Light-Activated Hypoxia-Sensitive Covalent Organic Framework for Tandem-Responsive Drug Delivery

Hypoxia-responsive theranostic nanoplatform with intensified chemo-photothermal/photodynamic ternary therapy and fluorescence tracing in colorectal cancer ablation

Photothermal therapy (PTT) is an emerging cancer therapeutic modality displaying the great potential to clinical patients. However, the conventional PTT is suffering from restrictions of heat resistance of tumor cells (e.g. the overexpression of heat shock proteins, HSPs) and adverse effects to normal cells. To break the shackles, herein, a hypoxia-responsive theranostic nanoplatform (GA/BN LIP) was designed for achieving synergistic chemotherapy, photothermal therapy (PTT), and photodynamic therapy (PDT) through overcoming heat-shock response, while enabling fluorescence tracing. The GA/BN LIP consisted of a hypoxia-responsive liposomal material (DSPE-AZO-PEG) as the shell, surface-functionalized with cRGD peptides targeted binding to integrin αVβ3 receptor expressed in tumors. The GA/BN LIP co-delivered gambogic acid (GA) as HSP90 inhibitor and hypoxia-responsive photosensitizer Bcy-NO2. After GA/BN LIP entering tumor cells by integrin αVβ3 receptor-mediated endocytosis, drugs were specifically released in response to hypoxic conditions due to lysis of liposomes. GA not only directly killed tumor cells to realize chemotherapy, but also sensitized tumor cells to PTT by downregulating HSP90 protein expression, meantime Bcy-NO2 targeted mitochondria for combined PTT and PDT. Intriguingly, the reduction of Bcy-NO2 by nitroreductase (NTR) resulted in the restoration of fluorescence, achieving real-time monitoring of the theranostic process in live cells. In conclusion, this theranostic system, designed to target the hypoxic tumor microenvironment, utilized a sensitization mechanism to enhance the synergistic effects of chemo/PTT/PDT therapy, resulting in improved antitumor efficacy in both in vitro and in vivo studies.

Covalent organic frameworks (COFs)-mediated multimodal sonodynamic therapy for the anticancer applications

As a promising anticancer modality, sonodynamic therapy (SDT) is becoming popular with the cooperative services of covalent organic frameworks (COFs). In this review, a comprehensive observation about the COFs-mediated SDT is preached by focusing on the fast-track advances in the cancer treatments. Here, the review not only systematically shows the theranostic applications of COFs-based nanodrugs, but also deeply describes the COFs-mediated SDT according to the Type-I and Type-II activation mechanisms. More importantly, the review hierarchically narrates many successes in the COFs-coordinated multimodal SDT/X platforms, highlighting their competitive superiority and improvements in the anticancer applications. In addition, the review also proposes some possible challenges of COFs-mediated SDT strategies. Accordingly, the development of COFs and SDT in the anticancer platform will promote the technological innovation of nanodrugs and facilitate the close exchange of cancer-related events.

Homologous-Targeting Porous Type I/II Nanophotosensitizers for Efficient Delivery of STING Agonists and Enhanced Photodynamic Cancer Immunotherapy

Immunotherapy as a transformative cancer treatment modality frequently struggles with the immunosuppressive tumor microenvironment, which hinders effective immune responses. In this report, we construct biomimetic tumor cell membrane-cloaked porous covalent organic framework (COF) nanophotosensitizers (CMSCOFs) to synergistically enhance photodynamic therapy (PDT) and stimulate interferon genes (STING)-mediated immunotherapy. CMSCOF is prepared from porphyrin and benzothiadiazole-based units and cloaked with 4T1 cancer cell membranes for homologous tumor targeting. The porous structure of COF enables efficient encapsulation of the non-nucleotide STING agonist SR717. Upon 660 nm light irradiation, CMSCOFs trigger both type I and II photodynamic effects by producing both superoxide (O2•-) and singlet oxygen (1O2). The tumor cell membrane-cloaked design improves the stability of the nanophotosensitizers and mimics the natural cancer cells for enhanced blood circulation, tumor accumulation, and homologous-targeting to tumors. Inside tumor tissues, this unique CMSCOF design leads to enhanced immunogenic cell death (ICD) of tumor cells upon exposure to light irradiation. Furthermore, the encapsulated STING agonist SR717 is released after cellular internalization to activate the STING pathway and elicit a potent antitumor immune response. This synergistic approach effectively reverses the immunosuppressive tumor microenvironment, enhances cytotoxic T cell infiltration, and suppresses both primary and metastatic tumors, demonstrating the potential of CMSCOF nanophotosensitizers as a promising platform for photodynamic cancer immunotherapy.

Efficient enrichment and sensitive determination of endocrine disruptors in PPCPs by novel magnetic covalent organic framework extraction coupled with HPLC-MS/MS

Endocrine-disrupting chemicals (EDCs) are a growing class of pollutants commonly found in environmental matrices due to their extensive use in pharmaceuticals and personal care products (PPCPs). In this study, a novel magnetic covalent organic framework (COF), Fe3O4-COOH@TFP-BHBD, was successfully synthesized and utilized as an adsorbent for magnetic solid-phase extraction (MSPE) of EDCs from PPCPs. The core-shell structured adsorbent demonstrated a high specific surface area, strong magnetic responsiveness and excellent stability. A COF-MSPE-high-performance liquid chromatography-tandem mass spectrometry (COF-MSPE-HPLC-MS/MS) method was developed for the quantitative analysis of EDCs in PPCPs. Under the optimized condition, the detection and quantification limits of this method reached as low as 0.001-0.007 ng/mL and 0.004-0.025 ng/mL, respectively. This method was validated and proven capable to analyze real PPCP samples, while the spiked recovery rates in ranged from 85.62 to 107.83 % with RSD of 2.28-8.58 %. Moreover, the adsorption mechanism was investigated using density functional theory (DFT) calculations. The DFT results revealed that the efficient enrichment capacity of Fe3O4-COOH@TFP-BHBD for EDCs can be attributed to π-π interactions and hydrogen bondings. This proposed method provides excellent adsorption ability and sensitivity for the extraction and precise detection of EDCs in PPCPs.

Porphyrin-based covalent organic framework with NIR absorption: Preparation, hyaluronic acid modification, and cascading a hypoxia-sensitive drug for synergistic therapy of cancer phototherapy/chemotherapy

Porphyrins are popular photosensitizers for photodynamic therapy of diseases. However, the poor water solution and short absorption wavelengths of porphyrins limit their clinical application. In this work, a novel worm-like porphyrin covalent organic framework (Por-COF) with excellent dispersibility and near-infrared absorption was prepared via a facile method. First, a pH-responsive macromolecule was prepared using Schiff base bonds between porphyrin and terephthalaldehyde, and the spatial arrangement of macromolecules was controlled to prepare Por-COF. Second, the hypoxia-responsive drug tirapazamine (TPZ) and tumor-targeted hyaluronic acid (HA) were loaded to Por-COF through the electrostatic effect to prepare a multifunction nanomedicine (Por-COF@TPZ/HA) that could simultaneously produce abundant reactive oxygen species and high temperature via808 nm laser irradiation. TPZ was cascaded for the synergistic therapy of cancers. In vitro cytotoxicity showed that the inhibition rate of cell activity in the Por-COF@TPZ/HA + Laser group was 1.2 times higher than that in the Por-COF/HA + Laser group. In vivo experiments also demonstrated that the aggravated tumor hypoxia caused by photodynamic therapy could activate TPZ to achieve high-efficiency chemotherapy. Combined photodynamic-photothermal therapy and chemotherapy had an outstanding synergistic effect. This work provides a promising method for Por-COF preparation and a feasible strategy for the synergistic therapy of cancers.

Hypoxia-Targeted-Therapy: Mussel-inspired hollow polydopamine nanocarrier containing MoS2 nanozyme and tirapazamine with anti-angiogenesis property for synergistic tumor therapy

Photothermal therapy (PTT) using thermal and tumor microenvironment-responsive reagents is promising for cancer treatment. This study demonstrates an effective PTT nanodrug consisting of hollow-structured, thermally sensitive polydopamine nanobowls (HPDA NB), molybdenum sulfide (MoS2) nanozyme, and tirapazamine (TPZ; a hypoxia-responsive drug), with a structure of HPDA@TPZ/MoS NBs, which is hereafter denoted as HPTZMoS NBs. With the Fenton-like activity, the HPTZMoS NBs in the presence of H2O2 catalyze the formation of hydroxyl radicals, providing chemodynamic therapy (CDT) effect and deactivating glutathione. Under acidic conditions, HPTZMoS NBs facilitate the release of sulfide ions (S2-) and TPZ, providing a combination of chemotherapy (CT) and hydrogen sulfide (H2S) gas therapy (GT). Under an 808-nm NIR laser irradiation, the HPTZMoS NBs efficiently convert photo energy to thermal energy, providing PTT and improved CDT, CT, and GT effects. Upon treatment with an NIR laser and H2O2, a synergistic effect leads to substantial tumor cell eradication. Additionally, HPTZMoS NBs disrupt vascular endothelial growth factor (VEGF-A165)-induced cell migration in human umbilical vein endothelial cells through its strong interaction with VEGF-A165. In vivo studies in 4T1-tumor-bearing mice confirm that HPTZMoS NBs induces significant tumor destruction through a combination of PTT, hyperthermia-induced CDT, GT, and CT pathways. This study presents a multifaceted, highly selective nanotherapy platform with potent anti-angiogenesis properties, holding significant promise for future clinical applications.

Multieffect Specific Nanovesicles for Homing Resistant Tumors and Overcoming Osimertinib-Acquired Resistance in NSCLC

Acquired resistance to osimertinib (Osi) remains a major obstacle in the treatment of patients with EGFR-mutant non-small cell lung cancer (NSCLC). AXL elevation is a known key mechanism of Osi-resistance, and therapeutic strategies remain scarce. Emerging evidence reveals that an increased intracellular glutathione (GSH) level induces Osi resistance. In this study, a new mechanism is identified by which GSH regulates AXL expression via glutathione peroxidase 4 (GPX4) in Osi-resistant cells. A multifunctional covalent organic framework (COF) nanoplatform for GSH consumption, AXL inhibition, and co-delivery of the AXL inhibitor (Brigatinib) and Osi is creatively constructed to confirm whether Osi sensitivity improves by simultaneously targeting GSH-AXL resistance mechanisms. Furthermore, it is coated, for the first time, the COF carrier system with specific vesicles to precisely home it into resistant tumors, where CDH2 adhesion molecules play a crucial role. The engineered multifunctional antiresistance-specific nanovesicles effectively inhibited the GSH-AXL axis, induced apoptosis in Osi-resistant cells both in vitro and in vivo, and delayed the progression of Osi-resistant tumors. Overall, these findings provide a novel strategy to overcome the Osi-acquired resistance caused by high AXL levels in NSCLC.

Covalent Organic Frameworks for Green Energy: Synthesis, Properties, and Applications

Covalent organic frameworks (COFs) are a new type of porous organic crystalline material, which have become an emerging platform for promoting the development of green energy technology due to their high surface area, adjustable pores, low skeleton density, and easy functionalization. In recent years, with the continuous advancement of synthesis technology, the synthesis efficiency and sustainability of COFs have been significantly improved, from traditional solvothermal methods to the emergence of various green synthesis strategies such as ion thermal, mechanochemical, and ultrasound assisted methods. This article reviews the main synthesis methods of COFs and explores their applications in the field of green energy, such as photocatalysis, gas adsorption and separation, electrocatalysis, battery, supercapacitor and Proton exchange membrane fuel cell. By analyzing the performance and mechanism of COFs in these applications in detail, this article further looks forward to the challenges and future development trends faced by COFs in green energy technology, aiming to provide valuable reference and inspiration for researchers in related fields.

Covalent organic frameworks in cancer theranostics: advancing biomarker detection and tumor-targeted therapy

In recent years, covalent organic frameworks (COFs) have garnered considerable attention in the field of onco-nanotechnology as a new type of nanoporous construct due to their promising physicochemical properties, ease of modification, and ability to be coupled with several moieties and therapeutic molecules. They can not only be used as biocompatible nanocarriers to deliver therapeutic payloads to the tumor zone selectively but can also be combined with a variety of therapeutic modalities to achieve the desired treatments. This review comprehensively presented recent achievements and progress in COF-based cancer diagnosis, detection, and cancer therapy to provide a better prospect for further research. Herein our primary emphasis lies on exploring the application of COFs as potential sensors for cancer-derived biomarkers that have received comparatively less attention in previous discussions. While the utilization of COFs in solid tumor therapy has faced significant challenges in scientific research and clinical applications, we reviewed the most promising features that underscore their potential in cancer theranostics.

Mannose functionalized small molecule nanodrug self-assembled from amphiphilic prodrug connected by disulfide bonds for synergistic cancer chemotherapy and photodynamic/photothermal therapy

Compared to conventional nanocarrier-based drug delivery technology, small-molecule-assembled nanomaterials provide various advantages, including higher drug loading efficiency, lower excipient-related toxicity, and a simpler formulation process. Our research constructed a mannonse-modified small-molecule-assembled nanodrug for synergistic photodynamic/chemotherapy against A549 cancer cells. The hydrophobic hypoxic-activated agent tirapazamine (TPZ) and a hydrophilic fluorescence probe Cyanine 3 (Cy3) constitute this amphiphilic prodrug via a glutathione (GSH)-responsive linkage, which could self-assemble into stable nanoparticles (NPs) and encapsulate a newly synthesized photosensitizer (SeBDP). To enhance the tumor targeting capability, we introduced a tumor-targeted nanodrug SeBDP@TPZ-S-S-Cy/Man NPs by co-assembling mannose-modified lipid (DSPE-PEG-Man). The GSH-responsive linkage of TPZ-S-S-Cy can be rapidly cleaved by GSH to release the therapeutic agents and fluorescent molecule. The released SeBDP generate reactive oxygen species (ROS) to specifically kill cancer cells and elevate hypoxia, thereby enhancing the cytotoxicity of TPZ. SeBDP@TPZ-S-S-Cy/Man NPs exhibited high selectivity and efficiency for in vivo combination therapy without adverse effects to normal tissues. Our findings demonstrate that SeBDP@TPZ-S-S-Cy/Man NPs have great potential for enhancing cancer treatment both in vitro and in vivo by combining an oxygen depletion prodrug with a hypoxia-activated antitumor agent. Thus, the GSH-sensitive self-assembled nanodrug from an amphiphilic hypoxia-activated prodrug, could serve as a potential drug carrier in targeted synergistic cancer therapy.

Boosting Multicolor Emission Enhancement in Two-Dimensional Covalent-Organic Frameworks via the Pressure-Tuned π-π Stacking Mode

Covalent-organic frameworks (COFs) are dynamic covalent porous organic materials constructed from emissive molecular organic building blocks. However, most two-dimensional (2D) COFs are nonemissive or weakly emissive in the solid state owing to the intramolecular rotation and vibration together with strong π-π interactions. Herein, we report a pressure strategy to achieve the bright multicolor emission from yellow to red in the 2D triazine triphenyl imine COF (TTI-COF). Intriguingly, the TTI-COF experiences a 24-fold enhancement under a mild pressure of 2.7 GPa compared with the initial state. Joint experimental and theoretical results reveal that the restricted intramolecular chemical bond vibrations and the reduced π-π interactions originating from the offset stacking mode account for the significant pressure-induced emission enhancement. Furthermore, such piezochromic behavior may be ascribed to the decreased energy gap and enhanced intermolecular interaction. Our investigation offers constructive guidelines for designing 2D COF materials with high photoluminescence performance.

Hypoxia-Responsive Covalent Organic Framework Nanoplatform for Breast-Cancer-Targeted Cocktail Immunotherapy via Triple Therapeutic Switch Mechanisms

Covalent organic frameworks (COFs), known for their exceptional in situ encapsulation and precise release capabilities, are emerging as pioneering drug delivery systems. This study introduces a hypoxia-responsive COF designed to encapsulate the chemotherapy drug gambogic acid (GA) in situ. Bimetallic gold-palladium islands were grown on UiO-66-NH2 (UiO) to form UiO@Au-Pdislands (UAPi), which were encapsulated with GA through COF membrane formation, resulting in a core-shell structure (UAPiGC). Further modification with hyaluronic acid (HA) created UiO@Au-Pdislands@GA-COF@HA (UAPiGCH) for enhanced tumor targeting. In the hypoxic tumor microenvironment, the COF collapses, releasing GA and UAPi, initiating a triple therapeutic response: nanozyme-catalyzed therapy, near-infrared II (NIR-II) mild photothermal therapy (mild-PTT), and chemotherapy. UAPi exhibits catalase (CAT)-like and peroxidase (POD)-like activities, generating oxygen to alleviate hypoxia and reactive oxygen species (ROS) for tumor destruction. GA acts as a chemotherapeutic agent and inhibits heat shock protein 90 (HSP90), enhancing photothermal sensitivity. In vitro and in vivo studies confirm UAPiGCH's ability to induce pyroptosis, stimulate dendritic cell maturation, and boost T cell infiltration, demonstrating its potential as a precise therapeutic nanoplatform. This strategy integrates multiple therapies into a hypoxia-responsive system, offering promising applications in cancer treatment.

Covalent Organic Frameworks for Membrane Separation

Membranes with switchable wettability, solvent resistance, and toughness have emerged as promising materials for separation applications. However, challenges like limited mechanical strength, poor chemical stability, and structural defects during membrane fabrication hinder their widespread adoption. Covalent organic frameworks (COFs), crystalline materials constructed from organic molecules connected by covalent bonds, offer a promising solution due to their high porosity, stability, and customizable properties. The ordered structures and customizable functionality provide COFs with a lightweight framework, large surface area, and tunable pore sizes, which have attracted increasing attention for their applications in membrane separations. Recent research has extensively explored the preparation strategies of COF membranes and their applications in various separation processes. This review uniquely delves into the influence of various COF membrane fabrication techniques, including interfacial polymerization, layer-by-layer assembly, and in situ growth, on membrane thickness and performance. It comprehensively explores the design strategies and potential applications of these methods, with a particular focus on gas separation, oil/water separation, and organic solvent nanofiltration. Furthermore, future opportunities, challenges within this field, and potential directions for future development are proposed.

Local Regulation of Mitochondrial Respiratory for Enhancing Photodynamic Therapy and Breaking Chemoresistance in Hypoxia

The hypoxic condition in solid tumors induces therapy resistance, limited therapeutic efficacy, and tumor recurrence, especially for chemotherapy and aerobic photodynamic therapy (PDT). To address this matter, an O2 regulator (SNP@Ato) is designed for breaking chemoresistance and enhancing PDT, which is constructed by loading Atovaquone (Ato) through self-assembly and host-guest interaction between β-cyclodextrin functionalized tetraphenylporphyrin (TPP-CD4) and thioketal-linked camptothecin/azobenzene (Azo-TK-CPT). Specifically, the porphyrin units in SNP@Ato are in "Off state" due to the photoinduced electron transfer (PET) effect between the porphyrin units and azobenzene. After encountering the hypoxic condition in solid tumors, SNP@Ato is dissociated by the cleaved azobenzene on account of over-expressed azo-reductase. Then the mitochondrial respiratory of cancer cells would be suppressed with the participation of Ato, generating a local hypoxia relief for sensitized chemotherapy and enhanced PDT. Accompanied by efficient PDT, the TK linker is broken by ROS, and the CPT is released from the prodrugs. Compared with the SNP group without oxygen-regulator, SNP@Ato exhibits a remarkable improvement of the therapeutic effect against hypoxic tumors in vitro and in vivo. This work proposes a novel paradigm for overcoming hypoxia-induced therapeutic resistance.

Advancements in framework materials for enhanced energy harvesting

Energy harvesting, the process of capturing ambient energy from various sources and converting it into usable electrical power, has attracted a lot of attention due to its potential to provide long-term and self-sufficient energy solutions. This comprehensive review thoroughly explores the use of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) for energy harvesting by piezoelectric and triboelectric nanogenerators (PENGs and TENGs). It begins by classifying and outlining the structural diversity of MOFs and COFs, which is key to understanding their importance in energy applications. Key characterization techniques are focused on emphasizing their importance in optimizing material properties for efficient energy conversion. The working mechanisms of PENGs and TENGs are discussed, focusing on their ability to transform mechanical energy into electrical energy and their advantages in operation. The use of MOFs and COFs in energy harvesting applications is then discussed, including synthesis procedures, unique characteristics relevant to electricity conversion, and various practical applications such as self-powered sensors and wearable electronics. Current challenges such as stability, scalability, and performance improvements are explored, as well as proposed future improvements to help advance current research. Finally, the study highlights the importance of framework materials for the development of energy harvesting systems, providing an invaluable resource for academics and engineers seeking to exploit the potential of these materials for renewable energy sources. The goal of this article is to stimulate further invention and implementation of efficient materials-based energy harvesting framework devices by integrating recent advances and mapping future possibilities.

Engineered hypoxia-responsive albumin nanoparticles mediating mitophagy regulation for cancer therapy

Hypoxic tumors present a significant challenge in cancer therapy due to their ability to adaptation in low-oxygen environments, which supports tumor survival and resistance to treatment. Enhanced mitophagy, the selective degradation of mitochondria by autophagy, is a crucial mechanism that helps sustain cellular homeostasis in hypoxic tumors. In this study, we develop an azocalix[4]arene-modified supramolecular albumin nanoparticle, that co-delivers hydroxychloroquine and a mitochondria-targeting photosensitizer, designed to induce cascaded oxidative stress by regulating mitophagy for the treatment of hypoxic tumors. These nanoparticles are hypoxia-responsive and release loaded guest molecules in hypoxic tumor cells. The released hydroxychloroquine disrupts the mitophagy process, thereby increasing oxidative stress and further weakening the tumor cells. Additionally, upon laser irradiation, the photosensitizer generates reactive oxygen species independent of oxygen, inducing mitochondria damage and mitophagy activation. The dual action of simultaneous spatiotemporal mitophagy activation and mitophagy flux blockade results in enhanced autophagic and oxidative stress, ultimately driving tumor cell death. Our work highlights the effectiveness of hydroxychloroquine-mediated mitophagy blockade combined with mitochondria-targeted photosensitizer for cascade-amplified oxidative stress against hypoxic tumors.

Targeting tumor microenvironments with gold nanoparticles for enhanced photothermal therapy

Gold nano-drug delivery system-mediated photothermal therapy (PTT) has been widely studied in the field of anti-tumor. In order to achieve accurate drug release and improve photothermal efficiency, nano-drug delivery strategies targeting tumor microenvironment (TME) have become a hot research topic in recent years. This paper introduces four characteristics of the TME: hypoxia, low pH, high level of reactive oxygen species (ROS), and overexpression of enzymes. These differences between tumor and normal tissue become effective targets for tumor therapy. This paper summarizes the gold nano-drug delivery system that can target these four characteristics, so as to realize a large amount of drug aggregation at the tumor site and achieve efficient photothermal therapy. Moreover, the multi-response nano-drug delivery system can further control drug delivery and improve therapeutic effects. Finally, this paper also summarizes the gold nanoparticles for tumor therapy that have entered clinical trials so far. The purpose of this review is to discuss the research progress of enhanced photothermal therapy with gold nano-drug delivery systems targeting the TME, with a view to providing a reference for the future development of novel anti-tumor nanoplatforms and the clinical translation of gold nanoparticles.

Covalent organic framework-based ratiometric electrochemical sensing platform for ultrasensitive determination of amyloid-β 42 oligomer

Accurate and sensitive detection of amyloid-β 42 oligomer (Aβ42O) is of great significance for early diagnosis of Alzheimer's disease (AD). Herein, a signal on-off ratiometric electrochemical immunosensor was developed for highly selective and quantitative determination of Aβ42O by using novel covalent organic frameworks (COFs) composites as the sensing platform. This immunosensor produced two independent electrochemical signals from the [Fe(CN)6]3-/4- and methylene blue (MB) probes at different potentials based on the electrocatalytic activity of gold nanoparticle-functionalized porphyrinyl COFs nanocomposites toward [Fe(CN)6]3-/4- and the signal probe of MB encapsulated in the aptamer-modified alkynyl COFs. Because the two signals of [Fe(CN)6]3-/4- and MB changed in opposite directions, a signal on-off mode was generated which can correct the results by introducing a reference signal and effectively eliminate background interference. Under optimal experimental conditions, the current ratio (IMB/I[Fe(CN)6]3-/4-) was well linearly related to the logarithmic value of Aβ42O concentrations in the range of 10 pM to 1 μM, and the detection limit was 5.1 pM (S/N = 3). Additionally, the immunosensor exhibited satisfactory performance in case of real cerebrospinal fluid samples. The designed ratiometric electrochemical immunosensor provides a valuable route for early diagnosis of AD and our results also pave the way for designing of sensing platforms using COF-based nanomaterials and extending their functions and applications to bioanalysis.

Polymorphic Supramolecular Therapeutic Platforms with Precise Dye/Drug Ratio to Perform Synergistic Chemo-Photo Anti-Tumor Therapy and Long-Term Immune Protection

Malignant tumor has become one of the hellish killers threatening the health of people around the world, its diagnosis and treatment has become the concerns of public. However, the optimal therapeutic dose, undesired side-effect, and long-term immune activation were key and bottleneck problems in tumor treatment. Herein, different batches of supramolecular therapeutic platforms, including vesicles, spherical nanoparticles, and cylindrical nanorods, with precise ratios of dye to drug (1:2) and multiple stimulus responsiveness were constructed by host-guest complexation between cyanine-camptothecin conjugates (IR780-CPT2) and β-cyclodextrin (β-CD) pendent hydrophilic copolymers. The reduction responsiveness, near-infrared photothermal conversion and singlet oxygen (1O2) generation performances endowed these platforms excellent cancer cells killing effect in both of in vitro cellular experiments and in vivo mice models. More importantly, without affecting the weight of mice, the maturation of dendritic cells, proliferation of T cells, up-regulation of high mobility group protein B1, and reduction of immunosuppressive regulatory T cells were detected after employing a synergistic chemo-photo therapy, demonstrating the body's immune effect was successfully activated. Thus, during the treatment of primary tumor, the distal tumor was also inhibited. We believe this work could provide a distinctive way to fabricate supramolecular theranostic platforms with different morphologies and improve antitumor and antimetastasis capabilities.

A Noncationic Biocatalytic Nanobiohybrid Platform for Cytosolic Protein Delivery Through Controlled Perturbation of Intracellular Redox Homeostasis

Intracellular delivery of proteins has largely been relying on cationic nanoparticles to induce efficient endosome escape, which, however, poses serious concerns on the inflammatory and cytotoxic effects. Herein, a versatile noncationic nano biohybrid platform is introduced for efficient cytosolic protein delivery by utilizing a nano-confined biocatalytic reaction. This platform is constructed by co-immobilizing glucose oxidase (GOx) and the target protein into nanoscale hydrogen-bonded organic frameworks (HOFs). The biocatalytic reaction of nano-confined GOx is leveraged to induce controlled perturbation of intracellular redox homeostasis by sustained hydrogen peroxide (H2O2) production and diminishing the flux of the pentose phosphate pathway (PPP). This in turn induces the endosome escape of nanobiohybrids. Concomitantly, GOx-mediated hypoxia leads to overexpression of azo reductase that initiated the materials' self-destruction for releasing target proteins. These biological effects collectively induce highly efficient cytosolic protein delivery. The versatility of this delivery platform is further demonstrated for various types of proteins, different protein loading approaches (in situ immobilization or post-adsorption), and in multiple cell lines. Finally, the protein delivery efficiency and biosafety are demonstrated in a tumor-bearing mouse model. This nanohybrid system opens up new avenues for intracellular protein delivery and is expected to be extensively applicable for a broad range of biomolecuels.

Hypoxia-Activated Biodegradable Porphyrin-Based Covalent Organic Frameworks for Photodynamic and Photothermal Therapy of Wound Infection

Wound infections have gradually become a major threat to human health. Recently, covalent organic frameworks (COFs) have shown great potential in antibacterial and wound healing; however, difficult biodegradability and long-time in vivo retention limit their further application. Herein, biodegradable COFs containing porphyrin backbones and hypoxia-sensitive azobenzene group, namely, HRCOFs, are fabricated for photodynamic therapy (PDT) and photothermal therapy (PTT) of wound infection. Due to the introduction of a porphyrin molecule, HRCOFs can produce singlet oxygen (1O2) under 660 nm laser irradiation. The prepared HRCOFs can also generate thermal energy under 808 nm NIR laser irradiation. HRCOFs show excellent synergetic antibacterial ability against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. The in vivo experiments also demonstrate synergistic PDT and PTT effects of HRCOFs against wound infection. Importantly, HRCOFs are response to wound microenvironment, can be degraded for clearance, and avoid some adverse effects caused by long-time retention in vivo, exhibiting good biocompatibility. In general, the obtained biodegradable HRCOFs with both photodynamic and photothermal effects can be used for antibacterial infections and provide great value for promoting wound healing.

Dual Recognition Strategy-Based Ratiometric Electrochemical Assay for Ultrasensitive and Accurate Detection of Specific Circulating Tumor Cells

Sensitive, specific, and accurate detection of circulating tumor cells (CTCs) is of great importance in the diagnosis and prognosis of cancer. Herein, an ultrasensitive ratiometric electrochemical biosensor was designed with a dual recognition strategy for highly specific and accurate detection of circulating MCF-7 human breast cancer cells based on gold film-modified porous organic cages loaded with ferrocene (Au/Fc@POCs) as the substrate and methylene blue-encapsulated covalent organic frameworks (MB@COFs) as the label material, producing two independent electrochemical signals from the Fc and MB probes, respectively. As the concentration of MCF-7 cells increases, the electrochemical signal of MB enhances significantly while the oxidation signal of Fc decreases remarkably. Under optimal experimental conditions, the ratios (IMB/IFc) between the double signals showed a broad dynamic range of 10 to 1 × 107 cells/mL with an effectively lower detection limit of 1 cells/mL (S/N = 3). Furthermore, the biosensor was able to accurately enumerate MCF-7 cells in human serum samples with excellent results. In this work, the developed ratiometric electrochemical biosensor offers a reliable and sensitive strategy for the quantitative determination of circulating MCF-7 human breast cancer cells as well as an effective approach for the clinical detection of rare cancer cells, especially in early stage cancer diagnosis.

Stimuli-Responsive Covalent Organic Frameworks for Cancer Therapy

Chemotherapy as a common anticancer therapeutic modality is often challenged by various obstacles such as poor stability, low solubility, and severe side effects of chemotherapeutic agents as well as multidrug resistance of cancerous cells. Nanoparticles in the role of carriers for chemotherapeutic drugs and platforms for combining different therapeutic approaches have effectively participated in overcoming such drawbacks. In particular, nanoparticles able to induce their therapeutic effect in response to specific stimuli like tumor microenvironment characteristics (e.g., hypoxia, acidic pH, high levels of glutathione, and overexpressed hydrogen peroxide) or extrinsic stimulus of laser light bring about more precise and selective treatments. Among them, nanostructures of covalent organic frameworks (COFs) have drawn great interest in biomedical fields during recent years. Possessing large surface area, high porosity, structural stability, and customizable architecture, these biocompatible porous crystalline polymers properly translate to promising platforms for drug delivery and induction of combination therapies. With the focus on stimuli-responsive characteristics of nanoscale COFs, this study aims to propose an overview of their potentiality in cancer treatment on the basis of chemotherapy alone or in combination with sonodynamic, chemodynamic, photodynamic, and photothermal therapies.

Photothermal Conversion Porous Organic Polymers: Design, Synthesis, and Applications

Solar energy is a primary form of renewable energy, and photothermal conversion is a direct conversion process with tunable conversion efficiency. Among various kinds of photothermal conversion materials, porous organic polymers (POP) are widely investigated owing to their controllable molecular design, tailored porous structures, good absorption of solar light, and low thermal conductivity. A variety of POP, such as conjugated microporous polymers (CMP), covalent organic frameworks (COF), hyper-crosslinked porous polymers (HCP), polymers of intrinsic microporosity (PIM), porous ionic polymers (PIP), are developed and applied in photothermal conversion applications of seawater desalination, latent energy storage, and biomedical fields. In this review, a comprehensive overview of the recent advances in POP for photothermal conversion is provided. The micro molecular structure characteristics and macro morphology of POP are designed for applications such as seawater desalination, latent heat energy storage, phototherapy and photodynamic therapy, and drug delivery. Besides, a probe into the underlying mechanism of structural design for constructing POP with excellent photothermal conversion performance is methodicalized. Finally, the remaining challenges and prospective opportunities for the future development of POP for solar energy-driven photothermal conversion applications are elucidated.

An "AND" logic gate-based supramolecular therapeutic nanoplatform for combatting drug-resistant non-small cell lung cancer

Despite targeted therapies like epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), non-small cell lung cancer (NSCLC) remains a clinical challenge due to drug resistance hampering their efficacy. Here, we designed an "AND" logic gate-based supramolecular therapeutic platform (HA-BPY-GEF-NPs) for the treatment of EGFR-TKI resistant NSCLC. This system integrates both internal and external stimuli-responsive mechanisms that need to be activated in a preset sequence, enabling it to precisely control drug release behavior for enhancing therapeutic precision. By programming the system to respond to sequential near-infrared (NIR) irradiation and enzyme (cathepsin B) inputs, the release of gefitinib is effectively confined to the tumor region. Moreover, the NIR irradiation induces reactive oxygen species production, suppressing tumor growth and inhibiting bypass signaling pathways. The designed drug delivery system offers a highly controlled and targeted therapeutic approach, effectively inhibiting tumor growth, suppressing bypass signaling pathways, and overcoming EGFR-TKI resistance, thus offering a potential solution for maximizing therapeutic benefits.

Porous Organic Polymer-Based Nanocomposites for Hypoxia Relieving and Enhanced Chemotherapy in Hepatocellular Carcinoma

Uncontrolled proliferation and altered metabolism of cancer cells result in an imbalance of nutrients and oxygen supply, and persuade hypoxia. Hypoxia, in turn, activates the transcription gene HIF-1α, which eventually upregulates the efflux transporter P-gp and induces multidrug resistance (MDR). Thus, hypoxia leads to the development of resistance to conventional therapies. Therefore, the fabrication of a nanoscale porous system enriched with upconversion nanoparticles to target cancer cells, evade hypoxia, and enhance anticancer therapy is the key goal of this article. Herein, upconversion nanoparticles are embedded in a nanoscale porous organic polymer (POP) and further conjugated with a targeting moiety and a catalase molecule. The nanoscale POP embedded in UCNPs is generated at room temperature. The targeting ligand, lactobionic acid, is attached after polymer coating, which effectively targets liver cancer cells. Then, catalase is grafted effectively to produce oxygen. Endogenously generated oxygen alleviates hypoxia in liver cancer cells. The drug- and catalase-loaded composite exhibit greater cytotoxicity in hypoxic liver cells than in normal cells by overcoming hypoxia and downregulating the hypoxia-inducible factors.

Light-Enhanced Tandem-Responsive Nano Delivery Platform for Amplified Anti-tumor Efficiency

Designing nanomedicines with low toxicity, high targeting, excellent therapeutic effects, and precise release is always the major challenges in clinical cancer treatment. Here, we report a light-enhanced tandem-responsive nano delivery platform COF-B@X-03 for amplified anti-tumor efficiency. Biotin-loaded COF-B@X-03 could precisely target tumor cells, and the azo and hydrazone bonds in it would be depolymerized by the overexpressed azoreductase and acidic microenvironment in hypoxic tumors. In vitro experimental results indicate mitochondrial and endoplasmic reticulum stress caused by COF-B@X-03 under light is the direct cause of tumor cell death. In vivo experimental data prove COF-B@X-03 achieves low oxygen dependent phototherapy, and the maintenance of intratumoral hypoxia provides the possibility for the continuous degradation of COF-B@X-03 to generate more reactive oxygen species for tumor photodynamic therapy by released X-03. In the end, COF-B@X-03 phototherapy group achieves higher tumor inhibition rate than X-03 phototherapy group, which is 81.37 %. Meanwhile, COF-B@X-03 significantly eliminates the risk of tumor metastasis. In summary, the construction of this tandem-responsive nano delivery platform provides a new direction for achieving efficient removal of solid tumors in clinical practice.

Hypoxia-accelerating pyroptosis nanoinducers for promoting image-guided cancer immunotherapy

Precise image-guided cancer immunotherapy holds immense potential in revolutionizing cancer treatment. The strategies facilitating activatable imaging and controlled therapeutics are highly desired yet to be developed. Herein, we report a new pyroptosis nanoinducer that integrates aggregation-induced emission luminogen (AIEgen) and DNA methyltransferase inhibitor with hypoxia-responsive covalent organic frameworks (COFs) for advanced image-guided cancer immunotherapy. We first synthesize and compare three donor-acceptor type AIEgens featuring varying numbers of electron-withdrawing units, and find that the incorporation of two acceptors yields the longest response wavelength and most effective photodynamic therapy (PDT) property, surpassing the performance of analogs with one or three acceptor groups. A COF-based nanoplatform containing AIEgen and pyroptosis drug is successfully constructed via the one-pot method. The intra-COF energy transfer significantly quenches AIEgen, in which both fluorescence and PDT properties greatly enhance upon hypoxia-triggered COF degradation. Moreover, the photodynamic process exacerbates hypoxia, accelerating pyroptosis drug release. The nanoagent enables sensitive delineation of tumor site through in situ activatable fluorescence signature. Thanks to the exceptional ROS production capabilities and hypoxia-accelerating drug release, the nanoagent not only inhibits primary tumor growth but also impedes the progression of distant tumors in 4T1 tumor-bearing mice through potent pyroptosis-mediated immune response. This research introduces a novel strategy for achieving activatable phototheranostics and self-accelerating drug release for synergetic cancer immunotherapy.

Macromolecular Nano-Assemblies for Enhancing the Effect of Oxygen-Dependent Photodynamic Therapy Against Hypoxic Tumors

In oxygen (O2)-dependent photodynamic therapy (PDT), photosensitizers absorb light energy, which is then transferred to ambient O2 and subsequently generates cytotoxic singlet oxygen (1O2). Therefore, the availability of O2 and the utilization efficiency of generated 1O2 are two significant factors that influence the effectiveness of PDT. However, tumor microenvironments (TMEs) characterized by hypoxia and limited utilization efficiency of 1O2 resulting from its short half-life and short diffusion distance significantly restrict the applicability of PDT for hypoxic tumors. To address these challenges, numerous macromolecular nano-assemblies (MNAs) have been designed to relieve hypoxia, utilize hypoxia or enhance the utilization efficiency of 1O2. Herein, we provide a comprehensive review on recent advancements achieved with MNAs in enhancing the effectiveness of O2-dependent PDT against hypoxic tumors.

Covalent Organic Framework-Based Theranostic Platforms for Restricting H1N1 Influenza Virus Infection

Background

Influenza A (H1N1) virus is a highly contagious respiratory disease that causes severe illness and death. Vaccines and antiviral drugs are limited by viral variation and drug resistance, so developing efficient integrated theranostic options appears significant in anti-influenza virus infection.

Methods

In this study, we designed and fabricated covalent organic framework (COF) based theranostic platforms (T705@DATA-COF-Pro), which was composed of an RNA polymerase inhibitor (favipiravir, T705), the carboxyl-enriched COF (DATA-COF) nano-carrier and Cy3-labeled single DNA (ssDNA) probe.

Results

The multi-porosity COF core provided an excellent micro-environment and smooth delivery for T705. The ssDNA probe coating bound to the nucleic acids of H1N1 selectively, thus controlling drug release and allowing fluorescence imaging. The combination of COF and probe triggered the synergism, promoting drug further therapeutic outcomes. With the aid of T705@DATA-COF-Pro platforms, the H1N1-infected mouse models lightly achieved diagnosis and significantly prolonged survival.

Conclusion

This research underscores the distinctive benefits and immense potential of COF materials in nano-preparations for virus infection, offering novel avenues for the detection and treatment of H1N1 virus infection.

Mesoporous manganese nanocarrier target delivery metformin for the co-activation STING pathway to overcome immunotherapy resistance

Targeting the stimulator of interferon genes (STING) pathway is a promising strategy to overcome primary resistance to immune checkpoint inhibitors in non-small cell lung cancer with the STK11 mutation. We previously found metformin enhances the STING pathway and thus promotes immune response. However, its low concentration in tumors limits its clinical use. Here, we constructed high-mesoporous Mn-based nanocarrier loading metformin nanoparticles (Mn-MSN@Met-M NPs) that actively target tumors and respond to release higher concentration of Mn2+ ions and metformin. The NPs significantly enhanced the T cells to kill lung cancer cells with the STK11 mutant. The mechanism shows that enhanced STING pathway activation promotes STING, TBKI, and IRF3 phosphorylation through Mn2+ ions and metformin release from NPs, thus boosting type I interferon production. In vivo, NPs in combination with a PD-1 inhibitor effectively decreased tumor growth. Collectively, we developed a Mn-MSN@Met-M nanoactivator to intensify immune activation for potential cancer immunotherapy.

Covalent Organic Frameworks as Potential Drug Carriers and Chemotherapeutic Agents for Ovarian Cancers

Anticancer drugs are often associated with limitations such as poor stability in aqueous solutions, limited cell membrane permeability, nonspecific targeting, and irregular drug release when taken orally. One possible solution to these problems is the use of nanocarriers of drug molecules, particularly those with targeting ability, stimuli-responsive properties, and high drug loading capacity. These nanocarriers can improve drug stability, increase cellular uptake, allow specific targeting of cancer cells, and provide controlled drug release. While improving the therapeutic efficacy of cancer drugs, contemporary researchers also aim to reduce their associated side effects, such that cancer patients are offered with a more effective and targeted treatment strategy. Herein, a set of nine porous covalent organic frameworks (COFs) were tested as drug delivery nanocarriers. Among these, paclitaxel loaded in COF-3 was most effective against the proliferation of ovarian cancer cells. This study highlights the emerging potential of COFs in the field of therapeutic drug delivery. Due to their biocompatibility, these porous COFs provide a viable substrate for controlled drug release, making them attractive candidates for improving drug delivery systems. This work also demonstrates the potential of COFs as efficient drug delivery agents, thereby opening up new opportunities in the field of sarcoma therapy.

Covalent organic frameworks (COFs) as carrier for improved drug delivery and biosensing applications

Porous organic frameworks (POFs) represent a significant subclass of nanoporous materials in the field of materials science, offering exceptional characteristics for advanced applications. Covalent organic frameworks (COFs), as a novel and intriguing type of porous material, have garnered considerable attention due to their unique design capabilities, diverse nature, and wide-ranging applications. The unique structural features of COFs, such as high surface area, tuneable pore size, and chemical stability, render them highly attractive for various applications, including targeted and controlled drug release, as well as improving the sensitivity and selectivity of electrochemical biosensors. Therefore, it is crucial to comprehend the methods employed in creating COFs with specific properties that can be effectively utilized in biomedical applications. To address this indispensable fact, this review paper commences with a concise summary of the different methods and classifications utilized in synthesizing COFs. Second, it highlights the recent advancements in COFs for drug delivery, including drug carriers as well as the classification of drug delivery systems and biosensing, encompassing drugs, biomacromolecules, small biomolecules and the detection of biomarkers. While exploring the potential of COFs in the biomedical field, it is important to acknowledge the limitations that researchers may encounter, which could impact the practicality of their applications. Third, this paper concludes with a thought-provoking discussion that thoroughly addresses the challenges and opportunities associated with leveraging COFs for biomedical applications. This review paper aims to contribute to the scientific community's understanding of the immense potential of COFs in improving drug delivery systems and enhancing the performance of biosensors in biomedical applications.

Tailoring β-ketoenamine covalent organic framework with azo for blue light-driven selective oxidation of amines with oxygen

Covalent organic frameworks (COFs) present bright prospects in visible light photocatalysis with abundant active sites and exceptional stability. Tailoring an established COF with photoactive group is a prudent strategy to extend visible light absorption toward broad photocatalysis. Here, a β-ketoenamine COF, TpBD-COF, constructed with 1,3,5-triformylphloroglucinol (Tp) and 4,4'-biphenyldiamine (BD), is tailored with azo to validate this strategy. The insertion of azo into BD affords 4,4'-azodianiline (Azo); TpAzo-COF is successfully constructed with Tp and Azo. Intriguingly, the insertion of azo enhances π-conjugation, thereby facilitating visible light absorption and intramolecular electron transfer. Moreover, TpAzo-COF, with an appropriate electronic structure and impressive specific surface area of 1855 m2 g-1, offers substantial active sites conducive to the reduction of oxygen (O2) to superoxide. Compared with TpBD-COF, TpAzo-COF exhibits superior performance for blue light-driven oxidation of amines with O2. Superoxide controls the selective formation of product imines. This work foreshadows the remarkable capacity of tailoring COFs with photoactive group toward broad visible light photocatalysis.

Hydrazone-functionalized nanoscale covalent organic frameworks as a nanocarrier for pH-responsive drug delivery enhanced anticancer activity

Nanoscale covalent organic frameworks (NCOFs) as emerging drug-delivery nanocarriers have received much attention in biomedicine in recent years. However, there are few reports on the application of pH-responsive NCOFs for drug delivery nanosystems. In this work, hydrazone-decorated NCOFs as pH-triggered molecular switches are designed for efficient cancer therapy. These functionalized NCOFs with hydrazone groups on the channel walls (named NCOFs-NHNH2) are obtained via a post-synthetic modification strategy. Subsequently, the anticancer drug doxorubicin (DOX) as the model molecule is loaded through covalent linkage to yield NCOFs-NN-DOX. Finally, soybean phospholipid (SP) is coated on the surface of HNTs-NN-DOX, named NCOFs-NN-DOX@SP, to further enhance the dispersibility, stability and biocompatibility of HNTs in physiological solution. NCOFs-NN-DOX@SP showed an excellent and intelligent sustained-release effect with an almost sixfold increase at pH = 5.2 than at pH = 7.4. In vitro cell toxicity and imaging assays of NCOFs-NN-DOX@SP exhibited an enhanced therapeutic effect on Lewis lung carcinoma (LLC) cells, demonstrating that the fabricated NCOFs have a great potential in cancer therapy. Thus, this work provides a new way toward designing stimulus-responsive functionalized NCOFs and promotes their potential application as an on-demand drug delivery system in the field of cancer treatment.

Radioactive hybrid semiconducting polymer nanoparticles for imaging-guided tri-modal therapy of breast cancer

Due to the rapid progression and aggressive metastasis of breast cancer, its diagnosis and treatment remain a great challenge. The simultaneous inhibition of tumor growth and metastasis is necessary for breast cancer to obtain ideal therapeutic outcomes. We herein report the development of radioactive hybrid semiconducting polymer nanoparticles (SPNH) for imaging-guided tri-modal therapy of breast cancer. Two semiconducting polymers are used to form SPNH with a diameter of around 60 nm via nano-coprecipitation and they are also labeled with iodine-131 (131I) to enhance the imaging functions. The formed SPNH show good radiolabeling stability and excellent photodynamic and photothermal effects under 808 nm laser irradiation to produce singlet oxygen (1O2) and heat. Moreover, SPNH can generate 1O2 with ultrasound irradiation via their sonodynamic properties. After intravenous tail vein injection, SPNH can effectively accumulate in the subcutaneous 4T1 tumors of living mice as verified via fluorescence and single photon emission computed tomography (SPECT) imaging. With the irradiation of tumors using an 808 nm laser and US, SPNH mediate photodynamic therapy (PDT), photothermal therapy (PTT) and sonodynamic therapy (SDT) to kill tumor cells. Such a tri-modal therapy leads to an improved efficacy in inhibiting tumor growth and suppressing tumor metastasis compared to the sole SDT and combinational PDT-PTT. This study thus demonstrates the applications of SPNH to diagnose tumors and combine different therapies for effective breast cancer treatment.

An activatable azophenyl fluorescent probe for hypoxic fluorescence imaging in living cells

Cellular hypoxia is a common pathological process in various diseases. Detecting cellular hypoxia is of great scientific significance for early diagnosis of tumors. The hypoxia fluorescence probe analysis method can efficiently and conveniently evaluate the hypoxia status in tumor cells. These probes are covalently linked by hypoxic recognition groups and organic fluorescent molecules. Currently, the fluorescent molecules used in these probes often exhibit the aggregation-caused quenching effect, which is not conducive to fluorescence imaging in water. Herein, an activatable hypoxia fluorescence probe was constructed by covalently linking aggregation-induced emission luminogens to the hypoxic recognition group azobenzene. It does not emit fluorescence in solution and in solid state under light excitation due to the presence of photosensitive azo bonds. It can be cleaved by intracellular azoreductase into fluorescent amino derivatives with aggregation-induced emission characteristic. As the concentration of oxygen in cells decreases, its fluorescence intensity increases, making it suitable for fluorescence imaging to detect hypoxic environment in live cancer cells. This work broadens the molecular design approach for activatable hypoxia fluorescent probes.

One-Dimensional Covalent Organic Framework with Improved Charge Transfer for Enhanced Electrochemiluminescence

We present a dimensional regulating charge transfer strategy to achieve an enhanced electrochemiluminescence (ECL) by constructing a one-dimensional pyrene-based covalent organic framework (1D-COF). The dual-chain-like edge architecture in 1D-COF facilitates the stabilization of aromatic backbones, the enhancement of electronic conjugations, and the decrease of energy loss. The 1D-COF generates enhanced anodic (92.5-fold) and cathodic (3.2-fold) signals with tripropylamine (TPrA) and K2S2O8 as the anodic and cathodic coreactants, respectively, compared with 2D-COF. The anodic and cathodic ECL efficiencies of 1D-COF are 2.08- and 3.08-fold higher than those of 2D-COF, respectively. According to density functional theory (DFT), the rotational barrier energy (ΔE) of 1D-COF enhances sharply with the increase of dihedral angle, suggesting that the architecture in 1D-COF restrains the intramolecular spin of aromatic chains, which facilitates the decrease of nonradiative transitions and the enhancement of ECL. Furthermore, 1D-COF can be used to construct an ECL biosensor for sensitive detection of dopamine.

Nano-Engineering Strategies for Tumor-Specific Therapy

Nanodelivery systems (NDSs) provide promising prospects for decreasing drug doses, reducing side effects, and improving therapeutic effects. However, the bioapplications of NDSs are still compromised by their fast clearance, indiscriminate biodistribution, and limited tumor accumulation. Hence, engineering modification of NDSs aiming at promoting tumor-specific therapy and avoiding systemic toxicity is usually needed. An NDS integrating various functionalities, including flexible camouflage, specific biorecognition, and sensitive stimuli-responsiveness, into one sequence would be "smart" and highly effective. Herein, we systematically summarize the related principles, methods, and progress. At the end of the review, we predict the obstacles to precise nanoengineering and prospects for the future application of NDSs.

Covalent organic frameworks-derived carbon nanospheres based nanoplatform for tumor specific synergistic therapy via oxidative stress amplification and calcium overload

Combinational therapy in cancer treatment that integrates the merits of different therapies is an effective approach to improve therapeutic outcomes. Herein, a simple nanoplatform (N-CNS-CaO2-HA/Ce6 NCs) that synergized chemodynamic therapy (CDT), photodynamic therapy (PDT), photothermal therapy (PTT), and Ca2+ interference therapy (CIT) has been developed to combat hypoxic tumors. With high photothermal effect, excellent peroxidase-like activity, and inherent mesoporous structure, N-doped carbon nanospheres (N-CNSs) were prepared via in situ pyrolysis of an established nanoscale covalent organic frameworks (COFs) precursor. These N-CNSs acted as PTT/CDT agents and carriers for the photosensitizer chlorin e6 (Ce6), thereby yielding a minimally invasive PDT/PTT/CDT synergistic therapy. Hyaluronic acid (HA)-modified CaO2 nanoparticles (CaO2-HA NPs) coated on the surface of the nanoplatform endowed the nanoplatform with O2/H2O2 self-supply capability to respond to and modulate the tumor microenvironment (TME), which greatly facilitated the tumor-specific performance of CDT and PDT. Moreover, the reactive oxygen species (ROS) produced during PDT and CDT enhanced the Ca2+ overloading due to CaO2 decomposition, amplifying the intracellular oxidative stress and leading to mitochondrial dysfunction. Notably, the HA molecules not only increased the cancer-targeting efficiency but also prevented CaO2 degradation during blood circulation, providing double insurance of tumor-selective CIT. Such a nanotherapeutic system possessed boosted antitumor efficacy with minimized systemic toxicity and showed great potential for treating hypoxic tumors.

Template-Free Self-Assembly of Hollow Microtubular Covalent Organic Frameworks for Oral Delivery of Insulin

Covalent organic frameworks (COFs) have demonstrated versatile application potential since their discovery. Although the structure of COFs is orderly arranged, the synthesis of controllable macrostructures still faces challenges. Herein, we report, to our knowledge, the first template-free self-assembled COF-18 Å hollow microtubule (MT-COF-18 Å) structure and its use for insulin delivery that exhibits high loading capacity, gastroresistance, and glucose-responsive properties. The hollow MT-COF-18 Å was achieved by a template-free method benefiting from the mixed solvents of mesitylene and dioxane. The formation mechanism and morphology changes with insulin loading and release were observed. In Caco-2 cells, the transferrin-coated system demonstrated enhanced insulin cellular uptake and transcellular transport, which indicated great potential for oral applications. Additionally, the composites presented sustained glycemic control and effective insulin blood concentrations without noticeable toxicity in diabetic rats. This work shows that hollow microtubular COFs hold great promise in loading and delivery of biomolecules.

Hypoxia-triggered degradable porphyrinic covalent organic framework for synergetic photodynamic and photothermal therapy of cancer

Nanomedicines receive great attention in cancer treatment. Nevertheless, nonbiodegradable and long-term retention still limit their clinical translation. Herein, we successfully synthesize a hypoxia-triggered degradable porphyrinic covalent organic framework (HPCOF) for antitumor therapy in vivo. HPCOF possesses wide absorption in near infrared region (NIR) which endows HPCOF excellent photothermal conversion efficiency and photoacoustic (PA) imaging ability. Moreover, HPCOF exhibits excellent photodynamic and photothermal effect under special-wavelength laser irradiation. For the first time, the in vitro and in vivo tests demonstrate that HPCOF shows effective therapeutic effect for the combination of PDT and PTT under the monitoring of PA imaging. Importantly, in tumor region, HPCOF could be triggered by hypoxia microenvironment and collapsed gradually, then cleared from the body after treatment. This work fabricates a novel COF for cancer treatment and testifies great potential of HPCOF in clinical application with reducing long-term toxicity.

Nanocarriers address intracellular barriers for efficient drug delivery, overcoming drug resistance, subcellular targeting and controlled release

The cellular barriers are major bottlenecks for bioactive compounds entering into cells to accomplish their biological functions, which limits their biomedical applications. Nanocarriers have demonstrated high potential and benefits for encapsulating bioactive compounds and efficiently delivering them into target cells by overcoming a cascade of intracellular barriers to achieve desirable therapeutic and diagnostic effects. In this review, we introduce the cellular barriers ahead of drug delivery and nanocarriers, as well as summarize recent advances and strategies of nanocarriers for increasing internalization with cells, promoting intracellular trafficking, overcoming drug resistance, targeting subcellular locations and controlled drug release. Lastly, the future perspectives of nanocarriers for intracellular drug delivery are discussed, which mainly focus on potential challenges and future directions. Our review presents an overview of intracellular drug delivery by nanocarriers, which may encourage the future development of nanocarriers for efficient and precision drug delivery into a wide range of cells and subcellular targets.

Strategies for utilizing covalent organic frameworks as host materials for the integration and delivery of bioactives

Covalent organic frameworks (COFs), a new and developing class of porous framework materials, are considered a type of promising carrier for the integration and delivery of bioactives, which have diverse fascinating merits, such as a large specific surface area, designable and specific porosity, stable and orderly framework structure, and various active sites. However, owing to the significant differences among bioactives (including drugs, proteins, nucleic acid, and exosomes), such as size, structure, and physicochemical properties, the interaction between COFs and bioactives also varies. In this review, we firstly summarize three strategies for the construction of single or hybrid COF-based matrices for the delivery of cargos, including encapsulation, covalent binding, and coordination bonding. Besides, their smart response release behaviors are also categorized. Subsequently, the applications of cargo@COF biocomposites in biomedicine are comprehensively summarized, including tumor therapy, central nervous system (CNS) modulation, biomarker analysis, bioimaging, and anti-bacterial therapy. Finally, the challenges and opportunities in this field are briefly discussed.

Strengthening the Combinational Immunotherapy from Modulating the Tumor Inflammatory Environment via Hypoxia-Responsive Nanogels

Despite the success of immuno-oncology in clinical settings, the therapeutic efficacy is lower than the expectation due to the immunosuppressive inflammatory tumor microenvironment (TME) and the lack of functional lymphocytes caused by exhaustion. To enhance the efficacy of immuno-oncotherapy, a synergistic strategy should be used that can effectively improve the inflammatory TME and increase the tumor infiltration of cytotoxic T lymphocytes (CTLs). Herein, a TME hypoxia-responsive nanogel (NG) is developed to enhance the delivery and penetration of diacerein and (-)-epigallocatechin gallate (EGCG) in tumors. After systemic administration, diacerein effectively improves the tumor immunosuppressive condition through a reduction of MDSCs and Tregs in TME, and induces tumor cell apoptosis via the inhibition of IL-6/STAT3 signal pathway, realizing a strong antitumor effect. Additionally, EGCG can effectively inhibit the expression of PD-L1, restoring the tumor-killing function of CTLs. The infiltration of CTLs increases at the tumor site with activation of systemic immunity after the combination of TIM3 blockade therapy, ultimately resulting in a strong antitumor immune response. This study provides valuable insights for future research on eliciting effective antitumor immunity by suppressing adverse tumor inflammation. The feasible strategy proposed in this work may solve the urgent clinical concerns of the dissatisfactory checkpoint-based immuno-oncotherapy.

Light-Enhanced Hypoxia-Responsive Gene Editing for Hypoxia-Resistant Photodynamic and Immunotherapy

Hypoxia is a key hallmark of solid tumors and can cause resistance to various treatments such as photodynamics and immunotherapy. Microenvironment-responsive gene editing provides a powerful tool to overcome hypoxia resistance and remodel hypoxic microenvironments for enhanced tumor therapy. Here, a light-enhanced hypoxia-responsive multifunctional nanocarrier is developed to perform spatiotemporal specific dual gene editing for enhanced photodynamic and immunotherapy in breast cancer. As a gated molecule of nanocarrier, the degradation of azobenzene moieties under hypoxic conditions triggers controllable release of Cas9 ribonucleoprotein in hypoxic site of the tumor. Hyaluronic acid is conjugated with chloramine e6 to coat mesoporous silica nanoparticles for targeted delivery in tumors and generation of high levels of reactive oxygen species, which can result in increased hypoxia levels for effective cleavage of azobenzene bonds to improve gene editing efficiency and reduce toxic side effects with light irradiation. Moreover, dual targeting HIF-1α and PD-L1 in the anoxic microenvironments can overcome hypoxia resistance and remodel immune microenvironments, which reduces tumor plasticity and resistance to photodynamic and immunotherapy. In summary, a light-enhanced hypoxia responsive nanocomposite is developed for controllable gene editing which holds great promise for synergistic hypoxia-resistant photodynamic and immunotherapy.

Covalent Organic Frameworks: Opportunities for Rational Materials Design in Cancer Therapy

Nanomedicines are extensively used in cancer therapy. Covalent organic frameworks (COFs) are crystalline organic porous materials with several benefits for cancer therapy, including porosity, design flexibility, functionalizability, and biocompatibility. This review examines the use of COFs in cancer therapy from the perspective of reticular chemistry and function-oriented materials design. First, the modification sites and functionalization methods of COFs are discussed, followed by their potential as multifunctional nanoplatforms for tumor targeting, imaging, and therapy by integrating functional components. Finally, some challenges in the clinical translation of COFs are presented with the hope of promoting the development of COF-based anticancer nanomedicines and bringing COFs closer to clinical trials.

Oxygen-tolerant CO2 electroreduction over covalent organic frameworks via photoswitching control oxygen passivation strategy

The direct use of flue gas for the electrochemical CO2 reduction reaction is desirable but severely limited by the thermodynamically favorable oxygen reduction reaction. Herein, a photonicswitching unit 1,2-Bis(5'-formyl-2'-methylthien-3'-yl)cyclopentene (DAE) is integrated into a cobalt porphyrin-based covalent organic framework for highly efficient CO2 electrocatalysis under aerobic environment. The DAE moiety in the material can reversibly modulate the O2 activation capacity and electronic conductivity by the framework ring-closing/opening reactions under UV/Vis irradiation. The DAE-based covalent organic framework with ring-closing type shows a high CO Faradaic efficiency of 90.5% with CO partial current density of -20.1 mA cm-2 at -1.0 V vs. reversible hydrogen electrode by co-feeding CO2 and 5% O2. This work presents an oxygen passivation strategy to realize efficient CO2 electroreduction performance by co-feeding of CO2 and O2, which would inspire to design electrocatalysts for the practical CO2 source such as flue gas from power plants or air.

Hypoxia and Singlet Oxygen Dual-Responsive Micelles for Photodynamic and Chemotherapy Therapy Featured with Enhanced Cellular Uptake and Triggered Cargo Delivery

Introduction

Combination therapy provides better outcomes than a single therapy and becomes an efficient strategy for cancer treatment. In this study, we designed a hypoxia- and singlet oxygen-responsive polymeric micelles which contain azo and nitroimidazole groups for enhanced cellular uptake, repaid cargo release, and codelivery of photosensitizer Ce6 and hypoxia-activated prodrug tirapazamine TPZ (DHM-Ce6@TPZ), which could be used for combining Ce6-mediated photodynamic therapy (PDT) and PDT-activated chemotherapy to enhance the therapy effect of cancer.

Methods

The hypoxia- and singlet oxygen-responsive polymeric micelles DHM-Ce6@TPZ were prepared by film hydration method. The morphology, physicochemical properties, stimuli responsiveness, in vitro singlet oxygen production, cellular uptake, and cell viability were evaluated. In addition, the in vivo therapeutic effects of the micelles were verified using a tumor xenograft mice model.

Results

The resulting dual-responsive micelles not only increased the concentration of intracellular photosensitizer and TPZ, but also facilitated photosensitizer and TPZ release for enhanced integration of photodynamic and chemotherapy therapy. As a photosensitizer, Ce6 induced PDT by generating toxic singlet reactive oxygen species (ROS), resulting in a hypoxic tumor environment to activate the prodrug TPZ to achieve efficient chemotherapy, thereby evoking a synergistic photodynamic and chemotherapy therapeutic effect. The cascade synergistic therapeutic effect of DHM-Ce6@TPZ was effectively evaluated both in vitro and in vivo to inhibit tumor growth in a breast cancer mice model.

Conclusion

The designed multifunctional micellar nano platform could be a convenient and powerful vehicle for the efficient co-delivery of photosensitizers and chemical drugs for enhanced synergistic photodynamic and chemotherapy therapeutic effect of cancer.

Chemical Sensors Based on Covalent Organic Frameworks

Covalent organic frameworks (COFs) are a type of crystalline porous polymer composed of light elements through strong covalent bonds. COFs have attracted considerable attention due to their unique designable structures and excellent material properties. Currently, COFs have shown outstanding potential in various fields, including gas storage, pollutant removal, catalysis, adsorption, optoelectronics, and their research in the sensing field is also increasingly flourishing. In this review, we focus on COF-based sensors. Firstly, we elucidate the fundamental principles of COF-based sensors. Then, we present the primary application areas of COF-based sensors and their recent advancements, encompassing gas, ions, organic compounds, and biomolecules sensing. Finally, we discuss the future trends and challenges faced by COF-based sensors, outlining their promising prospects in the field of sensing.