Tuning the physicochemical properties of reticular covalent organic frameworks (COFs) for biomedical applications

Insights into the Biological Activity and Bio-Interaction Properties of Nanoscale Imine-Based 2D and 3D Covalent Organic Frameworks

Covalent Organic Frameworks (COFs) emerged as versatile materials with promising potential in  biomedicine. Their customizable functionalities and tunable pore structures make them valuable for various biomedical applications such as biosensing, bioimaging, antimicrobial activity, and targeted drug delivery. Despite efforts made to create nanoscale COFs (nCOFs) to enhance their interaction with biological systems, a comprehensive understanding of their inherent biological activities remains a significant challenge. In this study, a thorough investigation is conducted into the biocompatibility and anti-neoplastic properties of two distinct imine-based nCOFs. The approach involved an in-depth analysis of these nCOFs through in vitro experiments with various cell types and in vivo assessments using murine models. These findings revealed significant cytotoxic effects on tumor cells. Moreover, the activation of multiple cellular death pathways, including apoptosis, necroptosis, and ferroptosis is determined, supported by evidence at the molecular level. In vivo evaluations exhibited marked inhibition of tumor growth, associated with the elevated spontaneous accumulation of nCOFs in tumor tissues and the modulation of cell death-related protein expression. The research contributes to developing a roadmap for the characterization of the intricate interactions between nCOFs and biological systems and opens new avenues for exploiting their therapeutic potential in advanced biomedical applications.

cRGD-Peptide Modified Covalent Organic Frameworks for Precision Chemotherapy in Triple-Negative Breast Cancer

This study presents the use of nanoscale covalent organic frameworks (nCOFs) conjugated with tumor-targeting peptides for the targeted therapy of triple-negative breast cancer (TNBC). While peptides have previously been used for targeted delivery, their conjugation with COFs represents an innovative approach in this field. In particular, we have developed alkyne-functionalized nCOFs chemically modified with cyclic RGD peptides (Alkyn-nCOF-cRGD). This configuration is designed to specifically target αvβ3 integrins that are overexpressed in TNBC cells. These nCOFs exhibit excellent biocompatibility and are engineered to selectively disintegrate under acidic conditions, allowing for precise and localized drug release in tumor environment. Doxorubicin, a chemotherapeutic agent, has been encapsulated in these nCOFs with high loading efficiency. The therapeutic potential of Alkyn-nCOF-cRGD has been demonstrated in vitro and in vivo models. It shows significantly improved drug uptake and targeted cell death in TNBC, highlighting the efficacy of receptor-mediated endocytosis and pH-controlled drug release. This strategy leverages the unique properties of nCOFs with targeted drug delivery to achieve significant advances in personalized cancer therapy and set a new standard for precision chemotherapeutic delivery.

Bridging host-guest chemistry with molecule chemistry-covalent organic polyrotaxanes (COPRs): from synthesis to inactivation of bacterial pathogens

As a thriving artificial material, covalent organic frameworks (COFs), boasting inherent structural designability and functional adaptability, and with compositions akin to biological macromolecules, have emerged as a rising star in the field of material science. However, the progression of COFs is significantly impeded by the arduous and intricate preparation procedures of novel building blocks, as well as the inefficient development process of new reactions. An efficient, uncomplicated, and versatile functionalization approach, which has the potential to not only facilitate customized preparation of COFs based on application demands but also enable precise performance control, has become a focal point of research. The formulation of multi-functional COFs through efficient and cost-effective methods poses a critical challenge for the practical application of COFs. This review aims to present the preparation of COFs by amalgamating rigid molecular chemistry with flexible supramolecular host-guest chemistry, adopting a "couple hardness with softness" strategy to meticulously construct intelligent covalent organic polyrotaxanes (COPRs) using conventional reactions. Herein, novel building blocks can be acquired by amalgamating existing macrocycle complexes with framework blocks. The amalgamation of supramolecular chemistry bolsters the capabilities to generate, sense, respond, and amplify distinctive signals, thereby expediting the advancement of multifaceted materials with sophisticated structures. Concurrently, the infusion of supramolecular force endows COPRs with exceptional performance, facilitating multi-mode collaborative antibacterial therapy. This comprehensive review not only promotes the efficient utilization of resources but also stimulates the rapid advancement of framework materials.

Ion transport mechanisms in covalent organic frameworks: implications for technology

Covalent organic frameworks (COFs) have emerged as promising materials for ion conduction due to their highly tunable structures and excellent electrochemical stability. This review paper explores the mechanisms of ion conduction in COFs, focusing on how these materials facilitate ion transport across their ordered structures, which is crucial for applications such as solid electrolytes in batteries and fuel cells. We discuss the design strategies employed to enhance ion conductivity, including pore size optimization, functionalization with ionic groups, and the incorporation of solvent molecules and salts. Additionally, we examine the various applications of ion-conductive COFs, particularly in energy storage and conversion technologies, highlighting recent advancements and future directions in this field. This review paper aims to provide a comprehensive overview of the current state of research on ion-conductive COFs, offering insights into their potential to design highly ion-conductive COFs considering not only fundamental studies but also practical perspectives for advanced electrochemical devices.

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.

Fluorescent covalent organic frameworks - promising bioimaging materials

Fluorescent covalent organic frameworks (COFs) have emerged as promising candidates for imaging living cells due to their unique properties and adjustable fluorescence. In this mini-review, we provide an overview of recent advancements in fluorescent COFs for bioimaging applications. We discuss the strategies used to design COFs with desirable properties such as high photostability, excellent biocompatibility, and pH sensitivity. Additionally, we explore the various ways in which fluorescent COFs are utilized in bioimaging, including cellular imaging, targeting specific organelles, and tracking biomolecules. We delve into their applications in sensing intracellular pH, reactive oxygen species (ROS), and specific biomarkers. Furthermore, we examine how functionalization techniques enhance the targeting and imaging capabilities of fluorescent COFs. Finally, we discuss the challenges and prospects in the field of fluorescent COFs for bioimaging in living cells, urging further research in this exciting area.

A review of recent advancement in covalent organic framework (COFs) synthesis and characterization with a focus on their applications in antibacterial activity

The primary objective of this review is to present a comprehensive examination of the synthesis, characterization, and antibacterial applications of covalent organic frameworks (COFs). COFs represent a distinct category of porous materials characterized by a blend of advantageous features, including customizable pore dimensions, substantial surface area, and adaptable chemical properties. These attributes position COFs as promising contenders for various applications, notably in the realm of antibacterial activity. COFs exhibit considerable potential in the domain of antibacterial applications, owing to their amenability to functionalization with antibacterial agents. The scientific community is actively exploring COFs that have been imbued with metal ions, such as copper or silver, given their observed robust antibacterial properties. These investigations strongly suggest that COFs could be harnessed effectively as potent antibacterial agents across a diverse array of applications. Finally, COFs hold immense promise as a novel class of materials for antibacterial applications, shedding light on the synthesis, characterization, and functionalization of COFs tailored for specific purposes. The potential of COFs as effective antibacterial agents beckons further exploration and underscores their potential to revolutionize antibacterial strategies in various domains.

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.

A PEDOT enhanced covalent organic framework (COF) fluorescent probe for in vivo detection and imaging of Fe3

Simple and accurate in vivo monitoring of Fe3+ is essential for gaining a better understanding of its role in physiological and pathological processes. A novel fluorescent probe was synthesized via in situ solid-state polymerization of 3,4-ethylenedioxythiophene (PEDOT) in the pore channels of a covalent organic framework (COF). The PEDOT@COF fluorescent probe exhibited an absolute quantum yield (QY) 3 times higher than COF. In the presence of Fe3+ the PEDOT@COF 475 nm fluorescence emission, 365 nm excitation, is quenched within 180 s. Fluorescence quenching is linear with Fe3+ in the concentration range of 0-960 μM, with a detection limit of 0.82 μM. The fluorescence quenching mechanism was attributed to inner filter effect (IEF), photoinduced electron transfer (PET) and static quenching (SQE) between PEDOT@COF and Fe3+. A paper strip-based detector was designed to facilitate practical applicability, and the PEDOT@COF probe successfully applied to fluorescence imaging of Fe3+ levels in vivo. This work details a tool of great promise for enabling detailed investigations into the role of Fe3+ in physiological and pathological diseases.

Covalent organic frameworks: Pioneering remediation solutions for organic pollutants

Covalent Organic Frameworks (COFs) have emerged as a promising class of crystalline porous materials with customizable structures, high surface areas, and tunable functionalities. Their unique properties make them attractive candidates for addressing environmental contamination caused by pharmaceuticals, pesticides, industrial chemicals, persistent organic pollutants (POPs), and endocrine disruptors (EDCs). This review article provides a comprehensive overview of recent advancements and applications of COFs in removing and remedying various environmental contaminants. We delve into the synthesis, properties, and performance of COFs and their potential limitations and future prospects.

An erythrocyte membrane-camouflaged fluorescent covalent organic framework for starving/nitric oxide/immunotherapy of triple-negative breast cancer

It is a great challenge to effectively treat triple-negative breast cancer (TNBC) due to lack of therapeutic targets and drug resistance of systemic chemotherapy. Rational design of nanomedicine with good hemocompatibility is urgently desirable for combination therapy of TNBC. Herein, an erythrocyte membrane-camouflaged fluorescent covalent organic framework (COF) loaded with an NO donor (hydroxyurea, Hu), glucose oxidase (GOx) and cytosine-phosphate-guanine oligonucleotides (CPG) (COF@HGC) was developed for imaging-guided starving/nitric oxide (NO)/immunization synergistic treatment of TNBC. The substances of HGC are easily co-loaded onto the COF due to the ordered pore structure and large surface area. And a folic acid-modified erythrocyte membrane (FEM) is coated on the surface of COF@HGC to improve targeted therapy and haemocompatibility. When COF@HGC@FEM is internalized into tumor cells, hemoglobin (Hb) on FEM and GOx loaded on the COF can trigger cascade reactions to kill tumor cells due to the simultaneous production of NO and exhaustion of glucose. Meanwhile, the COF with excellent fluorescence properties can be used as a self-reporter for bioimaging. Furthermore, the CPG can reprogram tumor-associated macrophages from tumor-supportive phenotype to anti-tumor phenotype and enhance immunotherapy. Through the "three-in-one" strategy, the biomimetic nanoplatform can effectively inhibit tumor growth and reprogram the tumor immunosuppression microenvironment in the TNBC mouse model.

Visual Multifunctional Aggregation-Induced Emission-Based Bacterial Cellulose for Killing of Multidrug-Resistant Bacteria

Multidrug-resistant (MDR) bacteria-related wound infections are a thorny issue. It is urgent to develop new antibacterial wound dressings that can not only prevent wounds from MDR bacteria infection but also promote wound healing. Herein, an aggregation-induced emission (AIE) molecule BITT-composited bacterial cellulose (BC) is presented as wound dressings. BC-BITT composites have good transparency, making it easy to monitor the wound healing process through the composite membrane. The BC-BITT composites retain the advantages of biocompatible BC, and display photodynamic and photothermal synergistic antibacterial effects under irradiation of a 660 nm laser. Furthermore, the BC-BITT composites show excellent wound healing performance in a mouse full-thickness skin wound model infected by MDR bacteria, simultaneously with negligible toxicity. This work paves a way for treating clinically troublesome wound infections.

A fluorescence biosensor based on DNA aptamers-COF for highly selective detection of ATP and thrombin

Due to their distinctive physical, chemical, electrical, and optical properties as well as their prospective uses, 2D covalent organic framework (COF) have attracted much attention. Herein, TaTPA-COF was effectively synthesized from the condensation of TTA and TFPA using a facile solvothermal method and characterized by SEM image, FT-IR spectra, and PXRD pattern. The generated bulk TaTPA-COF materials combined with DNA aptamers are utilized as the acceptor (quencher) for the highly sensitive and selective detection of adenosine 5'-triphosphate (ATP) and thrombin, with a novel fluorescence biosensing platform and a proof-of-concept application.

Microenvironment Restruction of Emerging 2D Materials and their Roles in Therapeutic and Diagnostic Nano-Bio-Platforms

Engineering advanced therapeutic and diagnostic nano-bio-platforms (NBPFs) have emerged as rapidly-developed pathways against a wide range of challenges in antitumor, antipathogen, tissue regeneration, bioimaging, and biosensing applications. Emerged 2D materials have attracted extensive scientific interest as fundamental building blocks or nanostructures among material scientists, chemists, biologists, and doctors due to their advantageous physicochemical and biological properties. This timely review provides a comprehensive summary of creating advanced NBPFs via emerging 2D materials (2D-NBPFs) with unique insights into the corresponding molecularly restructured microenvironments and biofunctionalities. First, it is focused on an up-to-date overview of the synthetic strategies for designing 2D-NBPFs with a cross-comparison of their advantages and disadvantages. After that, the recent key achievements are summarized in tuning the biofunctionalities of 2D-NBPFs via molecularly programmed microenvironments, including physiological stability, biocompatibility, bio-adhesiveness, specific binding to pathogens, broad-spectrum pathogen inhibitors, stimuli-responsive systems, and enzyme-mimetics. Moreover, the representative therapeutic and diagnostic applications of 2D-NBPFs are also discussed with detailed disclosure of their critical design principles and parameters. Finally, current challenges and future research directions are also discussed. Overall, this review will provide cutting-edge and multidisciplinary guidance for accelerating future developments and therapeutic/diagnostic applications of 2D-NBPFs.

Recent progress in covalent organic frameworks for cancer therapy

Covalent organic frameworks (COFs) have gained tremendous interest in cancer therapy owing to their multifunctional properties, such as biocompatibility, tunable cavities, excellent crystallinity, ease of modification/functionalization, and high flexibility. These unique properties offer multiple benefits, such as high loading capacity, prevention from premature leakage, targeted delivery to the tumor microenvironment (TME), and release of therapeutic agents in a controlled manner, which makes them effective and excellent nanoplatforms for cancer therapeutics. In this review, we outline recent advances in using COFs as delivery system for chemotherapeutic agents, photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), cancer diagnostics, and combinatorial therapy for cancer therapeutics. We also summarize current challenges and future directions of this unique research field. Teaser: This review highlights recent advances in covalent organic frameworks as multifaceted nanoplatform with recent case studies for improving therapeutic outcomes for cancer therapeutics.

Metalated covalent organic frameworks: from synthetic strategies to diverse applications

Covalent organic frameworks (COFs) are a class of organic crystalline porous materials discovered in the early 21st century that have become an attractive class of emerging materials due to their high crystallinity, intrinsic porosity, structural regularity, diverse functionality, design flexibility, and outstanding stability. However, many chemical and physical properties strongly depend on the presence of metal ions in materials for advanced applications, but metal-free COFs do not have these properties and are therefore excluded from such applications. Metalated COFs formed by combining COFs with metal ions, while retaining the advantages of COFs, have additional intriguing properties and applications, and have attracted considerable attention over the past decade. This review presents all aspects of metalated COFs, from synthetic strategies to various applications, in the hope of promoting the continued development of this young field.

Covalent organic frameworks and multicomponent reactions: an endearing give-and-take relationship

Covalent organic frameworks (COFs) are porous and crystalline materials which are assembled by dynamic covalent bonds with two- or three-dimensional (2D or 3D) features. Unlike other polymers, COFs have significant...