Cancer Treatment through Nanoparticle-Facilitated Fenton Reaction

Research Progress of Micro/Nanomotors for Cancer Treatment

Nanomaterials have been widely used in cancer treatment and have achieved remarkable results. However, the specificity of the tumor microenvironment and a series of biological barriers (such as blood flow, cell membrane, dense tissue, etc.) have caused many obstacles faced by nanomaterials after entering the human body, which makes traditional drug delivery vehicles have insurmountable difficulties, such as low delivery efficiency, poor permeability, etc. The micro/nanomotors with autonomous movement capabilities provide the possibility to solve the above problems. Therefore, this review summarizes the current researches of micro/nanomotors strategies to overcome the different biological barriers of nanomaterials in cancer treatment. The advantages and disadvantages of three typical micro/nanomotors (biological, physical and chemical micro/nanomotors) in cancer treatment are summarized separately, and the future design of micro/nanomotors more suitable for tumor environment was discussed.

Rational design of nanomedicine for photothermal-chemodynamic bimodal cancer therapy

Given the diversity, complexity, and heterogeneity of persistent tumors, traditional nanoscale monotherapeutic systems suffer from dissatisfactory curative efficiency with incidence of metastasis or relapse. In parallel, the trend of clinical research on the basis of nanomedicines has increasingly shifted from monotherapy toward combinatorial therapy for admirable synergetic performances. In this regard, cutting-edge nanomedicines harnessing photothermal-chemodynamic bimodal therapy (PTT/CDT) have opened up a highly-efficient and relatively-safe cancer theranostic paradigm. Still, the integration of PTT/CDT functional units into one nanomedicine remains a herculean but meaningful task to achieve notable super-additive effects. This review aims to elucidate underlying synergistic interactions of PTT/CDT and highlight intriguing designs of nanomedicines for PTT/CDT including nanomaterial selection, performance optimization, multimodal therapy, visualization strategies, and targeting strategies. Furthermore, an outlook on further improvements of PTT/CDT is provided, emphasizing significant scientific issues that require remediation for clinical translation. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

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.

Recent Advances in Nanomaterial-Assisted Combinational Sonodynamic Cancer Therapy

Ultrasound (US)-triggered sonodynamic therapy (SDT), as a promising noninvasive therapeutic modality, has received ever-increasing attention in recent years. Its specialized chemical agents, named sonosensitizers, are activated by low-intensity US to produce lethal reactive oxygen species (ROS) for oncotherapy. Compared with phototherapeutic strategies, SDT provides many noteworthy opportunities and benefits, such as deeper penetration depth, absence of phototoxicity, and fewer side effects. Nevertheless, previous studies have also demonstrated its intrinsic limitations. Thanks to the facile engineering nature of nanotechnology, numerous novel nanoplatforms are being applied in this emerging field to tackle these intrinsic barriers and achieve continuous innovations. In particular, the combination of SDT with other treatment strategies has demonstrated a superior efficacy in improving anticancer activity relative to that of monotherapies alone. Therefore, it is necessary to summarize the nanomaterial-assisted combinational sonodynamic cancer therapy applications. Herein, the design principles in achieving synergistic therapeutic effects based on nanomaterial engineering methods are highlighted. The ultimate goals are to stimulate the design of better-quality combined sonodynamic treatment schemes and provide innovative ideas for the perspectives of SDT in promoting its future transformation to clinical application.

A pH-Responsive Polymer-CeO2 Hybrid to Catalytically Generate Oxidative Stress for Tumor Therapy

Catalytic generation of reactive oxygen species has been developed as a promising methodology for tumor therapy. Direct O₂^•- production from intratumor oxygen exhibits exceptional tumor therapeutic efficacy. Herein, this therapy strategy is demonstrated by a pH-responsive hybrid of porous CeO₂ nanorods and sodium polystyrene sulfonate that delivers high oxidative activity for O₂^•- generation within acidic tumor microenvironments for chemodynamic therapy and only limited oxidative activity in neutral media to limit damage to healthy organs. The hydrated polymer-nanorod hybrids with large hydrodynamic diameters form nanoreactors that locally trap oxygen and biological substrates inside and improve the charge transfer between the catalysts and substrates in the tumor microenvironment, leading to enhanced catalytic O₂^•- production and consequent oxidation. Together with successful in vitro and in vivo experiments, these data show that the use of hybrids provides a compelling opportunity for the delivery selective chemodynamic tumor therapy.

Smart Porous Core-Shell Cuprous Oxide Nanocatalyst with High Biocompatibility for Acid-Triggered Chemo/Chemodynamic Synergistic Therapy

The rational integration of chemotherapy and hydroxyl radical (·OH)-mediated chemodynamic therapy (CDT) holds great potential for cancer treatment. Herein, a smart biocompatible nanocatalyst based on porous core-shell cuprous oxide nanocrystals (Cu₂ O-PEG (polyethylene glycol) NCs) is reported for acid-triggered chemo/chemodynamic synergistic therapy. The in situ formed high density of hydrophilic PEG outside greatly improves the stability and compatibility of NCs. The porosity of Cu₂ O-PEG NCs shows the admirable capacity of doxorubicin (DOX) loading (DOX@Cu₂ O-PEG NCs) and delivery. Excitingly, Cu (Cu^+/2+ ) and DOX can be controllably released from DOX@Cu₂ O-PEG NCs in a pH-responsive approach. The released Cu⁺ exerts Fenton-like catalytic activity to generate toxic ·OH from intracellular overexpressed hydrogen peroxide (H₂ O₂ ) for CDT via reactive oxygen species (ROS)-involved oxidative damage. Exactly, DOX can not only induce cell death for chemotherapy but also enhance CDT by self-supplying endogenous H₂ O₂ . After the intravenous injection, Cu₂ O-PEG NCs can effectively accumulate in tumor region via passive targeting improved by external high-density PEG shell. Additionally, the effect of boosted CDT combined with chemotherapy presents excellent in vivo antitumor ability without causing distinct systemic toxicity. It is believed that this smart nanocatalyst responding to the acidity provides a novel paradigm for site-specific cancer synergetic therapy.

Nanoplatform-based cascade engineering for cancer therapy

Various therapeutic techniques have been studied for treating cancer precisely and effectively, such as targeted drug delivery, phototherapy, tumor-specific catalytic therapy, and synergistic therapy, which, however, evoke numerous challenges due to the inherent limitations of these therapeutic modalities and intricate biological circumstances as well. With the remarkable advances of nanotechnology, nanoplatform-based cascade engineering, as an efficient and booming strategy, has been tactfully introduced to optimize these cancer therapies. Based on the designed nanoplatforms, pre-supposed cascade processes could be triggered under specific conditions to generate/deliver more therapeutic species or produce stronger tumoricidal effects inside tumors, aiming to achieve cancer therapy with increased anti-tumor efficacy and diminished side effects. In this review, the recent advances in nanoplatform-based cascade engineering for cancer therapy are summarized and discussed, with an emphasis on the design of smart nanoplatforms with unique structures, compositions and properties, and the implementation of specific cascade processes by means of endogenous tumor microenvironment (TME) resources and/or exogenous energy inputs. This fascinating strategy presents unprecedented potential in the enhancement of cancer therapies, and offers better controllability, specificity and effectiveness of therapeutic functions compared to the corresponding single components/functions. In the end, challenges and prospects of such a burgeoning strategy in the field of cancer therapy will be discussed, hopefully to facilitate its further development to meet the personalized treatment demands.

The Role of Carbonate in Catalytic Oxidations

CO₂, HCO₃^-, and CO₃^2- are present in all aqueous media at pH > 4 if no major effort is made to remove them. Usually the presence of CO₂/HCO₃^-/CO₃^2- is either forgotten or considered only as a buffer or proton transfer catalyst. Results obtained in the last decades point out that carbonates are key participants in a variety of oxidation processes. This was first attributed to the formation of carbonate anion radicals via the reaction OH^• + CO₃^2- → CO₃^•- + OH^-. However, recent studies point out that the involvement of carbonates in oxidation processes is more fundamental. Thus, the presence of HCO₃^-/CO₃^2- changes the mechanisms of Fenton and Fenton-like reactions to yield CO₃^•- directly even at very low HCO₃^-/CO₃^2- concentrations. CO₃^•- is a considerably weaker oxidizing agent than the hydroxyl radical and therefore a considerably more selective oxidizing agent. This requires reconsideration of the sources of oxidative stress in biological systems and might explain the selective damage induced during oxidative stress. The lower oxidation potential of CO₃^•- probably also explains why not all pollutants are eliminated in many advanced oxidation technologies and requires rethinking of the optimal choice of the technologies applied. The role of percarbonate in Fenton-like processes and in advanced oxidation processes is discussed and has to be re-evaluated. Carbonate as a ligand stabilizes transition metal complexes in uncommon high oxidation states. These high-valent complexes are intermediates in electrochemical water oxidation processes that are of importance in the development of new water splitting technologies. HCO₃^- and CO₃^2- are also very good hole scavengers in photochemical processes of semiconductors and may thus become key participants in the development of new processes for solar energy conversion. In this Account, an attempt to correlate these observations with the properties of carbonates is made. Clearly, further studies are essential to fully uncover the potential of HCO₃^-/CO₃^2- in desired oxidation processes.

Free radicals for cancer theranostics

Free radicals were generally regarded as highly reactive, transient and harmful species. In fact, some of the free radicals can also be inactive, long-lived and beneficial for our health. These properties of free radicals provide future possibilities for their application in various fields. Owning to their open-shell electronic structure, free radicals exhibit unique advantages in biomedical applications, such as high reactivity, photoacoustic and photothermal conversion ability, molecular magnetic. In this review, recent progress on free radicals and their applications in cancer theranostics are presented. Typical materials that exhibit controlled generation of free radicals and their applications for photodynamic therapy (PDT), chemodynamic therapy (CDT), sonodynamic therapy (SDT), gas therapy, hypoxic cancer treatment, photothermal therapy (PTT), photoacoustic imaging (PAI) and magnetic resonance imaging (MRI) are summarized and discussed.

A Metal-Polymer Hybrid Biomimetic System for use in the Chemodynamic-Enhanced Photothermal Therapy of Cancers

This article reports the fabrication of a smart biomimetic enzyme system, which incorporates a pH-responsive chemodynamic therapy (CDT) combined with a photothermal (PTT) therapy approach in resolving the high recurrence rate of deadly cancers. The resulting enzyme system comprises copper sulfide (CuS) nanoparticle (NP) cores as Fenton-like catalysts, and a photothermal-active generation 5 poly(amidoamine) (G5) dendrimer as a template for the entrapment of Cu NPs and the compression of glucose oxidase (GOD). GOD is introduced to produce H₂ O₂ necessary in the sequential Fenton-like reaction, and this generates hydroxyl radicals that kill the cancerous cells. Polyethylene glycol is added to the system to improve biocompatibility. Mechanism study suggests that the constructed CuS/G5-GOD-based system has a better Fenton-like catalytic activity than a Fe₃ O₄ -GOD-based system. This allows the further inhibition on the residual tumors from recurrence and metastasis through CDT after being treated by PTT. The developed smart nanoscale biomimetic system shows high efficiency for breast cancer suppression from recurrence and metastasis by combining PTT with a pH-responsive CDT. It has the potential to resolve the essential issue of cancer recurrence after its initial clinic treatment.

Progress of Iron-Based Nanozymes for Antitumor Therapy

Artificial nanoscale enzyme-mimics (nanozymes) are promising functional alternatives to natural enzymes and have aroused great interest due to their inherent in vivo stability, affordability, and high catalytic ability. Iron-based nanozymes are one of the most investigated synthetic nanomaterials with versatile enzyme-like catalytic properties and have demonstrated remarkable relevance to a variety of biomedical applications, especially biocatalytic therapy against tumor indications. Nevertheless, despite the recent advances in biology and nanotechnology, the therapeutic performance of iron-based nanozymes in vivo is still limited by technical issues such as low catalytic efficiency and lack of tumor specificity. In this mini review, we briefly summarized the representative studies of iron-based nanozymes, while special emphasis was placed on the current challenges and future direction regarding the therapeutic implementation of iron-based nanozymes for the development of advanced tumor therapies with improved availability and biosafety.

A pH-activated autocatalytic nanoreactor for self-boosting Fenton-like chemodynamic therapy

The emergence of hydroxyl radical (˙OH)-mediated chemodynamic therapy (CDT) by the Fenton or Fenton-like reaction holds great potential for improving anticancer efficacy. Herein, an activatable autocatalytic nanoreactor (HT@GOx-DMONs) was developed for self-boosting Fenton-like CDT via decorating Cu²⁺-based metal-organic frameworks (MOFs) on glucose oxidase (GOx)-loaded dendritic mesoporous organosilica nanoparticles (DMONs) for the first time. The obtained nanoreactor could prevent the premature leakage of Cu²⁺ and GOx in neutral physiological environments conducted by the gatekeeper of growing carboxylate MOF (HKUST-1), but the explosive release of agents was realized due to the activated degradation of external HKUST-1 in acidic condition of endo/lysosomes, which thereby endowed this nanoreactor with the performance of pH-triggered ˙OH generation driven by Cu⁺-mediated autocatalytic Fenton-like reaction. Excitingly, Cu²⁺-induced glutathione (GSH) depletion and GOx-catalyzed H₂O₂ self-sufficiency unlocked by acid dramatically enhanced ˙OH generation. As expected, the effect of self-amplified CDT based on Cu²⁺-containing HT@GOx-DMONs presented wonderful in vitro toxicity and in vivo antitumor ability without leading to significant side-effects. The resulting nanoreactor with GSH consumption and H₂O₂ self-supply activated by acid may provide a promising paradigm for on-demand CDT.

Amphiphilic phenylalanine derivatives that temporally generate reactive oxygen species from water in the presence of Au(iii) ions

Amphiphilic derivatives of phenylalanine (ADFs) have strong self-assembling propensities and yield low molecular weight hydrogels on multiple occassions. The interaction of ADFs with metal ions can result in the morphological changes in the self-assemblies. Herein, we report the interesting consequences of the interaction between four N-protected ADFs with Au(iii) ions. In the case of ADF 1, the original nanofibrillar morphology of the self-assemblies spontaneously transformed into uniform nanoglobules of ∼80 nm in diameter upon addition of Au(iii) ions. A subsequent reduction of the Au(iii) ions to Au(0) nanoparticles (AuNPs) and the surface decoration of the nanoglobules with AuNPs were observed in the course of the next six to eight hours. Simultaneously, multiple reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂), hydroxyl radicals (˙OH), singlet oxygen and superoxide ions were also found to be present in the reaction medium. These ROS originate from water used as the reaction medium. The ROS production and the reduction of Au(iii) were inhibited upon deaeration of the reaction medium and the use of heavy water (D₂O) or organic solvents as the reaction medium, while an increase in the pH of the aqueous medium intensified both these processes. We exploited the temporal ROS generation using the mixture of 1 and Au(iii) ions towards anticancer therapy by enhancing the intracellular ROS levels. It is expected that this effort can be expanded into a viable anticancer therapy in the near future by modulating the amount and the rate of ROS-generation through judicious choice of the peptidic ligands and metal ions.

Functional gadolinium-based nanoscale systems for cancer theranostics

Cancer theranostics is a new strategy for combating cancer that integrates cancer imaging and treatment through theranostic agents to provide an efficient and safe way to improve cancer prognosis. Design and synthesis of these cancer theranostic agents are crucial since these agents are required to be biocompatible, tumor-specific, imaging distinguishable and therapeutically efficacious. In this regard, several types of gadolinium (Gd)-based nanomaterials have been introduced to combine different therapeutic agents with Gd to enhance the efficacy of therapeutic agents. At the same time, the entire treatment procedure could be monitored via imaging tools due to incorporation of Gd ions, Gd chelates and Gd/other imaging probes in the theranostic agents. This review aims to overview recent advances in the Gd-based nanomaterials for cancer theranostics and perspectives for Gd nanomaterial-based cancer theranostics are provided.

A Biomimetic Polymer Magnetic Nanocarrier Polarizing Tumor-Associated Macrophages for Potentiating Immunotherapy

The progress of antitumor immunotherapy is usually limited by tumor-associated macrophages (TAMs) that account for the highest proportion of immunosuppressive cells in the tumor microenvironment, and the TAMs can also be reversed by modulating the M2-like phenotype. Herein, a biomimetic polymer magnetic nanocarrier is developed with selectively targeting and polarizing TAMs for potentiating immunotherapy of breast cancer. This nanocarrier PLGA-ION-R837 @ M (PIR @ M) is achieved, first, by the fabrication of magnetic polymer nanoparticles (NPs) encapsulating Fe₃ O₄ NPs and Toll-like receptor 7 (TLR7) agonist imiquimod (R837) and, second, by the coating of the lipopolysaccharide (LPS)- treated macrophage membranes on the surface of the NPs for targeting TAMs. The intracellular uptake of the PIR @ M can greatly polarize TAMs from M2 to antitumor M1 phenotype with the synergy of Fe₃ O₄ NPs and R837. The relevant mechanism of the polarization is deeply studied through analyzing the mRNA expression of the signaling pathways. Different from previous reports, the polarization is ascribed to the fact that Fe₃ O₄ NPs mainly activate the IRF5 signaling pathway via iron ions instead of the reactive oxygen species-induced NF-κB signaling pathway. The anticancer effect can be effectively enhanced through potentiating immunotherapy by the polarization of the TAMs in the combination of Fe₃ O₄ NPs and R837.

Theranostic lyotropic liquid crystalline nanostructures for selective breast cancer imaging and therapy

Herein, we report the development of theranostic lyotropic liquid crystalline nanostructures (LCN's) loaded with unique MnO nanoparticles (MNPs) for selective cancer imaging and therapy. MNPs serves as a fluorescent agent as well as a source of manganese (Mn²⁺) and enables localized oxidative stress under the hallmarks of cancer (acidosis, high H₂O₂ level). In pursuit of synergistic amplification of Mn²⁺ antitumor activity, betulinic acid (BA) is loaded in LCN's. In this investigation, nano-architecture of LCN's phase interface is established via SAXS, Cryo-TEM and Cryo-FESEM. Intriguing in vitro studies showed that the LCN's triggered hydroxyl radical production and exhibited greater selective cytotoxicity in cancer cells, ensuring the safety of normal cells. Significant tumor ablation is realized by the 96.5 % of tumor growth inhibition index of LCN's as compared to control group. Key insights into on-site drug release, local anti-cancer response, and tumor location are gained through precise guidance of fluorescent MNPs. In addition, comprehensive assessment of the safety, pharmacokinetics and tumor distribution behavior of LCN's is performed in vivo or ex vivo. This work emphasizes the promise of modulating tumor microenvironment with smart endogenous stimuli sensitive nano systems to achieve advanced comprehensive cancer nano-theranostics without any external stimulus. STATEMENT OF SIGNIFICANCE: Effective diagnosis and treatment approaches with maximum anti-cancer activity and minimal side-effects are critical to ameliorate cancer therapy. Compared to radiation, photodynamic and photothermal therapy, the specific and selective activation of tumor microenvironmental endogenous stimuli for the logical generation of cytotoxic OH^· free radicals serves as an efficient therapeutic strategy for chemodynamic-cancer treatment. In this investigation, MnO nanoparticles fulfill two needs (fluorescence-based optical imaging and a source of Mn²⁺ based chemodynamic therapy) in one unit. This approach also ensures the safety of normal cells, as the toxic OH^· free radical activity is substantially suppressed under the mild alkaline/H₂O₂ conditions in normal cell microenvironment.

X-ray and NIR light dual-triggered mesoporous upconversion nanophosphor/Bi heterojunction radiosensitizer for highly efficient tumor ablation

Developing a multi-functional radiosensitizer with high efficiency and low toxicity remains challenging. Herein, we report a mesoporous heterostructure radiosensitizer (UCNP@NBOF-FePc-PFA) containing Lu-based upconversion nanophosphor (UCNP) and Bi-based nanomaterial loaded with iron phthalocyanine for X-ray and NIR light dual-triggered tri-modal tumor therapy. NaLuF₄:Yb,Tm, a Lu-based UCNP, offers radiosensitization and upconversion luminescence for optical bio-imaging. However, Bi has a higher X-ray mass attenuation coefficient than Lu. Thus, after stepwise fabrication, Na_0.2Bi_0.8O_0.35F_1.91:Yb (NBOF) was assembled with the UCNP to form a mesoporous heterostructure composite. This enhanced the radiosensitization effect and drug load to realize multi-modal tumor therapy. After coating it with folate-conjugated amphiphilic PEG (PFA), UCNP@NBOF-FePc-PFA realized tumor photothermal/photodynamic/radio-therapy. The structure of UCNP@NBOF-FePc-PFA was well characterized. Different properties triggered by X-ray and NIR light were evaluated. Finally, a highly efficient tumor ablation effect was demonstrated in vitro and in vivo. Consequently, this kind of nanocomposite provides a unique strategy for designing a theranostic platform for oncotherapy. STATEMENT OF SIGNIFICANCE: The synergy of enhanced radiotherapy and photothermal/photodynamic therapy is found to improve tumor therapeutic efficacy. On that basis, a heterostructure nanohybrid containing Lu-based UCNP and Bi-based mesoporous material is synthesized. The heterostructure nanohybrid can be loaded with FePc and decorated with folate-modified amphiphilic PEG to form a multi-functional theranostic nano-platform. The platform exhibits upconversion luminescence capacity, X-ray attenuation property, photothermal effect, and X-ray and NIR dual-light triggered ROS generation capability. These features can not only enable upconversion luminescence/CT bioimaging of living beings but also be applied to the photothermal/photodynamic/radio- synergistic tumor ablation. To sum up, the nanomaterial offers a novel method for the construction of a new theranostic platform.

Endogenous Labile Iron Pool-Mediated Free Radical Generation for Cancer Chemodynamic Therapy

Current chemodynamic therapy (CDT) primarily relies on the delivery of transition metal ions with Fenton activity to trigger hydroxyl radical production from hydrogen peroxide. However, administration of an excess amount of exogenous Fenton-type heavy metals may cause potential adverse effects to human health, including acute and chronic damages. Here, we present a new CDT strategy that uses intracellular labile iron pool (LIP) as the endogenous source of Fenton-reactive metals for eliciting free radical generation, and the discovery of hydroperoxides (R'OOH) as an optimal LIP-mediated chemodynamic agent against cancer. By simulating the metabolic fates of peroxo compounds within cells, R'OOH was found to have excellent free radical-producing ability in the presence of labile iron(II) and to suffer only moderate elimination by glutathione/glutathione peroxidase, which contributes to its superior chemodynamic efficacy. The LIP-initiated nontoxic-to-toxic transition of R'OOH, together with increased LIP levels in tumor cells, enabled efficient and specific CDT of cancer. Moreover, pH/labile iron(II) cascade-responsive nanomedicines comprising encapsulated methyl linoleate hydroperoxide and LIP-increasing agent in pH-sensitive polymer particles were fabricated to realize enhanced CDT. This work not only paves the way to using endogenous Fenton-type metals for cancer therapy but also offers a paradigm for the exploration of high-performance chemodynamic agents activated by intracellular LIP.

Broaden sources and reduce expenditure: Tumor-specific transformable oxidative stress nanoamplifier enabling economized photodynamic therapy for reinforced oxidation therapy

Cancer cells immersed in inherent oxidative stress are more vulnerable to exogenous oxidative damages than normal cells. Reactive oxygen species (ROS)-mediated oxidation therapy preferentially aggravating tumor oxidative stress to disrupt redox homeostasis, has emerged as an effective and specific anticancer treatment. Herein, following an ingenious strategy of “broaden sources and reduce expenditure”, we designed a versatile tumor-specific oxidative stress nanoamplifier enabling economized photodynamic therapy (PDT), to achieve synergistic oxidative stress explosion for superior oxidation therapy.

Methods: Cinnamaldehyde (CA) as a therapeutic ROS generator was first conjugated to hyaluronic acid (HA) through acid-labile hydrazone bond to synthesize tailored amphiphilic HA@CA conjugates, which could surprisingly self-assemble into uniform nanofibers in aqueous media. Photosensitizer protoporphyrin (PpIX) was efficiently encapsulated into HA@CA nanofibers and transformed HA@CA nanofibers to final spherical HA@CAP.

Results: With beneficial pH-responsiveness and morphology transformation, improved bioavailability and selective tumor accumulation, HA@CAP combining ROS-based dual chemo/photodynamic treatment modalities could induce cytotoxic ROS generation in a two-pronged approach to amplify tumor oxidative stress, termed “broaden sources”. Moreover, utilizing CA-induced H₂O₂ production and cascaded Fenton reaction in mitochondria to consume intracellular overloaded Fe(II), HA@CAP could skillfully block endogenic heme biosynthesis pathway on site to restrain undesired elimination of PpIX for economized PDT, termed “reduce expenditure”. Both in vitro and in vivo results demonstrated the superior antitumor performance of HA@CAP.

Conclusion: This study offered an inspiring strategy of “broaden sources and reduce expenditure” to specifically boost tumor oxidative stress for reinforced oxidation therapy.

MicroRNA-874-3p Aggravates Doxorubicin-Induced Renal Podocyte Injury via Targeting Methionine Sulfoxide Reductase B3

Clinical application of doxorubicin (Dox) is limited due to its serious side effects including nephrotoxicity, and kidney podocytes play important roles in renal diseases. MicroRNAs (miRNAs) are critical regulators associated with human diseases. The purpose of this study was to explore a novel target in adjusting Dox-induced renal podocyte injury. Through a double luciferase reporter gene experiment, it was found that miR-874-3p directly targeted methionine sulfoxide reductase B3 (MsrB3). During the tests of miR-874-3p inhibitor and MsrB3 siRNA in human podocytes or miR-874-3p antagomir in mice, we found that the expression levels of downstream oxidative stress and apoptosis-related proteins were regulated by miR-874-3p/MsrB3 signal to alleviate or aggravate renal podocyte injury. The data in the present work showed that miR-874-3p aggravated Dox-caused renal podocyte injury by promoting apoptosis and oxidative damage via inhibiting MsrB3. Therefore, miR-874-3p/MsrB3 should be considered as a new therapeutic target in controlling renal podocyte injury induced by Dox.

Mussel-Inspired Polydopamine: The Bridge for Targeting Drug Delivery System and Synergistic Cancer Treatment

Polydopamine (PDA), a mussel-inspired molecule, has been recognized as attractive in cancer therapy due to a number of inherent advantages, such as good biocompatibility, outstanding drug-loading capacity, degradability, superior photothermal conversion efficiency, and low tissue toxicity. Furthermore, due to its strong adhesive property, PDA is able to functionalize various nanomaterials, facilitating the construction of a PDA-based multifunctional platform for targeted or synergistic therapy. Herein, recent PDA research, including targeted drug delivery, single-mode therapy, and diverse synergistic therapies against cancer, are summarized and discussed. For synergistic therapy, advanced developments are highlighted, such as photothermal/radiotherapy, chemo-/photothermal/gene therapy, photothermal/immune therapy, and photothermal/photodynamic/immune therapy. Finally, the challenges and promise of PDA for biomedical applications in the future are discussed.

A Glucose/Oxygen-Exhausting Nanoreactor for Starvation- and Hypoxia-Activated Sustainable and Cascade Chemo-Chemodynamic Therapy

Fenton reaction-mediated chemodynamic therapy (CDT) can kill cancer cells via the conversion of H₂ O₂ to highly toxic HO•. However, problems such as insufficient H₂ O₂ levels in the tumor tissue and low Fenton reaction efficiency severely limit the performance of CDT. Here, the prodrug tirapazamine (TPZ)-loaded human serum albumin (HSA)-glucose oxidase (GOx) mixture is prepared and modified with a metal-polyphenol network composed of ferric ions (Fe³⁺ ) and tannic acid (TA), to obtain a self-amplified nanoreactor termed HSA-GOx-TPZ-Fe³⁺ -TA (HGTFT) for sustainable and cascade cancer therapy with exogenous H₂ O₂ production and TA-accelerated Fe³⁺ /Fe²⁺ conversion. The HGTFT nanoreactor can efficiently convert oxygen into HO• for CDT, consume glucose for starvation therapy, and provide a hypoxic environment for TPZ radical-mediated chemotherapy. Besides, it is revealed that the nanoreactor can significantly elevate the intracellular reactive oxygen species content and hypoxia level, decrease the intracellular glutathione content, and release metal ions in the tumors for metal ion interference therapy (also termed "ion-interference therapy" or "metal ion therapy"). Further, the nanoreactor can also increase the tumor's hypoxia level and efficiently inhibit tumor growth. It is believed that this tumor microenvironment-regulable nanoreactor with sustainable and cascade anticancer performance and excellent biosafety represents an advance in nanomedicine.

A smart theranostic agent based on Fe-HPPy@Au/DOX for CT imaging and PTT/chemotherapy/CDT combined anticancer therapy

We herein explored a smart Fe-HPPy@Au/DOX theranostic agent for CT diagnosis and PTT/chemotherapy/CDT synergistic treatment of cancer. When the Fe-HPPy@Au/DOX theranostic agent entered the tumor, the tumor environment accelerated the trapped Fe ions release to catalyze the production of ˙OH for CDT. NIR irradiation drove the PTT, and at the same time improved the CDT by increasing the production of ˙OH and triggered DOX release for chemotherapy. In addition, the Au nanoparticles on the surface of Fe-HPPy@Au nanocomposites could be used as a CT imaging agent and catalyzer to produce H₂O₂ for enhanced CDT.

Recent Advances in Nanostrategies Capable of Overcoming Biological Barriers for Tumor Management

Engineered nanomaterials have been extensively employed as therapeutics for tumor management. Meanwhile, the complex tumor niche along with multiple barriers at the cellular level collectively hinders the action of nanomedicines. Here, the advanced strategies that hold promise for overcoming the numerous biological barriers facing nanomedicines are summarized. Starting from tumor entry, methods that promote tissue penetration of nanomedicine and address the hypoxia issue are also highlighted. Then, emphasis is given to the significance of overcoming both physical barriers, such as membrane-associated efflux pumps, and biological features, such as resistance to apoptosis. The pros and cons for an individual approach are presented. In addition, the associated technical problems are discussed, along with the importance of balancing the therapeutic merits and the additional cost of sophisticated nanomedicine designs.

Marriage of black phosphorus and Cu2+ as effective photothermal agents for PET-guided combination cancer therapy

The use of photothermal agents (PTAs) in cancer photothermal therapy (PTT) has shown promising results in clinical studies. The rapid degradation of PTAs may address safety concerns but usually limits the photothermal stability required for efficacious treatment. Conversely, PTAs with high photothermal stability usually degrade slowly. The solutions that address the balance between the high photothermal stability and rapid degradation of PTAs are rare. Here, we report that the inherent Cu²⁺-capturing ability of black phosphorus (BP) can accelerate the degradation of BP, while also enhancing photothermal stability. The incorporation of Cu²⁺ into BP@Cu nanostructures further enables chemodynamic therapy (CDT)-enhanced PTT. Moreover, by employing ⁶⁴Cu²⁺, positron emission tomography (PET) imaging can be achieved for in vivo real-time and quantitative tracking. Therefore, our study not only introduces an “ideal” PTA that bypasses the limitations of PTAs, but also provides the proof-of-concept application of BP-based materials in PET-guided, CDT-enhanced combination cancer therapy.

A balance between high stability and rapid degradation is required for effective photothermal anti-cancer agents. Here, the authors use Cu²⁺ to accelerate the degradation of black phosphorus nanosheets while enhancing its photothermal ability and apply this material for PET-guided, CDT-enhanced combination cancer therapy in mice.

Designing Stimuli-Responsive Upconversion Nanoparticles that Exploit the Tumor Microenvironment

Tailoring personalized cancer nanomedicines demands detailed understanding of the tumor microenvironment. In recent years, smart upconversion nanoparticles with the ability to exploit the unique characteristics of the tumor microenvironment for precise targeting have been designed. To activate upconversion nanoparticles, various bio-physicochemical characteristics of the tumor microenvironment, namely, acidic pH, redox reactants, and hypoxia, are exploited. Stimuli-responsive upconversion nanoparticles also utilize the excessive presence of adenosine triphosphate (ATP), riboflavin, and Zn²⁺ in tumors. An overview of the design of stimulus-responsive upconversion nanoparticles that precisely target and respond to tumors via targeting the tumor microenvironment and intracellular signals is provided. Detailed understanding of the tumor microenvironment and the personalized design of upconversion nanoparticles will result in more effective clinical translation.

Metal-Organic Frameworks with Enhanced Photodynamic Therapy: Synthesis, Erythrocyte Membrane Camouflage, and Aptamer-Targeted Aggregation

Here, ferric oxide-loaded metal-organic framework (FeTCPP/Fe₂O₃ MOF) nanorice was designed and constructed by the liquid diffusion method. The introduction of iron metal nodes and the loading of Fe₂O₃ can effectively catalyze the Fenton reaction to produce hydroxyl radicals (^•OH) and overcome the hypoxic environment of tumor tissue by generating oxygen. The monodispersity and porosity of the porphyrin photosensitizers in the MOF structure exposed more active sites, which promoted energy exchange between porphyrin molecules and oxygen molecules for photodynamic therapy (PDT) treatment. Therefore, the generated hydroxyl radicals and singlet oxygen (¹O₂) can synergistically act on tumor cells to achieve the purpose of improving tumor therapy. Then the erythrocyte membrane was camouflaged to enhance blood circulation and tissue residence time in the body, and finally, the targeted molecule AS1411 aptamer was modified to achieve the high enrichment of MOF photosensitizers on a tumor domain. As a result, the MOF nanorice camouflaged by the erythrocyte membrane can effectively reduce side effects and improve the therapeutic effect of PDT and chemo-dynamic therapy (CDT). The study not only improved the efficacy of PDT and CDT in essence from the MOF nanorice but also used the camouflage method to further concentrate FeTCPP/Fe₂O₃ on the tumor sites, achieving the goal of multiple gains. These results will provide theoretical and practical directions for the development of tumor-targeted MOF nanomaterials.

Blocking ACAT-1 Activity for Tumor Therapy with Fluorescent Hyperstar Polymer-Encapsulated Avasimible

Targeting the distinct cholesterol metabolism of tumor cells is proposed as a novel way to treat tumors. Blocking acyl-CoA cholesterol acyltransferase-1 (ACAT-1) by the inhibitor avasimible (Ava), which elevates intracellular free cholesterol levels, is shown to effectively induce apoptosis. However, Ava faces disadvantages of poor water solubility, a short half-life, and no capability for fluorescence detection, which have greatly limited its application. Herein, a fluorescent hyperstar polymer (FHSP) is developed to encapsulate Ava to improve its ability to inhibit HeLa cells and K562 cells. The results of this study show that the obtained Ava-FHSP micelles possess a high drug loading capacity of 22.7% and bright green fluorescence. Ava and Ava-FHSP are cytotoxic to both HeLa and K562 cells and cause reductions in cell size, nuclear lysis, and chromatin condensation and hindered proliferation of both cell types by causing S phase cell cycle arrest. Further mechanistic analysis indicates that Ava-FHSP reduces the protein and messenger RNA expression of ACAT-1 and significantly increases intracellular free cholesterol levels, which can increase endoplasmic reticulum stress and finally cause cell apoptosis. All these results suggest that this fluorescent hyperstar polymer represents a potential therapeutic tumor strategy by changing the cholesterol metabolism of tumor cells.

Au2Pt-PEG-Ce6 nanoformulation with dual nanozyme activities for synergistic chemodynamic therapy / phototherapy

Although synergistic therapy for tumors has displayed significant promise for effective treatment of cancer, developing a simple and effective strategy to build a multi-functional nanoplatform is still a huge challenge. By virtue of the characteristics of tumor microenvironment, such as hypoxia, slight acidity and H₂O₂ overexpression, Au₂Pt-PEG-Ce6 nanoformulation is constructed for collaborative chemodynamic/phototherapy of tumors. Specifically, the Au₂Pt nanozymes with multiple functions are synthesized in one step at room temperature. The photosensitizer chlorin e6 (Ce6) is covalently linked to Au₂Pt nanozymes for photodynamic therapy (PDT). Interestingly, the Au₂Pt nanozymes possess catalase- and peroxidase-like activities simultaneously, which not only can generate O₂ for relaxation of tumor hypoxia and enhancement of PDT efficiency but also can produce ∙OH for chemodynamic therapy (CDT). In addition, the high photothermal conversion efficiency (η = 31.5%) of Au₂Pt-PEG-Ce6 nanoformulation provides the possibility for photoacoustic (PA) and photothermal (PT) imaging guided photothermal therapy (PTT). Moreover, the presence of high-Z elements (Au and Pt) in Au₂Pt-PEG-Ce6 nanoformulation endows it with the ability to act as an X-ray computed tomography (CT) imaging contrast agent. All in all, the Au₂Pt-PEG-Ce6 exhibits great potential in multimodal imaging-guided synergistic PTT/PDT/CDT with remarkably tumor specificity and enhanced therapy.

Metal-Based Nanocatalyst for Combined Cancer Therapeutics

As a classical nanocatalyst-based therapeutic modality, chemodynamic therapy (CDT) has received more and more attention. To improve the therapeutic efficacy of CDT, various metal-based nanocatalysts have been designed and constructed to catalyze the Fenton or Fenton-like reaction in the past few years. However, the therapeutic efficacy of certain CDT is still restricted by the tumor microenvironment, such as limited concentration of intracellular H₂O₂, inappropriate pH condition, as well as overexpressed glutathione (GSH). Therefore, many other therapeutic modalities, such as photodynamic therapy (PDT), photothermal therapy (PTT), starvation therapy, chemotherapy, and gas therapy, have been utilized to combine with CDT for increasing the tumor treatment performance. In this review, we summarized the development of combinatory therapeutic modalities based on CDT in recent years.

"Watson-Crick G[triple bond, length as m-dash]C"-inspired supramolecular nanodrug of methotrexate and 5-fluorouracil for tumor microenvironment-activatable self-recognizing synergistic chemotherapy

Carrier-free nanodrugs, generated via the straightforward small-molecule self-assembly of anticancer drugs, provide a promising route for cancer chemotherapy. However, their low structural stability, lack of targeting specificity, and poor stimulus responsiveness are still limiting their therapeutic effect. Inspired by Watson-Crick G[triple bond, length as m-dash]C base pairing, the FDA-approved chemo-drug methotrexate (MTX, which can bind with folate receptors) and 5-fluorouracil (5-FU, a DNA/RNA synthetase inhibitor) were adopted for direct assembly into self-recognizing MTX-5-FU nanoparticles via "Watson-Crick-like base pairing"-driven precise supramolecular assembly. Sequentially, our synthesized weak acidity-responsive polyethylene glycol (PEG) was inserted onto the nanoparticle surface to temporarily shield the self-targeting function of MTX and prolong the blood circulation time. Once PEG-MTX-5-FU nanoparticles reached the weakly acidic tumor microenvironment, the PEG corona could be cleaved from their surface and then MTX could be re-exposed to recover its self-recognition ability and significantly elevate tumor cell uptake; furthermore, the de-PEGylated MTX-5-FU nanoparticles could respond to the stronger acidity of lysosome, triggering core disassembly and thus the burst release of both MTX and 5-FU. Further in vitro and in vivo studies consistently confirmed that the nanodrugs exhibited preferable accumulation at the tumor sites with highly synergistic chemotherapeutic effects. The supramolecular recognition-inspired, cascade-triggered self-targeting and controlled release of nanodrugs could be a promising strategy to improve synergistic chemotherapy.

One Stone Two Birds: Zr-Fc Metal-Organic Framework Nanosheet for Synergistic Photothermal and Chemodynamic Cancer Therapy

Metal-organic frameworks (MOFs) have been identified as promising materials for the delivery of therapeutics to cure cancer owing to their intrinsic porous structure. However, in a majority of cases, MOFs act as only a delivery cargo for anticancer drugs while little attention has been focused on the utilization of their intriguing physical and chemical properties for potential anticancer purposes. Herein for the first time, an ultrathin (16.4 nm thick) ferrocene-based MOF (Zr-Fc MOF) nanosheet has been synthesized for synergistic photothermal therapy (PTT) and Fenton reaction-based chemodynamic (CDT) therapy to cure cancer without additional drugs. The Zr-Fc MOF nanosheet acts not only as an excellent photothermal agent with a prominent photothermal conversion efficiency of 53% at 808 nm but also as an efficient Fenton catalyst to promote the conversion of H₂O₂ into hydroxyl radical (^•OH). As a consequence, an excellent therapeutic performance has been achieved in vitro as well as in vivo through this combinational effect. This work aims to construct an "all-in-one" MOF nanoplatform for PTT and CDT treatments without incorporating any additional therapeutics, which may launch a new era in the investigation of MOF-based synergistic therapy platforms for cancer therapy.

Structure of a Zinc Porphyrin-Substituted Bacterioferritin and Photophysical Properties of Iron Reduction

The iron storage protein bacterioferritin (Bfr) binds up to 12 hemes b at specific sites in its protein shell. The heme b can be substituted with the photosensitizer Zn(II)-protoporphyrin IX (ZnPP), and photosensitized reductive iron release from the ferric oxyhydroxide {[FeO(OH)]n} core inside the ZnPP-Bfr protein shell was demonstrated [Cioloboc, D., et al. (2018) Biomacromolecules 19, 178-187]. This report describes the X-ray crystal structure of ZnPP-Bfr and the effects of loaded iron on the photophysical properties of the ZnPP. The crystal structure of ZnPP-Bfr shows a unique six-coordinate zinc in the ZnPP with two axial methionine sulfur ligands. Steady state and transient ultraviolet-visible absorption and luminescence spectroscopies show that irradiation with light overlapping the Soret absorption causes oxidation of ZnPP to the cation radical ZnPP•+ only when the ZnPP-Bfr is loaded with [FeO(OH)]n. Femtosecond transient absorption spectroscopy shows that this photooxidation occurs from the singlet excited state (1ZnPP*) on the picosecond time scale and is consistent with two oxidizing populations of Fe3+, which do not appear to involve the ferroxidase center iron. We propose that [FeO(OH)]n clusters at or near the inner surface of the protein shell are responsible for ZnPP photooxidation. Hopping of the photoinjected electrons through the [FeO(OH)]n would effectively cause migration of Fe2+ through the inner cavity to pores where it exits the protein. Reductive iron mobilization is presumed to be a physiological function of Bfrs. The phototriggered Fe3+ reduction could be used to identify the sites of iron mobilization within the Bfr protein shell.

Janus γ-Fe2O3/SiO2-based nanotheranostics for dual-modal imaging and enhanced synergistic cancer starvation/chemodynamic therapy

Multimodal cancer synergistic therapy exhibited remarkable advantages over monotherapy in producing an improved therapeutic efficacy. In this work, Janus-type γ-Fe₂O₃/SiO₂ nanoparticles (JFSNs) are conjugated with glucose oxidase (GOx) for synergistic cancer starvation/chemodynamic therapy. The γ-Fe₂O₃ hemisphere of JFSNs can perform photoacoustic/T₂ magnetic resonance dual-modal imaging of tumors. GOx on the surface of JFSNs catalyzes the decomposition of glucose and produces H₂O₂ for cancer starvation therapy. Subsequently, the γ-Fe₂O₃ hemisphere catalyzes the disproportionation of H₂O₂ to generate highly reactive hydroxyl radicals in an acidic tumor microenvironment. The close distance between GOx and JFSNs ensures adequate contact between the γ-Fe₂O₃ hemisphere and its substrate H₂O₂, thus enhancing the catalytic efficiency. This synergy of glucose depletion, biotoxic H₂O₂ and hydroxyl radicals significantly suppresses 4T1 mammary tumor growth with minimal adverse effects.

An open source and reduce expenditure ROS generation strategy for chemodynamic/photodynamic synergistic therapy

The therapeutic effect of reactive oxygen species (ROS)-involved cancer therapies is significantly limited by shortage of oxy-substrates, such as hypoxia in photodynamic therapy (PDT) and insufficient hydrogen peroxide (H2O2) in chemodynamic therapy (CDT). Here, we report a H2O2/O2 self-supplying nanoagent, (MSNs@CaO2-ICG)@LA, which consists of manganese silicate (MSN)-supported calcium peroxide (CaO2) and indocyanine green (ICG) with further surface modification of phase-change material lauric acid (LA). Under laser irradiation, ICG simultaneously generates singlet oxygen and emits heat to melt the LA. The exposed CaO2 reacts with water to produce O2 and H2O2 for hypoxia-relieved ICG-mediated PDT and H2O2-supplying MSN-based CDT, acting as an open source strategy for ROS production. Additionally, the MSNs-induced glutathione depletion protects ROS from scavenging, termed reduce expenditure. This open source and reduce expenditure strategy is effective in inhibiting tumor growth both in vitro and in vivo, and significantly improves ROS generation efficiency from multi-level for ROS-involved cancer therapies.

Highly Efficient 2D NIR-II Photothermal Agent with Fenton Catalytic Activity for Cancer Synergistic Photothermal-Chemodynamic Therapy

Photothermal therapy (PTT) has emerged as a promising cancer therapeutic modality with high therapeutic specificity, however, its therapeutic effectiveness is limited by available high-efficiency photothermal agents (PTAs), especially in the second near-infrared (NIR-II) biowindow. Here, based on facile liquid-exfoliated FePS3 nanosheets, a highly efficient NIR-II PTA with its photothermal conversion efficiency of up to 43.3% is demonstrated, which is among the highest reported levels in typical PTAs. More importantly, such Fe-based 2D nanosheets also show superior Fenton catalytic activity facilitated by their ultrahigh specific surface area, simultaneously enabling cancer chemodynamic therapy (CDT). Impressively, the efficiency of CDT could be further remarkably enhanced by its photothermal effect, leading to cancer synergistic PTT/CDT. Both in vitro and in vivo studies reveal a highly efficient tumor ablation under NIR-II light irradiation. This work provides a paradigm for cancer CDT and PTT in the NIR-II biowindow via a single 2D nanoplatform with desired therapeutic effect. Furthermore, with additional possibilities for magnetic resonance imaging, photoacoustic tomography, as well as drug loading, this Fe-based 2D material could potentially serve as a 2D "all-in-one" theranostic nanoplatform.