Elastic SiC Aerogel for Thermal Insulation: A Systematic Review.

SiC aerogels with their lightweight nature and exceptional thermal insulation properties have emerged as the most ideal materials for thermal protection in hypersonic vehicles; However, conventional SiC aerogels are prone to brittleness and mechanical degradation when exposed to complex loads such as shock and mechanical vibration. Hence, preserving the structural integrity of aerogels under the combined influence of thermal and mechanical external forces is crucial not only for stabling their thermal insulation performance but also for determining their practicality in harsh environments. This review focuses on the optimization of design based on the structure-performance of SiC aerogels, providing a comprehensive review of the inherent correlations among structural stability, mechanical properties, and insulation performance. First, the thermal transfer mechanism of aerogels from a microstructural perspective is studied, followed by the relationship between the building blocks of SiC aerogels (0D particles, 1D nanowires/nanofibers) and their compression performance (including compressive resilience, compressive strength, and fatigue resistance). Moreover, the strategy to improve the high-temperature oxidation resistance and insulation performance of SiC aerogels is explored. Lastly, the challenges and future breakthrough directions for SiC aerogels are presented.

Sample-to-Answer Robotic ELISA.

Enzyme-linked immunosorbent assays (ELISA), as one of the most used immunoassays, have been conducted ubiquitously in hospitals, research laboratories, etc. However, the conventional ELISA procedure is usually laborious, occupies bulky instruments, consumes lengthy operation time, and relies considerably on the skills of technicians, and such limitations call for innovations to develop a fully automated ELISA platform. In this paper, we have presented a system incorporating a robotic-microfluidic interface (RoMI) and a modular hybrid microfluidic chip that embeds a highly sensitive nanofibrous membrane, referred to as the Robotic ELISA, to achieve human-free sample-to-answer ELISA tests in a fully programmable and automated manner. It carries out multiple bioanalytical procedures to replace the manual steps involved in classic ELISA operations, including the pneumatically driven high-precision pipetting, efficient mixing and enrichment enabled by back-and-forth flows, washing, and integrated machine vision for colorimetric readout. The Robotic ELISA platform has achieved a low limit of detection of 0.1 ng/mL in the detection of a low sample volume (15 µL) of chloramphenicol within 20 min without human intervention, which is significantly faster than that of the conventional ELISA procedure. Benefiting from its modular design and automated operations, the Robotic ELISA platform has great potential to be deployed for a broad range of detections in various resource-limited settings or high-risk environments, where human involvement needs to be minimized while the testing timeliness, consistency, and sensitivity are all desired.

Engineering Covalent Heterointerface Enables Superelastic Amorphous SiC Meta-Aerogels.

SiC is an exceptionally competitive material for porous ceramics owing to its excellent high-temperature mechanical stability. However, SiC porous ceramics suffer from serious structural damage and mechanical degradation under thermal shock due to the hard SiC microstructure and weak bonding networks. Here, we report a scalable interface-engineering protocol to reliably assemble flexible amorphous SiC nanofibers into lamellar cellular meta-aerogels by designing a covalent heterointerface. This approach allows the construction of a strong binding architecture within the resilient nanofiber skeleton network, thereby achieving structurally stable, mechanically robust, and durable SiC porous ceramics. The optimized amorphous SiC meta-aerogels (a-SiC MAs) exhibit the integrated properties of ultralight with a density of 4.84 mg cm-3, temperature-invariant superelastic, fatigue-resistant at low 5% permanent deformation after 1000 cycles of compression, and ultralow thermal conductivity (19 mW m-1 K-1). These characteristics provide a-SiC MAs potential application value in the thermal protection field.

Design and Development of Robust, Daylight-Activated, and Rechargeable Biocidal Polymeric Films as Promising Active Food Packaging Materials.

The emerging infectious diseases have created one of the major practical needs to develop active packaging materials with durable antibacterial and antiviral properties for the food industry. To meet this demand, the development of new technologies applicable to food contact surfaces is highly desired but challenging. The recent discovery of the photoactive properties of vitamin K (VK) derivatives has raised great expectations as promising candidates in functional film development due to the generation of biocidal reactive oxygen species (ROS) by these compounds. Inspired by the excellent photoactivity of one of the light-stable VK derivatives, menadione (VK3), under visible daylight irradiation, we demonstrate a protocol for the fabrication of daylight-mediated biocidal packaging materials by incorporating VK3 into a poly (ethylene-co-vinyl acetate) (EVA) matrix. The VK3 (i.e., 1-5% w/w) incorporated EVA films successfully demonstrated the production of ROS and antibacterial and antiviral performance against Escherichia coli, Listeria innocua, and T7 bacteriophage, respectively, under daylight exposure conditions. The results revealed that the addition of a proper percentage of VK3 significantly enhanced the ROS productivity of the films and created a novel daylight-induced microbial killing performance on the films. The biocidal functions of the films are long-lasting and rechargeable when exposed to light repeatedly, making them a viable contender for replacing currently available conventional packaging films.

Discovery of Peptidic Ligands against the SARS-CoV-2 Spike Protein and Their Use in the Development of a Highly Sensitive Personal Use Colorimetric COVID-19 Biosensor.

In addition to efficacious vaccines and antiviral therapeutics, reliable and flexible in-home personal use diagnostics for the detection of viral antigens are needed for effective control of the COVID-19 pandemic. Despite the approval of several PCR-based and affinity-based in-home COVID-19 testing kits, many of them suffer from problems such as a high false-negative rate, long waiting time, and short storage period. Using the enabling one-bead-one-compound (OBOC) combinatorial technology, several peptidic ligands with a nanomolar binding affinity toward the SARS-CoV-2 spike protein (S-protein) were successfully discovered. Taking advantage of the high surface area of porous nanofibers, immobilization of these ligands on nanofibrous membranes allows the development of personal use sensors that can achieve low nanomolar sensitivity in the detection of the S-protein in saliva. This simple biosensor employing naked-eye reading exhibits detection sensitivity comparable to some of the current FDA-approved home detection kits. Furthermore, the ligand used in the biosensor was found to detect the S-protein derived from both the original strain and the Delta variant. The workflow reported here may enable us to rapidly respond to the development of home-based biosensors against future viral outbreaks.

A landscape review of controlled release urea products: Patent objective, formulation and technology.

Fertiliser has been a vital part of agriculture due to it boosting crop productivity and preventing starvation throughout the world. Despite this huge contribution, the application of nitrogen (N) fertilisers results in N leaching and the formation of greenhouse gases, which threaten the environment and human health. To minimise the impacts, slow/controlled release fertilisers (S/CRFs) have been being developed since the beginning of the 20th century. Despite the efforts made over a century, the basic terminological and classification information of these fertilisers remains vague. The scientific knowledge published in S/CRF patents has also been overlooked since the beginning. This review focused on the information gaps, clarified the definitions, differentiation and classification methods that have been randomly used in previous literature. The objectives, formulations and technologies of 109 controlled release urea patents involving sulphur coated urea, polymer coated urea and urea matrix fertilisers published in the years since these products emerged were also reviewed to 1) highlight the overlooked scientific knowledge in the patents; 2) understand the evolutionary processes and current research states of the products; 3) clarify research preferences and challenges to date; 4) identify remaining gaps for the future direction. It is expected that the organised basic information and the patent knowledge highlighted in this paper can be new resources and foster the development of S/CRFs in the future.

Improving the Sensitivity of Nanofibrous Membrane-Based ELISA for On-Site Antibiotics Detection.

An ultrasensitive and portable colorimetric enzyme-linked immunosorbent assay (ELISA) sensor for antibiotics was fabricated by immobilizing antibodies inside the largely porous and highly hydrophilic nanofibrous membranes. Different from regular electrospun nanofibrous membranes where antibodies may frequently be blocked by the heterogeneous porous structure and sterically crowded loaded on the surface, the controlled microporous structure and increased hydrophilicity of nanofibrous membranes could improve the diffusion properties of antibodies, reduce the sterically crowding effect, and dramatically improve the sensitivity of the membrane-based ELISA. The limitation of detection (LOD) for chloramphenicol (CAP) reached 0.005 ng/mL, around 200 times lower than the conventional paper-based ELISA, making quantitative analysis and portable on-site detection achievable via the use of smartphones. The successful design and fabrication of the nanofibrous membrane-based ELISA with novel features overcome the structural drawbacks of regular electrospun nanofibrous membranes and provide new paths to develop highly sensitive on-site detection of hazardous chemical agents.

Diffusion of Protein Molecules through Microporous Nanofibrous Polyacrylonitrile Membranes.

Porous nanofibrous membranes have ultrahigh specific surface areas and could be broadly employed in protein purification, enzyme immobilization, and biosensors with enhanced selectivity, sensitivity, and efficiency. However, large biomolecules, such as proteins, have hindered diffusion behavior in the micro-porous media, significantly reducing the benefits provided by the nanofibrous membranes. The study of protein diffusion in polyacrylonitrile (PAN) nanofibrous membranes produced under varied humidity and polymer concentration of electrospinning revealed that heterogeneous structures of the nanofibrous membranes possess much smaller effective pore sizes than the measured pore sizes, which significantly affects the diffusion of large molecules through the system though sizes of proteins and pH conditions also have great impacts. Only when the measured membrane pore size is at least 1000 times higher than the protein size, the diffusion behavior of the protein is predictable in the system. The results provide insights into the design and applications of proper nanofibrous materials for improved applications in protein purification and immobilizations.

Design and fabrication of a highly sensitive and naked-eye distinguishable colorimetric biosensor for chloramphenicol detection by using ELISA on nanofibrous membranes.

Enzyme-linked immunoassay (ELISA) is highly specific and selective towards target molecules and is convenient for on-site detection. However, in many cases, lack of high sensitivity makes it hard to reveal a significant colorimetric signal for detecting a trace amount of target molecules. Thus, analytical instruments are required for detection, which limits the application of ELISA for on-site detection. In the present study, a highly sensitive and naked-eyed detectable colorimetric biosensor for chloramphenicol (CAP) was prepared by incorporating ELISA onto surfaces of microporous and nanofibrous membranes. The high specific surface areas of the nanofibers significantly increased the number of antibodies covalently linked onto the fiber surfaces and binding capacity of the sensor with antigens present in a sample. With such an integration, the sensitivity of the ELISA sensor was dramatically increased, and a trace number of targets could reveal a naked-eye detectable color. The immunoassay sensor exhibited a significant naked-eye distinguishable color to chloramphenicol (CAP) at 0.3 ng/mL. The successful design and fabrication of the nanofibrous membrane immunoassay sensor provide new paths towards the development of on-site inspection sensors without the assistance from any instrument.

Developing an Injectable Nanofibrous Extracellular Matrix Hydrogel With an Integrin αvß3 Ligand to Improve Endothelial Cell Survival, Engraftment and Vascularization.

Endothelial cell (EC) transplantation via injectable collagen hydrogel has received much attention as a potential treatment for various vascular diseases. However, the therapeutic effect of transplanted ECs is limited by their poor viability, which partially occurs as a result of cellular apoptosis triggered by the insufficient cell-extracellular matrix (ECM) engagement. Integrin binding to the ECM is crucial for cell anchorage to the surrounding matrix, cell spreading and migration, and further activation of intracellular signaling pathways. Although collagen contains several different types of integrin binding sites, it still lacks sufficient specific binding sites for ECs. Previously, using one-bead one-compound (OBOC) combinatorial technology, we identified LXW7, an integrin αvß3 ligand, which possessed a strong binding affinity to and enhanced functionality of ECs. In this study, to improve the EC-matrix interaction, we developed an approach to molecularly conjugate LXW7 to the collagen backbone, via a collagen binding peptide SILY, in order to increase EC specific integrin binding sites on the collagen hydrogel. Results showed that in the in vitro 2-dimensional (2D) culture model, the LXW7-treated collagen surface significantly improved EC attachment and survival and decreased caspase 3 activity in an ischemic-mimicking environment. In the in vitro 3-dimensional (3D) culture model, LXW7-modified collagen hydrogel significantly improved EC spreading, proliferation, and survival. In a mouse subcutaneous implantation model, LXW7-modified collagen hydrogel improved the engraftment of transplanted ECs and supported ECs to form vascular network structures. Therefore, LXW7-functionalized collagen hydrogel has shown promising potential to improve vascularization in tissue regeneration and may be used as a novel tool for EC delivery and the treatment of vascular diseases.

Flexible and Washable Poly(Ionic Liquid) Nanofibrous Membrane with Moisture Proof Pressure Sensing for Real-Life Wearable Electronics.

Real-life wearable electronics with long-term stable sensing performance are of significant practical interest to public. Wearable pressure sensors with washable, comfortable, breathable, and stable sensing ability are a key requirement to meet the desire. However, effects of ubiquitous ambient moisture and intrinsic defects of current capacitive sensing materials are two factors leading to unstable sensing performance of current pressure sensors. Existing ionic liquid-based materials (i.e., ionic hydrogel, ionic film, or ionic/elastomers composite) have been used for efficient capacitive pressure sensing but are highly sensitive and especially affected by moisture. In this work, we introduce a washable capacitive pressure-sensing textile based on the use of a hydrophobic poly(ionic liquid) nanofibrous membrane (PILNM) with good mechanical properties and satisfactory moisture proof sensing performance. The PILNM membranes possessing rich ions and microporous structures are novel ideal polymeric dielectric materials for amplification of signals with negligible stimulations. Moreover, the PILNMs exhibit very high stable sensing signals under moisture interference (up to 70% relative humidity) and repeated washings (more than 10 washings), especially suitable for wearable electronics. Notably, the PILNM-based wearable pressure-sensing textiles offer high sensitivity for low pressure and bent chord length changes with a low-pressure detection limit even under harsh deformations. Owing to the superior performance, the PILNM-based wearable pressure-sensing textiles are comfortable to wear and suitable for monitoring different human motions and pulse vibrations at various body positions. Meanwhile, the assembled multiple wearable pressure-sensing array can spatially map the contact area of the pressure stimuli and synchronously reflect finger movements.

Design and Synthesis of Core-Shell Carbon Polymer Dots with Highly Stable Fluorescence in Polymeric Materials.

In recent years, fluorescent carbon dots have attracted great attention due to their good luminescence and low toxicity. Here, blue fluorescent core-shell structured carbon polymer dots (CPDs) with high stability under a wide range of pH values, long storage time and excellent fluorescence in various solvents and even in solid state were prepared by hydrothermal synthesis of dendritic tris(2-aminoethyl)amine (TAEA) and citric acid. The CPDs core structure provides strong fluorescent luminescence, a shell structure of the core possesses high amount of dendritic primary amino groups connected by ethylene groups to the core. This unique structure prevents aggregation of the cores and self-quenching effect of CPDs. As a result, the CPDs have high fluorescence in both aqueous and hydrophobic solutions and even as pure solid-state powder. In addition, the CPDs are also insensitive to pH of solutions, and the fluorescence intensity of the solution was stable in the pH range of 4-14. The CPDs embedded polymer films and fibers revealed excellent fluorescent properties.

Effects of divalent anionic catalysts on cross-linking of cellulose with 1,2,3,4-butanetetracarboxylic acid.

1,2,3,4-Butanetetracarboxylic acid (BTCA) can efficiently esterify cellulose with pyrophosphoric acid (PPA) as a catalyst to remove protons of reaction intermediates. However, valence and relative concentration ratio (RCR) of catalyst anions correlating to pH of finishing bath played a critical role in the reactions. Results here indicated that wrinkle recovery angle, tensile strength retention and ester absorbance of fabrics treated at pH of 2.8 showed higher values. It was a competing reaction for BTCA molecules to esterify or depolymerize cellulose. Importantly, divalent PPA anions were more efficient than monovalent ones in catalyzing the esterification between anhydrides and cellulose, which was confirmed by FTIR results and two-dimensional correlation spectroscopy analyses and by the RCRs of PPA anions and their changing rates versus pH. Furthermore, the higher catalytic efficiency of divalent anions was proved by the selected model catalysts. Meaningfully, the fabrics treated at pH≤3.2 presented good durability.

Scalable fabrication of sulfated silk fibroin nanofibrous membranes for efficient lipase adsorption and recovery.

Fabricating adsorptive materials for fast and high efficient adsorption of enzymes is critical to match the great demands for separation and recovery of enzymes used as biocatalysts. However, it has proven extremely challenging. Here, we report a cost-effective strategy to construct the sulfated group surface-functionalized silk fibroin nanofibrous membranes (SS-SFNM) under mild conditions for positively charged Candida rugosa lipase adsorption. The naturally abundant silk is thus reconstructed into nanofibrous membranes with tunable surface functions. Thereby, the resultant SS-SFNM exhibited excellent adsorption performance towards lipase, including a superior adsorption capacity of 148 mg g-1, fast adsorption equilibrium within 3 h and good reversibility. The fabrication of such fascinating silk-based materials may provide new chance into the design and development of multi-functional membranes for various separated applications.

Ultrasensitive label-free electrochemical immunosensor based on PVA-co-PE nanofibrous membrane for the detection of chloramphenicol residues in milk.

An ultrasensitive label-free amperometric immunosensor for the detection of chloramphenicol (CAP) residues in milk has been developed by using a screen-printed carbon electrode laminated with a layer of poly (vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membrane that is covalently immobilized with a CAP antibody (anti-CAP). The performance of the PVA-co-PE nanofiber membrane (PVA-co-PE NFM) on the electrode was compared with a PVA-co-PE casted membrane (PVA-co-PE CM), necessary fabrication steps and performance of the sensors were investigated by electrochemical impedance spectroscopy (EIS). The application of the PVA-co-PE NFM decreased the electron-transfer-resistance by about 4 times compared with a conventional PVA-co-PE casted membrane. Under the optimal conditions, the established immunosensor exhibited high sensitivity for determination of CAP in a range 0.01-10 ng mL-1, with a limit of detection of 0.0047 ng mL-1. In addition to the good selectivity, reusability and stability over time, the prepared immunosensor was successfully used in the detection of CAP in milk samples without any pretreatment.

Reusable anionic sulfonate functionalized nanofibrous membranes for cellulase enzyme adsorption and separation.

Poly (vinyl alcohol-co-ethylene) nanofibrous membranes (PVA-co-PE NFM) were successfully modified by sodium-3-sulfobenzoate to become negatively charged with sulfonate groups, and the sulfonated (PVA-co-PE) nanofiber membrane SS (PVA-co-PE NFM) was used in non-covalent adsorption of cellulases via electrostatic attraction. The modified NFM showed excellent adsorption to the enzyme molecules due to the incorporated static charge interaction with the fibers, high open-porosity and ultrahigh surface areas of the nanofibers. Such unique morphology and chemical structures lead to the adsorption capacity of 130 mg g-1 and reusability for 5 cycles without significant change in catalytic functions. The morphology changes of the nanofibrous membranes were observed by using a scanning electron microscopy, and chemical structures of the membranes were characterized by using FTIR and water contact angle measurements. SS (PVA-co-PE NFM) is a promising solid support media for enzyme immobilization, and the immobilized enzymes can be applied in industrial applications.

A reverse micelle strategy for fabricating magnetic lipase-immobilized nanoparticles with robust enzymatic activity.

Enzyme-immobilized nanoparticles that are both catalysis effective and recyclable would have wide applications ranging from bioengineering and food industry to environmental fields; however, creating such materials has proven extremely challenging. Herein, we present a scalable methodology to create Candida rugosa lipase-immobilized magnetic nanoparticles (L-MNPs) by the combination of nonionic reverse micelle method and Fe3O4 nanoparticles. Our approach causes the naturally abundant and sustainable Candida rugose lipase to ordered-assemble into nanoparticles with high catalytic activity and durability. The resultant L-MNPs exhibit the integrated properties of high porosity, large surface area, fractal dimension, robust enzymatic activity, good durability, and high magnetic saturation (59 emu g-1), which can effectively catalyze pentyl valerate esterification and be easily separated by an external magnet in 60 second. The fabrication of such fascinating L-MNPs may provide new insights for developing functional enzyme-immobilized materials towards various applications.

Spontaneous and efficient adsorption of lysozyme from aqueous solutions by naturally polyanion gel beads.

In this study, polyanionic alginate gel beads crosslinked by Ca2+ and glutaraldehyde have demonstrated a strong electrostatic interaction with specific proteins. Due to the naturally abundant carboxyl groups, the prepared alginate gel beads exhibited a relatively superior integrated adsorption performance toward lysozyme, including a superior adsorption capacity of 213mgg-1, fast adsorption equilibrium within 12h, good selectivity, and good reversibility. Compared with other protein adsorbents, the as-prepared adsorptive beads have the advantages of excellent adsorption performance, easy to prepare, convenient, efficient, reliable and environment-friendly to apply, which can serve as a more sustainable material in protein separation and purification.

Biocidal and Rechargeable N-Halamine Nanofibrous Membranes for Highly Efficient Water Disinfection.

There is a critical need for new efficient solutions to purify and disinfect water from source to point-of-use, especially for the water contaminated by pathogenic microbes. Traditional disinfection technologies are chemically intensive and limited, either by biofouling or by the irreversible consumption of disinfectants. Herein, we present a scalable methodology to create biocidal and rechargeable nanofibrous membranes (BNF membranes) by combining N-halamine antimicrobial agent with electrospun nanofibers. Our method allows intrinsically rechargeable N-halamine moieties to covalently incorporate into nanofibers with high biocidal activity and durability. The resulting BNF membranes exhibit integrated properties of high porosity, large surface area, robust mechanical strength, super hydrophilicity, rechargeable chlorination capability (>3000 ppm), and high bactericidal efficacy (99.9999% contact-killing), which enabled the BNF membranes effectively disinfect bacteria-contained water by direct filtration, with promising high durability and fluxes (10000 L m-2 h-1). The successful synthesis of BNF membranes also provides a versatile platform for exploring the antimicrobial N-halamine materials in a self-supporting, structurally adaptive, and nanofibrous form.

Mechanically Robust and Transparent N-Halamine Grafted PVA-co-PE Films with Renewable Antimicrobial Activity.

Antimicrobial polymeric films that are both mechanically robust and function renewable would have broad technological implications for areas ranging from medical safety and bioengineering to foods industry; however, creating such materials has proven extremely challenging. Here, a novel strategy is reported to create high-strength N-halamine incorporated poly(vinyl alcohol-co-ethylene) films (HAF films) with renewable antimicrobial activity by combining melt radical graft polymerization and reactive extrusion technique. The approach allows here the intrinsically rechargeable N-halamine moieties to be covalently incorporated into polymeric films with high biocidal activity and durability. The resulting HAF films exhibit integrated properties of robust mechanical strength, high transparency, rechargeable chlorination capability (>300 ppm), and long-term durability, which can effectively offer 3-5 logs CFU reduction against typical pathogenic bacterium Escherichia coli within a short contact time of 1 h, even at high organism conditions. The successful synthesis of HAF films also provides a versatile platform for exploring the applications of antimicrobial N-halamine moieties in a self-supporting, structurally adaptive, and function renewable form.