Colorimetry/fluorescence dual-mode detection of Salmonella typhimurium based on self-assembly of MCOF with Au NPs nanozyme coupled AIEgen

Sensitive, accurate, simple and quick monitoring of Salmonella typhimurium (S. typhimurium) in food is significant for preventing food poisoning, but still remains a challenge. Herein, a colorimetry/fluorescence dual-mode sensing strategy was fabricated to detect S. typhimurium by integrating the self-assembly of magnetic covalent organic framework (MCOF) with gold nanoparticles (Au NPs) as the peroxidase-mimicking nanozyme and aggregation-induced emission luminogen (AIEgen). S. typhimurium could competitive bind to aptamer conjugated Au NPs (Au NPs@apt), inhibit the self-assembly of MCOF with Au NPs, and shield the catalytic activity of AuNPs. After adding H2O2 and TPE-4A, the dark green solution changed to light with increasing S. typhimurium concentration, on the contrary, the fluorescent signals were generated. As a result, in colorimetry/fluorescence modes, S. typhimurium could be detected in the linear ranges of 103-108 CFU mL-1 and 101-107 CFU mL-1, with LODs of 1000 and 10 CFU mL-1, respectively. Importantly, different colors consistent with various S. typhimurium concentrations can be accurately classified by smartphone app and linear discriminant analysis (LDA). The smartphone-assisted data interpretation can generate complementary colorimetry and fluorescence signals without any sophisticated equipment and achieve on-site detection. Moreover, the proposed strategy could be explored for S. typhimurium monitoring in milk with satisfactory recoveries (97.6-100.4 %) in colorimetry and fluorescence mode and good classification and prediction performance in smartphone/LDA system, suggesting the feasibility and potential applications of the sensing platform.

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.

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.

Template-Free In Situ Encapsulation of Enzymes in Hollow Covalent Organic Framework Capsules for the Electrochemical Analysis of Biomarkers

Although capsule-like materials as host carriers for enzyme encapsulation have been a hot topic in recent years, creating an ideal microenvironment for enhanced enzymatic performance is still a formidable challenge. Herein, we created a template-free method to in situ encapsulate natural enzymes in hollow covalent organic framework (COF) capsules at room temperature. The COF crystallites migrated from the inner core and self-assembled at the outside walls during the inside-out Ostwald ripening process, retaining the enzymes in the cavity. The adjustable hollow structure of the enzyme@COF capsule allowed the basic vibration of the enzyme to maintain a certain degree of freedom, thus significantly enhancing the enzymatic bioactivity. The hollow enzyme@COF capsule has large mesoporous tunnels allowing the efficient transport. In addition, the enzyme encapsulated in the capsule showed superior activity and ultrahigh stability under various extreme conditions that may lead to enzyme inactivation, such as high temperature, organic solvents, chelates, and the denaturing agent. Finally, the prepared hollow GOx@COF capsule was used for electrochemical sensing of glucose in human serum, and the electrochemical sensor exhibited high selectivity and satisfactory test results. This research not only provides a new way for COFs to encapsulate enzymes but also has potential applications in biocatalysis and biosensing, making artificial organelles possible.

Recent Advances in Emerging Metal- and Covalent-Organic Frameworks for Enzyme Encapsulation

Enzyme catalysis enables complex biotransformation to be imitated. This biomimetic approach allows for the application of enzymes in a variety of catalytic processes. Nevertheless, enzymes need to be shielded by a support material under challenging catalytic conditions due to their intricate and delicate structures. Specifically, metal-organic frameworks and covalent-organic frameworks (MOFs and COFs) are increasingly popular for use as enzyme-carrier platforms because of their excellent tunability in structural design as well as remarkable surface modification. These porous organic framework capsules that host enzymes not only protect the enzymes against harsh catalytic conditions but also facilitate the selective diffusion of guest molecules through the carrier. This review summarizes recent progress in MOF-enzyme and COF-enzyme composites and highlights the pore structures tuned for enzyme encapsulation. Furthermore, the critical issues associated with interactions between enzymes and pore apertures on MOF- and COF-enzyme composites are emphasized, and perspectives regarding the development of high-quality MOF and COF capsules are presented.

Cationic Covalent Organic Framework as an Ion Exchange Material for Efficient Adsorptive Separation of Biomolecules

Although covalent organic frameworks (COFs) have earned significant interest in separation applications, the use of COFs in biomolecule separation remains unexplored. We examined the ionic COF Py-BPy²⁺-COF as an ion exchange material for biomolecule separation. After characterizing the properties of the synthesized COF with a variety of techniques, binding experiments with both large and small biomolecules were performed. High adsorption capacities of amino acids with different hydrophobicity and charge, as well as proteins of different isoelectric points and molecular weights, were determined in batch equilibrium experiments. Desorption experiments with mixtures of model proteins demonstrated an ability to successfully separate one protein from another with the selectivity hypothesized to be a combination of the isoelectric point, hydrophobicity, and ability to penetrate the crystalline material. Overall, the results demonstrated that Py-BPy²⁺-COF can be exploited as a robust crystalline anion exchange biomolecule separation material.

Fabrication of Biomolecule-Covalent-Organic-Framework Composites as Responsive Platforms for Smart Regulation of Fermentation Application

Exploration of novel material platforms to protect biological preservatives and realize intelligent regulation during fermentation is of great significance in industry. Herein, we established an intelligent responsive platform by introducing antimicrobial biomolecules (nisin) into rationally designed covalent organic frameworks (COFs), resulting in a new type of "smart formulation", which could responsively inhibit microbial contamination and ensure the orderly progression of the fermentation process. The encapsulated biomolecules retained their activity while exhibiting enhanced stability and pH-responsive releasing process (100% bacteriostatic efficiency at a pH of 3), which can ingeniously adapt to the environmental variation during the fermentation process and smartly fulfill the regulation needs. Moreover, the nisin@COF composites would not affect the fermentation strains. This study will pave a new avenue for the preparation of highly efficient and intelligent antimicrobial agents for the regulation of the fermentation process and play valuable roles in the drive toward green and sustainable biomanufacturing.

Bipolar Aggregation-Induced Electrochemiluminescence of Thiophene-Fused Conjugated Microporous Polymers

Herein, we synthesize the thiophene tetraphenylethene-based conjugated microporous polymer (ThT-CMP) using the tetraphenylethylene derivative [i.e., 1,1,2,2-tetrakis(4-bromophenyl)ethane (TPBE)] and 2,5-thiophenediboronic acid as the precursors. The aggregation of TPBE in the ThT-CMP can induce a strong dual-band bipolar electrochemiluminescence (AIECL) emission at 554 nm (anodic) and 559 nm (cathodic) with tri-n-propylamine (TPrA) and S₂O₈^2- as the coreactants, respectively. The anodic and cathodic ECL efficiencies are measured to be 11.49 and 3.82% with respect to the standard of the Ru(bpy)₃²⁺/TPrA system, respectively. We further develop a dipolar ECL sensor to sensitively detect rhodamine B (RhB) based on resonance energy transfer. This ECL sensor possesses a large dynamic range and high sensitivity. This research provides a new avenue of designing organic structures with the characteristic of bipolar AIECL for the development of luminescent devices.

Enrichment and Quantitative Determination of Free 3,5- Diiodothyronine, 3',5'-Diiodothyronine, and 3,5-Diiodothyronamine in Human Serum of Thyroid Cancer by Covalent Organic Hyper Cross-linked Poly-ionic Liquid

The incidence of thyroid cancer is increasing worldwide. So far, still no non-invasive clinical test biomarkers were developed for the diagnosis of thyroid cancer. The diiodothyronines (T2s) are precursors and metabolites of thyroid hormone (T4). Some reports predict that T2s may be associated with several thyroid diseases, especially the thyroid cancer. Detecting free T2s in human serum may help the diagnosis of thyroid cancer. However, few works have reported the detection of T2s due to their trace amounts. Here we developed a novel hyper organic cross-linked poly ionic liquid (PIL) material for the enrichment of three main compounds in T2s family, including 3,5- diiodothyronine (3,5-T2), 3',5'-diiodothyronine (3',5'-T2), and 3,5-diiodothyronamine (3,5-T2AM). This PIL material provided specific enrichment superiority for three T2s. After enrichment, the signal intensity of 3,5-T2, 3',5'-T2, and 3,5-T2AM increased 14, 132 and 1.6 folds, respectively, with LOQ of 76, 87, and 107 fM, respectively. Finally, we successfully applied PIL material coupled with HPLC-ESI-MS/MS in enrichment and quantitative determination of free 3,5-T2, 3',5'-T2, and 3,5-T2AM in human serum of 45 thyroid cancer patients and 15 healthy people. We also used free thyroid hormone (FT4) as the calibration reference to eliminate individual differences. We found that the levels of 3,5-T2 (P < 0.001), and 3',5'-T2 (P = 0.001) in patients with thyroid cancer were significantly higher than those in healthy people. Additionally, we further investigated the power of different T2 thyroid hormones divided FT4 to classify thyroid cancer patients and healthy people. And 3,5-T2/FT4 had the highest classification performance for discriminating thyroid cancer patients from healthy people at certain threshold, indicating that 3,5-T2/FT4 in human serum can act as potential biomarkers for "non-invasive" clinical diagnosis of thyroid cancer.

Self-templated synthesis of uniform hollow spheres based on highly conjugated three-dimensional covalent organic frameworks

Covalent organic frameworks (COFs) have served as a family of porous crystalline molecules for various promising applications. However, controllable synthesis of COFs with uniform morphology is paramount yet still remains quite challenging. Herein, we report self-templated synthesis of uniform and unique hollow spheres based on highly conjugated three-dimensional (3D) COFs with diameters of 500–700 nm. A detailed time-dependent study reveals the continuous transformation from initial nano sphere-like particles into uniform hollow spherical structures with Ostwald ripening mechanism. Particularly, the resulting 3D COF (3D-Sp-COF) is prone to transport ions more efficiently and the lithium-ion transference number (t⁺) of 3D-Sp-COF reaches 0.7, which even overwhelms most typical PEO-based polymer electrolytes. Inspiringly, the hollow spherical structures show enhanced capacitance performance with a specific capacitance of 251 F g⁻¹ at 0.5 A g⁻¹, which compares favorably with the vast majority of two-dimensional COFs and other porous electrode materials.

Covalent organic frameworks (COFs) are promising porous crystalline materials but controllable synthesis of COFs with uniform morphology remains challenging. Here, the authors report a self-templated synthesis of uniform and unique hollow spheres based on highly conjugated three-dimensional COFs.

Recent Developments of Carbon Dots in Biosensing: A Review

Early diagnosis of diseases is of great importance because it increases the chance of a cure and significantly reduces treatment costs. Thus, development of rapid, sensitive, and reliable biosensing techniques is essential for the benefits of human life and health. As such, various nanomaterials have been explored to improve performance of biosensors, among which, carbon dots (CDs) have received enormous attention due to their excellent performance. In this Review, the recent advancements of CD-based biosensors have been carefully summarized. First, biosensors are classified according to their sensing strategies, and the role of CDs in these sensors is elaborated in detail. Next, several typical CD-based biosensors (including CD-only, enzymatic, antigen-antibody, and nucleic acid biosensors) and their applications are fully discussed. Last, advantages, challenges, and perspectives on the future trends of CD-based biosensors are highlighted.

Nanoscale covalent organic frameworks as theranostic platforms for oncotherapy: synthesis, functionalization, and applications

Cancer nanomedicine is one of the most promising domains that has emerged in the continuing search for cancer diagnosis and treatment. The rapid development of nanomaterials and nanotechnology provide a vast array of materials for use in cancer nanomedicine. Among the various nanomaterials, covalent organic frameworks (COFs) are becoming an attractive class of upstarts owing to their high crystallinity, structural regularity, inherent porosity, extensive functionality, design flexibility, and good biocompatibility. In this comprehensive review, recent developments and key achievements of COFs are provided, including their structural design, synthesis methods, nanocrystallization, and functionalization strategies. Subsequently, a systematic overview of the potential oncotherapy applications achieved till date in the fast-growing field of COFs is provided with the aim to inspire further contributions and developments to this nascent but promising field. Finally, development opportunities, critical challenges, and some personal perspectives for COF-based cancer therapeutics are presented.

Redox-active, luminescent coordination nanosheet capsules containing magnetite

Two-dimensional coordination nanosheets (CONASHs) are grown at the spherical liquid–liquid interface of a dichloromethane droplet in water to form zero-dimensional nano- and micro-capsules using a simple dropping method, a syringe-pump method, and an emulsion method. Reaction of 1,3,5-tris[4-(4′-2,2′:6′,2″-terpyridyl)phenyl]benzene (1) with Fe(BF₄)₂ affords electrochromic Fe(tpy)₂ CONASH capsules and that of ligand 1 with ZnSO₄ does photoluminescent Zn₂(μ-O₂SO₂)₂(tpy)₂ CONASH capsules. Fe(tpy)₂ CONASH capsules containing magnetite particles were produced by the syringe-pump method by adding magnetite to the aqueous phase, with the assembly and dispersion of the magnetite-containing CONASH capsules being easily controlled with a magnet. This indicates that physicochemically functional CONASH capsules are suitable for incorporating other functional materials to develop hybrid systems.

Europium(III) functionalized 3D covalent organic framework for quinones adsorption and sensing investigation

Chemical functionalization is essential for tuning the physical-chemical characters and broadening the potential applications of covalent organic frameworks (COFs). Based on the multistep postsynthetic modification strategy, Eu (III)-functionalized 3D COF (Eu-3D-COF) was prepared by grafting of Eu (III) onto the carboxyl-funtionalized 3D-COF (COOH-3D-COF). With micropores dominated microspheres structure, Eu-3D-COF exhibited superior adsorption affinity to multi-rings contained quinones based on the π-π interaction, coordination and hydrogen-bonding interactions, especially to 9,10-phenanthrenequinone (PQ) whose adjacent carbonyl oxygens resulting preferable synergistic chelation interaction with Eu(III) was responsible for the maximum adsorption capacity, which was confirmed by instrumental characterizations. The adsorptivity of Eu-3D-COF was apparently improved in comparison with COOH-3D-COF. More importantly, grafting of Eu(III) turned on the fluorescence of the COF, making Eu-3D-COF also a superior chemosensor for sensing application. Its fluorescent can be selectively quenched by quinones, especially by PQ based on the PQ-Eu and PQ-COF interactions co-dominated energy transfer. Therefore, both as an adsorbent and a chemosensor, the multi-functional COF was explored for quinones adsorption and sensing detection investigation in detail. Eu-3D-COF has promising application potentials for hazardous quinones adsorption and sensing detection, which also opens new perspectives for inorganic-organic 3D-COF construction and multi-functional applications.