Amino acid-based metallo-supramolecular nanoassemblies capable of regulating cellular redox homeostasis for tumoricidal chemo-/photo-/catalytic combination therapy

Nanozymes, as nanomaterials with natural enzyme activities, have been widely applied to deliver various therapeutic agents to synergistically combat the progression of malignant tumors. However, currently common inorganic nanozyme-based drug delivery systems still face challenges such as suboptimal biosafety, inadequate stability, and inferior tumor selectivity. Herein, a super-stable amino acid-based metallo-supramolecular nanoassembly (FPIC NPs) with peroxidase (POD)- and glutathione oxidase (GSHOx)-like activities was fabricated via Pt4+-driven coordination co-assembly of l-cysteine derivatives, the chemotherapeutic drug curcumin (Cur), and the photosensitizer indocyanine green (ICG). The superior POD- and GSHOx-like activities could not only catalyze the decomposition of endogenous hydrogen peroxide into massive hydroxyl radicals, but also deplete the overproduced glutathione (GSH) in cancer cells to weaken intracellular antioxidant defenses. Meanwhile, FPIC NPs would undergo degradation in response to GSH to specifically release Cur, causing efficient mitochondrial damage. In addition, FPIC NPs intrinsically enable fluorescence/photoacoustic imaging to visualize tumor accumulation of encapsulated ICG in real time, thereby determining an appropriate treatment time point for tumoricidal photothermal (PTT)/photodynamic therapy (PDT). In vitro and in vivo findings demonstrated the quadruple orchestration of catalytic therapy, chemotherapeutics, PTT, and PDT offers conspicuous antineoplastic effects with minimal side reactions. This work may provide novel ideas for designing supramolecular nanoassemblies with multiple enzymatic activities and therapeutic functions, allowing for wider applications of nanozymes and nanoassemblies in biomedicine.

Single-Walled (Magnetic) Carbon Nanotubes in a Pectin Matrix in the Design of an Allantoin Delivery System

Single-walled carbon nanotubes (SWCNTs) outperform other materials due to their high conductivity, large specific surface area, and chemical resistance. They have numerous biomedical applications, including the magnetization of the SWCNT (mSWCNT). The drug loading and release properties of see-through pectin hydrogels doped with SWCNTs and mSWCNTs were evaluated in this study. The active molecule in the hydrogel structure is allantoin, and calcium chloride serves as a cross-linker. In addition to mixing, absorption, and swelling techniques, drug loading into carbon nanotubes was also been studied. To characterize the films, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, surface contact angle measurements, and opacity analysis were carried out. Apart from these, a rheological analysis was also carried out to examine the flow properties of the hydrogels. The study was also expanded to include N-(9-fluorenyl methoxycarbonyl)glycine-coated SWCNTs and mSWCNTs as additives to evaluate the efficiency of the drug-loading approach. Although the CNT additive was used at a 1:1000 weight ratio, it had a significant impact on the hydrogel properties. This effect, which was first observed in the thermal properties, was confirmed in rheological analyses by increasing solution viscosity. Additionally, rheological analysis and drug release profiles show that the type of additive causes a change in the matrix structure. According to TGA findings, even though SWCNTs and mSWCNTs were not coated more than 5%, the coating had a significant effect on drug release control. In addition to all findings, cell viability tests revealed that hydrogels with various additives could be used for visual wound monitoring, hyperthermia treatment, and allantoin release in wound treatment applications.

Current advances in modulating tumor hypoxia for enhanced therapeutic efficacy

Hypoxia is a common feature of most solid tumors, which promotes the proliferation, invasion, metastasis, and therapeutic resistance of tumors. Researchers have been developing advanced strategies and nanoplatforms to modulate tumor hypoxia to enhance therapeutic effects. A timely review of this rapidly developing research topic is therefore highly desirable. For this purpose, this review first introduces the impact of hypoxia on tumor development and therapeutic resistance in detail. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are also systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We provide a detailed discussion of the rationale and research progress of these strategies. Through a review of current trends, it is hoped that this comprehensive overview can provide new prospects for clinical application in tumor treatment. STATEMENT OF SIGNIFICANCE: As a common feature of most solid tumors, hypoxia significantly promotes tumor progression. Advanced nanoplatforms have been developed to modulate tumor hypoxia to enhanced therapeutic effects. In this review, we first introduce the impact of hypoxia on tumor progression. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We discuss the rationale and research progress of the above strategies in detail, and finally introduce future challenges for treatment of hypoxic tumors. By reviewing the current trends, this comprehensive overview can provide new prospects for clinical translatable tumor therapy.

A "One Arrow Three Eagle" Strategy to Improve CM-272 Primed Bladder Cancer Immunotherapy

Immunotherapy using an immune-checkpoint blockade has significantly improved its therapeutic effects. CM-272, which is a novel epigenetic inhibitor of G9a, induces immunogenic cell death (ICD) for recovering the sensitivity to anti-PD-1 antibodies; however, the efficacy of CM-272 is greatly limited by promoting the transcription activity of HIF-1α to form a hypoxic environment. Here, a Fe3+ -based nanoscale metal-organic framework (MIL-53) is used to load CM-272 (ultra-high loading rate of 56.4%) for realizing an MIL-53@CM-272 nanoplatform. After entering bladder cancer cells, Fe3+ not only promotes the decomposition of H2 O2 into O2 for O2 -compensated sonodynamic therapy but reduces the high level of glutathione in the tumor microenvironment (TME) for enhancing reactive oxygen species, including ferroptosis and apoptosis. MIL-53 carriers can be degraded in response to the TME, accelerating the release of CM-272, which helps achieve the maximum effectiveness in an O2 -sufficient TME by attenuating drug resistance. Furthermore, MIL-53@CM-272 enhances dendritic cell maturation and synergistically combines it with an anti-programmed cell death protein 1 antibody during the study of immune-related pathways in the transcriptomes of bladder cancer cells using RNA-seq. This study presents the first instance of amalgamating nanomedicine with CM-272, inducing apoptosis, ferroptosis, and ICD to achieve the "one arrow three eagle" effect.

Copper-coordinated nanoassemblies based on photosensitizer-chemo prodrugs and checkpoint inhibitors for enhanced apoptosis-cuproptosis and immunotherapy

Cuproptosis is a recently identified copper-dependent form of nonapoptotic cell death and holds great prospect in cancer treatment. One of the most intriguing aspects of cuproptosis is its ability to synergize with apoptosis-based cancer treatments. Herein, we presented a novel approach using copper-coordinated nanoassemblies (CCNAs) that were constructed by incorporating a photosensitizer Zinc Phthalocyanine (ZnPc)-chemotherapeutic (DOX) prodrug with a thioketal (TK) spacer and an IDO inhibitor (1-methyl tryptophan, 1-MT) as building blocks for Cu2+-coordination self-assembly to achieve combinational apoptosis-cuproptosis and immunotherapy. Upon NIR laser irradiation, the ZnPc component of CCNAs exhibited a photodynamic effect that generated reactive oxygen species (ROS). This triggered the release of DOX, leading to enhanced tumor cell apoptosis. Additionally, the presence of Cu2+ in the CCNAs not only enhanced the photodynamic process by catalyzing oxygen generation but also promoted the aggregation of toxic mitochondrial proteins, leading to cell cuproptosis. Importantly, the intensified cuproptosis-apoptosis effect triggered an immunogenic cell death (ICD) response. The released 1-MT complemented this response by reversing the immunosuppressive tumor microenvironment (ITM), synergistically amplifying anti-tumor immunity and suppressing the growth of primary and distant tumors. The findings of this study provide a new perspective on potential cancer treatments based on cuproptosis-apoptosis synergistic immunotherapy and stimulate further research in the design of advanced metal-coordinated nanomedicines. STATEMENT OF SIGNIFICANCE: The combination of cuproptosis and apoptosis that act with different mechanisms holds enormous potential in cancer treatment. Here, copper-coordinated nanoassemblies (CCNAs) based on photosensitizer-chemo prodrugs and checkpoint inhibitors were constructed for mediating cuproptosis-apoptosis and subsequently promoting cancer immunotherapy. CCNAs not only promoted the photodynamic effect and activation of chemotherapy through catalyzing the generation of oxygen but also induced toxic mitochondrial protein aggregation, leading to cell cuproptosis. These synergistic antitumor effects triggered robust immune responses with the aid of immune checkpoint blockade, almost eradicating primary tumors and inhibiting distant tumors by around 83 % without systemic toxicity.

Detection and Elimination of Senescent Cells with a Self-Assembled Senescence-Associated β-Galactosidase-Activatable Nanophotosensitizer

Senescent cells have become an important therapeutic target for many age-related dysfunctions and diseases. We report herein a novel nanophotosensitizing system that is responsive to the senescence-associated β-galactosidase (β-gal) for selective detection and elimination of these cells. It involves a dimeric zinc(II) phthalocyanine linked to a β-galactose unit via a self-immolative linker. This compound can self-assemble in aqueous media, forming stable nanoscale particles in which the phthalocyanine units are stacked and self-quenched for fluorescence emission and singlet oxygen production. Upon internalization into senescent HeLa cells, these nanoparticles interact with the overproduced senescence-associated β-gal inside the cells to trigger the disassembly process through enzymatic cleavage of the glycosidic bonds, followed by self-immolation to release the photoactive monomeric phthalocyanine units. These senescent cells can then be lit up with fluorescence and eliminated through the photodynamic action upon light irradiation with a half-maximal inhibitory concentration of 0.06 μM.

Nanomedicine Strategies in Conquering and Utilizing the Cancer Hypoxia Environment

Cancer with a complex pathological process is a major disease to human welfare. Due to the imbalance between oxygen (O2) supply and consumption, hypoxia is a natural characteristic of most solid tumors and an important obstacle for cancer therapy, which is closely related to tumor proliferation, metastasis, and invasion. Various strategies to exploit the feature of tumor hypoxia have been developed in the past decade, which can be used to alleviate tumor hypoxia, or utilize the hypoxia for targeted delivery and diagnostic imaging. The strategies to alleviate tumor hypoxia include delivering O2, in situ O2 generation, reprogramming the tumor vascular system, decreasing O2 consumption, and inhibiting HIF-1 related pathways. On the other side, hypoxia can also be utilized for hypoxia-responsive chemical construction and hypoxia-active prodrug-based strategies. Taking advantage of hypoxia in the tumor region, a number of methods have been applied to identify and keep track of changes in tumor hypoxia. Herein, we thoroughly review the recent progress of nanomedicine strategies in both conquering and utilizing hypoxia to combat cancer and put forward the prospect of emerging nanomaterials for future clinical transformation, which hopes to provide perspectives in nanomaterials design.

Single-atom nanozymes: classification, regulation strategy, and safety concerns

Nanozymes, nanomaterials possessing enzymatic activity, have been studied extensively by researchers. However, their complex composition, low density of active sites, and inadequate substrate selectivity have hindered the maturation and widespread acceptance of nanozymes. Single-atom nanozymes (SAzymes) with atomically dispersed active sites are leading the field of catalysis due to their exceptional performance. The maximum utilization rate of atoms, low cost, well-defined coordination structure, and active sites are the most prominent advantages of SAzymes that researchers favor. This review systematically categorizes SAzymes based on their support type and describes their specific applications. Additionally, we discuss regulation strategies for SAzyme activity and provide a comprehensive summary of biosafety challenges associated with these enzymes.

Nano-enabled colorectal cancer therapy

Colorectal cancer (CRC), one of the most common and deadliest diseases worldwide, poses a great health threat and social burden. The clinical treatments of CRC encompassing surgery, chemotherapy, and radiotherapy are challenged with toxicity, therapy resistance, and recurrence. In the past two decades, targeted therapy and immunotherapy have greatly improved the therapeutic benefits of CRC patients but they still suffer from drug resistance and low response rates. Very recently, gut microbiota regulation has exhibited a great potential in preventing and treating CRC, as well as in modulating the efficacy and toxicity of chemotherapy and immunotherapy. In this review, we provide a cutting-edge summary of nanomedicine-based treatment in colorectal cancer, highlighting the recent progress of oral and systemic tumor-targeting and/or tumor-activatable drug delivery systems as well as novel therapeutic strategies against CRC, including nano-sensitizing immunotherapy, anti-inflammation, gut microbiota modulation therapy, etc. Finally, the recent endeavors to address therapy resistance, metastasis, and recurrence in CRC were discussed. We hope this review could offer insight into the design and development of nanomedicines for CRC and beyond.

Smart Nanozymes for Cancer Therapy: The Next Frontier in Oncology

Nanomaterials that mimic the catalytic activity of natural enzymes in the complex biological environment of the human body are called nanozymes. Recently, nanozyme systems have been reported with diagnostic, imaging, and/or therapeutic capabilities. Smart nanozymes strategically exploit the tumor microenvironment (TME) by the in situ generation of reactive species or by the modulation of the TME itself to result in effective cancer therapy. This topical review focuses on such smart nanozymes for cancer diagnosis, and therapy modalities with enhanced therapeutic effects. The dominant factors that guide the rational design and synthesis of nanozymes for cancer therapy include an understanding of the dynamic TME, structure-activity relationships, surface chemistry for imparting selectivity, and site-specific therapy, and stimulus-responsive modulation of nanozyme activity. This article presents a comprehensive analysis of the subject including the diverse catalytic mechanisms of different types of nanozyme systems, an overview of the TME, cancer diagnosis, and synergistic cancer therapies. The strategic application of nanozymes in cancer treatment can well be a game changer in future oncology. Moreover, recent developments may pave the way for the deployment of nanozyme therapy into other complex healthcare challenges, such as genetic diseases, immune disorders, and ageing.

Hyaluronic acid coated nano-particles for H2O2-elevation augmented photo-/chemodynamic therapy

In recent years, the association of chemodynamic therapy (CDT) with photodynamic therapy (PDT) has attracted much attention due to their mutually reinforced property. Nevertheless, how to further strengthen their performance is still a big challenge. Given the PDT/CDT therapeutic mechanism, the H2O2 amount might affect their final performance. Thus, in this paper, our synthesized pH-responsive Fenton agents (ferrocene-cinnamaldehyde conjugates, Fc-CA) were encapsulated in hyaluronic acid (HA) coated porphyrin-based MOF to obtain supramolecular nano-particles (Fc-CA-PCN-HA). After the CD44-receptor mediated internalization, the released Fc-CA could further dissociate in the acidic pH micro-environment. The released CA can activate the NADPH oxidase to elevate the H2O2 amount which could be preferable to produce more ·OH through Fenton reaction for cancer cells apoptosis. Additionally, O2 was also generated in the CDT which could alleviate tumor hypoxia condition and be provided as the reactant for PDT to produce more 1O2. Thus, given the excellent cascade reactions induced therapeutic performance of Fc-CA-PCN-HA in vitro and in vivo, the H2O2-elevation strategy might further enhance the PDT/CDT outcomes.

Cancer Immunotherapy Elicited by Immunogenic Cell Death Based on Smart Nanomaterials

Cancer immunotherapy has been a revolutionary cancer treatment modality because it can not only eliminate primary tumors but also prevent metastases and recurrent tumors. Immunogenic cell death (ICD) induced by various treatment modalities, including chemotherapy, phototherapy, and radiotherapy, converts dead cancer cells into therapeutic vaccines, eliciting a systemic antigen-specific antitumor. However, the outcome effect of cancer immunotherapy induced by ICD has been limited due to the low accumulation efficiency of ICD inducers in the tumor site and concomitant damage to normal tissues. The boom in smart nanomaterials is conducive to overcoming these hurdles owing to their virtues of good stability, targeted lesion site, high bioavailability, on-demand release, and good biocompatibility. Herein, the design of targeted nanomaterials, various ICD inducers, and the applications of nanomaterials responsive to different stimuli, including pH, enzymes, reactive oxygen species, or dual responses are summarized. Furthermore, the prospect and challenges are briefly outlined to provide reference and inspiration for designing novel smart nanomaterials for immunotherapy induced by ICD.

Cupric-ion-promoted fabrication of oxygen-replenishing nanotherapeutics for synergistic chemo and photodynamic therapy against tumor hypoxia

Mixing a glutathione (GSH)-responsive carboxy zinc(II) phthalocyanine (ZnPc*) and CuSO₄·5H₂O in water with or without the presence of the anticancer drug SN38 resulted in the formation of self-assembled nanotherapeutics labeled as ZnPc*/Cu/SN38@NP and ZnPc*/Cu@NP, respectively. The Cu²⁺ ions not only promoted the self-assembly of the carboxy phthalocyanine through metal complexation, but also catalyzed the transformation of H₂O₂ to oxygen via a catalase-like reaction, rendering an oxygen-replenishing property to the nanosystems. Both nanosystems exhibited high stability in aqueous media, but the nanoparticles disassembled gradually in an acidic or GSH-enriched environment and inside human colorectal adenocarcinoma HT29 cells, releasing the encapsulated therapeutic components. The disassembly process together with the activation by the intracellular GSH led to relaxation of the intrinsic quenching of the nanophotosensitizers and restoration of the photoactivities of ZnPc*. Under a hypoxic condition, ZnPc*/Cu/SN38@NP could attenuate the intracellular hypoxia level and maintain the photodynamic activity due to its Cu²⁺-promoted oxygen-replenishing ability. The photodynamic effect of ZnPc* and the anticancer effect of SN38 worked cooperatively, causing substantial apoptotic cell death. The dual therapeutic actions could also effectively inhibit the tumor growth in HT29 tumor-bearing nude mice without initiating notable adverse effects to the mice. STATEMENT OF SIGNIFICANCE: The oxygen-dependent nature of photodynamic therapy generally reduces its efficacy against tumor hypoxia, which is a common characteristic of advanced solid tumors and usually leads to resistance toward various anticancer therapies. We report herein a facile approach to assemble a glutathione-responsive carboxy phthalocyanine-based photosensitizer and an anticancer drug in aqueous media, in which Cu(II) ions were used to promote the self-assembly through metal complexation and catalyze the conversion of H₂O₂ to oxygen through a catalase-like reaction, making the resulting nanoparticles possessing an oxygen-replenishing property that could promote the photodynamic effect against hypoxic cancer cells and tumors. The use of Cu(II) ions to achieve the aforementioned dual functions in the fabrication of advanced nano-photosensitizing systems has not been reported.

Oxygen-generating biocatalytic nanomaterials for tumor hypoxia relief in cancer radiotherapy

Radiotherapy (RT), the most commonly used treatment method in clinics, shows unique advantages such as strong penetration, high energy intensity, and low systemic side effects. However, in vivo tumor hypoxia seriously hinders the therapeutic effect of RT. Hypoxia is a common characteristic of locally advanced solid tumor microenvironments, which leads to the proliferation, invasion and metastasis of tumor cells. In addition, oxygen consumption during RT will further aggravate tumor hypoxia, causing a variety of adverse side effects. In recent years, various biocatalytic nanomaterials (BCNs) have been explored to regulate and reverse tumor hypoxia microenvironments during RT. In this review, the most recent efforts toward developing oxygen-generating BCNs in relieving tumor hypoxia in RT are focused upon. The classification, engineering nanocatalytical activity of oxygen-generating BCNs and combined therapy based on these BCNs are systematically introduced and discussed. The challenges and prospects of these oxygen-generating BCNs in RT applications are also summarized.

Photodynamic therapy: Innovative approaches for antibacterial and anticancer treatments

Photodynamic therapy is an alternative treatment mainly for cancer but also for bacterial infections. This treatment dates back to 1900 when a German medical school graduate Oscar Raab found a photodynamic effect while doing research for his doctoral dissertation with Professor Hermann von Tappeiner. Unexpectedly, Raab revealed that the toxicity of acridine on paramecium depends on the intensity of light in his laboratory. Photodynamic therapy is therefore based on the administration of a photosensitizer with subsequent light irradiation within the absorption maxima of this substance followed by reactive oxygen species formation and finally cell death. Although this treatment is not a novelty, there is an endeavor for various modifications to the therapy. For example, selectivity and efficiency of the photosensitizer, as well as irradiation with various types of light sources are still being modified to improve final results of the photodynamic therapy. The main aim of this review is to summarize anticancer and antibacterial modifications, namely various compounds, approaches, and techniques, to enhance the effectiveness of photodynamic therapy.

NIR-II Responsive Upconversion Nanoprobe with Simultaneously Enhanced Single-Band Red Luminescence and Phase/Size Control for Bioimaging and Photodynamic Therapy

Lanthanide based upconversion (UC) nanoprobes have emerged as promising agents for biological applications. Extending the excitation light to the second near-infrared (NIR-II), instead of the traditional 980/808 nm light, and realizing NIR-II responsive single-band red UC emission is highly demanded for bioimaging application, which has not yet been explored. Here, a new type of NIR-II (1532 nm) light responsive UC nanoparticles (UCNPs) with enhanced single-band red UC emission and controllable phase and size is designed by introducing Er³⁺ as sensitizer and utilizing Mn²⁺ as energy manipulator. Through tuning the content of Mn²⁺ in NaLnF₄ :Er/Mn, the crystal phase, size, and emitting color are readily controlled, and the red-to-green (R/G) ratio is significantly increased from ≈20 to ≈300, leading to NIR-II responsive single band red emission via efficient energy transfer between Er³⁺ and Mn²⁺ . In addition, the single band red emitting intensity can be further improved by coating shell to avoid the surface quenching effect. More importantly, NIR-II light activated red UC bioimaging and photodynamic therapy through loading photosensitizer of zinc phthalocyanine are successfully achieved for the first time. These findings provide a new strategy of designing NIR-II light responsive single-band red emissive UCNPs for biomedical applications.

A DNA-engineered metal-organic-framework nanocarrier as a general platform for activatable photodynamic cancer cell ablation

Activatable photodynamic cancer cell ablation constitutes a promising approach to performing highly effective photodynamic therapy (PDT) with mitigated phototoxicity. Regretfully, so far strategies to fabricate activatable PDT agents are only applicable to a limited number of photosensitizers (PSs). Herein, an activatable photodynamic cancer cell ablation platform that can be adopted for versatile PSs is presented. Thereinto, by engineering an iron(iii) carboxylate-based metal-organic framework (MOF), MIL-101(Fe), with DNA grafted after PS loading, both hydrophilic and hydrophobic PSs can undergo negligible unspecific leakage and significant suppression of photosensitization during delivery. Following the reaction between MIL-101 and H₂O₂ whose level is greatly increased inside the tumor, MIL-101 is selectively degraded to release the loaded PDT agents and recover their photosensitization, controllably killing cancer cells upon H₂O₂ activation. Such a strategy assisted by a DNA-functionalized MOF significantly expands the varieties of PSs applicable for activatable PDT.

Supramolecular catalytic nanomedicines based on coordination self-assembly of amino acids for cascade-activated and -amplified synergetic cancer therapy

Simple biomolecule-based supramolecular nanomedicines hold great promise in cancer therapy, but their clinical translation is greatly hindered by low tumor-specificity and unsatisfactory antitumor performance. Herein, we developed an amino acid basedsupramolecular nanomedicine that could be co-activated by multiple stimuli in tumor tissue to trigger cascade catalytic reactions in situ for synergetic therapy. The supramolecular nanomedicine was developed based on a combination of coordination and hydrophobic noncovalent interactions among amphiphilic amino acids, glucose oxidase (GOx), copper ions, as well as doxorubicin (DOX)-camptothecin (CPT) prodrugs. The cascade reactions including the catalytic oxidation of glucose to generate H₂O₂, GSH reducing Cu²⁺ to Cu⁺, a Fenton-like reaction between H₂O₂ and Cu⁺ to produce hydroxyl radicals (˙OH), and ˙OH-triggered rapid release of dual parent drugs were specifically activated in tumor cells. With these cascade reactions, the catalytic-chemo synergetic therapy was realized for high-efficiency tumor suppression.

Biomineralized Two-Enzyme Nanoparticles Regulate Tumor Glycometabolism Inducing Tumor Cell Pyroptosis and Robust Antitumor Immunotherapy

Currently, immune checkpoint therapy combined with chemotherapy and radiotherapy is a useful strategy for improving immunotherapy's therapeutic efficacy. However, chemotherapy and radiotherapy cause serious side effects, so finding safe and effective methods to combine with immunotherapy is critical. In this work, regulating tumor glycometabolism is found to induce tumor cell pyroptosis and regulate the degree of expression of programmed death-ligand 1 (PD-L1). Therefore, how to treat tumors by regulating tumor glycometabolism in combination with anti-PD-L1 therapy is investigated here. First, the biomineralization-like method is used to construct nanoparticles with two-enzymatic activity by hybridizing nanozymes and glucose oxidase (GOx). It has the ability to self-amplify regulation of the glycometabolism of tumor cells. It can also induce tumor cell pyroptosis and increase the expression of PD-L1 in tumor cells. To treat tumors, nanoparticles are further combined with anti-PD-L1, which substantially inhibits tumor development and significantly increases  the survival time of mice. Combination therapy also has a significant immunological memory effect, successfully preventing tumor recurrence and metastasis. This is thought to be the first study that combines tumor glycometabolism with immunocheckpoint blocking in cancer therapy. This innovative, safe, low-toxic, and highly effective anti-tumor strategy can have good prospects in clinical applications.

Tumor Microenvironment Stimuli-Responsive Single-NIR-Laser Activated Synergistic Phototherapy for Hypoxic Cancer by Perylene Functionalized Dual-Targeted Upconversion Nanoparticles

Although synergistic therapy has shown great promise for effective treatment of cancer, the unsatisfactory therapeutic efficacy of photothermal therapy/photodynamic therapy is resulted from the absorption wavelength mismatch, tumor hypoxia, photosensitizer leakage, and inability in intelligent on-demand activation. Herein, based on the characteristics of tumor microenvironment (TME), such as the slight acidity, hypoxia, and overexpression of H₂ O₂ , a TME stimuli-responsive and dual-targeted composite nanoplatform (UCTTD-PC4) is strategically explored by coating a tannic acid (TA)/Fe³⁺ nanofilm with good biocompatibility onto the upconversion nanoparticles in an ultrafast, green and simple way. The pH-responsive feature of UCTTD-PC4 remains stable during the blood circulation, while rapidly releases Fe³⁺ in the slightly acidic tumor cells, which results in catalyzing H₂ O₂ to produce O₂ and overcoming the tumor hypoxia. Notably, the emission spectrum of the UCTTD perfectly matches the absorption spectrum of the photosensitizer (perylene probe (PC4)) to achieve the enhanced therapeutic effect triggered by a single laser. This study provides a new strategy for the rational design and development of the safe and efficient single near-infrared laser-triggered synergistic treatment platform for hypoxic cancer under the guidance of multimodal imaging.

Self-assemblies with cascade effect to boost antitumor systemic immunotherapy

Bio-organic hybrid self-assemblies based on amino acids, conjugated polymers, Fe³⁺ and enzymes are fabricated with tumor environment-responsive and light-triggered NO release properties. By sequential energy consumption, NO attack and immune activation, FFPG shows boosted antitumor activity toward both primary and distant tumors. The three-level cascade strategy (starvation/NO/immunotherapy) adopted in this work offers a pathway to address the dilemma of low cure rate of malignant tumors.

Tumor oxygenation nanoliposome synergistic hypoxia-inducible-factor-1 inhibitor enhanced Iodine-125 seed brachytherapy for esophageal cancer

Iodine-125 (¹²⁵I) brachytherapy has become one of the most effective palliative treatment options for advanced esophageal cancer. However, resistance toward ¹²⁵I brachytherapy caused by pre-existing tumor hypoxia and hypoxia-inducible factor 1 (HIF-1) signaling pathway activation represents a significant limitation in esophageal cancer treatment. To circumvent these problems, herein, we proposed an innovative strategy to alleviate radioresistance of brachytherapy by co-encapsulating catalase (CAT) and HIF-1 inhibitor-acriflavine (ACF) into the hydrophilic cavities of liposome, termed as "ACF-CAT@Lipo". Under overexpressed H₂O₂ stimulation in the tumor region, the fabricated ACF-CAT@Lipo can generate an amount of O₂ and alleviate tumor hypoxia in vitro and in vivo. Furthermore, cooperating with ACF, the expression of hypoxia-related protein (e.g. HIF-1α, VEGF, MMP-2) are obviously decreased. Importantly, the copious oxygenation and the significant inhibition expression of HIF-1α can further improve the radiosensitivity of ¹²⁵I brachytherapy and finally realize the eradication of esophageal cancer in vivo. The oxygen enrichment and HIF-1 inhibition function of ACF-CAT@Lipo provides a new strategy to overcome the brachytherapy resistance of esophageal cancer therapy.

Acriflavine, an Acridine Derivative for Biomedical Application: Current State of the Art

Acriflavine (ACF) has been known for years as an antibacterial drug. The identification of key oncogenic mechanisms has brought, in recent years, a significant increase in studies on ACF as a multipurpose drug that would improve the prognosis for cancer patients. ACF interferes with the expression of the hypoxia inducible factor, thus acting on metastatic niches of tumors and significantly enhancing the effects of other anticancer therapies. It has been recognized as the most potent HIF-1 inhibitor out of the 336 drugs approved by the FDA. This work presents up-to-date knowledge about the mechanisms of action of ACF and its related prodrug systems in the context of anticancer and SARS-CoV-2 inhibitory properties. It explains the multitask nature of this drug and suggests mechanisms of ACF’s action on the coronavirus. Other recent reports on ACF-based systems as potential antibacterial and antiviral drugs are also described.

Recent Strategies to Address Hypoxic Tumor Environments in Photodynamic Therapy

Photodynamic therapy (PDT) has become a promising method of cancer treatment due to its unique properties, such as noninvasiveness and low toxicity. The efficacy of PDT is, however, significantly reduced by the hypoxia tumor environments, because PDT involves the generation of reactive oxygen species (ROS), which requires the great consumption of oxygen. Moreover, the consumption of oxygen caused by PDT would further exacerbate the hypoxia condition, which leads to angiogenesis, invasion of tumors to other parts, and metastasis. Therefore, many research studies have been conducted to design nanoplatforms that can alleviate tumor hypoxia and enhance PDT. Herein, the recent progress on strategies for overcoming tumor hypoxia is reviewed, including the direct transport of oxygen to the tumor site by O₂ carriers, the in situ generation of oxygen by decomposition of oxygen-containing compounds, reduced O₂ consumption, as well as the regulation of tumor microenvironments. Limitations and future perspectives of these technologies to improve PDT are also discussed.

Recent Advances in Antimicrobial Nano-Drug Delivery Systems

Infectious diseases are among the major health issues of the 21st century. The substantial use of antibiotics over the years has contributed to the dissemination of multidrug resistant bacteria. According to a recent report by the World Health Organization, antibacterial (ATB) drug resistance has been one of the biggest challenges, as well as the development of effective long-term ATBs. Since pathogens quickly adapt and evolve through several strategies, regular ATBs usually may result in temporary or noneffective treatments. Therefore, the demand for new therapies methods, such as nano-drug delivery systems (NDDS), has aroused huge interest due to its potentialities to improve the drug bioavailability and targeting efficiency, including liposomes, nanoemulsions, solid lipid nanoparticles, polymeric nanoparticles, metal nanoparticles, and others. Given the relevance of this subject, this review aims to summarize the progress of recent research in antibacterial therapeutic drugs supported by nanobiotechnological tools.

Fluorescence-Reporting-Guided Tumor Acidic Environment-Activated Triple Photodynamic, Chemodynamic, and Chemotherapeutic Reactions for Efficient Hepatocellular Carcinoma Cell Ablation

Tumor acidic environment-activated combination therapy holds great promise to significantly decrease side effects, circumvent multiple drug resistance, and improve therapeutic outcomes for cancer treatment. Herein, Sorafenib/ZnPc(PS)₄@Fe^III-TA nanoparticles (SPFT) are designed with acid-environment turned-on fluorescence to report the activation of triple therapy including photodynamic, chemodynamic, and chemotherapy on hepatocellular carcinoma. The SPFT are composed of SP cores formulated via self-assembly of sorafenib and ZnPc(PS)₄, with high drug loading efficiency, and Fe^III-TA shells containing FeCl₃ and tannic acid. Importantly, the nanoparticles suppress reactive oxygen species (ROS) generation of ZnPc(PS)₄ due to their formation in nanoparticles, while assisting simultaneous uptake of the uploaded drugs in cancer cells. The tumor acidic environment initiates Fe^III-TA decomposition and accelerates a chemodynamic reaction between Fe^II and H₂O₂ to generate toxic ^•OH. Then, the SP core is decomposed to separate ZnPc(PS)₄ and sorafenib, which leads to fluorescence turning-on of ZnPc(PS)₄, expedited photodynamic reactions, and burst release of sorafenib. Notably, SPFT shows low dark cytotoxicity to normal cells but exerts high potency on hepatocellular carcinoma cells under near-infrared light irradiation, which is much more potent than either sorafenib or ZnPc(PS)₄ alone. This research offers a facile nanomedicine design strategy for cancer therapy.

Double-activation of mitochondrial permeability transition pore opening via calcium overload and reactive oxygen species for cancer therapy

BACKGROUND

Calcium ions (Ca²⁺) participates in various intracellular signal cascades and especially plays a key role in pathways relevant to cancer cells. Mitochondrial metabolism stimulated by calcium overload can trigger the opening of the mitochondrial permeability transition pore (MPTP), which leads to cancer cell death.

METHODS

Herein, a mitochondrial pathway for tumour growth inhibition was built via the double-activation of MPTP channel. Fe²⁺ doped covalent organic frameworks (COF) was synthesised and applied as template to grow CaCO₃ shell. Then O₂ was storaged into Fe²⁺ doped COF, forming O₂-FeCOF@CaCO₃ nanocomposite. After modification with folic acid (FA), O₂-FeCOF@CaCO₃@FA (OFCCF) can target breast cancer cells and realize PDT/Ca²⁺ overload synergistic treatment.

RESULTS

COF can induce the production of ¹O₂ under 650 nm irradiation for photodynamic therapy (PDT). Low pH and hypoxia in tumour microenvironment (TME) can activate the nanocomposite to release oxygen and Ca²⁺. The released O₂ can alleviate hypoxia in TME, thus enhancing the efficiency of COF-mediated PDT. Abundant Ca²⁺ were released and accumulated in cancer cells, resulting in Ca²⁺ overload. Notably, the reactive oxygen species (ROS) and Ca²⁺ overload ensure the sustained opening of MPTP, which leads to the change of mitochondria transmembrane potential, the release of cytochrome c (Cyt c) and the activation of caspases 3 for cancer cell apoptosis.

CONCLUSION

This multifunctional nanosystem with TME responded abilities provided a novel strategy for innovative clinical cancer therapy.

Nanozymes: Versatile Platforms for Cancer Diagnosis and Therapy

Natural enzymes usually suffer from high production cost, ease of denaturation and inactivation, and low yield, making them difficult to be broadly applicable. As an emerging type of artificial enzyme, nanozymes that combine the characteristics of nanomaterials and enzymes are promising alternatives. On the one hand, nanozymes have high enzyme-like catalytic activities to regulate biochemical reactions. On the other hand, nanozymes also inherit the properties of nanomaterials, which can ameliorate the shortcomings of natural enzymes and serve as versatile platforms for diverse applications. In this review, various nanozymes that mimic the catalytic activity of different enzymes are introduced. The achievements of nanozymes in different cancer diagnosis and treatment technologies are summarized by highlighting the advantages of nanozymes in these applications. Finally, future research directions in this rapidly developing field are outlooked.

Systems chemistry of peptide-assemblies for biochemical transformations

During the billions of years of the evolutionary journey, primitive polymers, involved in proto metabolic pathways with low catalytic activity, played critical roles in the emergence of modern enzymes with remarkable substrate specificity. The precise positioning of amino acid residues and the complex orchestrated interplay in the binding pockets of evolved enzymes promote covalent and non-covalent interactions to foster a diverse set of complex catalytic transformations. Recent efforts to emulate the structural and functional information of extant enzymes by minimal peptide based assemblies have attempted to provide a holistic approach that could help in discerning the prebiotic origins of catalytically active binding pockets of advanced proteins. In addition to the impressive sets of advanced biochemical transformations, catalytic promiscuity and cascade catalysis by such small molecule based dynamic systems can foreshadow the ancestral catalytic processes required for the onset of protometabolism. Looking beyond minimal systems that work close to equilibrium, catalytic systems and compartments under non-equilibrium conditions utilizing simple prebiotically relevant precursors have attempted to shed light on how bioenergetics played an essential role in chemical emergence of complex behaviour. Herein, we map out these recent works and progress where diverse sets of complex enzymatic transformations were demonstrated by utilizing minimal peptide based self-assembled systems. Further, we have attempted to cover the examples of peptide assemblies that could feature promiscuous activity and promote complex multistep cascade reaction networks. The review also covers a few recent examples of minimal transient catalytic assemblies under non-equilibrium conditions. This review attempts to provide a broad perspective for potentially programming functionality via rational selection of amino acid sequences leading towards minimal catalytic systems that resemble the traits of contemporary enzymes.

Liposome-Based Nanoencapsulation of a Mitochondria-Stapling Photosensitizer for Efficient Photodynamic Therapy

Mitochondria-targeting photodynamic therapy (PDT) can block mitochondrial function and trigger the inherent proapoptotic cascade signal of mitochondria, which has been considered to have the potential to amplify the efficiency of PDT. However, the dynamic change of mitochondrial membrane potential (MMP) makes most cationic photosensitizers easily fall off from the mitochondria, which greatly limits the efficiency of PDT. Here, we have developed a smart liposome encapsulation method based on a mitochondria-stapling photosensitizer for efficient theranostic photodynamic therapy. The stapling photosensitizer can be covalently bound inside mitochondria via two reaction sites without a falloff effect, regardless of the change of MMP. As a result, the liposome-based nanophotosensitizer showed a high efficiency of PDT (IC₅₀ = 0.98 μM) under 630 nm light. At the same time, the nanophotosensitizer had fluorescence imaging-guided ability to monitor abnormal mitochondrial morphology during PDT. Importantly, the results of mice experiments also showed that the liposome-based nanophotosensitizer possessed excellent antitumor PDT activity because the released photosensitizer can stay inside mitochondria during the whole process of PDT.

Tunable Assembly of Organic-Inorganic Molecules into Hierarchical Superstructures as Ligase Mimics for Enhancing Tumor Photothermal Therapy

The assembly of molecules into hierarchical superstructures is ubiquitous in the construction of novel geometrically complex hierarchical superstructures, attracting great attention. Herein, a metal-ligand cross-linking strategy is developed for the fabrication of ferric ion-dopamine coordination hierarchical superstructures. A range of superstructures with highly complex morphologies, such as flower-like, octopus-like, and hedgehog-like superstructures, are synthesized. The mechanism for formation of hierarchical superstructures involves the pre-cross-linking of ferric ion with dopamine molecules, the fabrication of iron-dopamine precursors aggregated into the spherical aggregates, the nanoscale aggregates sintering and ordering themselves upon equilibration, the nanodots polymerizing into nanorods, and finally the nanorods self-assembling into hierarchical superstructures. In-depth research illustrates that as the permittivity (ξ) of the reaction system increases, the resulting hierarchical superstructures tend to converge into spherical shape. As a proof of concept, the 0D nanospheres, 1D nanorods, and 3D hierarchical superstructures are fabricated through adjusting system permittivity. The hierarchical superstructure is utilized as peroxidase-like ligase mimics to enhance the effect of tumor photothermal treatment. Further in vitro and in vivo assays demonstrate that the hierarchical superstructure can effectively ablate tumor cells. This work opens new horizons in hierarchical superstructures with complex architectures, and has great potential in nanozymology, biomedical science, and catalysis.

On-demand assembly of polymeric nanoparticles for longer-blood-circulation and disassembly in tumor for boosting sonodynamic therapy

Sonodynamic therapy (SDT) is one of the promising strategies for tumor therapy, but its application is usually hindered by fast clearance in blood-circulation, abnormal tumor microenvironment, and inefficient generation of reactive oxygen species. To solve these problems, we proposed an on-demand assembly-disassembly strategy, where the assembly is favorable for longer-blood-circulation and then the disassembly in tumor is favorable for boosting SDT. Hematoporphyrin monomethyl ether (HMME) as the model of organic sonosensitizers were conjugated with hyaluronic acid (HA). Then HA-HMME was mixed with catalase (CAT) and assembled into polymeric nanoparticles (CAT@HA-HMME NPs) with size of ∼80 nm. CAT@HA-HMME NPs exhibit good biocompatibility and a longer blood half-time (t_1/2 = 4.17 h) which is obviously longer than that (∼0.82 h) of HMME molecules. After HA receptor-mediated endocytosis of cancer cells, CAT@HA-HMME NPs can be cleaved by endogenous hyaluronidase, resulting in the on-demand disassembly in tumor to release HA-HMME molecules and CAT. The CAT catalyzes the endogenous H₂O₂ into O₂ to relieve the hypoxic microenvironment, and the released HA-HMME exhibits a higher ROS generation ability, greatly boosting SDT for the inhibition of tumor growth. Therefore, the on-demand assembly-disassembly strategy may provide some insight in the design and development of nanoagents for tumor therapy.

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On-demand assembly from molecules to nanoparticles for longer-blood-circulation.

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On-demand disassembly in presence of hyaluronidase (in tumor) for boosting sonodynamic effects.

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Efficient damage on cancer cells in-vitro and Significant inhibition of the tumor growth due to the enhanced SDT.

Perspective for Single Atom Nanozymes Based Sensors: Advanced Materials, Sensing Mechanism, Selectivity Regulation, and Applications

Nanozymes are a kind of nanomaterial mimicking enzyme catalytic activity, which has aroused extensive interest in the fields of biosensors, biomedicine, and climate and ecosystems management. However, due to the complexity of structures and composition of nanozymes, atomic scale active centers have been extensively investigated, which helps with in-depth understanding of the nature of the biocatalysis. Single atom nanozymes (SANs) cannot only significantly enhance the activity of nanozymes but also effectively improve the selectivity of nanozymes owing to the characteristics of simple and adjustable coordination environment and have been becoming the brightest star in the nanozyme spectrum. The SANs based sensors have also been widely investigated due to their definite structural features, which can be helpful to study the catalytic mechanism and provide ways to improve catalytic activity. This perspective presents a comprehensive understanding on the advances and challenges on SANs based sensors. The catalytic mechanisms of SANs and then the sensing application from the perspectives of sensing technology and sensor construction are thoroughly analyzed. Finally, the major challenges, potential future research directions, and prospects for further research on SANs based sensors are also proposed.

A hydrogen peroxide economizer for on-demand oxygen production-assisted robust sonodynamic immunotherapy

The outcome of sonodynamic immunotherapy is significantly limited by tumor hypoxia. To overcome this obstacle, one common solution is to catalyze the conversion of endogenous H₂O₂ into O₂. However, the effectiveness of this strategy is limited by the insufficient concentration of H₂O₂ in the tumor microenvironment (TME). Herein, we developed a H₂O₂ economizer for on-demand O₂ supply and sonosensitizer-mediated reactive oxygen species production during ultrasound activation, thereby alleviating hypoxia-associated limitations and augmenting the efficacy of sonodynamic immunotherapy. Methods: The H₂O₂ economizer is constructed by electrostatic adsorption and π-π interactions between the Fe-doped polydiaminopyridine (Fe-PDAP) nanozyme and chlorin e6. By employing a biomimetic engineering strategy with cancer cell membranes, we addressed the premature leakage issue and increased tumor-site accumulation of nanoparticles (membrane-coated Fe-PDAP/Ce6, MFC). Results: The prepared MFC could significantly attenuate the catalytic activity of Fe-PDAP by reducing their contact with H₂O₂. Ultrasound irradiation promoted MFC dissociation and the exposure of Fe-PDAP for a more robust O₂ supply. Moreover, the combination of MFC-enhanced sonodynamic therapy with anti-programmed cell death protein-1 antibody (aPD-1) immune checkpoint blockade induced a strong antitumor response against both primary tumors and distant tumors. Conclusion: This as-prepared H₂O₂ economizer significantly alleviates tumor hypoxia via reducing H₂O₂ expenditure and that on-demand oxygen-elevated sonodynamic immunotherapy can effectively combat tumors.

Biomimetically constructing a hypoxia-activated programmable phototheranostics at the molecular level

A programmable strategy at the molecular level to modulate the ratio of a catalyst and photosensitizer to maximize the collaborative efficiency of anti-angiogenesis and PDT.

Albumin-mediated “Unlocking” of supramolecular prodrug-like nanozymes toward selective imaging-guided phototherapy

An adaptive nanozyme without producing off-target toxicity has been successfully applied in phototherapy.

Conquering the Hypoxia Limitation for Photodynamic Therapy

Photodynamic therapy (PDT) has aroused great research interest in recent years owing to its high spatiotemporal selectivity, minimal invasiveness, and low systemic toxicity. However, due to the hypoxic nature characteristic of many solid tumors, PDT is frequently limited in therapeutic effect. Moreover, the consumption of O₂ during PDT may further aggravate the tumor hypoxic condition, which promotes tumor proliferation, metastasis, and invasion resulting in poor prognosis of treatment. Therefore, numerous efforts have been made to increase the O₂ content in tumor with the goal of enhancing PDT efficacy. Herein, these strategies developed in past decade are comprehensively reviewed to alleviate tumor hypoxia, including 1) delivering exogenous O₂ to tumor directly, 2) generating O₂ in situ, 3) reducing tumor cellular O₂ consumption by inhibiting respiration, 4) regulating the TME, (e.g., normalizing tumor vasculature or disrupting tumor extracellular matrix), and 5) inhibiting the hypoxia-inducible factor 1 (HIF-1) signaling pathway to relieve tumor hypoxia. Additionally, the O₂ -independent Type-I PDT is also discussed as an alternative strategy. By reviewing recent progress, it is hoped that this review will provide innovative perspectives in new nanomaterials designed to combat hypoxia and avoid the associated limitation of PDT.

Self-adjuvanting photosensitizer nanoparticles for combination photodynamic immunotherapy

Combination cancer immunotherapy that synergizes the advantages of multiple therapeutic agents has shown great potential in tumor treatment. Herein, we report the one-step assembly of therapeutic nanoparticles (NPs) to co-deliver photosensitizers and adjuvants for combination photodynamic therapy (PDT) and immunotherapy. The NPs are obtained via self-assembly of chlorin e6 (Ce6) and imidazoquinoline-based TLR7 agonists (IMDQ), which results in a high loading efficacy of 72.2% and 27.8% for Ce6 and IMDQ, respectively. Upon laser irradiation, the resulting NPs could not only effectively induce photodynamic immunogenic cancer cell death, but also elicit robust antitumor immunity, leading to significant inhibition of both primary and distant tumors in a bilateral tumor model. This study demonstrates the potential of self-assembled NPs in co-delivering multiple therapeutics for potential immunotherapy to enhance the antitumor efficacy.

Nanostructured Phthalocyanine Assemblies with Efficient Synergistic Effect of Type I Photoreaction and Photothermal Action to Overcome Tumor Hypoxia in Photodynamic Therapy

Most photodynamic therapy (PDT) paradigms work through the highly O₂-dependent type II photoreaction to generate singlet oxygen (¹O₂). The hypoxic microenvironment of solid tumors severely hampers therapeutic outcomes. Here, we present a novel design that could transfer the photophysical and photochemical properties of traditional phthalocyanine-based photosensitizers from type II photoreaction to efficient type I photoreaction and vibrational relaxation-induced photothermal conversion. These features enable the obtained nanostructured phthalocyanine assemblies (e.g., NanoPcAF) to display excellent phototherapies under both normoxic and hypoxic conditions. Moreover, NanoPcAF has a high level of accumulation in tumor tissues after intravenous injection, and 94% of tumor growth is inhibited in a preclinical model at a NanoPcAF dose of 0.8 nmol g^-1 and light dose of 300 J cm^-2.

Metal-Coordinated Supramolecular Self-Assemblies for Cancer Theranostics

Metal-coordinated supramolecular nanoassemblies have recently attracted extensive attention as materials for cancer theranostics. Owing to their unique physicochemical properties, metal-coordinated supramolecular self-assemblies can bridge the boundary between traditional inorganic and organic materials. By tailoring the structural components of the metal ions and binding ligands, numerous multifunctional theranostic nanomedicines can be constructed. Metal-coordinated supramolecular nanoassemblies can modulate the tumor microenvironment (TME), thus facilitating the development of TME-responsive nanomedicines. More importantly, TME-responsive organic-inorganic hybrid nanomaterials can be constructed in vivo by exploiting the metal-coordinated self-assembly of a variety of functional ligands, which is a promising strategy for enhancing the tumor accumulation of theranostic molecules. In this review, recent advancements in the design and fabrication of metal-coordinated supramolecular nanomedicines for cancer theranostics are highlighted. These supramolecular compounds are classified according to the order in which the coordinated metal ions appear in the periodic table. Furthermore, the prospects and challenges of metal-coordinated supramolecular self-assemblies for both technical advances and clinical translation are discussed. In particular, the superiority of TME-responsive nanomedicines for in vivo coordinated self-assembly is elaborated, with an emphasis on strategies that enhance the accumulation of functional components in tumors for an ideal theranostic outcome.

Encapsulating an acid-activatable phthalocyanine-doxorubicin conjugate and the hypoxia-sensitive tirapazamine in polymeric micelles for multimodal cancer therapy

A zinc(ii) phthalocyanine (ZnPc) was conjugated to doxorubicin (Dox) via an acid-labile hydrazone linker. The resulting ZnPc-Dox conjugate was then encapsulated into polymeric micelles formed through self-assembly of a block copolymer of poly(ethylene glycol) and poly(d,l-lactide) both in the absence and presence of the hypoxia-activated prodrug tirapazamine (TPZ) to give ZnPc-Dox@micelles and ZnPc-Dox/TPZ@micelles respectively. These polymeric micelles exhibited an excellent stability in aqueous media, but underwent disassembly in an acidic environment. Upon internalisation into HT29 human colorectal carcinoma cells, fluorescence due to ZnPc and Dox could be observed in the cytoplasm and nucleus respectively for both nanosystems. This observation suggested the disassembly of the polymeric micelles and the cleavage of the hydrazone linker in ZnPc-Dox in the acidic intracellular compartments. These micelles were slightly cytotoxic against HT29 cells in the dark due to the chemotherapeutic effect of Dox and/or TPZ. Upon light irradiation, ZnPc-Dox@micelles showed higher cytotoxicity. The IC50 value under a normoxic condition (0.35 μM based on ZnPc-Dox) was significantly lower than that under hypoxia (>1 μM). With an additional therapeutic component, ZnPc-Dox/TPZ@micelles exhibited higher photocytotoxicity with IC50 values of 0.20 μM and 0.78 μM under normoxia and hypoxia respectively. It is believed that the photodynamic action of this nanosystem consumed the intracellular oxygen and hence triggered the hypoxia-mediated chemotherapeutic action of TPZ. The multimodal antitumor effects of these polymeric micelles were also validated on HT29 tumour-bearing nude mice.

Enhanced anti-tumor efficacy by inhibiting HIF-1α to reprogram TAMs via core-satellite upconverting nanoparticles with curcumin mediated photodynamic therapy

Tumor hypoxic stress after photodynamic therapy (PDT) will be inevitably exacerbated by the vascular blocking effects and oxygen consumption in the tumor microenvironment (TME) which usually leads to compromised efficacy and clinical performance. Increasing evidence links the hypoxia induced up-regulation of hypoxia inducible factor 1α (HIF-1α) with immunosuppressive TME, including the polarization of M2 phenotype tumor associated macrophages (TAMs), which promote the recurrence and metastasis. Here, we reported NIR-triggered core-satellite upconverting nanoparticles (CSNPs) with curcumin (Cur) embedded as a difunctional photosensitizer, which could realize PDT in deep tumors with long excitation wavelength (980 nm) and reverse the immunosuppressive TME induced by up-regulated HIF-1α at the same time. This Cur-loaded CSNPs (Cur-CSNPs)-mediated PDT could successfully induce the immunogenic cell death (ICD) of triple negative breast cancer (TNBC) cell lines (4T1 and MDA-MB-231) in vitro and repolarize the 4T1 cells co-cultured TAMs from pro-tumor M2 to the anti-tumor M1 phenotype. Furthermore, Cur-CSNPs-mediated PDT could suppress the 4T1 tumor growth in primary and distant sites through the synergistic immunotherapeutic effects in vivo by priming M1 type TAMs and CD4+/CD8+ T cells' infiltration. Our data highlight the novel application of CSNPs-embedded Cur as a difunctional photosensitizer to enhance the anti-tumor efficacy of PDT.

Construction of Peroxidase-like Metal-Organic Frameworks in TiO2 Nanochannels: Robust Free-Standing Membranes for Diverse Target Sensing

The high cost and easy denaturation of natural enzymes under environmental conditions hinder their practical usefulness in sensing devices. In this study, peroxidase (POD)-like metal-organic frameworks (MOFs) were in situ grown in the nanochannels of an anodized TiO₂ membrane (TiO₂NM) as an electrochemical platform for multitarget sensing. By directly using a nanochannel wall as the precursor of metal nodes, Ti-MOFs were in situ derived on the nanochannel wall. Benefitting from the presence of bipyridine groups on the ligands, the MOFs in the nanochannels provide plenty of sites for Fe³⁺ anchoring, thus endowing the resulting membrane (named as Fe³⁺:MOFs/TiO₂NM) with remarkable POD-like activity. Such Fe³⁺-induced POD-like activity is very sensitive to thiol-containing molecules owing to the strong coordination effect of thiols on Fe³⁺. Most importantly, the POD-like activity of nanochannels can be in situ characterized by the current-potential (I-V) properties via catalyzing the oxidation of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) substrate to the corresponding positively charged product ABTS^•+. As a proof-of-concept application, the free-standing POD-like membranes were applied as a label-free assay in sensing cysteine, as well as monitoring acetylcholinesterase (AChE) activity through the generated thiol-containing product. Furthermore, based on the toxicity effect of organophosphorus (OP) compounds on AChE, the robust membranes were successfully utilized to evaluate the toxicity of diverse OP compounds. The POD-like nanochannels open up an innovative way to expand the application of nanochannel-based electrochemical sensing platforms in drug inspection, food safety, and environmental pollution.

Self-Assembling Porphyrins as a Single Therapeutic Agent for Synergistic Cancer Therapy: A One Stone Three Birds Strategy

Combining photodynamic therapy (PDT), chemodynamic therapy (CDT), and ferroptosis is a valuable means for an enhanced anticancer effect. However, traditional combination of PDT/CDT/ferroptosis faces several hurdles, including excess glutathione (GSH) neutralization and preparation complexity. In this work, a versatile multifunctional nanoparticle (HCNP) self-assembled from two porphyrin molecules, chlorin e6 and hemin, is developed. The as-constructed HCNPs exhibit a peroxidase-mimic catalytic activity, which can lead to the in situ generation of endogenous O2, thereby enhancing the efficacy of PDT. Furthermore, the generation of hydroxyl radicals (•OH) in the tumor environment in reaction to the high level of H2O2 and the simultaneous disruption of intracellular GSH endow the HCNPs with the capacity of enhanced CDT, resulting in a more effective therapeutic outcome in combination with PDT. More importantly, GSH depletion further leads to the inactivation of GSH peroxide 4 and induced ferroptosis. Both in vitro and in vivo results showed that the combination of PDT/CDT/ferroptosis realizes highest antitumor efficacy significantly under laser irradiation. Therefore, by integrating the superiorities of O2 and •OH generation capacity, GSH-depletion effect, and bioimaging into a single nanosystem, the HCNPs are a promising single therapeutic agent for tumor PDT/CDT/ferroptosis combination therapy.

Defect Engineering Enables Synergistic Action of Enzyme-Mimicking Active Centers for High-Efficiency Tumor Therapy

Perusing redox nanozymes capable of disrupting cellular homeostasis offers new opportunities to develop cancer-specific therapy, but remains challenging, because most artificial enzymes lack enzyme-like scale and configuration. Herein, for the first time, we leverage a defect engineering strategy to develop a simple yet efficient redox nanozyme by constructing enzyme-mimicking active centers and investigated its formation and catalysis mechanism thoroughly. Specifically, the partial Fe doping in MoO_x (donated as Fe-MoO_v) was demonstrated to activate structure reconstruction with abundant defect site generation, including Fe substitution and oxygen vacancy (OV) defects, which significantly enable the binding capacity and catalytic activity of Fe-MoO_v nanozymes in a synergetic fashion. More intriguingly, plenty of delocalized electrons appear due to Fe-facilitated band structure reconstruction, directly contributing to the remarkable surface plasmon resonance effect in the near-infrared (NIR) region. Under NIR-II laser irradiation, the designed Fe-MoO_v nanozymes are able to induce substantial disruption of redox and metabolism homeostasis in the tumor region via enzyme-mimicking cascade reactions, thus significantly augmenting therapeutic effects. This study that takes advantage of defect engineering offers new insights into developing high-efficiency redox nanozymes.

Biomimetic Nanozymes Based on Coassembly of Amino Acid and Hemin for Catalytic Oxidation and Sensing of Biomolecules

Nanoassemblies based on self-assembly of biological building blocks are promising in mimicking the nanostructures, properties, and functionalities of natural enzymes. However, it remains a challenge to design of biomimetic nanozymes with tunable nanostructures and enhanced catalytic activities starting from simple biomolecules. Herein, the construction of nanoassemblies through coassembly of an amphiphilic amino acid and hemin is reported. The nanostructures and morphologies of the resulting nanoassemblies are readily controlled by tuning the molar ratio between the amino acid and hemin, thus leading to tailored peroxidase-mimicking activities of the nanoassemblies. Importantly, the optimized nanoassemblies exhibit a remarkable catalytic efficiency that is comparable to the natural counterpart when considering molecular mass along with good robustness in multiple catalytic cycles. The nanoassemblies are effectively integrated as biomimetic nanozymes in a sensing system for catalytic detection of glucose. Therefore, this work demonstrates that nanozymes with advanced catalytic capabilities can be constructed by self-assembly of minimalist biological building blocks and may thus promote the rational design and catalytic applications of biomimetic nanozymes.

Preparation of zinc phthalocyanine-loaded amphiphilic phosphonium chitosan nanomicelles for enhancement of photodynamic therapy efficacy

To increase the solubility and the encapsulation of zinc phthalocyanine (ZnPc) photosensitizer for photodynamic therapy (PDT), a positively charged amphiphilic phosphonium chitosan nanomicelle with multi-benzene structure was developed, and its application to PDT was explored. N-acetyl-l-phenylalanine-(4-carboxybutyl) triphenylphosphonium bromide chitosan (CTPB-CS-NAP), a chitosan derivative with tunable amphiphilicity, was synthesized first. ZnPc was encapsulated in CTPB-CS-NAP at the critical micelle concentration (CMC) of 4.898 mg/L by a hydrophobic self-assembly method to form ZnPc-loaded nanomicelles (ZnPc@CTPB-CS-NAP). The method gives the highest encapsulation efficiency and drug loading of 89.4 % and 22.3 %, respectively. ZnPc@CTPB-CS-NAP is stably dispersed in aqueous solution and shows the average particle size of 103±5 nm. PDT experiments suggest the phototoxicity of ZnPc@CTPB-CS-NAP is much higher than that of ZnPc, but no obvious dark cytotoxicity is observed. Our study has provided a new strategy for improving the photodynamic therapy efficacy of hydrophobic photosensitizer by the encapsulation with chitosan derivative carriers.

Nanomaterials for Tumor Hypoxia Relief to Improve the Efficacy of ROS-Generated Cancer Therapy

Given the fact that excessive levels of reactive oxygen species (ROS) induce damage to proteins, lipids, and DNA, various ROS-generating agents and strategies have been explored to induce cell death and tumor destruction by generating ROS above toxic threshold. Unfortunately, hypoxia in tumor microenvironment (TME) not only promotes tumor metastasis but also enhances tumor resistance to the ROS-generated cancer therapies, thus leading to ineffective therapeutic outcomes. A variety of nanotechnology-based approaches that generate or release O2 continuously to overcome hypoxia in TME have showed promising results to improve the efficacy of ROS-generated cancer therapy. In this minireview, we present an overview of current nanomaterial-based strategies for advanced cancer therapy by modulating the hypoxia in the TME and promoting ROS generation. Particular emphasis is put on the O2 supply capability and mechanism of these nanoplatforms. Future challenges and opportunities of design consideration are also discussed. We believe that this review may provide some useful inspiration for the design and construction of other advanced nanomaterials with O2 supply ability for overcoming the tumor hypoxia-associated resistance of ROS-mediated cancer therapy and thus promoting ROS-generated cancer therapeutics.