Tailored Chemodynamic Nanomedicine Improves Pancreatic Cancer Treatment via Controllable Damaging Neoplastic Cells and Reprogramming Tumor Microenvironment

Proton nanomodulators for enhanced Mn2+-mediated chemodynamic therapy of tumors via HCO3- regulation

BACKGROUND

Mn2+-mediated chemodynamic therapy (CDT) has been emerged as a promising cancer therapeutic modality that relies heavily on HCO3- level in the system. Although the physiological buffers (H2CO3/HCO3-) provide certain amounts of HCO3-, the acidity of the tumor microenvironment (TME) would seriously affect the HCO3- ionic equilibrium (H2CO3 ⇌ H+ + HCO3-). As a result, HCO3- level in the tumor region is actually insufficient to support effective Mn2+-mediated CDT.

RESULTS

In this study, a robust nanomodulator MnFe2O4@ZIF-8 (PrSMZ) with the capability of in situ self-regulation HCO3- is presented to enhance therapeutic efficacy of Mn2+-mediated CDT. Under an acidic tumor microenvironment, PrSMZ could act as a proton sponge to shift the HCO3- ionic equilibrium to the positive direction, significantly boosting the generation of the HCO3-. Most importantly, such HCO3- supply capacity of PrSMZ could be finely modulated by its ZIF-8 shell thickness, resulting in a 1000-fold increase in reactive oxygen species (ROS) generation. Enhanced ROS-dependent CDT efficacy is further amplified by a glutathione (GSH)-depletion ability and the photothermal effect inherited from the inner core MnFe2O4 of PrSMZ to exert the remarkable antitumor effect on mouse models.

CONCLUSIONS

This work addresses the challenge of insufficient HCO3- in the TME for Mn2+-mediated Fenton catalysts and could provide a promising strategy for designing high-performance Mn2+-mediated CDT agents to treat cancer effectively.

The interaction between UBR7 and PRMT5 drives PDAC resistance to gemcitabine by regulating glycolysis and immune microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is a common malignant tumor of the digestive tract. Although gemcitabine and other therapeutic agents are effective in patients with advanced and metastatic pancreatic cancer, drug resistance has severely limited their use. However, the mechanisms of gemcitabine resistance in pancreatic cancer are poorly understood. In this study, ATAC-seq, ChIP-seq, and RNA-seq were performed to compare chromatin accessibility and gene expression in a patient-derived tumor xenograft (PDX) model of pancreatic cancer with or without gemcitabine resistance. Analyzing these sequencing data, we found a dramatic change in chromatin accessibility in the PDX model of gemcitabine-resistant tissues and identified a key gene, UBR7, which plays an important role in mediating gemcitabine resistance. Further research found that depletion of UBR7 significantly increased pancreatic carcinogenesis and the immunosuppressive microenvironment. Mechanistically, depleted UBR7 increased the stability of PRMT5, thereby promoting glycolysis in pancreatic cancer cells. Finally, an inhibitor that blocks PRMT5 (DS-437) significantly reduced gemcitabine resistance in pancreatic cancer caused by UBR7 depletion. In conclusion, our results illustrate that the UBR7-PRMT5 axis is a key metabolic regulator of PDAC and a promising target for the clinical treatment of gemcitabine resistance in PDAC.

Gelatin-coated glutathione depletion and oxygen generators in potentiated chemotherapy for pancreatic cancer

Chemotherapy is generally acknowledged as an effective method for pancreatic cancer (PC). However, its treatment efficacy is often compromised due to inefficient drug delivery and drug resistance propensity of tumor tissues. The purpose of this study is to design and develop a novel drug delivery system (Manganese-doped mesoporous silica nanoparticles, Mn-MSN) in which paclitaxel (PTX), a conventional chemotherapeutic agent used to effectively treat pancreatic cancer clinically. Through cross-linking with glutaraldehyde, gelatin (Ge) was encapsulated on the carrier surface, endowing the nanoparticles (Ge-Mn-MSN@PTX) with excellent biocompatibility, low hemolytic activity, and enzyme-responsive degradation. Mn was added for the following purposes: (1) catalyzing hydrogen peroxide (H2O2) to generate oxygen (O2), thereby alleviating tumor hypoxia and drug resistance; (2) depleting glutathione (GSH), inducing intracellular lipid peroxidation and ferroptosis; (3) enabling real-time monitoring of the therapeutic efficacy of the nanoparticles via magnetic resonance imaging (MRI). The experimental results demonstrated that Ge-Mn-MSN@PTX has satisfactory biosafety, antitumor activity, controlled drug release as well as imaging tracking capabilities. In the SW1990 nude mice model, the Ge-Mn-MSN@PTX effectively inhibited tumor growth by suppressing the expression of the resistance protein P-glycoprotein (P-gp) and inducing ferroptosis. In conclusion, the designed gelatin-coated Mn-MSN shows potential for application in future pancreatic cancer therapy.

Emerging Chemodynamic Nanotherapeutics for Cancer Treatment

Chemodynamic therapy (CDT) has emerged as a transformative paradigm in the realm of reactive oxygen species -mediated cancer therapies, exhibiting its potential as a sophisticated strategy for precise and effective tumor treatment. CDT primarily relies on metal ions and hydrogen peroxide to initiate Fenton or Fenton-like reactions, generating cytotoxic hydroxyl radicals. Its notable advantages in cancer treatment are demonstrated, including tumor specificity, autonomy from external triggers, and a favorable side-effect profile. Recent advancements in nanomedicine are devoted to enhancing CDT, promising a comprehensive optimization of CDT efficacy. This review systematically elucidates cutting-edge achievements in chemodynamic nanotherapeutics, exploring strategies for enhanced Fenton or Fenton-like reactions, improved tumor microenvironment modulation, and precise regulation in energy metabolism. Moreover, a detailed analysis of diverse CDT-mediated combination therapies is provided. Finally, the review concludes with a comprehensive discussion of the prospects and intrinsic challenges to the application of chemodynamic nanotherapeutics in the domain of cancer treatment.

AI-powered omics-based drug pair discovery for pyroptosis therapy targeting triple-negative breast cancer

Due to low success rates and long cycles of traditional drug development, the clinical tendency is to apply omics techniques to reveal patient-level disease characteristics and individualized responses to treatment. However, the heterogeneous form of data and uneven distribution of targets make drug discovery and precision medicine a non-trivial task. This study takes pyroptosis therapy for triple-negative breast cancer (TNBC) as a paradigm and uses data mining of a large TNBC cohort and drug databases to establish a biofactor-regulated neural network for rapidly screening and optimizing compound pyroptosis drug pairs. Subsequently, biomimetic nanococrystals are prepared using the preferred combination of mitoxantrone and gambogic acid for rational drug delivery. The unique mechanism of obtained nanococrystals regulating pyroptosis genes through ribosomal stress and triggering pyroptosis cascade immune effects are revealed in TNBC models. In this work, a target omics-based intelligent compound drug discovery framework explores an innovative drug development paradigm, which repurposes existing drugs and enables precise treatment of refractory diseases.

An iron-containing nanomedicine for inducing deep tumor penetration and synergistic ferroptosis in enhanced pancreatic cancer therapy

Pancreatic cancer is an aggressive and challenging malignancy with limited treatment options, largely attributed to the dense tumor stroma and intrinsic drug resistance. Here, we introduce a novel iron-containing nanoparticle formulation termed PTFE, loaded with the ferroptosis inducer Erastin, to overcome these obstacles and enhance pancreatic cancer therapy. The PTFE nanoparticles were prepared through a one-step assembly process, consisting of an Erastin-loaded PLGA core stabilized by a MOF shell formed by coordination between Fe3+ and tannic acid. PTFE demonstrated a unique capability to repolarize tumor-associated macrophages (TAMs) into the M1 phenotype, leading to the regulation of dense tumor stroma by modulating the activation of tumor-associated fibroblasts (TAFs) and reducing collagen deposition. This resulted in enhanced nanoparticle accumulation and deep penetration, as confirmed by in vitro multicellular tumor spheroids and in vivo mesenchymal-rich subcutaneous pancreatic tumor models. Moreover, PTFE effectively combated tumor resistance by synergistically employing the Fe3+-induced Fenton reaction and Erastin-induced ferroptosis, thereby disrupting the redox balance. As a result, significant tumor growth inhibition was achieved in mice-bearing tumor model. Comprehensive safety evaluations demonstrated PTFE's favorable biocompatibility, highlighting its potential as a promising therapeutic platform to effectively address the formidable challenges in pancreatic cancer treatment.

Metastable FeSe2 nanosheets as a one-for-all platform for stepwise synergistic tumor therapy

The urgent need to curb the rampant rise in cancer has impelled the rapid development of nanomedicine. Under the above issue, transition metal compounds have received special attention considering their physicochemical and biochemical properties. However, how to take full advantage of the valuable characteristics of nanomaterials based on their spatial structures and chemical components for synergistic tumor therapy is a worthwhile exploration. In this work, a tailored two-dimensional (2D) FeSe2 nanosheet (NS) platform is proposed, which integrates enzyme activity and drug efficacy through the regulation of itsstability. Specifically, metastable FeSe2 NSs can serve as dual nanozymes in an intact state, depleting GSH and increasing ROS to induce oxidative stress in the tumor microenvironment (TME). With the gradual degradation of the FeSe2 in TME, its degraded products can amplify the Fenton reaction and GSH consumption, enhance the expression of inflammatory factors, and achieve effective near-infrared (NIR)-light irradiation-enhanced synergistic photothermal therapy (PTT) and chemodynamic therapy (CDT). Our exploration further confirmed such a strategy that may integrate carrier activity and drug action into a metastable nanoplatform for tumor synergistic therapy. These results prompt the consideration of the rational design of a one-for-all carrier that can exhibit multifunctional properties and nanomedicine efficacy for versatile therapeutic applications in the future.

NIR-II-Absorbing NDI Polymer with Superior Penetration Depth for Enhanced Photothermal Therapy Efficiency of Hepatocellular Carcinoma

Introduction

Hepatocellular carcinomas (HCC) have a high morbidity and mortality rate, and is difficult to cure and prone to recurrence when it has already developed. Therefore, early detection and efficient treatment of HCC is necessary.

Methods

In this study, we synthesized a novel NDI polymer with uniform size, long-term stability, and high near-infrared two-zone (NIR-II) absorption efficiency, which can greatly enhance the effect of photothermal therapy (PTT) after intravenous injection into Huh-7-tumor bearing mice.

Results

The in vitro and in vivo studies showed that NDI polymer exhibited excellent NIR-guided PTT treatment, and the antitumor effect was approximately 88.5%, with obvious antimetastatic effects.

Conclusion

This study developed an NDI polymer-mediated integrated diagnostic and therapeutic modality for NIR-II fluorescence imaging and photothermal therapy.

Nanodrug-bacteria conjugates-mediated oncogenic collagen depletion enhances immune checkpoint blockade therapy against pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) cancer cells specifically produce abnormal oncogenic collagen to bind with integrin α3β1 receptor and activate the downstream focal adhesion kinase (FAK), protein kinase B (AKT), and mitogen-activated protein kinase (MAPK) signaling pathway. Collectively, this promotes immunosuppression and tumor proliferation and restricts the response rate of clinical cancer immunotherapies.

METHODS

Here, by leveraging the hypoxia tropism and excellent motility of the probiotic Escherichia coli strain Nissle 1917 (ECN), we developed nanodrug-bacteria conjugates to penetrate the extracellular matrix (ECM) and shuttle the surface-conjugated protein cages composed of collagenases and anti-programmed death-ligand 1 (PD-L1) antibodies to PDAC tumor parenchyma.

FINDINGS

We found the oncogenic collagen expression in human pancreatic cancer patients and demonstrated its interaction with integrin α3β1. We proved that reactive oxygen species (ROS) in the microenvironment of PDAC triggered collagenase release to degrade oncogenic collagen and block integrin α3β1-FAK signaling pathway, thus overcoming the immunosuppression and synergizing with anti-PD-L1 immunotherapy.

CONCLUSIONS

Collectively, our study highlights the significance of oncogenic collagen in PDAC immunotherapy, and consequently, we developed a therapeutic strategy that can deplete oncogenic collagen to synergize with immune checkpoint blockade for enhanced PDAC treatment efficacy.

FUNDING

This work was supported by the University of Wisconsin Carbone Cancer Center Research Collaborative and Pancreas Cancer Research Task Force, UWCCC Transdisciplinary Cancer Immunology-Immunotherapy Pilot Project, and the start-up package from the University of Wisconsin-Madison (to Q.H.).

Advances in Nanodynamic Therapy for Cancer Treatment

Nanodynamic therapy (NDT) exerts its anti-tumor effect by activating nanosensitizers to generate large amounts of reactive oxygen species (ROS) in tumor cells. NDT enhances tumor-specific targeting and selectivity by leveraging the tumor microenvironment (TME) and mechanisms that boost anti-tumor immune responses. It also minimizes damage to surrounding healthy tissues and enhances cytotoxicity in tumor cells, showing promise in cancer treatment, with significant potential. This review covers the research progress in five major nanodynamic therapies: photodynamic therapy (PDT), electrodynamic therapy (EDT), sonodynamic therapy (SDT), radiodynamic therapy (RDT), and chemodynamic therapy (CDT), emphasizing the significant role of advanced nanotechnology in the development of NDT for anti-tumor purposes. The mechanisms, effects, and challenges faced by these NDTs are discussed, along with their respective solutions for enhancing anti-tumor efficacy, such as pH response, oxygen delivery, and combined immunotherapy. Finally, this review briefly addresses challenges in the clinical translation of NDT.

A Journey of Challenges and Victories: A Bibliometric Worldview of Nanomedicine since the 21st Century

Nanotechnology profoundly affects the advancement of medicine. Limitations in diagnosing and treating cancer and chronic diseases promote the growth of nanomedicine. However, there are very few analytical and descriptive studies regarding the trajectory of nanomedicine, key research powers, present research landscape, focal investigative points, and future outlooks. Herein, articles and reviews published in the Science Citation Index Expanded of Web of Science Core Collection from first January 2000 to 18th July 2023 are analyzed. Herein, a bibliometric visualization of publication trends, countries/regions, institutions, journals, research categories, themes, references, and keywords is produced and elaborated. Nanomedicine-related academic output is increasing since the COVID-19 pandemic, solidifying the uneven global distribution of research performance. While China leads in terms of publication quantity and has numerous highly productive institutions, the USA has advantages in academic impact, commercialization, and industrial value. Nanomedicine integrates with other disciplines, establishing interdisciplinary platforms, in which drug delivery and nanoparticles remain focal points. Current research focuses on integrating nanomedicine and cell ferroptosis induction in cancer immunotherapy. The keyword "burst testing" identifies promising research directions, including immunogenic cell death, chemodynamic therapy, tumor microenvironment, immunotherapy, and extracellular vesicles. The prospects, major challenges, and barriers to addressing these directions are discussed.

Recent Advances on NIR-II Light-Enhanced Chemodynamic Therapy

Chemodynamic therapy (CDT) is a particular oncological therapeutic strategy by generates the highly toxic hydroxyl radical (•OH) from the dismutation of endogenous hydrogen peroxide (H2O2) via Fenton or Fenton-like reactions. However, single CDT therapies have been limited by unsatisfactory efficacy. Enhanced chemodynamic therapy (ECDT) triggered by near-infrared (NIR) is a novel therapeutic modality based on light energy to improve the efficiency of Fenton or Fenton-like reactions. However, the limited penetration and imaging capability of the visible (400-650 nm) and traditional NIR-I region (650-900 nm) light-amplified CDT restrict the prospects for its clinical application. Combined with the high penetration/high precision imaging characteristics of the second near-infrared (NIR-II,) nanoplatform, it is expected to kill deep tumors efficiently while imaging the treatment process in real-time, and more notably, the NIR-II region radiation with wavelengths above 1000 nm can minimize the irradiation damage to normal tissues. Such NIR-II ECDT nanoplatforms have greatly improved the effectiveness of CDT therapy and demonstrated extraordinary potential for clinical applications. Accordingly, various strategies have been explored in the past years to improve the efficiency of NIR-II Enhanced CDT. In this review, the mechanisms and strategies used to improve the performance of NIR-II-enhanced CDT are outlined.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

Redox-Activatable Magnetic Nanoarchitectonics for Self-Enhanced Tumor Imaging and Synergistic Photothermal-Chemodynamic Therapy

Oral squamous cell carcinoma (OSCC) is a prevalent malignancy of the head and neck region associated with high recurrence rates and poor prognosis under current diagnostic and treatment methods. The development of nanomaterials that can improve diagnostic accuracy and therapeutic efficacy is of great importance for OSCC. In this study, a redox-activatable nanoarchitectonics is designed via the construction of dual-valence cobalt oxide (DV-CO) nanospheres, which can serve as a contrast agent for magnetic resonance (MR) imaging, and exhibit enhanced transverse and longitudinal relaxivities through the release and redox of Co3+ /Co2+ in an acidic condition with glutathione (GSH), resulting in self-enhanced T1 /T2 -weighted MR contrast. Moreover, DV-CO demonstrates properties of intracellular GSH-depletion and hydroxyl radicals (•OH) generation through a Fenton-like reaction, enabling strengthened chemodynamic (CD) effect. Additionally, DV-CO displays efficient near-infrared laser-induced photothermal (PT) effect, thereby exhibiting synergistic PT-CD therapy for suppressing OSCC tumor cells. It further investigates the tumor-specific self-enhanced MR imaging of DV-CO both in subcutaneous and orthotopic OSCC mouse models, and demonstrate the therapeutic effects of DV-CO in orthotopic OSCC mouse models. Overall, the in vitro and in vivo findings highlight the excellent theranositc potentials of DV-CO for OSCC and offer new prospects for future advancement of nanomaterials.

Cancer cell membrane-coated upconversion nanoparticles/ZnxMn1-xS core-shell nanoparticles for targeted photodynamic and chemodynamic therapy of pancreatic cancer

Oxidative stress induced by reactive oxygen species (ROS) is promising treatment approach for pancreatic ductal adenocarcinoma (PDAC), which is typically insensitive to conventional chemotherapy. In this study, BxPC-3 pancreatic cancer cell membrane-coated upconversion nanoparticles/ZnxMn1-xS core-shell nanoparticles (abbreviated as BUC@ZMS) were developed for tumor-targeted cancer therapy via synergistically oxidative stress and overcoming glutathione (GSH) overexpression. Using a combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT), the BUC@ZMS core-shell nanoparticles were able to elicit the death of pancreatic cancer cells through the high production of ROS. Additionally, the BUC@ZMS core-shell nanoparticles could deplete intracellular GSH and increase the sensitivity of tumor cells to oxidative stress. The in vivo results indicated that BUC@ZMS nanoparticles can accumulate specifically in tumor locations and suppress PDAC without generating obvious toxicity. Thus, it was determined that the as-prepared core-shell nanoparticles would be a viable treatment option for solid malignancies.

Cell-based Relay Delivery Strategy in Biomedical Applications

The relay delivery strategy is a two-step targeting approach based on two distinct modules in which the first step with an initiator is to artificially create a target/environment which can be targeted by the follow-up effector. This relay delivery concept creates opportunities to amplify existing or create new targeted signals through deploying initiators to enhance the accumulation efficiency of the following effector at the disease site. As the "live" medicines, cell-based therapeutics possess inherent tissue/cell homing abilities and favorable feasibility of biological and chemical modifications, endowing them the great potential in specifically interacting with diverse biological environments. All these unique capabilities make cellular products great candidates that can serve as either initiators or effectors for relay delivery strategies. In this review, we survey recent advances in relay delivery strategies with a specific focus on the roles of various cells in developing relay delivery systems.

Integrated supramolecular nanovalves for photothermal augmented chemodynamic therapy through strengthened amplification of oxidative stress

The amplified oxidative stress strategy has been emerged as one promising method to enhance the chemodynamic therapy (CDT) efficacy due to the H₂O₂ up-regulation and glutathione (GSH) down-regulation behavior in tumor cells. However, how to further achieve the satisfied CDT efficacy is still a big challenge. In this paper, the supramolecular nanovalves (SNs) with oxidative amplification agents cinnamaldehyde-(phenylboronic acid pinacol ester) conjugates (CA-BE) encapsulated inside were developed to accelerate and amplify the generation of ·OH and consumption of GSH while augmenting the CDT efficacy. SNs were obtained through ferrocene/Au modified mesoporous silica nanoparticles (MSN@Au-Fc) and active targeting β-cyclodextrin modified hyaluromic acid (HA-CD). After CD44 receptor-mediated cellular internalization, the CA-BE were released to elevate H₂O₂ amount and consume GSH for the desired generation of higher cytotoxic hydroxyl radicals (·OH). Moreover, the NIR-activated MSN@Au-Fc can increase the temperature for the accelerated and amplified oxidative stress. As such, the therapeutic efficacy of our synthesized CA-BE and the accompanied hyperthermia were augmented toward synergistically inhibiting tumor growth.

Role of tumor-associated macrophages in common digestive system malignant tumors

Many digestive system malignant tumors are characterized by high incidence and mortality rate. Increasing evidence has revealed that the tumor microenvironment (TME) is involved in cancer initiation and tumor progression. Tumor-associated macrophages (TAMs) are a predominant constituent of the TME, and participate in the regulation of various biological behaviors and influence the prognosis of digestive system cancer. TAMs can be mainly classified into the antitumor M1 phenotype and protumor M2 phenotype. The latter especially are crucial drivers of tumor invasion, growth, angiogenesis, metastasis, immunosuppression, and resistance to therapy. TAMs are of importance in the occurrence, development, diagnosis, prognosis, and treatment of common digestive system malignant tumors. In this review, we summarize the role of TAMs in common digestive system malignant tumors, including esophageal, gastric, colorectal, pancreatic and liver cancers. How TAMs promote the development of tumors, and how they act as potential therapeutic targets and their clinical applications are also described.

Recent Advances in Well-Designed Therapeutic Nanosystems for the Pancreatic Ductal Adenocarcinoma Treatment Dilemma

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant tumor with an extremely poor prognosis and low survival rate. Due to its inconspicuous symptoms, PDAC is difficult to diagnose early. Most patients are diagnosed in the middle and late stages, losing the opportunity for surgery. Chemotherapy is the main treatment in clinical practice and improves the survival of patients to some extent. However, the improved prognosis is associated with higher side effects, and the overall prognosis is far from satisfactory. In addition to resistance to chemotherapy, PDAC is significantly resistant to targeted therapy and immunotherapy. The failure of multiple treatment modalities indicates great dilemmas in treating PDAC, including high molecular heterogeneity, high drug resistance, an immunosuppressive microenvironment, and a dense matrix. Nanomedicine shows great potential to overcome the therapeutic barriers of PDAC. Through the careful design and rational modification of nanomaterials, multifunctional intelligent nanosystems can be obtained. These nanosystems can adapt to the environment's needs and compensate for conventional treatments' shortcomings. This review is focused on recent advances in the use of well-designed nanosystems in different therapeutic modalities to overcome the PDAC treatment dilemma, including a variety of novel therapeutic modalities. Finally, these nanosystems' bottlenecks in treating PDAC and the prospect of future clinical translation are briefly discussed.

Development of stimuli responsive polymeric nanomedicines modulating tumor microenvironment for improved cancer therapy

The complexity of the tumor microenvironment (TME) severely hinders the therapeutic effects of various cancer treatment modalities. The TME differs from normal tissues owing to the presence of hypoxia, low pH, and immune-suppressive characteristics. Modulation of the TME to reverse tumor growth equilibrium is considered an effective way to treat tumors. Recently, polymeric nanomedicines have been widely used in cancer therapy, because their synthesis can be controlled and they are highly modifiable, and have demonstrated great potential to remodel the TME. In this review, we outline the application of various stimuli responsive polymeric nanomedicines to modulate the TME, aiming to provide insights for the design of the next generation of polymeric nanomedicines and promote the development of polymeric nanomedicines for cancer therapy.

Therapeutic Strategies to Overcome Fibrotic Barriers to Nanomedicine in the Pancreatic Tumor Microenvironment

Pancreatic cancer is notorious for its dismal prognosis. The enhanced permeability and retention (EPR) effect theory posits that nanomedicines (therapeutics in the size range of approximately 10-200 nm) selectively accumulate in tumors. Nanomedicine has thus been suggested to be the "magic bullet"-both effective and safe-to treat pancreatic cancer. However, the densely fibrotic tumor microenvironment of pancreatic cancer impedes nanomedicine delivery. The EPR effect is thus insufficient to achieve a significant therapeutic effect. Intratumoral fibrosis is chiefly driven by aberrantly activated fibroblasts and the extracellular matrix (ECM) components secreted. Fibroblast and ECM abnormalities offer various potential targets for therapeutic intervention. In this review, we detail the diverse strategies being tested to overcome the fibrotic barriers to nanomedicine in pancreatic cancer. Strategies that target the fibrotic tissue/process are discussed first, which are followed by strategies to optimize nanomedicine design. We provide an overview of how a deeper understanding, increasingly at single-cell resolution, of fibroblast biology is revealing the complex role of the fibrotic stroma in pancreatic cancer pathogenesis and consider the therapeutic implications. Finally, we discuss critical gaps in our understanding and how we might better formulate strategies to successfully overcome the fibrotic barriers in pancreatic cancer.

Stepwise Coordination-Driven Metal-Phenolic Nanoparticle as a Neuroprotection Enhancer for Alzheimer's Disease Therapy

Current therapeutic strategies for Alzheimer's disease (AD) mainly focus on inhibition of aberrant amyloid-β peptide (Aβ) aggregation. However, these strategies cannot repair the side symptoms (e.g., high neuronal oxidative stress) triggered by Aβ accumulation and thus show limited effects on suppressing Aβ-induced neuronal apoptosis. Herein, we develop a stepwise metal-phenolic coordination approach for the rational design of a neuroprotection enhancer, K8@Fe-Rh/Pda NPs, in which rhein and polydopamine are effectively coupled to enhance the treatment of AD in APPswe/PSEN1dE9 transgenic (APP/PS1) mice. We discover that the polydopamine inhibits the aggregation of Aβ oligomers, and rhein helps repair damage to neurons triggered by Aβ aggregation. Based on molecular docking, we demonstrate that the polydopamine has a strong interaction with Aβ monomers/fibrils through its multiple recognition sites (e.g., catechol groups, imine groups, and indolic/catecholic π-systems), thereby reducing Aβ burden. Further investigation of the antioxidant mechanisms suggests that K8@Fe-Rh/Pda NPs promote the mitochondrial biogenesis via activating the sirtuin 1 (SIRT1)/peroxisome proliferator-activated receptor gamma coactivator 1-alpha pathway. This finally inhibits neuronal apoptosis. Moreover, an intravenous injection of these nanoparticles potently improves the cognitive function in APP/PS1 mice without adverse effects. Overall, our work provides a promising approach to develop advanced nanomaterials for multi-target treatment of AD.

Amorphous Ultra-Small Fe-Based Nanocluster Engineered and ICG Loaded Organo-Mesoporous Silica for GSH Depletion and Photothermal-Chemodynamic Synergistic Therapy

Intracellular oxidative amplification can effectively destroy tumor cells. Additionally, Fe-mediated Fenton reaction often converts cytoplasm H₂ O₂ to generate extensive hypertoxic hydroxyl radical (^• OH), leading to irreversible mitochondrion damage for tumor celleradication, which is widely famous as tumor chemodynamic therapy (CDT). Unfortunately, intracellular overexpressed glutathione (GSH) always efficiently scavenges ^• OH, resulting in the significantly reduced CDT effect. To overcome this shortcoming and improve the oxidative stress in cytoplasm, Fe₃ O₄ ultrasmall nanoparticle encapsulated and ICG loaded organo-mesoporous silica nanovehicles (omSN@Fe-ICG) are constructed to perform both photothermal and GSH depletion to enhance the Fenton-like CDT, by realizing intracellular oxidative stress amplification. After this nanoagents are internalized, the tetrasulfide bonds in the dendritic mesoporous framework can be decomposed with GSH to amplify the toxic ROS neration by selectively converting H₂ O₂ to hydroxyl radicals through the released Fe-based nanogranules. Furthermore, the NIR laser-induced hyperthermia can further improve the Fenton reaction rate that simultaneously destroyed the mitochondria. As a result, the GSH depletion and photothermal assisted CDT can remarkably improve the tumor eradication efficacy.

A reactive oxygen species-replenishing coordination polymer nanomedicine disrupts redox homeostasis and induces concurrent apoptosis-ferroptosis for combinational cancer therapy

Reactive oxygen species (ROS) are important signal molecules and imbalanced ROS level could lead to cell death. Elevated ROS levels in tumor tissues offer an opportunity to design ROS-responsive drug delivery systems (DDSs) or ROS-based cancer therapy such as chemodynamic therapy. However, their anticancer efficacies are hampered by the ROS-consuming nature of these DDSs as well as the high concentration of reductive agents like glutathione (GSH). Here we developed a doxorubicin (DOX)-incorporated iron coordination polymer nanoparticle (PCFD) for efficient chemo-chemodynamic cancer therapy by using a cinnamaldehyde (CA)-based ROS-replenishing organic ligand (TCA). TCA can ROS-responsively release CA to supplement intracellular ROS and deplete GSH by a thiol-Michael addition reaction, which together with DOX-triggered ROS upregulation and Fe³⁺-enabled GSH depletion facilitated efficient DOX release and enhanced Fenton reaction, thereby inducing redox dyshomeostasis and cancer cell death in a concurrent apoptosis-ferroptosis way. Both in vitro and in vivo study revealed that ROS-replenishing PCFD exhibited much better anticancer effect than ROS-consuming control nanoparticle PAFD. The ingenious ROS-replenishing strategy could be expanded to construct versatile ROS-responsive DDSs and ROS-based nanomedicines with potentiated anticancer activity. STATEMENT OF SIGNIFICANCE: We develop a doxorubicin (DOX)-incorporated iron coordination polymer nanoparticle (PCFD) for efficient chemo-chemodynamic cancer therapy by using a cinnamaldehyde-based reactive oxygen species (ROS)-replenishing organic ligand. This functional ligand can ROS-responsively release cinnamaldehyde to supplement intracellular H₂O₂ and deplete glutathione (GSH) by a thiol-Michael addition reaction, which together with DOX-triggered ROS upregulation and Fe³⁺-enabled GSH depletion facilitates efficient DOX release and enhanced Fenton reaction, thereby inducing redox dyshomeostasis and cancer cell death in a concurrent apoptosis-ferroptosis way. Both in vitro and in vivo study reveal that ROS-replenishing PCFD exhibit much better anticancer effect than ROS consuming counterpart. This study provides a facile and straightforward strategy to design ROS amplifying nanoplatforms for cancer treatment.

Salicylic acid-based hypoxia-responsive chemodynamic nanomedicines boost antitumor immunotherapy by modulating immunosuppressive tumor microenvironment

The delivery of salicylic acid or its derivatives to tumor tissue in the form of nanomedicine is critical for the studies on their potential synergistic mechanism in tumor therapy and chemoprevention considering the dangerous bleeding in the high-dose oral administration. To deepen the understanding of their role in adjusting immunosuppressive tumor microenvironment (ITM), herein, we firstly developed a hypoxia-sensitive Fe-5,5'-azosalicylic acid nanoscale coordination polymer nanomedicines (FeNCPs) via a "old drugs new tricks" strategy for synergistic chemodynamic therapy (CDT) and remodulation of ITM to elevate antitumor immunotherapy effect. PEGylated FeNCPs could be reductively cleaved to release 5-aminosalicylic acid (5-ASA) and ferric ions by azo-reductase under hypoxic conditions, which could induce tumor cell death by Fenton reaction-catalysis enhanced CDT and 5-ASA-converted carboxylquinone to promote the production of •OH. Meanwhile, cyclooxygenase-2 (COX-2) and its enzymatic product prostaglandin E₂ (PGE₂), as immune negative regulatory molecules, can promote tumor progression and immune tolerance. The released 5-ASA as a COX inhibitor could suppress the expression of PGE₂, and Fe³⁺ was employed to reeducate M2-like tumor-associated macrophages (TAMs) to M1-like phenotype, which could initiate antitumor immune response to reach better antitumor immunotherapy. This work broadens the application of salicylic acid derivatives in antitumor immunotherapy, and provides a new strategy for their "old drugs new tricks". STATEMENT OF SIGNIFICANCE: Cyclooxygenase-2 (COX-2) and its enzymatic product prostaglandin E2 (PGE₂), as immune negative regulatory molecules, facilitate the differentiation of immune cells into immunosuppressive cells to build the immunosuppressive tumor microenvironment, which can promote tumor progression and immune tolerance. Thus, down-regulation of COX-2/PGE₂ expression may be a key approach to tumor treatments. Meanwhile, as a class of inhibitors of COX-2/PGE₂, the potential mechanism of aspirin or 5-aminosalicylic acid has been a mystery in tumor therapy and chemoprevention. To expand the application of aspirin family nanomedicine in biomedicine, herein, we firstly developed a hypoxia-sensitive Fe-5,5'-azosalicylic acid nanoscale coordination polymer nanomedicines via a "old drugs new tricks" strategy for synergistic chemodynamic therapy and remodulation of immunosuppressive tumor microenvironment to elevate antitumor immunotherapy effect.

Cartilage-Inspired Hydrogel with Mechanical Adaptability, Controllable Lubrication, and Inflammation Regulation Abilities

Cartilage is a key component in joints because of its load-bearing and lubricating abilities. However, osteoarthritis often leads to afunction of load-bearing/lubrication and occurrence of inflammation with overexpressed reactive oxygen species (ROS) and nitric oxide (NO). To address these issues, we fabricated a novel polyanionic hydrogel with abundant carboxylates/sulfonates ("CS" hydrogel), inspired by normal cartilage rich in anionic hyaluronate/sulfonate glycosaminoglycan/lubricin, and crosslinked it tightly by Fe3+ ("CS-Fe" hydrogel). The "CS-Fe" hydrogel displayed mechanical adaptability and shear resistance. A low coefficient of friction (∼0.02) appeared when a loose hydrogel layer was generated because of the photoreduction of Fe3+ to Fe2+ by UV irradiation. This biocompatible "CS-Fe" hydrogel suppressed the overexpressed hydroxyl radical (·OH) and NO in macrophages and protected chondrocytes/fibroblasts from aggressive inflammation. Moreover, the layered "CS-Fe" hydrogel avoided cell death of chondrocytes in sliding tests. The results demonstrate that this cartilage-inspired hydrogel is a promising candidate material in cartilage tissue engineering to especially address inflammation.

Advanced Biomaterials for Cell-Specific Modulation and Restore of Cancer Immunotherapy

The past decade has witnessed the explosive development of cancer immunotherapies. Nevertheless, low immunogenicity, limited specificity, poor delivery efficiency, and off-target side effects remain to be the major limitations for broad implementation of cancer immunotherapies to patient bedside. Encouragingly, advanced biomaterials offering cell-specific modulation of immunological cues bring new solutions for improving the therapeutic efficacy while relieving side effect risks. In this review, focus is given on how functional biomaterials can enable cell-specific modulation of cancer immunotherapy within the cancer-immune cycle, with particular emphasis on antigen-presenting cells (APCs), T cells, and tumor microenvironment (TME)-resident cells. By reviewing the current progress in biomaterial-based cancer immunotherapy, here the aim is to provide a better understanding of biomaterials' role in targeting modulation of antitumor immunity step-by-step and guidelines for rationally developing targeting biomaterials for more personalized cancer immunotherapy. Moreover, the current challenge and future perspective regarding the potential application and clinical translation will also be discussed.

Intracellular marriage of bicarbonate and Mn ions as "immune ion reactors" to regulate redox homeostasis and enhanced antitumor immune responses

Background

Different from Fe ions in Fenton reaction, Mn ions can function both as catalyst for chemodynamic therapy and immune adjuvant for antitumor immune responses. In Mn-mediated Fenton-like reaction, bicarbonate (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{HCO}}_{3}^{ - }$$\end{document}HCO3-), as the most important component to amplify therapeutic effects, must be present, however, intracellular \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{HCO}}_{3}^{ - }$$\end{document}HCO3- is strictly limited because of the tight control by live cells.

Results

Herein, Stimuli-responsive manganese carbonate-indocyanine green complexes (MnCO₃-ICG) were designed for intracellular marriage of bicarbonate and Mn ions as “immune ion reactors” to regulate intracellular redox homeostasis and antitumor immune responses. Under the tumor acidic environment, the biodegradable complex can release “ion reactors” of Mn²⁺ and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{HCO}}_{3}^{ - }$$\end{document}HCO3-, and ICG in the cytoplasm. The suddenly increased \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{HCO}}_{3}^{ - }$$\end{document}HCO3- in situ inside the cells regulate intracellular pH, and accelerate the generation of hydroxyl radicals for the oxidative stress damage of tumors cells because \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{HCO}}_{3}^{ - }$$\end{document}HCO3- play a critical role to catalyze Mn-mediated Fenton-like reaction. Investigations in vitro and in vivo prove that the both CDT and phototherapy combined with Mn²⁺-enhanced immunotherapy effectively suppress tumor growth and realize complete tumor elimination.

Conclusions

The combination therapy strategy with the help of novel immune adjuvants would produce an enhanced immune response, and be used for the treatment of deep tumors in situ.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01404-x.

Suppression of Energy Metabolism in Cancer Cells with Nutrient-Sensing Nanodrugs

Uncontrolled growth of tumor cells is highly dependent on the energy metabolism. Fasting-mimicking diet (FMD) is a low-calorie, low-protein, low-sugar diet representing a promising strategy for cancer treatment. However, triglyceride stored in adipose tissue is hydrolyzed into free fatty acids and glycerol for energy supply during FMD treatment. Herein, we design a nutrient-sensing nanodrug, VFETX, which is self-assembled with vitamin B1 (VB1), ferrous ions, and etomoxir (ETX). FMD treatment upregulate the expression of VB1 transporters on tumor cells, thereby increasing cellular uptake and tumor accumulation of VFETX. Importantly, treatments of VFETX and FMD synergistically inhibit the energy metabolism in tumor cells and subsequently markedly enhance cytotoxicity of ETX. As a result, VFETX nanodrugs efficiently inhibit the growth of two tumor models in vivo without obvious side effects. This study demonstrates the potential of FMD-assisted nutrient-sensing nanodrugs for cancer therapy.

Recent advances in targeted drug delivery for the treatment of pancreatic ductal adenocarcinoma

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) has become a serious health problem with high impact worldwide. The heterogeneity of PDAC makes it difficult to apply drug delivery systems (DDS) used in other cancer models, for example, the poorly developed vascular system makes anti-angiogenic therapy ineffective. Due to its various malignant pathological changes, drug delivery against PDAC is a matter of urgent concern. Based on this situation, various drug delivery strategies specially designed for PDAC have been generated.

AREAS COVERED

This review will briefly describe how delivery systems can be designed through nanotechnology and formulation science. Most research focused on penetrating the stromal barrier, exploiting and alleviating the hypoxic microenvironment, targeting immune cells, or designing vaccines, and combination therapies. This review will summarize the ways to reverse the malignant pathological features of PDAC and hopefully provide ideas for subsequent studies.

EXPERT OPINION

Drug delivery systems designed to achieve penetrating functions or to alleviate hypoxia and activate immunity have achieved good therapeutic results in animal models in several studies. In future studies, there is a need to deliver PDAC therapeutics in a more precise manner, or the use of drug carriers for multiple functions simultaneously, are potential therapeutic strategy.

A Smart Near-Infrared Carbon Dot-Metal Organic Framework Assemblies for Tumor Microenvironment-Activated Cancer Imaging and Chemodynamic-Photothermal Combined Therapy

Tumor microenvironment (TME)-activated cancer imaging and therapy is a key to achieving accurate diagnosis and treatment of cancer and reducing the side effects. Herein, smart near-infrared carbon dot-metal organic framework MIL-100 (Fe) assemblies are constructed to achieve TME-activated cancer imaging and chemodynamic-photothermal combined therapy. First, a near-infrared emission carbon dot (RCDs) is developed using glutathione (GSH) as the precursor. Then, the RCDs@MIL-100 self-assemblies are obtained using RCDs, FeCl₃ , and trimesic acid solutions as raw materials. After the RCDs@MIL-100 enters the TME, a high concentration of GSH reduces Fe³⁺ to Fe²⁺ and drains the GSH, triggering the collapse of RCDs@MIL-100 skeleton and the release of RCDs and Fe²⁺ , at which time the RCDs fluorescence is restored and in an "on" state to illuminate the tumor cells, which achieved cancer imaging. The released Fe²⁺ reacts with H₂ O₂ in the TME to form highly reactive hydroxyl radicals (•OH) by Fenton reaction, which achieves the chemodynamic therapy of tumors. Thus, efficient synergistic chemodynamic-photothermal dual mode therapy is achieved under fluorescence imaging guidance with TME response.

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.

Dynamic nano-assemblies based on two-dimensional inorganic nanoparticles: Construction and preclinical demonstration

Dynamic drug delivery systems (DDSs) have the ability of transforming their morphology and functionality in response to the biological microenvironments at the disease site and/or external stimuli, show spatio-temporally controllable drug delivery, and enhance the treatment efficacy. Due to the large surface area and modification flexibility, two-dimensional (2D) inorganic nanomaterials are being increasingly exploited for developing intelligent DDSs for biomedical applications. In this review, we summarize the engineering methodologies used to construct transformable 2D DDSs, including changing compositions, creating defects, and surface dot-coating with polymers, biomolecules, or nanodots. Then we present and discuss dynamic inorganic 2D DDSs whose transformation is driven by the diseased characteristics, such as pH gradient, redox, hypoxia, and enzyme in the tumor microenvironment as well as the external stimuli including light, magnetism, and ultrasound. Finally, the limitations and challenges of current transformable inorganic DDSs for clinical translation and their in vivo safety assessment are discussed.

Nanomedicine in Pancreatic Cancer: Current Status and Future Opportunities for Overcoming Therapy Resistance

Simple Summary

Despite access to a vast arsenal of anticancer agents, many fail to realise their full therapeutic potential in clinical practice. One key determinant of this is the evolution of multifaceted resistance mechanisms within the tumour that may either pre-exist or develop during the course of therapy. This is particularly evident in pancreatic cancer, where limited responses to treatment underlie dismal survival rates, highlighting the urgent need for new therapeutic approaches. Here, we discuss the major features of pancreatic tumours that contribute to therapy resistance, and how they may be alleviated through exploitation of the mounting and exciting promise of nanomedicines; a unique collection of nanoscale platforms with tunable and multifunctional capabilities that have already elicited a widespread impact on cancer management.

Abstract

The development of drug resistance remains one of the greatest clinical oncology challenges that can radically dampen the prospect of achieving complete and durable tumour control. Efforts to mitigate drug resistance are therefore of utmost importance, and nanotechnology is rapidly emerging for its potential to overcome such issues. Studies have showcased the ability of nanomedicines to bypass drug efflux pumps, counteract immune suppression, serve as radioenhancers, correct metabolic disturbances and elicit numerous other effects that collectively alleviate various mechanisms of tumour resistance. Much of this progress can be attributed to the remarkable benefits that nanoparticles offer as drug delivery vehicles, such as improvements in pharmacokinetics, protection against degradation and spatiotemporally controlled release kinetics. These attributes provide scope for precision targeting of drugs to tumours that can enhance sensitivity to treatment and have formed the basis for the successful clinical translation of multiple nanoformulations to date. In this review, we focus on the longstanding reputation of pancreatic cancer as one of the most difficult-to-treat malignancies where resistance plays a dominant role in therapy failure. We outline the mechanisms that contribute to the treatment-refractory nature of these tumours, and how they may be effectively addressed by harnessing the unique capabilities of nanomedicines. Moreover, we include a brief perspective on the likely future direction of nanotechnology in pancreatic cancer, discussing how efforts to develop multidrug formulations will guide the field further towards a therapeutic solution for these highly intractable tumours.

Manipulating Intratumoral Fenton Chemistry for Enhanced Chemodynamic and Chemodynamic-Synergized Multimodal Therapy

Chemodynamic therapy (CDT) uses the tumor microenvironment-assisted intratumoral Fenton reaction for generating highly toxic hydroxyl free radicals (•OH) to achieve selective tumor treatment. However, the limited intratumoral Fenton reaction efficiency restricts the therapeutic efficacy of CDT. Recent years have witnessed the impressive development of various strategies to increase the efficiency of intratumoral Fenton reaction. The introduction of these reinforcement strategies can dramatically improve the treatment efficiency of CDT and further promote the development of enhanced CDT (ECDT)-based multimodal anticancer treatments. In this review, the authors systematically introduce these reinforcement strategies, from their basic working principles, reinforcement mechanisms to their representative clinical applications. Then, ECDT-based multimodal anticancer therapy is discussed, including how to integrate these emerging Fenton reinforcement strategies for accelerating the development of multimodal anticancer therapy, as well as the synergistic mechanisms of ECDT and other treatment methods. Eventually, future direction and challenges of ECDT and ECDT-based multimodal synergistic therapies are elaborated, highlighting the key scientific problems and unsolved technical bottlenecks to facilitate clinical translation.

Fenton Metal Nanomedicines for Imaging-guided Combinatorial Chemodynamic Therapy against Cancer

Chemodynamic therapy (CDT) is considered as a promising modality for selective cancer therapy, which is realized via Fenton reaction-mediated decomposition of endogenous H₂O₂ to produce toxic hydroxyl radical (•OH) for tumor ablation. While extensive efforts have been made to develop CDT-based therapeutics, their in vivo efficacy is usually unsatisfactory due to poor catalytic activity limited by tumor microenvironment, such as anti-oxidative systems, insufficient H₂O₂, and mild acidity. To mitigate these issues, we have witnessed a surge in the development of CDT-based combinatorial nanomedicines with complementary or synergistic mechanisms for enhanced tumor therapy. By virtue of their bio-imaging capabilities, Fenton metal nanomedicines (FMNs) are equipped with intrinsic properties of imaging-guided tumor therapies. In this critical review, we summarize recent progress of this field, focusing on FMNs for imaging-guided combinatorial tumor therapy. First, various Fenton metals with inherent catalytic performances and imaging properties, including Fe, Cu and Mn, were introduced to illustrate their possible applications for tumor theranostics. Then, CDT-based combinatorial systems were reviewed by incorporating many other treatment means, including chemotherapy, photodynamic therapy (PDT), sonodynamic therapy (SDT), photothermal therapy (PTT), starvation therapy and immunotherapy. Next, various imaging approaches based on Fenton metals were presented in detail. Finally, challenges are discussed, and future prospects are speculated in the field to pave way for future developments.

Construction of a Single-Atom Nanozyme for Enhanced Chemodynamic Therapy and Chemotherapy

To fulfill the demand of precision and personalized medicine, single-atom catalysts (SACs) have emerged as a frontier in biomedical fields due to enzyme-mimic catalysis. Herein, we present a biocompatible and versatile nanoagent consisting of single-atom iron-containing nanoparticles (SAF NPs), DOX and A549 cell membrane (CM). The designed porous iron-based SACs originally served as a drug-carrying nanoplatform to release DOX selectively in a tumor microenvironment (TME) for chemotherapy (CT) due to their high loading capacity (155 %) for DOX; this signifies that SACs are promising candidates for universal cargo delivery. Besides, the designed single-atom nanoagent can perform like peroxidase, which effectively triggers an in situ tumor-specific Fenton reaction to generate abundant toxic hydroxyl radicals (⋅OH) selectively in the acidic TME for chemodynamic therapy (CDT). With the combination of CDT and CT, the constructed SAF NPs@DOX@CM nanoagent demonstrates better in vivo therapeutic performance than single-pathway therapy. In the meantime, after modification with CM, SAF NPs@DOX@CM can achieve homologous binding to target tumor tissues and avoid early clearance. This study presents a type of multifunctional SACs for enhanced cancer treatment via the capacity of a drug carrier combined with the enzymatic therapies of single-atom catalytic sites.

Chemodynamic nanomaterials for cancer theranostics

It is of utmost urgency to achieve effective and safe anticancer treatment with the increasing mortality rate of cancer. Novel anticancer drugs and strategies need to be designed for enhanced therapeutic efficacy. Fenton- and Fenton-like reaction-based chemodynamic therapy (CDT) are new strategies to enhance anticancer efficacy due to their capacity to generate reactive oxygen species (ROS) and oxygen (O2). On the one hand, the generated ROS can damage the cancer cells directly. On the other hand, the generated O2 can relieve the hypoxic condition in the tumor microenvironment (TME) which hinders efficient photodynamic therapy, radiotherapy, etc. Therefore, CDT can be used together with many other therapeutic strategies for synergistically enhanced combination therapy. The antitumor applications of Fenton- and Fenton-like reaction-based nanomaterials will be discussed in this review, including: (iþ) producing abundant ROS in-situ to kill cancer cells directly, (ii) enhancing therapeutic efficiency indirectly by Fenton reaction-mediated combination therapy, (iii) diagnosis and monitoring of cancer therapy. These strategies exhibit the potential of CDT-based nanomaterials for efficient cancer therapy.

Which is Better for Nanomedicines: Nanocatalysts or Single-Atom Catalysts?

With the rapid advancements in nanotechnology and materials science, numerous nanomaterials have been used as catalysts for nanomedical applications. Their design and modification according to the microenvironment of diseases have been shown to achieve effective treatment. Chemists are in pursuit of nanocatalysts that are more efficient, controllable, and less toxic by developing innovative synthetic technologies and improving existing ones. Recently, single-atom catalysts (SACs) with excellent catalytic activity and high selectivity have attracted increasing attention because of their accurate design as nanomaterials at the atomic level, thereby highlighting their potential for nanomedical applications. In this review, the recent advances in nanocatalysts and SACs are briefly summarized according to their synthesis, characterizations, catalytic mechanisms, and nanomedical applications. The opportunities and future scope for their development and the issues and challenges for their application as nanomedicine are also discussed. As far as it is known, the review is the systematic comparison of nanocatalysts and SACs, especially in the field of nanomedicine, which has promoted the development of nanocatalytic medicine.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.