Type II topoisomerases are ubiquitous enzymes that play a pivotal role in modulating the topological configuration of double-stranded DNA. These topoisomerases are required for DNA metabolism and have been extensively studied in both prokaryotic and eukaryotic organisms. However, our understanding of virus-encoded type II topoisomerases remains limited. One intriguing example is the African swine fever virus, which stands as the sole mammalian-infecting virus encoding a type II topoisomerase. In this work, we use several approaches including cryo-EM, X-ray crystallography, and biochemical assays to investigate the structure and function of the African swine fever virus type II topoisomerase, pP1192R. We determine the structures of pP1192R in different conformational states and confirm its enzymatic activity in vitro. Collectively, our results illustrate the basic mechanisms of viral type II topoisomerases, increasing our understanding of these enzymes and presenting a potential avenue for intervention strategies to mitigate the impact of the African swine fever virus.

Newcastle disease virus (NDV) belongs to Paramyxoviridae, which contains lethal human and animal pathogens. NDV RNA genome is replicated and transcribed by a multifunctional 250 kDa RNA-dependent RNA polymerase (L protein). To date, high-resolution structure of NDV L protein complexed with P protein remains to be elucidated, limiting our understanding of the molecular mechanisms of Paramyxoviridae replication/transcription. Here, we used cryo-EM and enzymatic assays to investigate the structure-function relationship of L-P complex. We found that C-terminal of CD-MTase-CTD module of the atomic-resolution L-P complex conformationally rearranges, and the priming/intrusion loops are likely in RNA elongation conformations different from previous structures. The P protein adopts a unique tetrameric organization and interacts with L protein. Our findings indicate that NDV L-P complex represents elongation state distinct from previous structures. Our work greatly advances the understanding of Paramyxoviridae RNA synthesis, revealing how initiation/elongation alternates, providing clues for identifying therapeutic targets against Paramyxoviridae.

The development of nanotechnology is becoming a major trend nowadays. Nanoparticles (NPs) have been widely used in fields including food, biomedicine, and cosmetics, endowing NPs more opportunities to enter the human body. It is well-known that the gut microbiome plays a key role in human health, and the exposure of intestines to NPs is unavoidable. Accordingly, the toxicity of NPs has attracted more attention than before. This review mainly highlights recent advances in the evaluation of NPs' toxicity in the gastrointestinal system from the existing cell-based experimental models, such as the original mono-culture models, co-culture models, three-dimensional (3D) culture models, and the models established on microfluidic chips, to those in vivo experiments, such as mice models, Caenorhabditis elegans models, zebrafish models, human volunteers, as well as computer-simulated toxicity models. Owing to these models, especially those more biomimetic models, the outcome of the toxicity of NPs acting in the gastrointestinal tract can get results closer to what happened inside the real human microenvironment.

Human noroviruses (huNoVs) cause epidemic acute gastroenteritis using histo-blood group antigens (HBGAs) as host receptors or attachment factors to initiate an infection. While most huNoVs have been shown to bind HBGAs, some known clinical isolates, such as GI.3 DSV and VA115, do not recognize any HBGAs and thus the molecular mechanism behind their infections remains elusive. In this study, we provided both phenotypic and structural evidence to show that huNoV DSV and VA115 recognize a group of glycans with terminal galactoses as ligands. First, through glycan array we found that both DSV and VA115 protruding (P) domain proteins bound two oligosaccharides that share common terminal galactoses. Then, by determination of the crystal structures of DSV/VA115 P proteins in complex with Galα1-3Galβ1-4Glc and/or NA2 N-Glycan, respectively, we showed that the terminal galactose is the main saccharide recognized by the two viral proteins. Our data demonstrated that GI huNoVs can interact with non-HBGA glycans through their conserved galactose binding site, shedding light on the mechanism of huNoV adaptation through recognizing new glycan receptors to facilitate their widespread nature in human population. These findings are also of significance in strategy development for huNoV control and prevention, as well as development of antiviral drugs. IMPORTANCE Human noroviruses (huNoVs) are the most important viral pathogens causing epidemic acute gastroenteritis worldwide. Previous studies indicated that histo-blood group antigens (HBGAs) are critical host-susceptibility factors affecting huNoV host susceptibility, host range, and probably prevalence. However, certain huNoVs, such as GI.3 DSV and VA115, do not recognize any HBGAs. This implies that other unknown host factors might exist and the molecular mechanism underlying their host receptor recognition or attachment remains elusive. In this study, we found that purified capsid protruding domain proteins from two GI.3 huNoVs specifically bind two glycans that contain a common terminal galactose. We solved the crystal structures of the complexes at atomic resolution and validated the vital amino acids involved in glycan recognition. Our findings elucidate the mechanism of GI.3 huNoV-non-HBGA glycan interaction, which explains why GI.3 virus strains could not bind human HBGAs, paving a way to the prevention and treatment of huNoV-associated diseases.

The coordination between neurogenesis and angiogenesis plays an important role in nerve tissue development and regeneration. Recently, using bioactive materials to drive neurogenic and angiogenic responses has gained increasing attention. Understanding the neurovascular link between regulatory cues offers valuable insight into the mechanisms underlying nerve regeneration and the design of new bioactive materials. In this study, we utilized a dual-functionalized peptide nanofiber hydrogel presenting the brain-derived neurotrophic factor and vascular endothelial growth factor mimetic peptides RGIDKRHWNSQ (RGI) and KLTWQELYQLKYKGI (KLT) to construct an artificial neurovascular microenvironment. The dual-functionalized peptide nanofiber hydrogel enhanced the neurite outgrowth of pheochromocytoma (PC12) cells and tube-like structures formation of human umbilical vein endothelial cells (HUVECs) in vitro , and promoted rapid lesion infiltration of neural and vascular cells in a rat brain injury model. Using indirect co-culture models, we found that the dual-functionalized peptide hydrogel effectively mediated neurovascular crosstalk by regulating secretion of paracrine factors from PC12 cells and HUVECs. When the two cells types were directly co-cultured on the dual-functionalized peptide hydrogel, the efficiency of cell-cell communication was enhanced, which further accelerated the differentiation and maturation of PC12 cells with an increased number of pseudopodia and spread morphology, and HUVECs tube-like structure formation. In summary, the dual-functionalized peptide nanofiber hydrogel successfully formed an artificial neurovascular niche to directly regulate the behaviors of neural and vascular cells and promote their neurovascular crosstalk through paracrine signaling and direct cell-cell contact.

Metabolites can directly reflect and modulate cell responses and phenotypical changes by influencing energy balances, intercellular signals, and many other cellular functions throughout the lifespan of cells. Taking into account the heterogeneity of cells, single-cell metabolite analysis offers an insight into the functional process within one cell. Microfluidics as a powerful tool has attracted significant interest in the single-cell metabolite analysis field. The microfluidic platform is possible to observe, classify, and stimulate individual cells. It can also transport single-cell to subsequent analysis steps in a fast and controllable way to determine and analyze the composition and content of metabolites. The reviews of topics in microfluidics for single-cell metabolite analysis have been published in the past few years. However, most of them focused on metabolite analysis with mass spectrometry. Here, we covered the advances of microfluidic devices for single-cell metabolite analysis, with a focus on single-cell isolation and manipulation. What is more, we summarized the detection methods and applications of single-cell metabolites.

The assembly of molecules into hierarchical superstructures is ubiquitous in the construction of novel geometrically complex hierarchical superstructures, attracting great attention. Herein, a metal-ligand cross-linking strategy is developed for the fabrication of ferric ion-dopamine coordination hierarchical superstructures. A range of superstructures with highly complex morphologies, such as flower-like, octopus-like, and hedgehog-like superstructures, are synthesized. The mechanism for formation of hierarchical superstructures involves the pre-cross-linking of ferric ion with dopamine molecules, the fabrication of iron-dopamine precursors aggregated into the spherical aggregates, the nanoscale aggregates sintering and ordering themselves upon equilibration, the nanodots polymerizing into nanorods, and finally the nanorods self-assembling into hierarchical superstructures. In-depth research illustrates that as the permittivity (ξ) of the reaction system increases, the resulting hierarchical superstructures tend to converge into spherical shape. As a proof of concept, the 0D nanospheres, 1D nanorods, and 3D hierarchical superstructures are fabricated through adjusting system permittivity. The hierarchical superstructure is utilized as peroxidase-like ligase mimics to enhance the effect of tumor photothermal treatment. Further in vitro and in vivo assays demonstrate that the hierarchical superstructure can effectively ablate tumor cells. This work opens new horizons in hierarchical superstructures with complex architectures, and has great potential in nanozymology, biomedical science, and catalysis.

Adhesion to many kinds of surfaces, including biological tissues, is important in many fields but has been proved to be extremely challenging. Furthermore, peeling from strong adhesion is needed in many conditions, but is sometimes painful. Herein, a mussel inspired hydrogel is developed to achieve both strong adhesion and trigger-detachment. The former is actualized by electrostatic interactions, covalent bonds, and physical interpenetration, while the latter is triggered, on-demand, through combining a thixotropic supramolecular network and polymer double network. The results of the experiments show that the hydrogel can adhere to various material surfaces and tissues. Moreover, triggered by shear force, non-covalent interactions of the supramolecular network are destroyed. This adhesion can be peeled easily. The possible mechanism involved is discussed and proved. This work will bring new insight into electronic engineering and tissue repair like skin care for premature infants and burn victims.

Fabricating concurrently stretchable and conductive hydrogel scaffold is highly desired in the development of myocardial tissue engineering, and also very challenging especially with the anisotropic conductive properties. Existing anisotropic-strategies are limited to specific nanomaterials, or time-consuming. Here, we present a simple and new stretch-induced strategy to make conductive nanotubes aligned in the hydrogel. With this strategy, we fabricated a new type of hybrid hydrogel that possesses excellent stretchability while enabling outstanding anisotropic conductivity (6 vs 30 S/cm). Hybrid hydrogels are also successfully applied as a therapeutic cardiac patch which induces an elongated cell morphology of cultured cardiomyocytes and enables a stable directional transmission of electric signals. This patch gave successful mitigation of myocardium infarction in rats. It is believed that this strategy, and this nanocomposite hydrogel have a promising application in tissue engineering.

Junin virus (JUNV) causes Argentine hemorrhagic fever, a debilitating human disease of high mortality rates and a great risk to public health worldwide. Studying the L protein that replicates and transcribes the genome of JUNV, and its regulator Z protein should provide critical clues to identify therapeutic targets for disrupting the life cycle of JUNV. Here we report the 3.54 Å cryo-EM structure of the JUNV L protein complexed with regulator Z protein. JUNV L structure reveals a conserved architecture containing signature motifs found in other L proteins. Structural analysis shows that L protein is regulated by binding of Z protein at the RNA product exit site. Based on these findings, we propose a model for the role of Z protein as a switch to turn on/off the viral RNA synthesis via its interaction with L protein. Our work unveils the mechanism of JUNV transcription, replication and regulation, which provides a framework for the rational design of antivirals for combating viral infections.

The development of high‐efficiency nanozymes is of great significance in the field of nanozymology, because this is one of the prerequisites for the sophisticated performance of nanozymes. Herein, the developed metal–ligand cross‐linking strategy engineers porous carbon nanorod supported ultra‐small iron carbide nanoparticles that possess excellent oxidase‐like and peroxidase‐like enzyme activities. The fabricated nanozyme can efficiently accelerate the oxidation of ascorbate (AA) to enhance cancer cells ablation efficacy. Due to the nanozyme having great surface atoms utilization ratio and large specific surface area, the AA can be rapidly and completely autoxidized within 20 min. Mechanism research demonstrates that the nanozyme's first activation of O 2 to generate superoxide free radicals (O 2 •− ) via the oxidase‐like pathway, then the O 2 •− directly oxidizes AA and produces hydrogen peroxide (H 2 O 2 ). Simultaneously, the H 2 O 2 transforms into the toxic hydroxyl radical through the peroxidase‐like pathway and induces tumor cell death. Further in vitro and in vivo assays show the significant enhancement of the anti‐tumor efficacy through AA oxidation which is catalyzed by the developed nanozyme. It is expected that this work will benefit not only the development of other efficient nanozymes, but also future advances in the field of AA oxidation induced tumor therapy.

Nitric oxide (NO) is known as one of the most important biomarkers of many diseases. However, the development of NO-triggered drug releasing platforms is challenging due to the low concentration and short lifetime of NO in vivo. In this work, a novel nitrite (NO2-)-responsive hydrogel (DHPL-GEL), which can be used for smart drug release depending on the severity of the NO-related disease, is demonstrated. A dihydropyridine cross-linking agent is designed to construct DHPL-GEL to enable the responsive degradation of the hydrogel triggered by NO2-. On-demand release of the drug loaded in DHPL-GEL was observed under the stimulation of various concentrations of NO2- at the physiological level both in vitro and in vivo. In the inflammatory arthritis rat model, the DHPL-GEL drug delivery system showed a better therapeutic effect and less side effects than the traditional therapy and nonresponsive hydrogel drug delivery system, demonstrating the promising application of the NO2--responsive hydrogel for the treatment of NO-related diseases.

As one of emerging applications of lab-on-a-chip, microfluidics contribution to pharmaceutical science has arose increasing attention. The demand of lab-on-a-chip technologies for pharmaceutical science led to the development of Pharm-Lab on a Chip, which represents chip-based platforms for whole chain of pharmacy applications from drug discovery to post marketing product management. Pharm-Lab on a Chip consist of all aspects of chip-based principles, techniques and devices for pharmaceutical analysis, pharmacological/toxicological test and pharmaceutical production. In this review, we focused on the recent advances in utilization of lab-on-a-chip for pharmaceutical analysis and test. The main contents including separation and analysis of drug molecules on a chip, construction of novel pharmacological/toxicological models on a chip, and the application of chip-based models for evaluating drug efficacy and safety. As a summary and prospect, we also try to give insight into the challenges and possible breakthrough of the development of Pharm-Lab on a Chip.