Nanofiber Sponge Research Articles

Graphene/Electrospun Carbon Nanofiber Sponge Composites Induced by Magnetic Particles for Mutil-Functional Pressure Sensor

Graphene/Electrospun Carbon Nanofiber Sponge Composites Induced by Magnetic Particles for Mutil-Functional Pressure Sensor

Clarification of yeast cell suspensions by a highly porous polyamide nanofiber sponge

Depth filtration is an attractive method for initial clarification of broth for removing cells and cell debris. Electrospun nanofibers with their large specific surface area and a porous structure are known as attractive materials in filtration processes. However, dead-end filtration of cells through nanofiber mats (NFM) always leads to cake formation and increasing resistance. In this study, for the first time, a nanofiber sponge (NFS) or nanofiber aerogel was synthetized from polyamide 6 (PA6) building blocks. The NFS was flexible, highly porous and mechanically stable. The pore size of the NFS was tuned between 8 and 26 µm during the cryogenic processing step. Volumetric flux and filtration efficiency of the NFS depended on the pore size and the results were compared with those for NFM from the same PA6 nanofiber material. Dead-end filtration of Saccharomyces cerevisiae was feasible at a low differential pressure of 3.5 kPa and cell filtration efficiency was > 99 %. Modelling of the filtration process revealed that cake formation is prevented by NFS filters since cells are able to penetrate into the filter and to adsorb on their internal surface. The filtration characteristics were also compared with commercial depth filters and revealed the high flux of NFS filters along with the possibility to avoid filter aids and a low environmental impact. PA6-NFS filters may become a new and cost effective generation of filters for removing different cells or cell debris from broth and other applications.

Conjugate Electrospun 3D Gelatin Nanofiber Sponge for Rapid Hemostasis (Adv. Healthcare Mater. 20/2021)

Nanofiber Sponges In article number 2100918, Jinglei Wu, Xiumei Mo, and co-workers develop a novel conjugate electrospinning strategy to prepare a 3D nanofiber sponge with low density, high surface area, compressibility. This method can be widely used in the preparation of various polymer nanofiber sponges. The obtained gelatin nanofiber sponge holds great potential as an absorbable hemostatic agent for rapid hemostasis.

A Chitosan Nanofiber Sponge for Oyster-Inspired Filtration of Microplastics

A Chitosan Nanofiber Sponge for Oyster-Inspired Filtration of Microplastics

Conjugate Electrospun 3D Gelatin Nanofiber Sponge for Rapid Hemostasis.

Developing an excellent hemostatic material with good biocompatibility and high blood absorption capacity for rapid hemostasis of deep non-compressible hemorrhage remains a significant challenge. Herein, a novel conjugate electrospinning strategy to prepare an ultralight 3D gelatin sponge consisting of continuous interconnected nanofibers. This unique fluffy nanofiber structure endows the sponge with low density, high surface area, compressibility, and ultrastrong liquid absorption capacity. In vitro assessments show the gelatin nanofiber sponge has good cytocompatibility, high cell permeability, and low hemolysis ratio. The rat subcutaneous implantation studies demonstrate good biocompatibility and biodegradability of gelatin nanofiber sponge. Gelatin nanofiber sponge aggregates and activates platelets in large quantities to accelerate the formation of platelet embolism, and simultaneously escalates other extrinsic and intrinsic coagulation pathways, which collectively contribute to its superior hemostatic capacity. In vivo studies on an ear artery injury model and a liver trauma model of rabbits demonstrate that the gelatin nanofiber sponge rapidly induce stable blood clots with least blood loss compared to gelatin nanofiber membrane, medical gauze, and commercial gelatin hemostatic sponge. Hence, the gelatin nanofiber sponge holds great potential as an absorbable hemostatic agent for rapid hemostasis.

Stretchable and Compressible Si3 N4 Nanofiber Sponge with Aligned Microstructure for Highly Efficient Particulate Matter Filtration under High-Velocity Airflow.

Particulate matter (PM) is one of the most severe air pollutants and poses a threat to human health. Air filters with high filtration efficiency applied to the source of PM are an effective way to reduce pollution. However, many of the present filtration materials usually fail because of their high pressure drop under high-velocity airflow and poor thermal stability at high temperatures. Herein, a highly porous Si3 N4 nanofiber sponge (Si3 N4 NFS) assembled by aligned and well-interconnected Si3 N4 nanofibers is designed and fabricated via chemical vapor deposition (CVD). The resulting ultralight Si3 N4 NFS (2.69mg cm-3 ) processes temperature-invariant reversible strechability (10% strain) and compressibility (50% strain), which enables its mechanical robustness under high-velocity airflow. The highly porous and aligned microstructure result in a Si3 N4 NFS with high filtration efficiency for PM2.5 (99.97%) and simultaneous low pressure drop (340Pa, only <0.33%of atmospheric pressure) even under a high gas flow velocity (8.72 m s-1 ) at a high temperature (1000°C). Furthermore, the Si3 N4 NFS air filter exhibits good long-term service ability and recyclability. Such Si3 N4 NFS with aligned microstructures for highly efficient gas filters provides new perspectives for the design and preparation of high-performance filtration materials.

3D PCL/Gelatin/Genipin Nanofiber Sponge as Scaffold for Regenerative Medicine.

Recent advancements in tissue engineering and material science have radically improved in vitro culturing platforms to more accurately replicate human tissue. However, the transition to clinical relevance has been slow in part due to the lack of biologically compatible/relevant materials. In the present study, we marry the commonly used two-dimensional (2D) technique of electrospinning and a self-assembly process to construct easily reproducible, highly porous, three-dimensional (3D) nanofiber scaffolds for various tissue engineering applications. Specimens from biologically relevant polymers polycaprolactone (PCL) and gelatin were chemically cross-linked using the naturally occurring cross-linker genipin. Potential cytotoxic effects of the scaffolds were analyzed by culturing human dermal fibroblasts (HDF) up to 23 days. The 3D PCL/gelatin/genipin scaffolds produced here resemble the complex nanofibrous architecture found in naturally occurring extracellular matrix (ECM) and exhibit physiologically relevant mechanical properties as well as excellent cell cytocompatibility. Samples cross-linked with 0.5% genipin demonstrated the highest metabolic activity and proliferation rates for HDF. Scanning electron microscopy (SEM) images indicated excellent cell adhesion and the characteristic morphological features of fibroblasts in all tested samples. The three-dimensional (3D) PCL/gelatin/genipin scaffolds produced here show great potential for various 3D tissue-engineering applications such as ex vivo cell culturing platforms, wound healing, or tissue replacement.

Preparation and Characterization of PTFE/PI Nanofiber Composite Assembled Sponges

Due to the ultralow density and high specific area, nanofibrous sponges show great potential in the field of filtration and separation. To prepare nanofibrous sponges for high temperature smoke filtration, polytetrafluoroethylene (PTFE) was chosen due to its corrosion resistance and high temperature resistance. PTFE nanofiber prepared via electrospinning shows irregular concave-convex pores in the fiber body, which can improve the specific surface area and further enhance filtration performance. However, sponges made of PTFE nanofiber suffered from severe shrinkage, which limited the development in sponge products. In this study, polyimide (PI) nanofiber converted from polyamic acids (PAAs) nanofiber was introduced into the PTFE sponges to reinforce the dimensional stability. The parameters that influenced the morphology, porosity, shrinkage ratio, and thermodynamic properties of the composite sponges were also investigated. Moreover, the filtration performance of the composite sponges was tested. Results indicated that PTFE/PI composite nanofiber sponges possessed high porosity (94.34–98.12 %), excellent thermal stability (above 550 °C), and decent filtration efficiency (the maximum filtration efficiency reached 99.97 % to PM 2.0) were prepared, which demonstrated the potential in the field of high-temperature filtration.

Perfusion Cultivation of Artificial Liver Extracellular Matrix in Fibrous Polymer Sponges Biomimicking Scaffolds for Tissue Engineering.

A major challenge in tissue engineering and artificial scaffolding is to combine easily tunable scaffolds biomimicking the extracellular matrix of native organs with delivery-controlled cell culturing to create fully cellularized, large artificial 3D scaffolds. Aiming at bioartificial liver construction, we present our research using galactose-functionalized, ultraporous polylactide 3D nanofiber sponges fabricated out of electrospun fibers. Sponge biomodification by blend galactosylation and in-solution coating is performed, respectively, using a polylactide-galactose carrier-copolymer that promotes cell delivery and features a pronounced autofluorescence. It allows us to verify the galactosylation success, evaluate its quality, and record dye-free, high-resolution images of the sponge network using confocal laser scanning microscopy. The galactose carrier and its impact on scaffold cellularization is validated in benchmark to several reference systems. Verification of the human hepatic cell asialoglycoprotein receptor presence and galactose interaction in culture is performed by Cu2+ receptor-blocking experiments. The culture results are extensively investigated in and ex situ to trace and quantify the cell culture progress, cell activity, and viability at different culture stages. Bioreactor cultivation of sponges reveals that the galactose carrier does not only facilitate cell adhesion but also enhances cellular distribution throughout the scaffold. The promising 3D culture results allow us to move forward to create mature in vitro liver model research systems. The elaboration into ex vivo testing platforms could help judging native cell material interactions with drugs or therapeutics, without the need of direct human or animal testing.

A shape-stable phase change composite prepared from cellulose nanofiber/polypyrrole/polyethylene glycol for electric-thermal energy conversion and storage

The design of shape-stable phase change composites (PCCs) with electrothermal conversion/storage performance provides a new direction for their potential applications in advanced electric energy storage. Herein, a cellulose nanofiber sponge coated with polypyrrole (PPy@CNF) was constructed and used to incorporate polyethylene glycol (PEG) to afford the PPy@CNF-PEG composite. The resulting PPy@CNF-PEG composite exhibited good shape-stable property and high melting enthalpy (169.7 J/g). Even when compressed at 440 times its own weight, the composite still maintained its original shape and gave off no molten PEG. By applying small voltages (1.75–1.9 V), it was also shown that the composite converted electricity to heat with efficiencies (up to 85.1%). This work demonstrates a simple, effective and general strategy to prepare biomass-derived composites with high electrothermal conversion efficiency for smart electric devices devoting to energy conversion and storage.

Tannic acid/CaII anchored on the surface of chitin nanofiber sponge by layer-by-layer deposition: Integrating effective antibacterial and hemostatic performance

Massive blood loss and bacterial infection are major challenges for global public health. However, traditional wound dressings cannot fully meet the current clinical needs in controlling bleeding and avoiding infection. In this study, we prepared a chitin nanofiber suspension by green mechanical grinding and homogenizing, which could be used for developing a porous chitin nanofiber sponge by freeze drying. Then tannic acid/CaII was anchored on the surface of chitin nanofiber sponge by layer-by-layer deposition based on the coordination complex of tannic acid and Ca2+. These porous chitin nanofiber sponges with meso-macroporous structure could accelerate platelet aggregation for hemostasis. Hemostasis tests also demonstrated that the Ca2+ and TA in the TA/CaII coating on chitin nanofiber sponge could accelerate platelet activity and shorten the hemostatic time both in vitro and in vivo. Besides, the TA in the TA/CaII coating enhanced the antibacterial properties of the sponge, which depended the content of TA/CaII. Based on these results, it could be inferred that the chitin nanofiber sponges anchored TA/CaII coating had rapid hemostatic and antibacterial properties, which would have great potential for designing hemostatic product in clinical application.

Furan and Pyran Functional Groups Driven the Surface of Nitrogen‐Doped Nanofiber Sponges

AbstractHighly surface oxidized, nitrogen‐doped, and nitrogen functionalized carbon nanotube sponge (N‐CFS) were produced at 1020 °C using two sprayers approach in an aerosol‐assisted chemical vapor deposition (AACVD) experiment. The structure of N‐CFS consisted of entangled and corrugated carbon nanofibers of ∼200 nm diameter, also showing junctions and knots. TEM characterizations revealed that the carbon nanofiber exhibits stacked graphitic layers in a transversal way with positive curvature. Superficial chemical analysis by XPS showed that the N‐CFSs contain an atomic concentration of oxygen and nitrogen of 9.2% and 2.9%, respectively. The high‐resolution XPS scans deconvolution‐analysis revealed high percentages for C−O bonds, pyrrolic nitrogen doping, NH3 functionalization, and Si−C interactions. The cyclic voltammetry measurements did not display a redox process despite the high oxygen concentration at the surface. Hydrophobic functional groups containing C−O bonds do not participate in a redox process (furan, pyran, epoxy, methoxy, ethoxy, among others) could mostly determine the electroactivity of N‐CFS. Based on density functional theory calculations, we determine that the furans transfer a high amount of electron and promote a positive curvature in thin carbon nanotubes. Graphitic materials with furans, pyrans, and epoxy functional groups could be used as an anode in lithium‐ion batteries.

Cellular Nanofiber Structure with Secretory Activity-Promoting Characteristics for Multicellular Spheroid Formation and Hair Follicle Regeneration.

Multicellular spheroids can mimic the in vivo microenvironment and maintain the unique functions of tissues, which has attracted great attention in tissue engineering. However, the traditional culture microenvironment with structural deficiencies complicates the culture and collection process and tends to lose the function of multicellular spheroids with the increase of cell passage. In order to construct efficient and functional multicellular spheroids, in this study, a chitosan/polyvinyl alcohol nanofiber sponge which has an open-cell cellular structure is obtained. The hair follicle (HF) regeneration model was employed to evaluate HF-inducing ability of dermal papilla (DP) multicellular spheroids which formed on the cellular structure nanofiber sponge. Through structural fine-tuning, the nanofiber sponge has appropriate elasticity for the creation of a three-dimensional dynamic microenvironment to regulate cellular behavior. The cellular structure nanofiber sponge tilts the balance of cell-substratum and cell-cell interactions to a state which is more conducive to the formation of controllable multicellular spheroids in a short time. More importantly, it improves the secretory activity of high-passaged dermal papilla cells and restores their intrinsic properties. Experiments using BALB/c nude mice show that cultured DP multicellular spheroids could effectively enhance HF-inducing ability. This novel system provides a simple and efficient strategy for multicellular spheroid formation and HF regeneration.

Tin Oxide Nanofiber and 3D Sponge Structure by Blow Spinning

SnO2 nanofibers show wide applications in many advancing areas, such as gas sensors and semiconductors. The traditional methods of fabricating SnO2 nanofibers include electrospinning, hydrothermal synthesis etc. In this work, SnO2 nanofibers were prepared by blow spinning, which is a convenient and high-efficient method. Meanwhile, a 3D sponge nanofiber network can be produced by accumulating fibers in a novel collector. While traditional SnO2 nanofibers obtained from previous work show high brittleness, the SnO2 nanofiber sponge has good resilience against external compression and can recover to its original shape.

Layered nanofiber sponge with an improved capacity for promoting blood coagulation and wound healing

Effective bleeding control and wound healing are very important and can be life saving. However, traditional wound dressings with structural deficiencies are not effective in controlling bleeding and promoting the regeneration of functional tissues. In this study, a three-dimensional (3D) layered nanofiber sponge was obtained by expanding two-dimensional (2D) nanofiber membranes into the third dimension. This sponge has a layered nanofiber structure, which increases the interfacial interaction between the sponge and blood cells to accelerate hemostasis. Through fine-tuning of structure, the 3D nanofiber sponge acquires properties beneficial to wound healing such as good elasticity and high permeability and fluid absorption ratio. The 3D nanofiber sponges are both highly compressible and resilient, providing tamponade for deep wounds and creating a good 3D dynamic microenvironment to regulate cellular behavior. Further research has demonstrated that the layered nanofiber structure could promote the regeneration of functional dermis and the restoration of differentiated adipocytes during the early repair phase. Experiments using model mice with full-thickness skin defects have shown that the layered nanofiber structure could effectively accelerate wound healing and reduce scar formation. This layered 3D nanofiber sponge design is easy to produce. Due to its excellent wound healing property, this porous nanofiber sponge has great potential for future clinical application as wound dressings.

Polymyxin B immobilized nanofiber sponge for endotoxin adsorption

Nanofiber sponge, which showed high porosity and excellent blood compatibility, was successfully prepared by electrospinning and freeze-drying technology. The APTT (activated partial thromboplastin time) and PT (prothrombin time) of human plasma with nanofiber sponge were a little longer than control groups, which revealed the nanofiber sponge has excellent blood compatibility. By activating the carboxyl groups on the fibers, PMB (polymyxin B) was successfully immobilized on the nanofiber sponge. The adsorption performance was researched in different solutions. The adsorption capacity in physiological saline solution was around 17,889 EU/mL and the adsorption equilibrium time was about 40 min. The adsorption behavior not only obeyed to second-order kinetic equation, but also was conformed to Langmuir model, which turned out to be chemical adsorption and monolayer adsorption. The endotoxin removal rate in BSA (bovine serum albumin) physiological saline solution was about 96.6%, and the BSA recovery rate was around 75.6%, which indicated the PMB immobilized nanofiber sponge adsorbed endotoxin selectively. The endotoxin removal rate of normal nanofiber sponge was about 17.3%, while it was around 99.6% when it comes to PMB immobilized-nanofiber sponge, which manifested PMB played an important role in endotoxin adsorption. The endotoxin removal rate in human plasma reached 90%, and the adsorption reached equilibrium within 60 min, which proved the PMB immobilized-nanofiber sponge would have great potential for applying in clinical blood purification.

Materials for energy storage: Review of electrode materials and methods of increasing capacitance for supercapacitors

Abstract Supercapacitors (SCs) have shown great promise as a possible solution to the increasing world demand for efficient energy storage. Two types of mechanisms for SCs exist (double-layer and pseudocapacitive), and each type utilizes a wide variety of materials. In this review, a detailed overview of the mechanisms employed by SCs is provided in the introduction, and many studies are compared in order to determine which materials produce electrodes with high capacitance and cyclability in SCs, and to summarize and gauge the state of such research. The types of materials looked at include graphene and graphene nanocomposites, activated carbons from renewable materials, conducting polymers, and transition metal dichalcogenides. Additionally, different methods of activation that are meant to increase specific capacitance are examined. Among the dozens of materials found in the literature during this study, the ones that exhibited the highest specific capacitances are rGO/PANI (Reduced Graphene Oxide/Polyaniline), and PANI-NFS/GF (Polyaniline Nanofiber Sponge Filled Graphene Foam) demonstrated impressive performances. These materials all exceeded the current expectations of SCs by remarkable amounts, and more research into similar materials is highly encouraged. As more fundamental studies carried out for understanding the mechanisms of SCs, energy density and specific capacitance values continue to improve. Production of SCs from renewable materials encourage optimism for environmentally friendly options soon becoming feasible for use on larger scales.

High efficiency 3D nanofiber sponge for bilirubin removal used in hemoperfusion.

The accumulation of bilirubin in the body could cause nervous system diseases and even endanger life in severe cases for people with liver damage or metabolic obstruction. Hemoperfusion has been considered as one of the most efficient treatments to remove extra bilirubin. Although, the current bilirubin adsorbents could adsorb the free bilirubin effectively, the albumin-bound bilirubin in plasma is hard to remove. Here, we develop a 3D nanofiber sponge fabricated by combination of electrospinning and improved gas-foaming techniques. The amino groups and BSA molecules were immobilized on the fiber surface as the affinity groups to adsorb bilirubin. The 3D nanofiber sponges have layered structure and significantly higher porosity than two-dimensional nanofiber membranes. The special 3D structure renders the sponge fully contact with the adsorbed liquid and reduces the diffusion distance of the adsorbate, thus increases the sponge's adsorption rate. The BSA immobilized nanofiber sponge showed large adsorption capacity in both aqueous solution (maximum adsorption capacity was 36.8237 mg/g) and plasma (maximum adsorption capacity was 25.2908 mg/g), rapid adsorption rate (achieved adsorption equilibrium in 60 min) and well blood compatibility.

High-Temperature Particulate Matter Filtration with Resilient Yttria-Stabilized ZrO2 Nanofiber Sponge.

Particulate matter (PM) is a major air pollutant in many regions, jeopardizing ecosystems and public health. Filtration at pollutant source is one of the most important ways to protect the environment, however, considering the high-temperature exhaust gas emissions, effective removal of PM and related pollutants from their sources remains a major challenge. In this study, a resilient, heat-resisting, and high-efficiency PM filter based on yttria-stabilized ZrO2 (YSZ) nanofiber sponge produced with a scalable solution blow spinning process is reported. The porous 3D sponge composed of YSZ nanofibers is lightweight (density of 20 mg cm-3 ) and resilient at both room temperature and high temperatures. At room-temperature conditions, the YSZ nanofiber sponge exhibits 99.4% filtration efficiency for aerosol particles with size in the range of 20-600 nm, associated with a low pressure drop of only 57 Pa under an airflow velocity of 4.8 cm s-1 . At a high temperature of 750 °C, the ceramic sponge maintains a high filtration efficiency of 99.97% for PM0.3-2.5 under a high airflow velocity of 10 cm s-1 . A practical vehicle exhaust filter to capture particles with filtration efficiency of >98.3% is also assembled. Hence, the YSZ nanofiber sponge has enormous potential to be applied in industry.

Efficient dye adsorption by highly porous nanofiber aerogels

Electrospun nanofiber membranes are frequently used in adsorption processes thanks to their high specific surface area, tailored surface functionality, and fiber uniformity. However, they are still facing challenges such as low mechanical stability and unfavorable mass transport properties. In this study, an ultra-light and robust 3D nanofiber aerogel (NFA) or nanofiber sponge with tunable porosity and flexibility was synthesized from short pullulan/polyvinyl alcohol/polyacrylic acid nanofibers using a freeze casting process followed by thermal crosslinking. We demonstrate time the application of such NFAs in batch and continuous adsorption systems and compare their performance with flat nanofiber membranes (NFM). The NFAs proved to be promising adsorbents for cationic dyes due to their high adsorption capacity (383 mg/g) and their reusability. Langmuir isotherm was a suitable model for describing the adsorption process. The endothermic system followed a pseudo second order kinetic model and intra-fiber adsorption is found to be involved in the adsorption process. Dye adsorption by 3D NFAs was four times faster than for the respective flat NFMs and when used in a continuous process as a deep-bed filter, the pressure drop through the NFA was reduced by a factor of 40 while maintaining equal adsorption performance as for the NFM.