Aramid nanofiber as an emerging nanofibrous modifier to enhance ultrafiltration and biological performances of polymeric membranes

Poloxamer 407 Combined with Polyvinylpyrrolidone To Prepare a High-Performance Poly(ether sulfone) Ultrafiltration Membrane

At present, the design and fabrication of polymer membranes with high permeability and good retention ability are still huge challenges. In this study, the commercial Poloxamer 407 (Pluronic F127) is selected as a multifunctional additive, and polyvinylpyrrolidone is used as a pore-forming agent to modify the poly(ether sulfone) membrane by liquid-liquid phase conversion technology to prepare an ultrafiltration membrane with excellent performance. The hydrophobic poly(propylene oxide) segment in Poloxamer 407 guarantees that this copolymer can be firmly anchored to the poly(ether sulfone) matrix, and the hydrophilic poly(ethylene oxide) segments in Poloxamer 407 impart a stronger hydrophilic nature to the modified membrane surface. Therefore, the permeability and hydrophilicity of the modified membrane are significantly improved and the modified membrane also has good stability. When the amount of Poloxamer 407 added to the casting solution reached 0.6 g, the water flux of the modified membrane was as high as 368 L m-2 h-1, and the rejection rate of bovine serum albumin was close to 98%. In the test to isolate organic small molecule dyes, the retention rate of the modified membrane to Congo red is 94.27%. In addition, the modified membrane shows an excellent water flux recovery rate and antifouling ability. It performs well in subsequent cycle tests and long-term membrane life tests and can be used repeatedly. Our work has resulted in poly(ether sulfone) membranes with good performance, which show great potential in the treatment of biomedical wastewater and the removal of industrial organic dye wastewater, it provides ideas for the development and application of amphiphilic polymer materials.

Impact of Membrane Modification and Surface Immobilization Techniques on the Hemocompatibility of Hemodialysis Membranes: A Critical Review

Despite significant research efforts, hemodialysis patients have poor survival rates and low quality of life. Ultrafiltration (UF) membranes are the core of hemodialysis treatment, acting as a barrier for metabolic waste removal and supplying vital nutrients. So, developing a durable and suitable membrane that may be employed for therapeutic purposes is crucial. Surface modificationis a useful solution to boostmembrane characteristics like roughness, charge neutrality, wettability, hemocompatibility, and functionality, which are important in dialysis efficiency. The modification techniques can be classified as follows: (i) physical modification techniques (thermal treatment, polishing and grinding, blending, and coating), (ii) chemical modification (chemical methods, ozone treatment, ultraviolet-induced grafting, plasma treatment, high energy radiation, and enzymatic treatment); and (iii) combination methods (physicochemical). Despite the fact that each strategy has its own set of benefits and drawbacks, all of these methods yielded noteworthy outcomes, even if quantifying the enhanced performance is difficult. A hemodialysis membrane with outstanding hydrophilicity and hemocompatibility can be achieved by employing the right surface modification and immobilization technique. Modified membranes pave the way for more advancement in hemodialysis membrane hemocompatibility. Therefore, this critical review focused on the impact of the modification method used on the hemocompatibility of dialysis membranes while covering some possible modifications and basic research beyond clinical applications.

Aramid Nanofibers-Reinforced Rhein Fibrous Hydrogels as Antibacterial and Anti-Inflammatory Burn Wound Dressings

Burn injuries are one of the most devastating traumas. The development of polymer-based hydrogel dressings to prevent bacterial infection and accelerate burn wound healing is continuously desired. Mechanical strong hydrogels that encapsulated antibacterial drugs have gained increasing attention. Herein, aramid nanofibers (ANFs)-reinforced rhein fibrous hydrogels (ANFs/Rhein) were fabricated through a one-pot procedure to serve as a possible treatment for the Staphylococcus aureus-infected burn wound. ANFs preserved the highly aligned backbones and the mechanical properties of Kevlar, and its combination with an antibacterial drug rhein produced a composite hydrogel that possesses favorable physicochemical properties including appropriate mechanical strength, high water holding capacity, satisfactory antibacterial efficiency, and excellent biocompatibility. As wound dressings, ANFs/Rhein hydrogels provided a moist environment for the wound site and released antibacterial drugs continuously to improve the wound healing rate by efficiently restraining bacterial infection, reducing inflammation, enhancing collagen deposition, and promoting the formation of blood vessels, in this way to offer a potential treatment strategy for bacteria-associated burn wound healing.

Experimental study on fabrication, biocompatibility and mechanical characterization of polyhydroxybutyrate-ball clay bionanocomposites for bone tissue engineering

The poly (3-hydroxybutyrate) (PHB)/ball clay nanocomposites (B1-B10) were synthesized using solvent casting method with different weight percentage of ball clay in PHB matrix. Scanning electron microscope (SEM) showed maximum root mean square roughness (188.73 μm) for 10% ball clay loading. Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) showed establishment of intercalated structure and formation of hydrogen bond between ball clay and PHB matrix. Contact angle values (67.3 - 51.3°) exhibited that the nanocomposites (B1-B10) are more hydrophilic than neat PHB (70.30°). Thermogravimetric (TGA) and differential scanning calorimetry (DSC) revealed maximum T_max (278 °C) and T_m (175 °C) for the nanocomposite B10 (PHB/PEG/ball clay: 80%/10%/10%). Maximum tensile strength (38.21 ± 0.15 MPa) and Young's modulus (1.74 ± 0.016 GPa) was observed for B10 nanocomposite. The values of protein adsorption, platelet adhesion, PT, APTT and complement activation for B10 nanocomposites were 165 ± 2 μg/cm², 72 ± 3 × 10⁹ platelets/cm², 23 ± 1 s, 44 ± 2 s, 102 ± 2 mg/dL and 631 ± 3 mg/dL, respectively. Hydroxyapatite formation was also observed for nanocomposite (B10) in in vitro simulated body fluid (SBF) study. Finally, the nanocomposite (B10) showed no harmful effect on MG-63 cells, indicating that they are physiologically safe.

Ultrafast formation of ANFs with kinetic advantage and new insight into the mechanism

Aramid nanofibers (ANFs) have important applications in many fields, including electrical insulation and battery separators. However, a few limitations seriously restrict the application of ANFs currently, such as low preparation efficiency and the unclear preparation mechanism. To overcome these limitations, the present work proposes a new view-point from the perspective of reaction kinetics. The preparation efficiency was proven to essentially rely on the effective c(OH^-). With a simple pre-treatment, a kinetic advantage was created and the preparation time of ANFs was reduced from multiple hours to 10 minutes, which was a considerable step towards practical applications. Moreover, the resultant ANF membranes still exhibited excellent properties in terms of mechanical strength (tensile strength > 160 MPa), thermal stability, light transmittance, and electrical insulation (above 90 kV mm^-1). This work not only presents an ultrafast method to produce ANFs but also provides new insights into the mechanism that will benefit the subsequent development of ANF-based materials.

Enhanced air filtration performances by coating aramid nanofibres on a melt-blown nonwoven

Nanofibre membranes with a small diameter and a large specific surface area are widely used in the filtration field due to their small pore size and high porosity. To date, aramid nanofibres (ANFs) have received extensive research interest because of their high stiffness and excellent temperature resistance. However, the preparation of ANFs usually takes a long time, which greatly hampers the practical application of these fibres. Herein, we report the preparation of ANFs by a modified deprotonation method at elevated temperature. Owing to the increase of temperature, the preparation cycle of ANFs was shortened to 8 hours. The resulting ANF dispersion was further coated on a polypropylene melt-blown nonwoven to form a composite nonwoven filter. With the submicron porous structure, the filtration efficiency, pressure drop and quality factor of the filter were 95.61%, 38.22 Pa and 0.082 Pa^-1, respectively. Compared to the pristine nonwoven, the filtration, mechanical, and heat insulation properties of the composite filter were also significantly improved. This work may offer a simple and efficient way for enhancing the air filtration performances of current filters.

Application of Aramid Nanofibers in Nanocomposites: A Brief Review

The diameter of fibers is a critical factor in determining their final applications. When the diameter of aramid fibers changes from microns to nanoscale, its range of applications will be greatly extended. In this short review, the preparation of aramid nanofibers (ANFs) with diameters from ten nanometers to more than one hundred nanometers is introduced. Due to their excellent mechanical properties and their chemical and thermal stability, ANFs have been widely used as novel nanomaterials and composited with other materials, mainly for use in reinforced composites, energy storage, filtration and adsorption, biomedicine and electromagnetic fields. In this short review, the application of ANFs and their composites during the last 10 years is concisely summarized and a brief perspective on ANFs and their composites is also presented.

Magnetic Copper Ferrite Nanoparticles Functionalized by Aromatic Polyamide Chains for Hyperthermia Applications

A new magnetic nanocomposite with a statistical star polymer structure was designed and synthesized. Nanocomposite fabrication is based on the polymerization of aromatic polyamide chains on the surface of functionalized magnetic copper ferrite nanoparticles (CuFe₂O₄ MNPs). This magnetic nanostructure was characterized by several analysis methods. All the analytical methods used, for instance, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, thermogravimetric, vibrating-sample magnetometer, and scanning electron microscopy (SEM), confirmed the formation of polyamide chains. The obtained images from SEM imaging showed a unique nanoflower morphology which was the proper orientation results of synthesized nanoplates. Finally, the magnetic nanostructure showed a good potential for hyperthermia applications, with a maximum specific absorption rate of 7 W/g for 1 mg/mL of the sample under a magnetic field in different frequencies (100, 200, 300, and 400 MHz) and 5 to 20 min time intervals.

Ultra-Robust Thermoconductive Films Made from Aramid Nanofiber and Boron Nitride Nanosheet for Thermal Management Application

The development of highly thermally conductive composites with excellent electrical insulation has attracted extensive attention, which is of great significance to solve the increasingly severe heat concentration issue of electronic equipment. Herein, we report a new strategy to prepare boron nitride nanosheets (BNNSs) via an ion-assisted liquid-phase exfoliation method. Then, silver nanoparticle (AgNP) modified BNNS (BNNS@Ag) was obtained by in situ reduction properties. The exfoliation yield of BNNS was approximately 50% via the ion-assisted liquid-phase exfoliation method. Subsequently, aramid nanofiber (ANF)/BNNS@Ag composites were prepared by vacuum filtration. Owing to the "brick-and-mortar" structure formed inside the composite and the adhesion of AgNP, the interfacial thermal resistance was effectively reduced. Therefore, the in-plane thermal conductivity of ANF/BNNS@Ag composites was as high as 11.51 W m-1 K-1, which was 233.27% higher than that of pure ANF (3.45 W m-1 K-1). The addition of BNNS@Ag maintained tensile properties (tensile strength of 129.14 MPa). Moreover, the ANF/BNNS@Ag films also had good dielectric properties and the dielectric constant was below 2.5 (103 Hz). Hence, the ANF/BNNS@Ag composite shows excellent thermal management performance, and the electrical insulation and mechanical properties of the matrix are retained, indicating its potential application prospects in high pressure and high temperature application environments.

Allyl and Benzyl Modified Aramid Nanofibers as an Enhancement in Polystyrene-Based Composites

Aramid nanofibers (ANFs) represent the most promising nanoscale building blocks for high-performance nanocomposites. But their applications are mostly limited to those polymers containing –OH or –NH₂ groups that can interact with ANFs through hydrogen bonding or others. In this paper, allyl and benzyl modified ANFs were successfully fabricated using a metallization method followed by functionalization with allyl and benzyl bromide. A series of modified aramid nanomaterials (ANMs) with different degrees of modification were prepared and their morphologies studied. The modified ANFs were added to polystyrene (PS) films as reinforcements. The mechanical properties of the resulting composite PS films including Young's modulus, toughness and yield strength were dramatically improved compared to those of pure PS film. These new types of reinforcement additives for non-polar polymer materials are presented in this paper.

Aramid Nanofiber Templated In Situ SNAr Polymerization for Maximizing the Performance of All-Organic Nanocomposites

The performance limits of conventional super engineering plastics with inorganic nanofillers are surpassed by all-organic nanocomposites prepared via in situ S_NAr polymerization of polysulfone (PSU) in the presence of a highly dispersed aramid nanofiber (ANF) solution. The latter is directly used, bypassing the energy-consuming, nanostructure-damaging workup process. Using only a 0.15 wt % nanofiller, the all-organic nanocomposite shows an ultimate tensile strength 1.6× higher and 3.4× tougher than neat PSU and its blending counterpart due to the mutually interactive filler and maximally homogenized matrix. The exceptional toughness of the ANF/PSU nanocomposite originates from the grafted PSU on the surface of ANF; it drives stress-delocalized deformation, as revealed by stress-absorbable viscoelastic behavior and ductile elongation of materials. This material is a promising candidate for use as a filler-interactive, high-performance nanocomposite.

Emerging biomaterials for downstream manufacturing of therapeutic proteins

Downstream processing is considered one of the most challenging phases of industrial manufacturing of therapeutic proteins, accounting for a large portion of the total production costs. The growing demand for therapeutic proteins in the biopharmaceutical market in addition to a significant rise in upstream titers have placed an increasing burden on the downstream purification process, which is often limited by high cost and insufficient capacities. To achieve efficient production and reduced costs, a variety of biomaterials have been exploited to improve the current techniques and also to develop superior alternatives. In this work, we discuss the significance of utilizing traditional biomaterials in downstream processing and review the recent progress in the development of new biomaterials for use in protein separation and purification. Several representative methods will be highlighted and discussed in detail, including affinity chromatography, non-affinity chromatography, membrane separations, magnetic separations, and precipitation/phase separations. STATEMENT OF SIGNIFICANCE: Nowadays, downstream processing of therapeutic proteins is facing great challenges created by the rapid increase of the market size and upstream titers, starving for significant improvements or innovations in current downstream unit operations. Biomaterials have been widely used in downstream manufacturing of proteins and efforts have been continuously devoted to developing more advanced biomaterials for the implementation of more efficient and economical purification methods. This review covers recent advances in the development and application of biomaterials specifically exploited for various chromatographic and non-chromatographic techniques, highlighting several promising alternative strategies.

Timesaving, High-Efficiency Approaches To Fabricate Aramid Nanofibers

Aramid nanofibers (ANFs) have become promising nanoscale building blocks due to their extraordinary performance. However, there are numerous challenges related to the preparation of ANFs, such as the lengthy preparation cycle (7-10 days), low preparation concentration (0.2 wt %), and high difficulty in quantitatively judging the end point of the deprotonation reaction. Herein, we report three time-saving and high-efficiency strategies (fibrillation, ultrasonication, and proton donor-assisted deprotonation) to prepare ANFs with excellent performance. The fiber micromorphology during the deprotonation and protonation recovery processes was first investigated. Then the end point of the deprotonation reaction was detected by Raman spectra and the cationic demand of the ANF/DMSO system. Finally, the size, preparation cycle, and performance of the corresponding ANFs and ANF films fabricated by different approaches were investigated in detail. The results showed that proton donor-assisted deprotonation significantly shortened the traditional preparation cycle from 7 days to 4 h, and is the most efficient method reported thus far. It is noteworthy that a high concentration of ANFs (4.0 wt %) could also be achieved within 12 h. Interestingly, the fabricated ANFs exhibit rigid morphology and a small diameter with a narrow size distribution (10.7 ± 1.0 nm). The resultant ANF film displays desired characteristics of high strength and toughness. The work offers a timesaving, feasible and effective strategy to realize the large-scale production for ANFs, which will facilitate the application of ANFs in the production of advanced nanomaterials.

Scalable Synthesis of Hide Substance-Chitosan-Hydroxyapatite: Novel Biocomposite from Industrial Wastes and Its Efficiency in Dye Removal

A novel porous polymer-inorganic hybrid biocomposite with various functional groups (hide substance/chitosan/hydroxyapatite) has been synthesized in simple, economic, and scalable process utilizing leather industry solid waste and seafood industry waste composed with hydroxyapatite. Physicochemical characterization of the material reveals formation of composites with homogenous distribution of the constituents in the material matrix. The composite is hard and porous (with 0.1632 cm3/g slit-shaped mesopores and micropores) having particle sizes 40-80 μm and a Brunauer-Emmett-Teller surface area of 55.54 m2/g. The material is polycrystalline in nature with a fair amount of amorphous substance and less hydrophilic in character than constituent polymers. The dye removal efficiency of the material has been tested with two model dyes, namely, methylene blue (MB) (cationic/basic dye) and sunset yellow (SY) (anionic/acid dye). Optimum adsorptions of 3.8 mg MB (pH 12, RT ≈ 27 °C) and 168 mg of SY (pH 3, RT ≈ 27 °C) have been found per gram of the composite material. Langmuir isotherm and pseudo second order rate models have been found to be the best-fit models to explain the equilibrium isotherm and kinetics of the adsorption process for both the dyes. However, higher and faster adsorption of SY in comparison with MB indicated higher binding efficiency of the material toward the acidic dye. Desorption of dyes from the dye-adsorbed material was studied using a suitable eluent of appropriate pH and recycling for five times showed without loss of efficiency. The prepared composite showed very high dye removal efficiency toward four different commercially used dyes (496 mg/g of Orange-NR, 477 mg/g of Red-VLN, 488 mg/g of Blue-113 dye, and 274 mg/g of Green-PbS dye) from their individual and cocktail solutions. It was also efficient to decolorize dye-bearing tannery exhaust bath. Hence, waste materials generated during industrial processes could be efficiently used for the decontamination of colored wastewater produced by various industries.

Visualizing and quantifying the nanoscale hydrophobicity and chemical distribution of surface modified polyethersulfone (PES) membranes

Chemical modifications bring unique properties into polymeric membranes that may have enhanced filtration or separation efficiencies, antifouling, antimicrobial activity and selectivity. However, there is a lack of nanoscale characterization of the chemical additive distribution and the impacts of chemical modifiers or additives on membrane surface properties, especially those at the nanoscale. In this study, a series of industrially relevant polyethersulfone (PES) membranes modified with poly (ethylene glycol) (PEG) and polyvinylpyrrolidone (PVP) were analysed systematically. Particularly, hydrophobicity and chemical distribution were scrutinized by atomic force microscopy (AFM) and AFM coupled with infrared analysis capability (AFM-IR) for the first time that successfully resolved nanoscale structural and chemical properties of the chemically modified PES membranes. Our results indicated the heterogeneous spatial distribution of PVP and PEG based on their characteristic IR bands and the resulting hydrophobicity distribution on modified membrane surfaces at the nanoscale. Particularly, we established a linear correlation (R² = 0.9449) between the measured adhesion force and water contact angles, which enabled the examination of local surface hydrophobicity. The PES membranes became more hydrophilic with the increasing blend of PVP and PEG. With AFM-IR, trace amounts (1-4%) of PVP could be identified sensitively on PES membranes based on their unique characteristic IR bands, which were not achieved by FTIR or IR mapping. Overall, these novel characterization approaches hold paramount importance for the design and quality control of polymer membrane modification and manufacturing.

Fabrication of membrane absorbers based on amphiphilic carbonaceous derivatives for selective endotoxin clearance

A new carrier-dispersed method based on amphiphilic carbonaceous particles (ACPs) was developed for the construction of functionalized blend membrane absorbers.