Hydrogen-bonded organic framework biomimetic entrapment allowing non-native biocatalytic activity in enzyme

In Situ Generation of Pyroptosis Inducer Mediated by Intracellular Labile Copper Pool for Safe and Robust Antitumor Immunotherapy

Pyroptosis has garnered increasing interest in the realm of cancer immunotherapy. Utilizing reactive oxygen species (ROS) to trigger oxidative stress is considered an effective strategy for promoting pyroptosis. However, existing catalytic nanoparticles used as pyroptosis inducers contain heavy metals, which inevitably cause potential side effects on normal tissues due to their high toxicity and off-target effects. Herein, a labile copper pool-mediated in situ pyroptosis inducer was designed and developed using a hydrogen-bonded organic framework (HOF)-based nanoplatform to achieve safe and robust antitumor immunotherapy. The nanoplatform could target mitochondria and elevate labile Cu2+ levels in cells, implementing the in situ synthesis of a pyroptosis inducer through the formation of catalytic nanoparticles with peroxidase (POD) and superoxide dismutase (SOD)-mimicking activities. Our results confirmed that the nanoplatform could generate high levels of ROS, resulting in pyroptotic cell death. When combined with antiprogrammed death receptor 1 therapy (αPD-1), the pyroptosis inducer exhibited excellent antitumor capacity in tumor models. Meanwhile, it exhibited minimal toxicity to healthy tissues due to the low intracellular copper concentration in normal cells. Overall, our work provides potential for the development of efficient and safe antitumor immunotherapy.

Channel-Directed Enzymatic Depolymerization within a Metal-Organic Framework

Controlled growth of metal-organic frameworks (MOFs) under mild conditions has enabled the production of hybrid biocomposites with potential applications in biocatalysis. While the structure and bioactivity of confined enzymes are retained, improving the mass transport across the porous architecture remains a challenge. Here, we report a biocompatible and scalable synthetic procedure of a phase-pure aluminum trimesate porous framework, MIL-110(Al), featuring accessible microporous channels. The method is compatible with the in situ encapsulation of enzymes via a Lewis acid-mediated mineralization, reaching high efficiencies, and with control over protein loading. Moreover, we demonstrate a favored channel-directed depolymerization in a model biocomposite, xylanase@MIL-110(Al), which successfully hydrolyzes the xylan polymer over consecutive cycles. This work emphasizes the possibility of improving the overall enzymatic performance in depolymerization reactions by using MOF-protective scaffolds featuring large accessible porosity.

Design, Synthesis, and Application of Immobilized Enzymes on Artificial Porous Materials

Enzymes have been recognized as highly efficient biocatalysts, whereas characteristics such as poor stability and single reaction type greatly significantly limit their wide application. Hence, the exploitation of suitable carriers for immobilized enzymes enables the provision of a protective layer for the enzyme, with the capability of chemical and biological cascade catalysis. Among the various immobilization carriers, metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs) have been emerging as a promising strategy to surpass the inherent instability and other limitations of free enzymes. Specifically, the integration of such artificial porous materials as carriers improves the stability and reusability of enzymes, while simultaneously affording a platform for multifunctional applications. Herein, this review systematically discusses the various preparation strategies and advantages of artificial porous materials, while elucidating the effects of different immobilization methods on enzyme activity. Furthermore, the innovative applications of artificial porous materials as multifunctional carriers in the field of enzyme immobilization fields such as enzyme carriers, photocatalysts, chemical catalysts and sensing are also comprehensively summarized here, thus demonstrating their multifunctional characteristics and promising applications in addressing complex biotransformation challenges.

Hydrogen-Bonded Organic Framework Nanozyme with Multi-Enzyme Activity for Chemiluminescence Sensing of Acetylcholinesterase and Screening Its Inhibitors

Strong and persistent chemiluminescence (CL) is essential for enhancing the detection accuracy and reproducibility of CL-based analytical methods. In this study, we explored the synergistic effects of amino groups present on the surface of hydrogen-bonded organic framework (HOF-PyTTA, where PyTTA is denoted as 4,4',4″,4‴-(pyrene-1,3,6,8-tetrayl)tetraaniline) materials and N-(4-aminobutyl-N-ethylisoluminol) (ABEI) for reducing gold nanoparticles (AuNPs) on the surface of HOFs. Additionally, we utilized the substantial specific surface area and abundant amino groups of HOFs to sequester Co2+ ions, resulting in the synthesis of HAACo material. The resulting HAACo exhibited remarkable peroxidase, oxidase, and catalase mimetic activities, enabling the luminol-H2O2 chemiluminescence system to maintain a glow-type CL phenomenon for more than 1 h. Subsequently, we developed a CL point-of-care testing (POCT) sensor that integrated the CL characteristics of HAACo with smartphone technology and 3D printing for the determination of acetylcholinesterase (AChE) activity in serum samples, as well as the screening for AChE inhibitors. The sensor demonstrated a linear detection range for AChE activity from 0.001 to 40 mU mL-1, with a detection limit of 0.00057 mU mL-1. The calculated IC50 for the AChE inhibitor tacrine was found to be 21.9 nmol L-1, indicating good selectivity and stability of the sensor. This work not only expands the applications of glow-type CL in biosensing but also enriches the utilization of HOF materials in analytical chemistry, paving the way for the development of multifunctional HOF-based materials for future applications.

Polyamine-Depleting Hydrogen-Bond Organic Frameworks Unleash Dendritic Cell and T Cell Vigor for Targeted CRISPR/Cas-Assisted Cancer Immunotherapy

Polyamines have tantalized cancer researchers as a potential means to rein in the rampant growth of cancer cells. However, clinical trials in recent decades have disappointed in delivering notable progress. Herein, a microfluidic-assisted synthetic hydrogen-bond organic framework (HOF) as a polyamine-depleting nanoplatforms designed to unleash the vigor of both dendritic cells (DCs) and T cells for precision cancer immunotherapy is reported. Upon internalization by tumor cells, the loaded plasma amine oxidase (PAO) in HOF efficiently depletes polyamines, remolding the tumor microenvironment and alleviating T-cell immunosuppression. This process also generates acrolein and H2O2, triggering CRISPR-assisted neoantigen generation. Specifically, Acrolein induces carbonyl stress, increasing mutational burdens. Simultaneously, HOF leverages the energy from the bis[2,4,5-trichloro-6-(pentyloxycarbonyl)phenyl] oxalate (CPPO)-H2O2 reaction for CRET-triggered singlet oxygen production, leading to thioether bond cleavage and release CRISPR-Cas9. Once released, CRISPR-Cas9 knocks out the DNA mismatch repair (MMR)-related MLH1 gene, further elevating mutational burdens and generating neoantigens, ideal targets for DCs. This dual-action strategy not only corrects T-cell immunosuppression but also enhances DC efficacy, presenting a powerful approach for tumor immunotherapy.

Integrating Enzymes with Reticular Frameworks To Govern Biocatalysis

Integrating enzymes with reticular frameworks offers promising avenues for access to functionally tailorable biocatalysis. This Minireview explores recent advances in enzyme-reticular framework hybrid biocomposites, focusing on the utilization of porous reticular frameworks, including metal-organic frameworks, covalent-organic frameworks, and hydrogen-bonded organic frameworks, to regulate the reactivity of an enzyme encapsulated inside mainly by pore infiltration and in situ encapsulation strategies. We highlight how pore engineering and host-guest interfacial interactions within reticular frameworks create tailored microenvironments that substantially impact the mass transfer and enzyme conformation, leading to biocatalytic rate enhancement, or imparting enzymes with non-native biocatalytic functions, including substrate selectivity and new activity. Additionally, the feasibility of leveraging the photothermal effect of a framework to optimize the local reaction temperature and photoelectric effect to elicit diverse photoenzyme-coupled reactions is also summarized in detail, which can expand the functional repertoire of biocatalytic transformations under light irradiation. This Minireview underscores the potential of reticular frameworks as tunable and reliable platforms to govern biocatalysis, offering pathways for engineering sustainable, efficient, and selective biocatalytic reactors in pharmaceutical, environmental, and energy-related applications.

Reusable Self-Powered Electrochromic Sensor Patch Based on Enzymatic Biofuel Cells for On-Site Visualized Monitoring of Lactic Acid

Wearable sensors have broad application potential in motion assessment, health monitoring, and medical diagnosis. However, relying on a specialized instrument for power supply and signal reading makes sensors unsuitable for on-site detection. To solve this problem, a reusable self-powered electrochromic sensor patch based on enzymatic biofuel cells were constructed to realize the on-site visualized monitoring. In this design, hydrophilic agarose hydrogel and SiO2 hydrophobic film were used to control the collection and elimination of sweat. Lactic acid (LA) served not only as a model analyte, but also as a fuel to convert chemical energy into electrical energy. The generated electrons further reduced the Prussian blue (PB) to Prussian white (PW), accompanied by visible color changes. It could achieve semiquantitative detection by reading color changes with the naked eye or quantitative detection by the output blue value and current signals. In order to reduce costs, the PB color was restored by applying voltage, causing the electrode to change from a faded state to a blue colored state again, thus, achieving the repeated use of the sensor patch. This work established a proof-of-concept for the design of a reusable self-powered electrochromic sensor patch that could provide innovative inspiration for the formation of a general visualized wearable patch.

Optimized Photochromic Performance of Spiropyran through Incorporation into Hydrogen-Bonded Organic Frameworks and Applications in Anticounterfeiting and Information Encryption

Photostimulus-responsive fluorescent materials are promising for anticounterfeiting and UV printing due to rapid response and simple preparation. In this paper, we propose a novel strategy to prepare photostimulus-responsive materials SP@HOF-olefin by integrating the photochromic molecule spiropyran (SP) with postsynthetic modified hydrogen-bonded organic frameworks (HOF-olefin). Compared to SP@HOF, the composites SP@HOF-olefin exhibit enhanced photochromic properties, such as a fast response speed, pronounced color contrast, and exceptional fatigue resistance. The improvements can be attributed to the reduction of residual carboxyl groups in the framework, which subsequently decreases the polarity of the framework. Besides, the SP loading content in SP@HOF-olefin was significantly enhanced. Furthermore, HOF-olefin can be transformed into HOF films via photopolymerization. These films demonstrated excellent flexibility, which can be folded and twisted at any angle ranging from 0 to 180°. By utilizing the photomask method, letters such as "Z", "T", "S", and "U", along with other patterns were successfully imprinted on the film. Besides, we investigated the utilization of these films in advanced anticounterfeiting applications. This work serves as a representative case demonstrating how functionalized HOFs improved the photochromic properties of SP, showcasing potential applications in anticounterfeiting and information encryption.

Magnetically Responsive Enzyme and Hydrogen-Bonded Organic Framework Biocomposites for Biosensing

The one-pot synthesis of multicomponent hydrogen-bonded organic framework (HOF) biocomposites is reported. The co-immoblization of enzymes and magnetic nanoparticles (MNPs) into the HOF crystals yielded biocatalysts (MNPs-enzyme@BioHOF-1) with dynamic localization properties. Using a permanent magnet, it is possible to separate the MNPs-enzyme@BioHOF-1 particles from a solution. Catalase (CAT) and glucose oxidase (GOx) show increased retention of their activity when coimmobilized with MNPs. MNPs-GOx@BioHOF-1 biocomposites are used to prepare a proof-of-concept glucose microfluidic biosensor, where a magnet allow to position and keep in place the biocomposite inside a microfluidic chip. The magnetic response of these biocatalysts can pave the way for new applications for the emerging HOF biocomposites.

Engineering enzyme conformation within liquid-solid hybrid microreactors for enhanced continuous-flow biocatalysis

The artificial engineering of an enzyme's structural conformation and dynamic properties to promote its catalytic activity and stability outside cellular environments is highly pursued in industrial biotechnology. Here, we describe an elegant strategy of combining the rationally designed liquid-solid hybrid microreactor with a tailor-made polyethylene glycol functional ionic liquid (PEG-IL) microenvironment to exercise a high level of control over the configuration of enzymes for practical continuous-flow biocatalysis. As exemplified by a lipase driven kinetic resolution reaction, the obtained system exhibits a 2.70 to 30.35-fold activity enhancement compared to their batch or traditional IL-based counterparts. Also, our results demonstrate that the thermal stability of encapsulated lipase can be significantly strengthened in the presence of PEG groups, showcasing a long-term continuous-flow stability even up to 1000 h at evaluated temperature of 60 oC. Through systematic experiment and molecular dynamics simulation studies, the conformational changes of the active site cavity in the modified lipases are correlated with enzymatic properties alteration, and the pronounced effects of PEG-groups in stabilizing enzyme's secondary structures by delaying unfolding at elevated temperatures are identified. We believe that this study will guide the design of high-performance enzymatic systems, promoting their utilization in real-world biocatalysis applications.

Rapid Assembly of Ultrafine Palladium Nanoparticle-Decorated HOF-101 Triggered by Guest Enzyme Encapsulation

Rapid enzyme immobilization is essential for enzyme catalysis and sensing applications, yet constructing effective immobilization systems is challenging due to the need to balance enzyme activity with the properties of the surrounding framework. Herein, taking glucose oxidase (GOx) as a model, a rapid and straightforward approach was presented for synthesizing palladium nanoparticles (PdNPs)-decorated GOx encapsulated in HOF-101 nanocomposite materials (designated as PdNPs/GOx@HOF-101) through an in situ photoreduction and enzyme-triggering HOF-101 encapsulation. The enzyme's surface residues trigger the nucleation of HOF-101 around it through the hydrogen-bonded bio interface, completing the self-assembly of HOF-101 in 0.5 h. Furthermore, the biocomposites loaded with ultrafine PdNPs show satisfactory photoelectrochemical (PEC) properties. As a proof-of-concept, a PEC biosensor was constructed by utilizing PdNPs/GOx@HOF-101 as a photoactive probe, which can quickly and sensitively detect glucose and simultaneously remain stable within the circumstance of 30-60 °C and pH 4-8. These attributes pave the way for diverse applications, including improved enzyme immobilization techniques, advanced biosensors, and more efficient biocatalytic processes.

Electro-Driven Multi-Enzymatic Cascade Conversion of CO2 to Ethylene Glycol in Nano-Reactor

Multi-enzymatic cascade reaction provides a new avenue for C─C coupling directly from CO2 under mild conditions. In this study, a new pathway with four enzymes including formate dehydrogenase (PaFDH), formaldehyde dehydrogenase (BmFADH), glycolaldehyde synthase (PpGALS), and alcohol dehydrogenase (GoADH) is developed for directly converting CO2 gas molecules to ethylene glycol (EG) in vitro. A rhodium-based NADH regeneration electrode is constructed to continuously provide the proton and electron of this multi-enzymatic cascade reaction. The prepared electrode can reach the Faradaic Efficiency (FE) of 82.9% at -0.6 V (vs. Ag/AgCl) and the NADH productivity of 0.737 mM h-1. Shortening the reaction path is crucial for multi-enzymatic cascade reactions. Here, a hydrogen-bonded organic framework (HOF) nano-reactor is successfully developed to immobilize four enzymes in one pot with a striking enzyme loading capacity (990 mg enzyme g-1 material). Through integrating and optimization of NADH electro-regeneration and enzymatic catalysis in one pot, 0.15 mM EG is achieved with an average conversion rate of 7.15 × 10-7 mmol CO2 min-1 mg-1 enzymes in 6 h. These results shed light on electro-driven multi-enzymatic cascade conversion of C─C coupling from CO2 in the nano-reactor.

Freestanding Hydrogen-Bonded Organic Framework Membrane for Efficient Wound Healing

Hydrogen-bonded organic frameworks (HOFs) are emerging as multifunctional materials with exceptional biocompatibility, abundant active sites, and tunable porosity, which are highly beneficial for advanced wound care. However, a significant challenge involves transforming pristine HOFs powders into lightweight, ultrathin, freestanding membranes compatible with soft biological systems. Herein, the study successfully develops shape-adaptive HOF-based matrix membranes (HMMs) using a polymer-assisted liquid-air interface technique. The HMMs conform seamlessly to tissues of different sizes and shapes, effectively stopping bleeding, and provide high water-vapor permeability. Notably, both in vitro and in vivo studies with mice wound models demonstrated that these tissue-conformable HMMs significantly accelerate wound healing by modulating the inflammatory environment of the injured tissue and promoting rapid re-epithelialization. Furthermore, RNA-seq analysis and mechanistic studies revealed that HMMs effectively reduce inflammation and facilitate the tissue transition from the proliferative stage to the remodeling stage of skin development. This work not only opens up new avenues for advanced wound care materials but also establishes a foundation for hybridizing HOFs with polymers for a wide range of potential applications.

Hydrogen-bonded supramolecular biohybrid frameworks for protein biomineralization constructed from natural phenolic building blocks

Hydrogen bond-mediated supramolecular crystalline materials, such as hydrogen-bonded organic frameworks, offer a promising strategy for protein biomineralization, yet the intricate design and multi-step synthesis of specific orthogonal units in molecular building blocks pose a significant synthetic challenge. Identifying new classes of natural building blocks capable of facilitating supramolecular framework construction while enabling stable protein binding has remained an elusive goal. Here, we introduce a versatile assembly strategy enabling the organization of diverse proteins and phenolic building blocks into highly crystalline hydrogen-bonded supramolecular phenolic frameworks (ProteinX@SPF). The natural ellagic acid (EA) exhibits a centrosymmetric structure with catechol groups on each molecular side, facilitating hydrogen bonding with protein amino acid residues for primary nucleation. Subsequently, EA self-assembles into ProteinX@SPF through hydrogen bonding and π-π interactions. The multiple hydrogen-bonding interactions impart structural rigidity and directional integrity, conferring ProteinX@SPF biohybrids with remarkable resistance to harsh conditions while preserving protein bioactivity. Additionally, the supramolecular stacking induced by π-π interactions endows ProteinX@SPF with long-range ordered nanochannels, which can serve as the gating to sieve the catalytic substrate and thus enhance the biocatalytic specificity. This work sheds light on biomineralization with natural building blocks for functional biohybrids, showing enormous potential in biocatalysis, sensing, and nanomedicine.

Scaling Laws for Protein Folding under Confinement

Spatial confinement significantly affects protein folding. Without the confinement provided by chaperones, many proteins cannot fold correctly. However, the quantitative effect of confinement on protein folding remains elusive. In this study, we observed scaling laws between the variation in folding transition temperature and the size of confinement, (Tf - Tfbulk)/Tfbulk ∼ L-ν. The scaling exponent v is significantly influenced by both the protein's topology and folding cooperativity. Specifically, for a given protein, v can decrease as the folding cooperativity of the model increases, primarily due to the heightened sensitivity of the unfolded state energy to changes in cage size. For proteins with diverse topologies, variations in topological complexity influence scaling exponents in multiple ways. Notably, v exhibits a clear positive correlation with contact order and the proportion of nonlocal contacts, as this complexity significantly enhances the sensitivity of entropy loss in the unfolded state. Furthermore, we developed a novel scaling argument yielding 5/3 ≤ ν ≤ 10/3, consistent with the simulation results.

Enhancing Performances of Enzyme/Metal-Organic Polyhedra Composites by Mixed-Protein Co-Immobilization

Protein immobilization using water-soluble ionic metal-organic polyhedra (MOPs) acting as porous spacers has recently been demonstrated as a potent strategy for the preparation of biocatalysts. In this article, we describe a mixed-protein approach to achieve biocomposites with adjustable enzyme contents and excellent immobilization efficiencies, in a systematic and well-controlled manner. Self-assembly of either cationic or anionic MOPs with bovine serum albumin or egg white lysozyme combined with enzymes (alkaline phosphatase, laccase or cytochrome c) led to solid-state catalysts with a high retention of enzyme activity. Furthermore, for all these systems, the dilution of enzymes within the solid-state composite led to noticeably improved catalytic performances, with both higher specific activity and affinity for substrate.

Hypoxia-Responsive Hydrogen-Bonded Organic Framework-Mediated Protein Delivery for Cancer Therapy

The efficient delivery of therapeutic proteins to tumor sites is a promising cancer treatment modality. Hydrogen-bonded organic frameworks (HOFs) are successfully used for the protective encapsulation of proteins; however, easy precipitation and lack of controlled release of existing HOFs limit their further application for protein delivery in vivo. Here, a hypoxia-responsive HOF, self-assembled from azobenzenedicarboxylate/polyethylene glycol-conjugated azobenzenedicarboxylate and tetrakis(4-amidiniumphenyl)methane through charge-assisted hydrogen-bonding, is developed for systemic protein delivery to tumor cells. The newly generated HOF platform efficiently encapsulates representative cytochrome C, demonstrating good dispersibility under physiological conditions. Moreover, it can respond to overexpressed reductases in the cytoplasm under hypoxic conditions, inducing fast intracellular protein release to exert therapeutic effects. The strategy presented herein can be applied to other therapeutic proteins and can be expanded to encompass more intrinsic tumor microenvironment stimuli. This offers a novel avenue for utilizing HOFs in protein-based cancer therapy.

Facile and scale-up syntheses of high-performance enzyme@meso-HOF biocatalysts

Facile immobilization is essential for the wide application of enzymes in large-scale catalytic processes. However, exploration of suitable enzyme supports poses an unmet challenge, particularly in the context of scale-up biocatalyst fabrication. In this study, we present facile and scale-up syntheses of high-performance enzyme biocatalysts via in situ encapsulation of cytochrome c (Cyt-c) as mono-enzyme and glucose oxidase (GOx)-horseradish peroxidase (HRP) as dual-enzyme cascade (GOx&HRP) systems, respectively, into a stable mesoporous hydrogen-bonded organic framework (meso-HOF) matrix. In situ encapsulation reactions occur under ambient conditions, and facilitate scale up (∼3 g per reaction) of enzyme@meso-HOF within a very short period (5-10 min). The resultant biocatalysts not only exhibit high enzyme loading (37.9 wt% for mono-enzyme and 22.8 wt% for dual-enzyme) with minimal leaching, but also demonstrate high catalytic activity, superior reusability, and durability. This study represents an example of scale-up fabrication of enzyme@meso-HOF biocatalysts on the gram level and highlights superior meso-HOFs as suitable host matrices for biomolecular entities.

Boosting the photocatalytic decontamination efficiency using a supramolecular photoenzyme ensemble

Continuous industrialization has raised daunting environmental concerns, and there is an urgent need to develop a sustainable strategy to tackle the contamination issues. Here, we report a supramolecular photoenzyme ensemble enabling the harvest of solar energy to remove contaminations in water. The well-sourced oxidoreductase, laccase, is confined into a photoactive hydrogen-bonded organic framework (PHOF) through an in situ encapsulation method. The direct electron migration between the oxidation center in a PHOF and the reduction center in laccase facilitates synergistic photoenzyme-coupled catalysis, showing two orders of magnitude higher activity than free laccase for pollutant degradation under visible light, without the need for sacrificial agents or costly co-mediators. Such high decontamination efficiency also surpasses the reported catalysts. The structure and decontamination function of this supramolecular photoenzyme ensemble remain highly stable in complex environment matrices, presenting desirable reusability and almost 100% conversion efficiency of pollutants for real sewage samples. Our conceptual photoenzyme hybrid catalyst offers important insights into green and sustainable water decontamination.

Fabricating Polymeric Micelles with Enrichment and Cavity Effect for In Situ Enzyme Imobilization from Natural Biosystems

Metal-organic frameworks and hydrogen-organic frameworks (MOFs and HOFs) are attractive hosts for enzyme immobilization, but they are limited to immobilizing the purified enzymes, making industrial upscaling unattractive. Herein, aptamer-modified dual thermoresponsive polymeric micelles with switchable self-assembly and core-shell structure are constructed, which enable selective immobilization of trypsin directly from complex biological systems through a cascade operation of separation and immobilization. Their steric self-assembly provides a large amount of adsorption sites on the soluble micellar shell, resulting in high adsorption capacity and excellent selectivity. Meanwhile, their aptamer affinity ligand and cavity maintain the native conformations of trypsin and offer protective effects even in harsh conditions. The maximum adsorption capacity of the polymeric micelles for trypsin was determined to be 197 mg/g at 60 min, superior to those of MOFs and HOFs. 67.2 and 86.6% of its original activity was retained for trypsin immobilized in the cavity under strong alkaline and acidic conditions, respectively.

Encapsulation of Immobilized β-Glucosidase with Calcium Metal-Organic Frameworks for Enhanced Stability in Hydrolysis of Cellobiose

β-Glucosidase (β-G) holds promising applications in various fields, such as biomass energy, food, pharmaceuticals, and environmental protection, yet its industrial application is still limited by issues of stability and recycling. Herein, we first immobilized β-G onto the surface of magnetic chitosan nanoparticles (MCS/β-G) through adsorption methods. Subsequently, utilizing the metal-organic framework (MOF), CaBDC, which possesses good stability under acidic conditions, we encapsulated MCS/β-G. The resulting biocatalyst (MCS/β-G@CaBDC) exhibited excellent activity and recyclability. MCS/β-G@CaBDC can convert 91.5% of cellobiose to glucose in 60 min and maintained 81.9% activity after 10 cycles. The apparent Km value of MCS/β-G@CaBDC was 0.148 mM, lower than free β-G (0.166 mM) and MCS/β-G (0.173 mM). The CaBDC layer increased the mass transfer resistance of the reaction but also triggered structural rearrangement of β-G during the encapsulation process. This resulted in the β-sheet content rising to 68.4%, which, in turn, contributed to enhancing the rigidity of β-G. Moreover, the saturated magnetic strength of this biocatalyst could reach 37.3 emu/g, facilitating its magnetic recovery. The biocatalyst prepared in this study exhibits promising application prospects, and the immobilization method can provide valuable insights into the field of enzyme immobilization.

A Hydrogen-Bonded Organic Framework Based on Triphenylamine for Photocatalytic Silane Hydroxylation

Employing hydrogen-bonded organic frameworks (HOFs) as mild photocatalysts for organic conversions is still considerably challenging. In this work, we synthesized a hydrogen-bonded organic framework (HOF-16) and achieved the photocatalytic oxidation of silanes to generate silanols. Considering the constraints imposed by the framework structure, a significant improvement in the efficacy of singlet oxygen (1O2) generation is observed. HOF-16 exhibits remarkable photocatalytic performance when it comes to silane hydroxylation, displaying high efficiency, low catalyst loading, and good recyclability. This research highlights the immense potential of HOFs in the realm of organic photocatalysis.

Pros and Cons in Various Immobilization Techniques and Carriers for Enzymes

In recent years, enzyme immobilization technology has been developed, and studies on immobilized enzyme materials have become very prominent. With the immobilization technique, enzymes and compatible carrier materials are combined or enzyme crystals/aggregates are used in a carrier-free fashion, by physical, chemical, or biochemical methods. As a kind of biocatalyst, immobilized enzymes can catalyze certain chemical reactions with high selectivity and high efficiency under relatively mild reaction conditions and eliminate pollution to the environment. Considering the current status and applications of immobilized enzyme technology and materials emerging in the last 5 years, this mini-review introduces the advantages and disadvantages of various enzyme immobilization techniques with carriers as well as the pros and cons of different materials for immobilization. The future prospects of immobilization technology and carrier materials are outlined, aiming to provide a reference for further research and applications of sustainable technology.

Enzyme Immobilization using Covalent Organic Frameworks: From Synthetic Strategy to COFs Functional Role

Enzymes, a class of biocatalysts, exhibit remarkable catalytic efficiency, specificity, and selectivity, governing many reactions that are essential for various cascades within living cells. The immobilization of structurally flexible enzymes on appropriate supports holds significant importance in facilitating biomimetic transformations in extracellular environments. Covalent organic frameworks (COFs) have emerged as ideal candidates for enzyme immobilization due to high surface tunability, diverse chemical/structural designs, exceptional stability, and metal-free nature. Various immobilization techniques have been proposed to fabricate COF-enzyme biocomposites, offering significant enhancements in activity and reusability for COF-immobilized enzymes as well as new insights into developing advanced enzyme-based applications. In this review, we provide a comprehensive overview of state-of-the-art strategies for immobilizing enzymes within COFs by focusing on their applicability and versatility. These strategies are systematically summarized and compared by categorizing them into postsynthesis immobilization and in situ immobilization, where their respective strengths and limitations are thoroughly discussed. Combined with an overview of critical emerging applications, we further elucidate the multifaceted roles of COFs in enzyme immobilization and subsequent applications, highlighting the advanced biofunctionality achievable through COFs.

A Hydrogen-Bonded Organic Framework-Based Mitochondrion-Targeting Bioorthogonal Platform for the Modulation of Mitochondrial Epigenetics

Bioorthogonal chemistry represents a powerful tool in chemical biology, which shows great potential in epigenetic modulation. As a proof of concept, the epigenetic modulation model of mitochondrial DNA (mtDNA) is selected because mtDNA establishes a relative hypermethylation stage under oxidative stress, which impairs the mitochondrion-based therapeutic effect during cancer therapy. Herein, we design a new biocompatible hydrogen-bonded organic framework (HOF) for a HOF-based mitochondrion-targeting bioorthogonal platform TPP@P@PHOF-2. PHOF-2 can activate a prodrug (pro-procainamide) in situ, which can specifically inhibit DNA methyltransferase 1 (DNMT1) activity and remodel the epigenetic modification of mtDNA, making it more susceptible to ROS damage. In addition, PHOF-2 can also catalyze artemisinin to produce large amounts of ROS, effectively damaging mtDNA and achieving better chemodynamic therapy demonstrated by both in vitro and in vivo studies. This work provides new insights into developing advanced bioorthogonal therapy and expands the applications of HOF and bioorthogonal catalysis.

A Biocompatible Hydrogen-Bonded Organic Framework (HOF) as Sonosensitizer and Artificial Enzyme for In-Depth Treatment of Alzheimer's Disease

Current phototherapeutic approaches for Alzheimer's disease (AD) exhibit restricted clinical outcomes due to the limited physical penetration and comprised brain microenvironment of noninvasive nanomedicine. Herein, a hydrogen-bonded organic framework (HOF) based sonosensitizer is designed and synthesized. Mn-TCPP, a planar molecule where Mn2+ ion is chelated in the core with a large p-conjugated system and 4 carboxylate acid groups, has been successfully used as building blocks to construct an ultrasound-sensitive HOF (USI-MHOF), which can go deep in the brain of AD animal models. The both in vitro and in vivo studies indicate that USI-MHOF can generate singlet oxygen (1O2) and oxidize β-amyloid (Aβ) to inhibit aggregation, consequently attenuating Aβ neurotoxicity. More intriguingly, USI-MHOF exhibits catalase (CAT)- and superoxide dismutase (SOD)-like activities, mitigating neuron oxidative stress and reprograming the brain microenvironment. For better crossing the blood-brain barrier (BBB), the peptide KLVFFAED (KD8) has been covalently grafted to USI-MHOF for improving BBB permeability and Aβ selectivity. Further, in vivo experiments demonstrate a significant reduction of the craniocerebral Aβ plaques and improvement of the cognition deficits in triple-transgenic AD (3×Tg-AD) mice models following deep-penetration ultrasound treatment. The work provides the first example of an ultrasound-responsive biocompatible HOF as non-invasive nanomedicine for in-depth treatment of AD.

Multivariate Silicification-Assisted Single Enzyme Structure Augmentation for Improved Enzymatic Activity-Stability Trade-Off

The ability to finely tune/balance the structure and rigidity of enzymes to realize both high enzymatic activity and long-term stability is highly desired but highly challenging. Herein, we propose the concept of the "silicazyme", where solid inorganic silica undergoes controlled hybridization with the fragile enzyme under moderate conditions at the single-enzyme level, thus enabling simultaneous structure augmentation, long-term stability, and high enzymatic activity preservation. A multivariate silicification approach was utilized and occurred around individual enzymes to allow conformal coating. To realize a high activity-stability trade-off the structure flexibility/rigidity of the silicazyme was optimized by a component adjustment ternary (CAT) plot method. Moreover, the multivariate organosilica frameworks bring great advantages, including surface microenvironment adjustability, reversible modification capability, and functional extensibility through the rich chemistry of silica. Overall silicazymes represent a new class of enzymes with promise for catalysis, separations, and nanomedicine.

Enzyme-Immobilized Porous Crystals for Environmental Applications

Developing efficient technologies to eliminate or degrade contaminants is paramount for environmental protection. Biocatalytic decontamination offers distinct advantages in terms of selectivity and efficiency; however, it still remains challenging when applied in complex environmental matrices. The main challenge originates from the instability and difficult-to-separate attributes of fragile enzymes, which also results in issues of compromised activity, poor reusability, low cost-effectiveness, etc. One viable solution to harness biocatalysis in complex environments is known as enzyme immobilization, where a flexible enzyme is tightly fixed in a solid carrier. In the case where a reticular crystal is utilized as the support, it is feasible to engineer next-generation biohybrid catalysts functional in complicated environmental media. This can be interpreted by three aspects: (1) the highly crystalline skeleton can shield the immobilized enzyme against external stressors. (2) The porous network ensures the high accessibility of the interior enzyme for catalytic decontamination. And (3) the adjustable and unambiguous structure of the reticular framework favors in-depth understanding of the interfacial interaction between the framework and enzyme, which can in turn guide us in designing highly active biocomposites. This Review aims to introduce this emerging biocatalysis technology for environmental decontamination involving pollutant degradation and greenhouse gas (carbon dioxide) conversion, with emphasis on the enzyme immobilization protocols and diverse catalysis principles including single enzyme catalysis, catalysis involving enzyme cascades, and photoenzyme-coupled catalysis. Additionally, the remaining challenges and forward-looking directions in this field are discussed. We believe that this Review may offer a useful biocatalytic technology to contribute to environmental decontamination in a green and sustainable manner and will inspire more researchers at the intersection of the environment science, biochemistry, and materials science communities to co-solve environmental problems.

Flexible hydrogen-bonded organic frameworks (HOFs): opportunities and challenges

Flexible behavior is one of the most fascinating features of hydrogen-bonded organic frameworks (HOFs), which represent an emerging class of porous materials that are self-assembled via H-bonding between organic building units. Due to their unique flexibility, HOFs can undergo structural changes or transformations in response to various stimuli (physical or chemical). Taking advantage of this unique structural feature, flexible HOFs show potential in multifunctional applications such as gas storage/separation, molecular recognition, sensing, proton conductivity, biomedicine, etc. While some other flexible porous materials have been extensively studied, the dynamic behavior of HOFs remains relatively less explored. This perspective highlights the inherent flexible properties of HOFs, discusses their different flexible behaviors, including pore size/shape changes, interpenetration/stacking manner, H-bond breaking/reconstruction, and local dynamic behavior, and highlights their potential applications. We believe that this perspective will not only contribute to HOF chemistry and materials science, but will also facilitate the ongoing extensive research on dynamic porous materials.

Structural Design and Energy and Environmental Applications of Hydrogen-Bonded Organic Frameworks: A Systematic Review

Hydrogen-bonded organic frameworks (HOFs) are emerging porous materials that show high structural flexibility, mild synthetic conditions, good solution processability, easy healing and regeneration, and good recyclability. Although these properties give them many potential multifunctional applications, their frameworks are unstable due to the presence of only weak and reversible hydrogen bonds. In this work, the development history and synthesis methods of HOFs are reviewed, and categorize their structural design concepts and strategies to improve their stability. More importantly, due to the significant potential of the latest HOF-related research for addressing energy and environmental issues, this work discusses the latest advances in the methods of energy storage and conversion, energy substance generation and isolation, environmental detection and isolation, degradation and transformation, and biological applications. Furthermore, a discussion of the coupling orientation of HOF in the cross-cutting fields of energy and environment is presented for the first time. Finally, current challenges, opportunities, and strategies for the development of HOFs to advance their energy and environmental applications are discussed.

Chiral CuxCoyS-CuzS Nanoflowers with Bioinspired Enantioselective Catalytic Performances

Nanomaterials with biomimetic catalytic abilities have attracted significant attention. However, the stereoselectivity of natural enzymes determined by their unique configurations is difficult to imitate. In this work, a kind of chiral CuxCoyS-CuzS nanoflowers (L/D-Pen-NFs) is developed, using porous CuxCoyS nanoparticles (NPs) as stamens, CuzS sheets as petals, and chiral penicillamine as surface stabilizers. Compared to the natural laccase enzyme, L/D-Pen-NFs exhibit significant advantages in catalytic efficiency, stability against harsh environments, recyclability, and convenience in construction. Most importantly, they display high enantioselectivity toward chiral neurotransmitters, which is proved by L- and D-Pen-NFs' different catalytic efficiencies toward chiral enantiomers. L-Pen-NFs are more efficient in catalyzing the oxidation of L-epinephrine and L-dopamine compared with D-Pen-NFs. However, their catalytic efficiency in oxidizing L-norepinephrine and L-DOPA is lower than that of D-Pen-NFs. The reason for the difference in catalytic efficiency is the distinct binding affinities between CuxCoyS-CuzS nano-enantiomers and chiral molecules. This work can spur the development of chiral nanostructures with biomimetic functions.

Hydration/Dehydration Induced Reversible Transformation between a Porous Hydrogen-Bonded Organic Framework and a Nonporous Molecular Crystal for Highly Efficient Gas Dehydration

Gas dehydration is a critical process in gas transportation and chemical reactions, yet traditional drying agents require an energy-intensive dehydration and regeneration step. Here, we present a nonporous molecular crystal called Melem that can be synthesized and scaled up through solid-state synthesis methods. Melem exhibits exceptional water selectivity in gas dehydration and can be reactivated under moderate conditions. According to the single-crystal structure and powder X-ray diffraction studies, a reversible structural transformation between Melem and its hydrated form, Melem-H2O, induced by hydration/dehydration processes has been observed. Melem displays water adsorption properties with a maximum uptake of 11 mmol·g-1 at p/p 0 = 0.92 and 298 K. Additionally, Melem retained consistent water capture capacities after 5 adsorption-desorption cycles. The remarkable gas dehydration performance of Melem was confirmed by column breakthrough experiments, which achieved a separation factor of up to 654.

Protein-Integrated Hydrogen-Bonded Organic Frameworks: Chemistry and Biomedical Applications

Hydrogen-bonded organic frameworks (HOFs) are porous nanomaterials that offer exceptional biocompatibility and versatility for integrating proteins for biomedical applications. This minireview concisely discusses recent advancements in the chemistry and functionality of protein-HOF interfaces. It particularly focuses on strategic methodologies, such as the careful selection of building blocks and the genetic engineering of proteins, to facilitate protein-HOF interactions. We examine the role of enzyme encapsulation within HOFs, highlighting its capability to preserve enzyme function, a crucial aspect for applications in biosensing and disease diagnosis. Moreover, we discuss the emerging utility of nanoscale HOFs for intracellular protein delivery, illustrating their applicability as nanoreactors for intracellular catalysis and neuroprotective biorthogonal catalysis within cellular compartments. We highlight the significant advancement of designing biodegradable HOFs tailored for cytosolic protein delivery, underscoring their promising application in targeted cancer therapies. Finally, we provide a perspective viewpoint on the design of biocompatible protein-HOF assemblies, underlining their promising prospects in drug delivery, disease diagnosis, and broader biomedical applications.

Engineered polymer nanoparticles as artificial chaperones facilitating the selective refolding of denatured enzymes

Molecular chaperones assist in protein refolding by selectively binding to proteins in their nonnative states. Despite progress in creating artificial chaperones, these designs often have a limited range of substrates they can work with. In this paper, we present molecularly imprinted flexible polymer nanoparticles (nanoMIPs) designed as customizable biomimetic chaperones. We used model proteins such as cytochrome c, laccase, and lipase to screen polymeric monomers and identify the most effective formulations, offering tunable charge and hydrophobic properties. Utilizing a dispersed phase imprinting approach, we employed magnetic beads modified with destabilized whole-protein as solid-phase templates. This process involves medium exchange facilitated by magnetic pulldowns, resulting in the synthesis of nanoMIPs featuring imprinted sites that effectively mimic chaperone cavities. These nanoMIPs were able to selectively refold denatured enzymes, achieving up to 86.7% recovery of their activity, significantly outperforming control samples. Mechanistic studies confirmed that nanoMIPs preferentially bind denatured rather than native enzymes, mimicking natural chaperone interactions. Multifaceted analyses support the functionality of nanoMIPs, which emulate the protective roles of chaperones by selectively engaging with denatured proteins to inhibit aggregation and facilitate refolding. This approach shows promise for widespread use in protein recovery within biocatalysis and biomedicine.

Hydrogen-Bonded Organic Framework Derived 2D N, O Co-Doped Carbon Nanobelt with Tunable Pseudocapacitive Contribution for Efficient Capacitive Deionization

Defect engineering is recognized as an attractive method for modulating the electronic structure and physicochemical characteristics of carbon materials. Exploiting heteroatom-doped porous carbon with copious active sites has attracted great attention for capacitive deionization (CDI). However, traditional methods often rely on the utilization of additional heteroatom sources and strong corrosive activators, suffering from low doping efficiency, insufficient doping level, and potential biotoxicity. Herein, hydrogen-bonded organic frameworks (HOFs) are employed as precursors to synthesize N, O co-doped porous carbon via a simple and green reverse defect engineering strategy, achieving controllable heavy doping of heteroatoms. The N, O co-doping triggers significant pseudocapacitive contribution and the surface pore structure supports the formation of the electric double layer. Therefore, when HOF-derived N, O co-doped carbon is used as CDI electrodes, a superior salt adsorption capacity of 32.29 ± 1.42 mg g-1 and an outstanding maximum salt adsorption rate of 10.58 ± 0.46 mg g-1 min-1 at 1.6 V in 500 mg L-1 NaCl solution are achieved, which are comparable to those of state-of-the-art carbonaceous electrodes. This work exemplifies the effectiveness of the reverse nitrogen-heavy doping strategy on improving the carbon structure, shedding light on the further development of rational designed electrode materials for CDI.

Pore-Engineered Hydrogen-Bonded Supramolecular Fluorosensor for Ultrasensitive Determination of Copper Ions

The selective quantification of copper ions (Cu2+) in biosamples holds great importance for disease diagnosis, treatment, and prognosis since the Cu2+ level is closely associated with the physiological state of the human body. While it remains a long-term challenge due to the extremely low level of free Cu2+ and the potential interference by the complex matrices. Here, a pore-engineered hydrogen-bonded organic framework (HOF) fluorosensor is constructed enabling the ultrasensitive and highly selective detection of free Cu2+. Attributing to atomically precise functionalization of active amino "arm" within the HOF pores and the periodic π-conjugated skeleton, this porous HOF fluorosensor affords high affinity toward Cu2+ through double copper-nitrogen (Cu─N) coordination interactions, resulting in specific fluorescence quenching of the HOF as compared with a series of substances ranging from other metal ions, metabolites, amino acids to proteins. Such superior fluorescence quenching effect endows the Cu2+ quantification by this new HOF sensor with a wide linearity of 50-20 000 nm, a low detection limit of 10 nm, and good recoveries (89.5%-115%) in human serum matrices, outperforming most of the reported approaches. This work highlights the practicability of hydrogen-bonded supramolecular engineering for designing facile and ultrasensitive biosensors for clinical free Cu2+ determination.

A Multienzyme Cascade Pathway Immobilized in a Hydrogen-Bonded Organic Framework for the Conversion of CO2

The reduction of carbon dioxide to valuable chemicals through enzymatic processes is regarded as a promising approach for the reduction of carbon dioxide emissions. In this study, an in vitro multi-enzyme cascade pathway is constructed for the conversion of CO2 into dihydroxyacetone (DHA). This pathway, known as FFFP, comprises formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH), formolase (FLS), and phosphite dehydrogenase (PTDH), with PTDH serving as the critical catalyst for regenerating the coenzyme NADH. Subsequently, the immobilization of the FFFP pathway within the hydrogen-bonded organic framework (HOF-101) is accomplished in situ. A 1.8-fold increase in DHA yield is observed in FFFP@HOF-101 compared to the free FFFP pathway. This enhancement can be explained by the fact that within FFFP@HOF-101, enzymes are positioned sufficiently close to one another, leading to the elevation of the local concentration of intermediates and an improvement in mass transfer efficiency. Moreover, FFFP@HOF-101 displays a high degree of stability. In addition to the establishment of an effective DHA production method, innovative concepts for the tailored synthesis of fine compounds from CO2 through the utilization of various multi-enzyme cascade developments are generated by this work.

Supramolecular polynuclear clusters sustained cubic hydrogen bonded frameworks with octahedral cages for reversible photochromism

Developing supramolecular porous crystalline frameworks with tailor-made architectures from advanced secondary building units (SBUs) remains a pivotal challenge in reticular chemistry. Particularly for hydrogen-bonded organic frameworks (HOFs), construction of geometrical cavities through secondary units has been rarely achieved. Herein, a body-centered cubic HOF (TCA_NH4) with octahedral cages was constructed by a C3-symmetric building block and NH4+ node-assembled cluster (NH4)4(COOH)8(H2O)2 that served as supramolecular secondary building units (SSBUs), akin to the polynuclear SBUs in reticular chemistry. Specifically, the octahedral cages could encapsulate four homogenous haloforms including CHCl3, CHBr3, and CHI3 with truncated octahedron configuration. Crystallographic evidence revealed the cages served as spatially-confined nanoreactors, enabling fast, broadband photochromic effect associated with the reversible photo/thermal transformation between encapsulated CHI3 and I2. Overall, this work provides a strategy by shaping SSBUs to expand the framework topology of HOFs and a prototype of hydrogen-bonded nanoreactors to accommodate reversible photochromic reactions.

Enhanced performance of enzymes confined in biocatalytic hydrogen-bonded organic frameworks for sensing of glutamate in the central nervous system

Glutamate (Glu) is a key excitatory neurotransmitter associated with various neurological disorders in the central nervous system, so its measurement is vital to both basic research and biomedical application. In this work, we propose the first example of using biocatalytic hydrogen-bonded organic frameworks (HOFs) as the hosting matrix to encapsulate glutamate oxidase (GLOD) via a de novo approach, fabricating a cascaded-enzyme nanoreactor for Glu biosensing. In this design, the ferriporphyrin ligands can assemble to form Fe-HOFs with high catalase-like activity, while offering a scaffold for the in-situ immobilization of GLOD. Moreover, the formed GLOD@Fe-HOFs are favorable for the efficient diffusion of Glu into the active sites of GLOD via the porous channels, accelerating the cascade reaction with neighboring Fe-HOFs. Consequently, the constructed nanoreactor can offer superior activity and operational stability in the catalytic cascade for Glu biosensing. More importantly, rapid and selective detection can be achieved in the cerebrospinal fluid (CSF) collected from mice in a low sample consumption. Therefore, the successful fabrication of enzyme@HOFs may offer promise to develop high-performance biosensor for further biomedical applications.

Biomolecules meet organic frameworks: from synthesis strategies to diverse applications

Biomolecules are essential in pharmaceuticals, biocatalysts, biomaterials, etc., but unfortunately they are extremely susceptible to extraneous conditions. When biomolecules meet porous organic frameworks, significantly improved thermal, chemical, and mechanical stabilities are not only acquired for raw biomolecules, but also molecule sieving, substrate enrichment, chirality property, and other functionalities are additionally introduced for application expansions. In addition, the intriguing synergistic effect stemming from elaborate and concerted interactions between biomolecules and frameworks can further enhance application performances. In this paper, the synthesis strategies of the so-called bio-organic frameworks (BOFs) in recent years are systematically reviewed and classified. Additionally, their broad applications in biomedicine, catalysis, separation, sensing, and imaging are introduced and discussed. Before ending, the current challenges and prospects in the future for this infancy-stage but significant research field are also provided. We hope that this review will offer a concise but comprehensive vision of designing and constructing multifunctional BOF materials as well as their full explorations in various fields.

Biomimetic Mineralization of Large Enzymes Utilizing a Stable Zirconium-Based Metal-Organic Frameworks

Enzymes are natural catalysts for a wide range of metabolic chemical transformations, including selective hydrolysis, oxidation, and phosphorylation. Herein, we demonstrate a strategy for the encapsulation of enzymes within a highly stable zirconium-based metal-organic framework. UiO-66-F4 was synthesized under mild conditions using an enzyme-compatible amino acid modulator, serine, at a modest temperature in an aqueous solution. Enzyme@UiO-66-F4 biocomposites were then formed by an in situ encapsulation route in which UiO-66-F4 grows around the enzymes and, consequently, provides protection for the enzymes. A range of enzymes, namely, lysozyme, horseradish peroxidase, and amano lipase, were successfully encapsulated within UiO-66-F4. We further demonstrate that the resulting biocomposites are stable under conditions that could denature many enzymes. Horseradish peroxidase encapsulated within UiO-66-F4 maintained its biological activity even after being treated with the proteolytic enzyme pepsin and heated at 60 °C. This strategy expands the toolbox of potential metal-organic frameworks with different topologies or functionalities that can be used as enzyme encapsulation hosts. We also demonstrate that this versatile process of in situ encapsulation of enzymes under mild conditions (i.e., submerged in water and at a modest temperature) can be generalized to encapsulate enzymes of various sizes within UiO-66-F4 while protecting them from harsh conditions (i.e., high temperatures, contact with denaturants or organic solvents).

Hydrogen-Bonded Supramolecular Nanotrap Enabling the Interfacial Activation of Hosted Enzymes

Engineering nanotraps to immobilize fragile enzymes provides new insights into designing stable and sustainable biocatalysts. However, the trade-off between activity and stability remains a long-standing challenge due to the inevitable diffusion barrier set up by nanocarriers. Herein, we report a synergetic interfacial activation strategy by virtue of hydrogen-bonded supramolecular encapsulation. The pore wall of the nanotrap, in which the enzyme is encapsulated, is modified with methyl struts in an atomically precise position. This well-designed supramolecular pore results in a synergism of hydrogen-bonded and hydrophobic interactions with the hosted enzyme, and it can modulate the catalytic center of the enzyme into a favorable configuration with high substrate accessibility and binding capability, which shows up to a 4.4-fold reaction rate and 4.9-fold conversion enhancements compared to free enzymes. This work sheds new light on the interfacial activation of enzymes using supramolecular engineering and also showcases the feasibility of interfacial assembly to access hierarchical biocatalysts featuring high activity and stability simultaneously.

Multistate structures in a hydrogen-bonded polycatenation non-covalent organic framework with diverse resistive switching behaviors

The inherent structural flexibility and reversibility of non-covalent organic frameworks have enabled them to exhibit switchable multistate structures under external stimuli, providing great potential in the field of resistive switching (RS), but not well explored yet. Herein, we report the 0D+1D hydrogen-bonded polycatenation non-covalent organic framework (HOF-FJU-52), exhibiting diverse and reversible RS behaviors with the high performance. Triggered by the external stimulus of electrical field E at room temperature, HOF-FJU-52 has excellent resistive random-access memory (RRAM) behaviors, comparable to the state-of-the-art materials. When cooling down below 200 K, it was transferred to write-once-read-many-times memory (WORM) behaviors. The two memory behaviors exhibit reversibility on a single crystal device through the temperature changes. The RS mechanism of this non-covalent organic framework has been deciphered at the atomic level by the detailed single-crystal X-ray diffraction analyses, demonstrating that the structural dual-flexibility both in the asymmetric hydrogen bonded dimers within the 0D loops and in the infinite π-π stacking column between the loops and chains contribute to reversible structure transformations between multi-states and thus to its dual RS behaviors.

Alternative protein encapsulation with MOFs: overcoming the elusive mineralization of HKUST-1 in water

Protein encapsulation by in situ formation of MOFs is a valuable strategy to immobilise and protect these bioentities. However the required biocompatible conditions limits the scope of MOFs under investigation, particularly in the case of hydrolytically unstable MOFs such as HKUST-1. We report alternative synthetic procedures to obtain protein@HKUST-1 biocomposites from related Cu-BTC dense biocomposites. pH dependent dense phase precursors are first obtained and their transformations into HKUST-1 are characterized. Encapsulation efficiency is affected by the protein's nature, and can be modulated by the sequential or simultaneous addition of MOF precursors.

Biodegradable Hydrogen-Bonded Organic Framework for Cytosolic Protein Delivery

Hydrogen-bonded organic frameworks (HOFs) are a novel class of porous nanomaterials that show great potential for intracellular delivery of protein therapeutics. However, the inherent challenges in interfacing protein with HOFs, and the need for spatiotemporally controlling the release of protein within cells, have constrained their therapeutic potential. In this study, we report novel biodegradable hydrogen-bonded organic frameworks, termed DS-HOFs, specially designed for the cytosolic delivery of protein therapeutics in cancer cells. The synthesis of DS-HOFs involves the self-assembly of 4-[tris(4-carbamimidoylphenyl) methyl] benzenecarboximidamide (TAM) and 4,4'-dithiobisbenzoic acid (DTBA), governed by intermolecular hydrogen-bonding interactions. DS-HOFs exhibit high efficiency in encapsulating a diverse range of protein cargos, underpinned by the hydrogen-bonding interactions between the protein residue and DS-HOF subcomponents. Notably, DS-HOFs are selectively degraded in cancer cells triggered by the distinct intracellular reductive microenvironments, enabling an enhanced and selective release of protein inside cancer cells. Additionally, we demonstrate that the efficient delivery of bacterial effector protein DUF5 using DS-HOFs depletes the mutant RAS in cancer cells to prohibit tumor cell growth both in vitro and in vivo. The design of biodegradable HOFs for cytosolic protein delivery provides a powerful and promising strategy to expand the therapeutic potential of proteins for cancer therapy.

Neuroprotective Bioorthogonal Catalysis in Mitochondria Using Protein-Integrated Hydrogen-Bonded Organic Frameworks

Mitochondria-targeted bioorthogonal catalysis holds promise for controlling cell function precisely, yet achieving selective and efficient chemical reactions within organelles is challenging. In this study, we introduce a new strategy using protein-integrated hydrogen-bonded organic frameworks (HOFs) to enable synergistic bioorthogonal chemical catalysis and enzymatic catalysis within mitochondria. Utilizing catalytically active tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium(II) to self-assemble with [1,1'-biphenyl]-4,4'-biscarboximidamide, we synthesized nanoscale RuB-HOFs that exhibit high photocatalytic reduction activity. Notably, RuB-HOFs efficiently enter cells and preferentially localize to mitochondria, where they facilitate bioorthogonal photoreduction reactions. Moreover, we show that RuB-HOFs encapsulating catalase can produce hydrogen sulfide (H2 S) in mitochondria through photocatalytic reduction of pro-H2 S and degrade hydrogen peroxide through enzymatic catalysis simultaneously, offering a significant neuroprotective effect against oxidative stress. Our findings not only introduce a versatile chemical toolset for mitochondria-targeted bioorthogonal catalysis for prodrug activation but also pave the way for potential therapeutic applications in treating diseases related to cellular oxidative stress.

Metal-Organic Framework-Based Artificial Organelle Corrects Microenvironment Interference for Accurate Intratumoral Glucose Analysis

Enzymatic catalysis with high efficiency allows them a great prospect in metabolite monitoring in living cells. However, complex tumor microenvironments, such as acidity, H2 O2 , and hypoxia, are bound to disturb catalytic reactions for misleading results. Here, we report a spatially compartmentalized artificial organelle to correct intratumoral glucose analysis, where the zeolitic imidazolate framework-8 immobilized glucose oxidase-horseradish peroxidase cascade core and catalase-directed shell act as signal transduction and guarding rooms respectively. The acid-digested core and stable shell provide appropriate spaces to boost biocatalytic efficiency with good tolerability. Notably, the endogenous H2 O2 is in situ decomposed to O2 by catalase, which not only overcomes the interference in signal output but also alleviates the hypoxic states to maximize glucose oxidation. The marked protective effect and biocompatibility render artificial organelles to correct the signal transduction for dynamic monitoring glucose in vitro and in vivo, achieving our goal of accurate intratumoral metabolite analysis.

In-situ encapsulation and construction of Lac@HOFs/hydrogel composite for enhancing laccase stability and azo dyes decolorization efficiency

Enzymes with high catalytic activity and stability have been used for the sustainable development of green chemical applications, such as water remediation. Immobilized laccase can be used to construct a synergistic system for adsorption and degradation, which has great potential for water remediation. Herein, a hydrogen-bonded organic framework was installed onto laccase in-situ to form a net-carboxylate-arranged defective cage, which enhanced its catalytic stability. Thereafter, the CMC/PVA/Lac@HOF-101 hydrogel was fabricated by freeze-thaw cycles using sodium carboxymethylcellulose and polyvinyl alcohol as carriers and copper (II) as a cross-linker. Notably, the MOFs/hydrogel as a protective carrier of laccase maintain long-term recyclability and catalytic stability. After the fifth catalytic cycle, approximately 66.7 % activity of the CP-Lac@HOF-101 was retained. When both free laccase and CP-Lac@HOF-101 were used for decolorization of Acid Orange 7 (AO), the removal rates were 10.9 % and 82.5 % after 5 h, respectively. Furthermore, even in the presence of metal cations, almost 60.0 % of the AO removal efficiency was achieved. The relationship between the structure of the azo dyes and decolorization efficiency of the synergistic system was further investigated. This study offers a method for constructing enzyme@HOF-based composite hydrogels and provides a promising water remediation strategy.

Hydrogen-bonded organic frameworks: new horizons in biomedical applications

Hydrogen-bonded organic frameworks (HOFs) are an emerging attractive class of highly crystalline porous materials characterized by significant biocompatibility, rich chemical functionalities and well-defined porosity. The unique advantages including metal-free nature and reversible binding manner significantly distinguish HOFs from other porous materials in the biotechnology and biomedical field. However, the relevant HOF studies still remain in their infancy despite the promising and remarkable results that have been presented in recent years. Due to the intricate and dynamic nature of physiological conditions, the major challenge lies in the stability and structural diversity of HOFs in vivo. In this Tutorial Review, we summarize the common building blocks for the construction of HOF-based functional biomaterials and the latest developments in the biological field. Moreover, we highlight current challenges regarding the stability and functionalization of HOFs along with the corresponding potential solutions. This Tutorial Review will have a profound effect in future years on the design and applications of HOF-based biomaterials.

Co-encapsulating Cofactor and Enzymes in Hydrogen-Bonded Organic Frameworks for Multienzyme Cascade Reactions with Cofactor Recycling

Use of hydrogen-bonded organic frameworks (HOFs) for enzyme immobilization faces challenges in the improvement of enzyme activity recovery and the assembly of cofactor-dependent multienzyme systems. Herein, we report a polyelectrolyte-assisted encapsulation approach (PAEA) that enables two cascades with four oxidoreductases and two nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) cofactors co-encapsulated in BioHOF-1 with excellent cargo loading and over 100 % cascade activity. The key role of the polyelectrolyte is to coat enzymes and tether NAD(P)H, thus interacting with HOF monomers in place of enzymes, avoiding the destruction of enzymes by HOF monomers. The versatility and efficiency of PAEA are further illustrated by an HOF-101-based bio-nanoreactor. Moreover, the immobilization by PAEA makes enzymes and NAD(P)H display excellent stability and recyclability. This study has demonstrated a facile and versatile PAEA for fabricating cofactor-dependent multienzyme cascade nanoreactors with HOFs.