Ionic Liquid-Mediated Dynamic Polymerization for Facile Aqueous-Phase Synthesis of Enzyme-Covalent Organic Framework Biocatalysts.

Utilizing covalent organic framework (COF) as a hypotoxic and porous scaffold to encapsulate enzyme (enzyme@COF) has inspired numerous interests at the intersection of chemistry, materials, and biological science. In this study, we report a convenient scheme for one-step, aqueous-phase synthesis of highly crystalline enzyme@COF biocatalysts. This facile approach relies on an ionic liquid (2 µL of imidazolium ionic liquid)-mediated dynamic polymerization mechanism, which can facilitate the in situ assembly of enzyme@COF under mild conditions. This green strategy is adaptive to synthesize different biocatalysts with highly crystalline COF "exoskeleton", as well evidenced by the low-dose cryo-EM and other characterizations. Attributing to the rigorous sieving effect of crystalline COF pore, the hosted lipase shows non-native selectivity for aliphatic acid hydrolysis. In addition, the highly crystalline linkage affords COF "exoskeleton" with higher photocatalytic activity for in situ production of H2 O2 , enabling us to construct a self-cascading photo-enzyme coupled reactor for pollutants degradation, with a 2.63-fold degradation rate as the poorly crystalline photo-enzyme reactor. This work showcases the great potentials of employing green and trace amounts of ionic liquid for one-step synthesis of crystalline enzyme@COF biocatalysts, and emphasizes the feasibility of diversifying enzyme functions by integrating the reticular chemistry of a COF.

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.

Structural and Functional Insights into the Biomineralized Zeolite Imidazole Frameworks.

Biomineralization is a natural process of mineral formation mediated by biomacromolecules, allowing access to hierarchical structures integrating biological, chemical, and material properties. In this contribution, we comprehensively investigate the biomineralization of zeolite imidazole frameworks (ZIFs) for one-step synthesis of an enzyme-MOF biocomposite, in terms of differential crystallization behaviors, fine microstructure of resultant ZIF biominerals, the enzyme's conformation evolution, and protective effect of ZIF mineral. We discover that the biomineralization ability is ZIF organic linker dependent and the biocatalytic function is highly related to the ZIF mineral species and their distinguishable topologies and defect structures. Importantly, a side-by-side analysis suggests that the protective effect of ZIF mineral toward the hosted enzyme is highly associated with the synergistic effect of size dimension and chemical microenvironment of the ZIF pores. This work provides important insight into the ZIF-dependent biomineralization behaviors and highlights the important role of the ZIF microstructure in its biocatalytic activity and durability, which has been underestimated previously.

Photonanozyme with Light Mediated Activity.

Since the discovery that Fe3 O4 nanoparticle has intrinsic natural peroxidase-like activity by Yan et al in 2007, mimicking native enzymes via nano-engineering (named as nanozyme) pays a new avenue to bypass the fragility and recyclability of natural enzymes and thus expedites the biocatalysis in multidisciplinary applications. In addition, the high programmability and structural stability attributes of nanozyme afford the ease of coupling with electromagnetic waves of different energies, providing great opportunities to construct photo-responsive nanozyme under user-defined electromagnetic waves, which is known as photo-nanozyme. In this concept, we aim to providing a summary of how electromagnetic waves with varying wavelengths can serve as external stimuli to induce or enhance the biocatalytic performance of photo-nanozymes, thereby offering fascinating functions that cannot be achieved by pristine nanozyme.

Pore-Environment-Dependent Photoresponsive Oxidase-Like Activity in Hydrogen-Bonded Organic Frameworks.

Mimicking the bioactivity of native enzymes through synthetic chemistry is an efficient means to advance the biocatalysts in a cell-free environment, however, remains long-standing challenges. Herein, we utilize structurally explicit hydrogen-bonded organic frameworks (HOFs) to mimic photo-responsive oxidase, and uncover the important role of pore environments on mediating oxidase-like activity by means of constructing isostructural HOFs. We discover that the HOF pore with suitable geometry can stabilize and spatially organize the catalytic substrate into a favorable catalytic route, as with the function of the native enzyme pocket. Based on the desirable photo-responsive oxidase-like activity, a visual and sensitive HOFs biosensor is established for the detection of phosphatase, an important biomarker of skeletal and hepatobiliary diseases. This work demonstrates that the pore environments significantly influence the nanozymes' activity in addition to the active center.

Photodynamic Hydrogen-Bonded Biohybrid Framework: A Photobiocatalytic Cascade Nanoreactor for Accelerating Diabetic Wound Therapy.

A diabetic wound causes thousands of infections or deaths around the world each year, and its healing remains a critical challenge because of the ease of multidrug-resistant (MDR) bacterial infection, as well as the intrinsic hyperglycemic and hypoxia microenvironment that inhibits the therapeutic efficiency. Herein, we pioneer the design of a photobiocatalytic cascade nanoreactor via spatially organizing the biocatalysts and photocatalysts utilizing a hydrogen-bonded organic framework (HOF) scaffold for diabetic wound therapy. The HOF scaffold enables it to disperse and stabilize the host cargos, and the formed long-range-ordered mesochannels also facilitate the mass transfer that enhances the cascade activity. This integrated HOF nanoreactor allows the continuous conversion of overexpressed glucose and H2O2 into toxic reactive oxygen species by the photobiocatalytic cascade. As a result, it readily reverses the microenvironment of the diabetes wound and exhibits an extraordinary capacity for wound healing through synergistic photodynamic therapy. This work describes the first example of constructing an all-in-one HOF bioreactor for antimicrobial diabetes wound treatment and showcases the promise of combined biocatalysis and photocatalysis achieved by using an HOF scaffold in biomedicine applications.

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

Nature programs the structural folding of an enzyme that allows its on-demand biofunctionality; however, it is still a long-standing challenge to manually modulate an enzyme's conformation. Here, we design an exogenous hydrogen-bonded organic framework to modulate the conformation of cytochrome c, and hence allow non-native bioactivity for the enzyme. The rigid hydrogen-bonded organic framework, with net-arranged carboxylate inner cage, is in situ installed onto the native cytochrome c. The resultant hydrogen-bonded nano-biointerface changes the conformation to a previously not achieved catalase-like species within the reported cytochrome c-porous organic framework systems. In addition, the preserved hydrogen-bonded organic framework can stabilize the encapsulated enzyme and its channel-like pores also guarantee the free entrance of catalytic substrates. This work describes a conceptual nanotechnology for manoeuvring the flexible conformations of an enzyme, and also highlights the advantages of artificial hydrogen-bonded scaffolds to modulate enzyme activity.

Atomically unveiling the structure-activity relationship of biomacromolecule-metal-organic frameworks symbiotic crystal.

Crystallization of biomacromolecules-metal-organic frameworks (BMOFs) allows for orderly assemble of symbiotic hybrids with desirable biological and chemical functions in one voxel. The structure-activity relationship of this symbiotic crystal, however, is still blurred. Here, we directly identify the atomic-level structure of BMOFs, using the integrated differential phase contrast-scanning transmission electron microscopy, cryo-electron microscopy and x-ray absorption fine structure techniques. We discover an obvious difference in the nanoarchitecture of BMOFs under different crystallization pathways that was previously not seen. In addition, we find the nanoarchitecture significantly affects the bioactivity of the BMOFs. This work gives an important insight into the structure-activity relationship of BMOFs synthesized in different scenarios, and may act as a guide to engineer next-generation materials with excellent biological and chemical functions.

Hydrogen-Bonded Biohybrid Framework-Derived Highly Specific Nanozymes for Biomarker Sensing.

Nanozymes are of particular interest due to their enzyme-mimicking activity and high stability that are favorable in biomedical sensing and immunoassays. In this work, we report a highly specific N-doped nanozyme through pyrolysis of framework-confined bovine serum albumin (BSA). This strategy allows one to translate the low-cost and featureless BSA into a highly active enzyme mimic. The obtained carbon nanozyme (denoted as HBF-1-C800) displays 3- to 7-fold enhancement on peroxidase (POD) activity compared with the conventional carbon nanozymes and also shows ca. 5-fold activity enhancement compared to the reported N-doping graphene. Such excellent POD activity originates from high N-doping efficiency, protein-induced defective sites, and the intrinsic porous structure of HBF-1-C800, which provides abundantly accessible active sites and accelerates substrate diffusion simultaneously. Importantly, the HBF-1-C800 nanozyme has highly specific POD activity and also enables resistance to several harsh conditions that should denature natural enzymes. These features allow it with high accuracy, stability, and sensitivity for biosensing applications. Moreover, HBF-1-C800 has been designed as a promising platform for colorimetric biosensing of several biomarkers including H2O2, glutathione, and glucose, with wide linear ranges and low limits of detection that are satisfied with the disease diagnosis.

A Biocatalytic Cascade in an Ultrastable Mesoporous Hydrogen-Bonded Organic Framework for Point-of-Care Biosensing.

Herein, we report the first example of using mesoporous hydrogen-bonded organic frameworks (MHOFs) as the protecting scaffold to organize a biocatalytic cascade. The confined microenvironment of MHOFs has robust and large transport channels, allowing the efficient transport of a wide range of biocatalytic substrates. This new MHOF-confined cascade system shows superior activity, extended scope of catalytic substrates, and ultrahigh stability that enables the operation of complex chemical transformations in a porous carrier. In addition, the advantages of MHOF-confined cascades system for point-of-care biosensing are also demonstrated. This study highlights the advantages of HOFs as scaffold for multiple enzyme assemblies, which has huge potential for mimicking complex cellular transformation networks in a controllable manner.

Smartphone-assisted robust enzymes@MOFs-based paper biosensor for point-of-care detection.

Portable devices featured with fast analysis and affordable methodologies for clinical diagnostics have stimulated the rapid development of point-of-care (POC) technologies, potentially lowering the mortality rate. Herein, we demonstrated a portable, robust, and user-friendly intelligent metal-organic frameworks (MOFs) paper device, called smartphone-assisted biomimetic MOFs nanoreactor colorimetric paper (SBMCP), for on-demand POC detection of endogenous biomolecules. The concept of this paper platform was analogous to the intracellular cascades signal transduction, wherein the single/multiple enzymes components trapped within a ZIF-8 exoskeleton allowed the sensitive and selective recognition of target analyte via the accessible micropores network of ZIF-8, and then transferred the recognition event to a visual color signal based on the cascade reaction. Meanwhile, the ZIF-8 exoskeleton also endowed the enzymes with significantly elevated stability. As a result, this robust and portable SBMCP sensor enabled the on-site analysis of different important disease-related biomolecules through modulating the enzyme cascades, combining with a custom-designed smartphone application for signal readout. In the SBMCP assay, no sophisticated instruments or professional skill of the user was required, only 5 µL sample volume was needed, and the whole analysis process could be achieved within a portable MOFs paper and pervasive smartphone, endowing this new assay with the merits of low-cost, time-saving and easy-to-use. We demonstrated this SBMCP sensor was capable of real-time colorimetric detection of glucose and uric acid in diabetes and gout events. It is believed that this portable biosensor platform proposed herein potentially represents promising alternatives for POC diagnosis, especially applicable in developing world and resource-limited settings.

Modulating the Biofunctionality of Metal-Organic-Framework-Encapsulated Enzymes through Controllable Embedding Patterns.

Embedding an enzyme within a MOF as exoskeleton (enzyme@MOF) offers new opportunities to improve the inherent fragile nature of the enzyme, but also to impart novel biofunctionality to the MOF. Despite the remarkable stability achieved for MOF-embedded enzymes, embedding patterns and conversion of the enzymatic biofunctionality after entrapment by a MOF have only received limited attention. Herein, we reveal how embedding patterns affect the bioactivity of an enzyme encapsulated in ZIF-8. The enzyme@MOF can maintain high activity when the encapsulation process is driven by rapid enzyme-triggered nucleation of ZIF-8. When the encapsulation is driven by slow coprecipitation and the enzymes are not involved in the nucleation of ZIF-8, enzyme@MOF tends to be inactive owing to unfolding and competing coordination caused by the ligand, 2-methyl imidazole. These two embedding patterns can easily be controlled by chemical modification of the amino acids of the enzymes, modulating their biofunctionality.

Assessing the Impacts of Drought on Grassland Net Primary Production at the Global Scale.

Quantitatively assessing the impacts of drought on grassland has significant implications to understand the degradation mechanism and prevention degraded grassland. In this study, we analyzed the relationship between grassland drought and grassland Net Primary Productivity (NPP) based on the self-calibrated Palmer Drought Severity Index (scPDSI) from 1982 to 2008. The results showed that the global grassland scPDSI value had a slightly increasing trend with the rate of 0.0119 per year (R2 = 0.195), indicating that the global grassland drought lighter to some extent during study period. Moreover, the correlation coefficient between annual grassland NPP and scPDSI was from -0.83 to 0.92. The grassland NPP decreased under mild drought from 1992 to 1996. Additionally, the correlation coefficient between scPDSI and NPP for each grassland type was: Closed Shrublands > Non-woody grassland > Savannas > Open Shrublands > Woody Savannas, indicating that drought had difference influences on the different grassland types. Our results might provide the underlying insights needed to be guide for the effects of extreme weather events on grassland NPP.

Assessment of Spatial Agglomeration of Agricultural Drought Disaster in China from 1978 to 2016.

Drought disaster space agglomeration assessment is one of the important components of meteorological disaster prevention and mitigation. Agriculture affected by drought disaster is not only a serious threat to world food security, but also an obstacle to sustainable development. Additionally, China is an important agricultural import and export country in the world. Therefore, we used the global Moran's I and the local indicators of spatial autocorrelation (LISA) to reveal the spatial agglomeration of agricultural drought disaster in China from1978 to 2016, respectively. The results showed that China's agricultural drought disaster presents local spatial autocorrelation of geographical agglomeration at national level during the study period. The spatial agglomeration regions of China's agricultural drought disaster were in Inner Mongolia, Jilin province, Heilongjiang province, Liaoning province, Shanxi province, Hebei province, Shandong province, Shaanxi province and Henan province, indicating that agricultural drought disaster mainly distributed in North and Northwest China, especially occurred in the Yellow River Basin and its north areas. We also found that the overall movement direction of agricultural drought disaster agglomeration regions was northwest, and the maximum moving distance was 722.16 km. Our results might provide insight in early warning and prevention for drought disaster.

Grassland dynamics in responses to climate variation and human activities in China from 2000 to 2013.

Improving our understanding of the impacts of climate variation and human activities on grassland dynamics is heightened by expectations that climate variation and human activities may induce grassland degradation. An accurate evaluation of the respective impacts of climate variation and human activities on grassland dynamics is crucial to understand the grassland degradation mechanism and to control the degraded grassland. In this study, net primary productivity (NPP) was selected as an indicator to reflect grassland dynamics. Meanwhile, the potential NPP (PNPP) and human-induced NPP (HNPP) calculated as the difference of PNPP and actual ANPP (ANPP) were used to assess the relative effects of climate variation and human activities on grassland NPP changes in China during 2000-2013. Results of grassland ANPP showed an overall increase than decrease in productivity (81.21% vs 18.79%) from 2000 to 2013. For the increase of ANPP, the relative contribution of climate variation and human activities to grassland NPP changes were 41.45% and 45.22%, respectively. Climate variation was the dominant factor that induced the increase in ANPP mainly in areas of Sichuan, Gansu, Ningxia and Inner Mongolia. An increase in Human-dominated ANPP mainly occurred in Tibet, Qinghai and Xinjiang. The decrease in ANPP is principally controlled by the effect of human activities than that of climate variation, especially in Inner Mongolia. Meanwhile, climate-dominated ANPP increase and human-dominated ANPP decrease mainly occurred in plain grassland, desert grassland and meadow across the six types of grasslands in China. Furthermore, in alpine sub-alpine meadow and alpine sub-alpine, while climate-dominated ANPP of grassland was found to be decreased, an increase in human-dominated ANPP was detected. The increase in precipitation and the implementation of ecological restoration programs were found to be effective in inducing the noticeable increased grassland ANPP since 2003. The findings of the current research recommend that the Chinese government should continue to implement the prohibiting graze policy across the country and extensively strengthen the implementation of the policy in Inner Mongolia and North Xinjiang, particularly in plain grassland, desert grassland and meadow.