/GSH levels rebound to a maximum peak (up to ∼280%) higher than the normal redox state after hitting the bottom within a short time (1 h). Notably, systematically triggered redox stress response can sensitize cells to an extremely endangered metastable state. The synergy of temporally photoactivated thermal stress can produce overwhelming oxidative stress, thus leading to significant inhibition of cancer cells. This work established a new paradigm of redox perturbator-based programed and combined cancer therapy.

Ferrocene-Containing Nucleic Acid-Based Energy-Storage Nanoagent for Continuously Photo-Induced Oxidative Stress Amplification

Regulation of cellular oxidative stress plays a critical role in revealing the molecular mechanisms of cellular activities and thus is a potential strategy for tumor treatment. Optical methods have been employed for intelligent regulation of oxidative stress in tumor regions. However, long-time continuous irradiation inevitably causes damage to normal tissues. Herein, a ferrocene-containing nucleic acid-based energy-storage nanoagent was designed to achieve the continuous photo-regulation of cellular oxidative stress in the dark. Specifically, the photoenergy stored in the agent could convert effectively and accelerate Fenton-like reaction continuously, augmenting cellular oxidative stress. This nanoagent could also silence oxidative damage repair genes to further amplify oxidative stress. This strategy not only provides oxidative stress regulation for studying the molecular mechanisms of biological activities, but also offers a promising step toward tumor microenvironment modulation.

An Ultrasmall Fe3 O4 -Decorated Polydopamine Hybrid Nanozyme Enables Continuous Conversion of Oxygen into Toxic Hydroxyl Radical via GSH-Depleted Cascade Redox Reactions for Intensive Wound Disinfection

Nanozyme-based chemodynamic therapy (CDT) for fighting bacterial infections faces several major obstacles including low hydrogen peroxide (H₂ O₂ ) level, over-expressed glutathione (GSH) in infected sites, and inevitable damage to healthy tissue with abundant nonlocalized nanozymes. Herein, a smart ultrasmall Fe₃ O₄ -decorated polydopamine (PDA/Fe₃ O₄ ) hybrid nanozyme is demonstrated that continuously converts oxygen into highly toxic hydroxyl radical (•OH) via GSH-depleted cascade redox reactions for CDT-mediated bacterial elimination and intensive wound disinfection. In this system, photonic hyperthermia of PDA/Fe₃ O₄ nanozymes can not only directly damage bacteria, but also improve the horseradish peroxidase-like activity of Fe₃ O₄ decorated for CDT. Surprisingly, through photothermal-enhanced cascade catalytic reactions, PDA/Fe₃ O₄ nanozymes can consume endogenous GSH for disrupting cellular redox homeostasis and simultaneously provide abundant H₂ O₂ for improving •OH generation, ultimately enhancing the antibacterial performance of CDT. Such PDA/Fe₃ O₄ can bind with bacterial cells, and reveals excellent antibacterial property against both Staphylococcus aureus and Escherichia coli. Most interestingly, PDA/Fe₃ O₄ nanozymes can be strongly retained in infected sites by an external magnet for localized long-term in vivo CDT and show minimal toxicity to healthy tissues and organs. This work presents an effective strategy to magnetically retain the therapeutic nanozymes in infected sites for highly efficient CDT with good biosafety.

Redox dyshomeostasis strategy for tumor therapy based on nanomaterials chemistry

Redox homeostasis, as an innate cellular defense mechanism, not only contributes to malignant transformation and metastasis of tumors, but also seriously restricts reactive oxygen species (ROS)-mediated tumor therapies, such as chemotherapy, radiotherapy, photodynamic therapy (PDT), and chemodynamic therapy (CDT). Therefore, the development of the redox dyshomeostasis (RDH) strategy based on nanomaterials chemistry is of great significance for developing highly efficient tumor therapy. This review will firstly introduce the basic definition and function of cellular redox homeostasis and RDH. Subsequently, the current representative progress of the nanomaterial-based RDH strategy for tumor therapy is evaluated, summarized and discussed. This strategy can be categorized into three groups: (1) regulation of oxidizing species; (2) regulation of reducing species and (3) regulation of both of them. Furthermore, the current limitations and potential future directions for this field will be briefly discussed. We expect that this review could attract positive attention in the chemistry, materials science, and biomedicine fields and further promote their interdisciplinary integration.

This review summarizes the current progress of the redox dyshomeostasis (RDH) strategy for tumor therapy. This strategy makes tumor cells more sensitive to current therapy patterns through using nanomaterials to disrupt redox homeostasis.

Metallic Nanoparticles for the Modulation of Tumor Microenvironment; A New Horizon

Cancer is one of the most critical human challenges which endangers many people’s lives every year with enormous direct and indirect costs worldwide. Unfortunately, despite many advanced treatments used in cancer clinics today, the treatments are deficiently encumbered with many side effects often encountered by clinicians while deploying general methods such as chemotherapy, radiotherapy, surgery, or a combination thereof. Due to their low clinical efficacy, numerous side effects, higher economic costs, and relatively poor acceptance by patients, researchers are striving to find better alternatives for treating this life-threatening complication. As a result, Metal nanoparticles (Metal NPs) have been developed for nearly 2 decades due to their important therapeutic properties. Nanoparticles are quite close in size to biological molecules and can easily penetrate into the cell, so one of the goals of nanotechnology is to mount molecules and drugs on nanoparticles and transfer them to the cell. These NPs are effective as multifunctional nanoplatforms for cancer treatment. They have an advantage over routine drugs in delivering anticancer drugs to a specific location. However, targeting cancer sites while performing anti-cancer treatment can be effective in improving the disease and reducing its complications. Among these, the usage of these nanoparticles (NPs) in photodynamic therapy and sonodynamic therapy are notable. Herein, this review is aimed at investigating the effect and appliances of Metal NPs in the modulation tumor microenvironment which bodes well for the utilization of vast and emerging nanomaterial resources.

Binary dimeric prodrug nanoparticles for self-boosted drug release and synergistic chemo-photodynamic therapy

Chemotherapy is the major strategy for cancer therapy, but its limited therapeutic efficiency and serious toxicity to normal tissues greatly restrict its clinical performance. Herein, we develop carrier-free self-activated prodrug nanoparticles combining chemotherapy and photodynamic therapy to enhance the antitumor efficiency. Reactive oxygen species (ROS)-responsive paclitaxel and porphyrin prodrugs are synthesized and co-assembled into nanoparticles without the addition of any adjuvants, which improves the drug content and reduces carrier-associated toxicity. After entering cancer cells, the obtained co-assembled nanoparticles can generate sufficient ROS upon light irradiation not only for photodynamic therapy, but also triggering on-demand drug release for chemotherapy, thus realizing self-enhanced prodrug activation and synergistic chemo-photodynamic therapy. This simple and effective carrier-free prodrug nanoplatform unifies the distinct traits of on-demand drug release and combination therapy, thus possessing great potential in advancing cancer treatment.

Ultrasound (US)-activated redox dyshomeostasis therapy reinforced by immunogenic cell death (ICD) through a mitochondrial targeting liposomal nanosystem

Introduction: An imbalance in redox homeostasis consistently inhibits tumor cell proliferation and further causes tumor regression. Thus, synchronous glutaminolysis inhibition and intracellular reactive oxygen (ROS) accumulation cause severe redox dyshomeostasis, which may potentially become a new therapeutic strategy to effectively combat cancer. Methods: Mitochondrial-targeting liposomal nanoparticles (abbreviated MLipRIR NPs) are synthesized by the encapsulation of R162 (inhibitor of glutamate dehydrogenase 1 [GDH1]) and IR780 (a hydrophobic sonosensitizer) within the lipid bilayer, which are exploited for ultrasound (US)-activated tumor dyshomeostasis therapy reinforced by immunogenic cell death (ICD). Results: R162 released from MLipRIR NPs disrupts the glutaminolysis pathway in mitochondria, resulting in downregulated enzymatic activity of glutathione peroxidase (GPx). In addition, loaded IR780 can generate high levels of ROS under US irradiation, which not only interrupts mitochondrial respiration to induce apoptosis but also consumes local glutathione (GSH). GSH depletion accompanied by GPx deactivation causes severe ferroptosis of tumor cells through the accumulation of lipid peroxides. Such intracellular redox dyshomeostasis effectively triggers immunogenic cell death (ICD), which can activate antitumor immunity for the suppression of both primary and distant tumors with the aid of immune checkpoint blockade. Conclusions: Taking advantage of multimodal imaging for therapy guidance, this nanoplatform may potentiate systemic tumor eradication with high certainty. Taken together, this state-of-the-art paradigm may provide useful insights for cancer management by disrupting redox homeostasis.

Sub 5 nm Gd3+ -Hemoporfin Framework Nanodots for Augmented Sonodynamic Theranostics and Fast Renal Clearance

Metal-organic nanomaterials have emerged as promising therapeutic agents to produce reactive oxygen species (ROS) under ultrasound (US) or light irradiation for tumor treatments. However, their relatively large sizes (ranging from tens to hundreds of nanometers) usually lead to low ROS utilization and body metabolism, thus enlarging their long-term toxicity and low therapeutic effect. To solve these shortcomings, herein the ultrasmall Gd³⁺ -hemoporfin framework nanodots (GdHF-NDs， ≈5 nm) is reported as efficient nano-sonosensitizers. Compared with GdHF aggregation (GdHF-A, ≈400 nm), the ultrasmall GdHF-NDs generate 2.3-fold toxic ROS amount under similar conditions, due to shorter diffusion path and larger relative specific surface area. When the GdHF-NDs dispersion is introvenously injected into tumor-bearing mouse, they are accumulated within tumors to provide high magnetic resonance imaging (MRI) contrast. Under US irradiation, the GdHF-NDs achieve a better sonodynamic therapeutic efficacy for tumors, compared with that from GdHF-A. More importantly, owing to ultrasmall size, most of GdHF-NDs can be rapidly cleared through the renal pathway. Therefore, GdHF-NDs can be used as a biosafety and high-performance sonodynamic agent for cancer theranostics.

Self-delivery nanomedicine for chemotherapy sensitized photodynamic therapy

A chlorine e6 (Ce6) and curcumin (Cur) based self-delivery nanomedicine (CeCu) is prepared for chemotherapy sensitized photodynamic therapy (PDT). The chemotherapeutic agent of Cur could inhibit the TrxR activity to destroy the cellular ROS-defence system for enhanced PDT, which provides synergistic effects for tumor precision therapy in consideration of the unfavorable tumor microenvironments.

The recent progress on metal-organic frameworks for phototherapy

Some infectious or malignant diseases such as cancers are seriously threatening the health of human beings all over the world. The commonly used antibiotic therapy cannot effectively treat these diseases within a short time, and also bring about adverse effects such as drug resistance and immune system damage during long-term systemic treatment. Phototherapy is an emerging antibiotic-free strategy to treat these diseases. Upon light irradiation, phototherapeutic agents can generate cytotoxic reactive oxygen species (ROS) or induce a temperature increase, which leads to the death of targeted cells. These two kinds of killing strategies are referred to as photodynamic therapy (PDT) and photothermal therapy (PTT), respectively. So far, many photo-responsive agents have been developed. Among them, the metal-organic framework (MOF) is becoming one of the most promising photo-responsive materials because its structure and chemical compositions can be easily modulated to achieve specific functions. MOFs can have intrinsic photodynamic or photothermal ability under the rational design of MOF construction, or serve as the carrier of therapeutic agents, owing to its tunable porosity. MOFs also provide feasibility for various combined therapies and targeting methods, which improves the efficiency of phototherapy. In this review, we firstly investigated the principles of phototherapy, and comprehensively summarized recent advances of MOF in PDT, PTT and synergistic therapy, from construction to modification. We expect that our demonstration will shed light on the future development of this field, and bring it one step closer to clinical trials.

A MnO2-coated multivariate porphyrinic metal-organic framework for oxygen self-sufficient chemo-photodynamic synergistic therapy

Lately, chemotherapy and photodynamic therapy (PDT) synergistic therapy has become a promising anti-cancer treatment mean. However, the hypoxia in tumor leads to huge impediments to the oxygen-dependentPDT effects. In this work, a multifunctional nanoplatform (TUDMP) based on a multivariable porphyrin-nMOFs core and a manganese dioxide (MnO₂) shell was prepared for relieving tumor hypoxia and enhancing chemo-photodynamic synergistic therapy performance. The obtained TUDMP nanoplatform could effectively catalyze the hydrolysis of hydrogen peroxide to generate oxygen and also lead to consumption of antioxidant GSH, thereby facilitating the production of cytotoxic reactive oxygen species (ROS) by photosensitizer under laser irradiation. More importantly, the decomposition of the MnO₂ shell would further promote the release of the loaded doxorubicin (DOX), and thus an efficient chemo-PDT synergistic therapy was realized. Both in vitro and in vivo experimental results demonstrated the oxygen self-sufficient multifunctional nanoplatform could exhibit significantly enhanced anticancer efficiencies compared with chemotherapy or PDT alone.

Recent Advances in Nanoscale Metal-Organic Frameworks Towards Cancer Cell Cytotoxicity: An Overview

Abstract

The fight against cancer has always been a prevalent research topic. Nanomaterials have the ability to directly penetrate cancer cells and potentially achieve minimally invasive, precise and efficient tumor annihilation. As such, nanoscale metal organic frameworks (nMOFs) are becoming increasingly attractive as potential therapeutic agents in the medical field due to their high structural variability, good biocompatibility, ease of surface functionalization as well as their porous morphologies with tunable cavity sizes. This overview addresses five different common strategies used to find cancer therapies, while summarizing the recent progress in using nMOFs as cytotoxic cancer cell agents largely through in vitro studies, although some in vivo investigations have also been reported. Chemo and targeted therapies rely on drug encapsulation and delivery inside the cell, whereas photothermal and photodynamic therapies depend on photosensitizers. Concurrently, immunotherapy actively induces the body to destroy the tumor by activating an immune response. By choosing the appropriate metal center, ligands and surface functionalization, nMOFs can be utilized in all five types of therapies. In the last section, the future prospects and challenges of nMOFs with respect to the various therapies will be presented and discussed.

Graphic Abstract

Optimized Combination of Photodynamic Therapy and Chemotherapy Using Gelatin Nanoparticles Containing Tirapazamine and Pheophorbide a

In combination therapy, synergetic effects of drugs and their efficient delivery are essential. Herein, we screened 12 anticancer drugs for combination with photodynamic therapy (PDT) using pheophorbide a (Pba). On the basis of combination index (CI) values in cell viability tests, we selected tirapazamine (TPZ) and developed self-assembled gelatin nanoparticles (NPs) containing both Pba and TPZ. The resulting TPZ-Pba-NPs showed a synergetic effect to kill tumor cells because TPZ was activated under the hypoxic conditions that originated from the PDT with Pba and laser irradiation. After they were injected into tumor-bearing mice via the tail vein, TPZ-Pba-NPs showed 3.17-fold higher blood concentration and 4.12-fold higher accumulation in tumor tissue 3 and 24 h postinjection, respectively. Upon laser irradiation to tumor tissue, TPZ-Pba-NPs successfully suppressed tumor growth by efficient drug delivery and synergetic effects in vivo. These overall results suggest that in vitro screening of drugs based on CI values, mechanism studies in hypoxia, and real-time in vivo imaging are promising strategies in developing NPs for optimized combination therapy.

Biocompatibility and biodegradability of metal organic frameworks for biomedical applications

Metal organic frameworks (MOFs) are a unique class of smart hybrid materials that have recently attracted significant interest for catalysis, separation and biomedical applications. Different strategies have been developed to overcome the limitations of MOFs for bio-applications in order to produce a system with high biocompatibility and biodegradability. In this review, we outline the chemical and physical factors that dictate the biocompatibility and biodegradability characteristics of MOFs including the nature of the metal ions and organic ligands, size, surface properties and colloidal stability. This review includes the in vitro biodegradation and in vivo biodistribution studies of MOFs to better understand their pharmacokinetics, organ toxicity and immune response. Such studies can guide the design of future bio-friendly systems that bring us closer to safely translating these platforms into the pharmaceutical consumer market.

Recent advances in cell membrane coated metal-organic frameworks (MOFs) for tumor therapy

In improving the tumor-targeting ability of metal-organic frameworks (MOFs) for tumor therapy and avoiding the clearance as well as capture by the immune system, there are still several challenges, which limit the development and bio-applications of MOFs. To overcome these challenges, various targeted modification strategies have been proposed. Amongst all the strategies, a promising cell membrane coating method has been explored and utilized for the syntheses of new cell membrane biomimetic MOFs (CMMs). Through such coating, various source cell membranes (e.g., red blood cell, immune cell, cancer cell, platelet, and fusion cell membranes) can be endowed with excellent properties such as long blood circulation, immune escape, and targeting ability. In the presented perspective, the synthetic method, characterization, and research progress in tumor therapy based on CMMs have been summarized. This is because, like many other technologies, the cell membrane coating technology also has several challenges to overcome. Hence, addressing and overcoming such challenges will promote and extend the bio-applications of MOFs which in the future may become a prospective carrier for cancer nano-medicine. Finally, the prospects and challenges of utilizing CMMs for tumor therapy have been discussed.

Modified nanoscale metal organic framework-based nanoplatforms in photodynamic therapy and further applications

Photodynamic therapy (PDT) has emerged as a modality in cancer treatment because it is less invasive and highly selective compared with conventional chemotherapy and radiation therapy. Nanoscale metal organic frameworks (nMOFs) have exhibited great potential for use in constructing nanoplatforms for improved PDT because of their unique structural advantages such as large surface areas, high porosities, tunable compositions and various other modifications. The large majority of current nMOF-based systems employ specific modifying groups to overcome the deficiencies previously observed when using older nMOFs in PDT. In this review, we summarize modifications to these systems such as enhancing singlet oxygen generation by introducing photoactive agents, alleviating tumor hypoxia and engineering active targeting abilities. The applications of MOF-based nanoparticles in synergistic cancer therapies that include PDT, as well as in theranostics are also discussed. Finally, we discuss some of the challenges faced in this field and the future prospects for the use of nMOFs in PDT.

Self-Amplification of Tumor Oxidative Stress with Degradable Metallic Complexes for Synergistic Cascade Tumor Therapy

The ferroptosis effect has been illuminated with a clear Fenton reaction mechanism that converts endogenous hydrogen peroxide (H₂O₂) into highly oxidative hydroxyl radicals (·OH) in ROS-amplified tumor therapy. This ferroptosis-related oxidation effect was then further enhanced by the enzyme-like roles of cisplatin (CDDP). This CDDP-induced apoptosis was promoted in reverse by ferroptosis via the depletion of glutathione (GSH) and prevention of DNA damage repair. Here, we have developed degradable metallic complexes (PtH@FeP) containing an Fe(III)-polydopamine (FeP) core and HA-cross-linked CDDP (PtH) shell, exaggerating in situ toxic ROS production via the synergistic effect of CDDP and Fe(III). Taken together, the rationally designed PtH@FeP provided a new strategy for self-amplified synergistic chemotherapy/ferroptosis/photothermal therapy (PTT) antitumor effects with a reduced dosage that facilitates clinical safety.

Redox Dyshomeostasis Strategy for Hypoxic Tumor Therapy Based on DNAzyme-Loaded Electrophilic ZIFs

Redox homeostasis is one of the main reasons for reactive oxygen species (ROS) tolerance in hypoxic tumors, limiting ROS-mediated tumor therapy. Proposed herein is a redox dyshomeostasis (RDH) strategy based on a nanoplatform, FeCysPW@ZIF-82@CAT Dz, to disrupt redox homeostasis, and its application to improve ROS-mediated hypoxic tumor therapy. Once endocytosed by tumor cells, the catalase DNAzyme (CAT Dz) loaded zeolitic imidazole framework-82 (ZIF-82@CAT Dz) shell can be degraded into Zn²⁺ as cofactors for CAT Dz mediated CAT silencing and electrophilic ligands for glutathione (GSH) depletion under hypoxia, both of which lead to intracellular RDH and H₂ O₂ accumulation. These "disordered" cells show reduced resistance to ROS and are effectively killed by ferrous cysteine-phosphotungstate (FeCysPW) induced chemodynamic therapy (CDT). In vitro and in vivo data demonstrate that the pH/hypoxia/H₂ O₂ triple stimuli responsive nanocomposite can efficiently kill hypoxic tumors. Overall, the RDH strategy provides a new way of thinking about ROS-mediated treatment of hypoxic tumors.

Porphyrin-Based Metal-Organic Framework Compounds as Promising Nanomedicines in Photodynamic Therapy

Porphyrin photosensitizers are widely used in photodynamic therapy (PDT) because of their unique diagnostic and therapeutic functions. However, many factors such as poor water solubility and instability of porphyrin compounds have limited their clinical application. Metal-organic frameworks (MOFs) have the beneficial characteristics of versatility, high porosity, and excellent biocompatibility. Porphyrin-MOF nanomaterials have attracted the attention of researchers because MOFs can effectively suppress the quenching caused by the self-aggregation of porphyrin compounds and promote drug delivery. This article reviews the latest applications of porphyrin-MOF nanomedicine in type II photodynamic therapy by increasing tumour cell oxygen concentration, depleting tumour cell functional molecules and releasing signal molecules. Current potential limitations and future applications are also emphasized and discussed herein.

Oxygen Self-Sufficient Core-Shell Metal-Organic Framework-Based Smart Nanoplatform for Enhanced Synergistic Chemotherapy and Photodynamic Therapy

The abnormal angiogenesis and insufficient oxygen supply in solid tumors lead to intratumoral hypoxia, which severely limits the efficacy of traditional photodynamic therapy (PDT). Here, a multifunctional nanoplatform (ZDZP@PP) based on a zeolitic imidazolate framework-67 (ZIF-67) core as a hydrogen peroxide catalyst, a zeolitic imidazolate framework-8 (ZIF-8) shell with a pH-responsive property, and a polydopamine-poly(ethylene glycol) (PDA-PEG) layer for improving the biocompatibility is fabricated for not only relieving tumor hypoxia but also enhancing the efficacy of combination chemo-photodynamic therapy. The chemotherapy drug doxorubicin (DOX) and photosensitizer protoporphyrin IX (PpIX) are encapsulated in different layers independently; thus, a unique two-stage stepwise release becomes possible. Moreover, the nanoplatform can effectively decompose hydrogen peroxide to produce oxygen and thus relieve tumor hypoxia, which further facilitates the production of cytotoxic reactive oxygen species (ROS) by PpIX under laser irradiation. Both in vitro and in vivo experimental results confirm that the combination chemo-photodynamic therapy with the ZDZP@PP nanoplatform can provide more effective cancer treatment than chemotherapy or PDT alone. Consequently, the oxygen self-sufficient multifunctional nanoplatform holds promising potential to overcome hypoxia and treat solid tumors in the future.

Inhibiting tumor oxygen metabolism and simultaneously generating oxygen by intelligent upconversion nanotherapeutics for enhanced photodynamic therapy

Hypoxia is one of the hallmarks of solid tumor, which heavily restricts the clinical cancer therapy treatments, especially for the oxygen (O2) -dependent photodynamic therapy (PDT). Herein, an intelligent multi-layer nanostructure was developed for decreasing the O2-consumption and elevating the O2-supply simultaneously. The cell respiration inhibitor -atovaquone (ATO) molecules were reserved in the middle mesoporous silicon layer, and thus were intelligently released at the tumor site after the degradation of gatekeeper of MnO2 layer, which effectively inhibit tumor respiration metabolism to elevate oxygen content. Meanwhile, the degradation of MnO2 layer can generate O2, further boosting oxygen content. Moreover, the inner upconversion nanostructures as the near infrared (NIR) light-transducers enable to activate photosensitizers for deep-tissue PDT. Systematic experiments demonstrate that this suppressing O2-consumption and O2-generation strategy improved oxygen supply to boost the singlet oxygen generation to eradicate cancer cells under NIR light excitation. Better still, superior trimodality imaging capabilities (computed tomography (CT), NIR-II window fluorescence, and tumor microenvironment-responsive T1-weighted magnetic resonance (MR) imaging) of the nanoplatform were evaluated. Our findings offer a promising aproach to conquer the serious hypoxia problem in cancer therapy by turning down the O2 metabolism aveneue and simultaneously generating O2.

The role of transporters in cancer redox homeostasis and cross-talk with nanomedicines

Tumor cell usually exhibits high levels of reactive oxygen species and adaptive antioxidant system due to the metabolic, genetic, and microenvironment-associated alterations. The altered redox homeostasis can promote tumor progression, development, and treatment resistance. Several membrane transporters are involved in the resetting redox homeostasis and play important roles in tumor progression. Therefore, targeting the involved transporters to disrupt the altered redox balance emerges as a viable strategy for cancer therapy. In addition, nanomedicines have drawn much attention in the past decades. Using nanomedicines to target or reset the redox homeostasis alone or combined with other therapies has brought convincing data in cancer treatment. In this review, we will introduce the altered redox balance in cancer metabolism and involved transporters, and highlight the recent advancements of redox-modulating nanomedicines for cancer treatment.

Hollow ferric-tannic acid nanocapsules with sustained O2 and ROS induction for synergistic tumor therapy

HFe-TA nanoparticles, with a fine hollow microstructure, are synthesized and incorporated with ICG for synergistic photo/chemodynamic therapy with enhanced efficacy.