Scalable Fabrication of Electrospun Nanofibrous Membranes Functionalized with Citric Acid for High-Performance Protein Adsorption

Facile fabrication of surface imprinted polymers based on nanofibrous aerogels for specific capture of lysozyme form egg white

The development of separation and purification materials with specific adsorption performance is essential to obtain high-purity proteins, especially in food industries. In this work, functional imprinting layers were introduced onto three-dimensional poly(vinyl alcohol-co-ethylene) nanofibrous aerogels (PVA-co-PE NFAs) to fabricate surface molecularly imprinted polymers for lysozyme specific capture. Citric acid (CA) modified PVA-co-PE NFAs (PCNAs) were used as substrate to immobilize the target lysozyme, and dopamine (DA) was selected as a functional monomer to generate imprinting layers with controllable thickness through self-polymerization. The obtained lysozyme imprinted PCNAs (LIPCNAs) exhibited an extreme high adsorption capacity (1010.33 mg/g), which is clearly superior to the currently reported imprinted protein adsorbents. The obtained LIPCNAs not only possessed imprinting factor (IF = 1.53) with reusability upon 10 cycles, but also capacity to extract lysozyme directly from egg white. The released lysozyme can maintain the initial secondary structure and biological activity.

Preparation of Functionalized Ethylene-Vinyl-Alcohol Nanofibrous Membrane Filter for Rapid and Cyclic Removing of Organic Dye from Aqueous Solution

A functionalized ethylene-vinyl-alcohol (EVOH) nanofibrous membrane (NFM) was fabricated via co-electrospinning H4SiW12O40 (SiW12) and EVOH first, and then grafting citric acid (CCA) on the electrospun SiW12@EVOH NFM. Characterization with FT-IR, EDX, and XPS confirmed that CCA was introduced to the surface of SiW12@EVOH NFM and the Keggin structure of SiW12 was maintained well in the composite fibers. Due to a number of carboxyl groups introduced by CCA, the as-prepared SiW12@EVOH-CCA NFM can form a high number of hydrogen bonds with CR, and thus can be used to selectively absorb congo red (CR) in aqueous solutions. More importantly, the CR enriched in the NFM can be rapidly degraded via photocatalysis. SiW12 in the NFM acted as a photocatalyst, and the hydroxyl groups in the NFM acted as an electron donor to accelerate the photodegradation rate of CR. Meanwhile, the SiW12@EVOH-CCA NFM was regenerated and then exhibited a relatively stable adsorption capacity in five cycles of filtration-regeneration. The bifunctional nanofibrous membrane filter showed potential for use in the thorough purification of dye wastewater.

Advances in high-throughput, high-capacity nonwoven membranes for chromatography in downstream processing: A review

Nonwoven membranes are highly engineered fibrous materials that can be manufactured on a large scale from a wide range of different polymers, and their surfaces can be modified using a large variety of different chemistries and ligands. The fiber diameters, surface areas, pore sizes, total porosities, and thicknesses of the nonwoven mats can be carefully controlled, providing many opportunities for creative approaches for the development of novel membranes with unique properties to meet the needs of the future of downstream processing. Fibrous membranes are already finding use in ultrafiltration, microfiltration, depth filtration, and, more recently, in membrane chromatography for product capture and impurity removal. This article summarizes the various methods of manufacturing nonwoven fabrics, and the many methods available for the modification of the fiber surfaces. It also reviews recent studies focused on the use of nonwoven fabric devices in membrane chromatography and provides some perspectives on the challenges that need to be overcome to increase binding capacities, decrease residence times, and reduce pressure drops so that eventually they can replace resin column chromatography in downstream process operations.

Butane Tetracarboxylic Acid Grafted on Polymeric Nanofibrous Aerogels for Highly Efficient Protein Absorption and Separation

Developing high-performance and low-cost protein purification materials is of great importance to meet the demands for highly purified proteins in biotechnological industries. Herein, a facile strategy was developed to design and construct high-efficiency protein absorption and separation media by combining aerogels' molding techniques and impregnation processes. Poly (ethylene-co-vinyl alcohol) (EVOH) nanofibrous aerogels (NFAs) were modified by grafting butane tetracarboxylic acid (BTCA) over them in situ. This modification was carried out using polyphosphoric acid as a catalyst. The resulting EVOH/BTCA NFAs exhibited favorable comprehensive properties. Benefiting from the highly interconnected porous structure, good underwater compressive properties, and abundant absorption ligands, the obtained EVOH/BTCA NFAs possessed a high static absorption capacity of 1082.13 mg/g to lysozyme and a short absorption equilibrium time of about 6 h. A high saturated dynamic absorption capacity for lysozyme (716.85 mg/g) was also realized solely by gravity. Furthermore, EVOH/BTCA NFAs displayed excellent reusability, good acid and alkaline resistance, and unique absorption selectivity performance. The successful synthesis of such aerogels can provide a potential candidate for next-generation protein absorbents for bio-separation and purification engineering.

A label-free electrochemical immunosensor based on decorated cellulose nanofibrous membrane for point-of-care diagnosis of amanitin poisoning via human urine

α-Amanitin (AMN) is one of the deadliest toxins from mushrooms, present in the deadly mushroom species Amanita phalloides. It is a bicyclic octapeptide and represents up to 40% of the amatoxins in mushrooms, damaging the liver and kidneys. Current methods of detecting amatoxins are time-consuming and require the use of expensive equipment. A novel label-free electrochemical immunosensor was successfully developed for rapid detection of α-amanitin, which was fabricated by immobilization of anti-α-amanitin antibodies onto a functionalized cellulose nanofibrous membrane-modified carbon screen-printed electrode. An oxidation peak of the captured amanitin on the tethered antibodies was observed at 0.45 V. The performance of the nanofibrous membrane on the electrode and necessary fabrication steps were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Due to its unique structural features and properties such as high specific surface area and microporous structure, the nanofibrous membrane as an immunosensor matrix for antibody tethering improved the electrochemical performance of the immunosensor by more than 3 times compared with cast membranes. Under the optimal conditions, the assembled immunosensor exhibited high sensitivity toward α-amanitin detection in the range of 0.009-2 ng mL-1 with a limit of detection of 8.3 pg mL-1. The results clearly indicate that the fabricated nanofiber-based-immunosensor is suitable for point-of-care detection of lethal α-amanitin in human urine without any pretreatment within 30 min.

Cation-exchange performance of a citric-acid esterified cellulose nanofibrous membrane for highly-selective proteins' permeability and adsorption capacity

The usage of low-cost, readily available, or even disposable, single-use membranes in macromolecules' purification and separation is still in the development phase. In this research, highly porous (>95 %), water- and compression stable cation-exchange membranes were prepared by freeze-casting using cellulose nanofibrils (CNF) and citric acid (CA) acting as a crosslinker and source of weak anionic (carboxylic) surface groups arising from the mono-esterified CA. The membranes were characterized by different analytical techniques, and evaluated for the ionic adsorption efficacy of different proteins in dead-end filtration mode using a Tri-buffer of pH 8. The membrane's internal microstructure (porosity and density) with the available (quantity and access) carboxylic groups was confirmed, to determine not only the proteins' specific (related to the net charged and molecular weight) adsorption dynamic (>52 % of positive Lysozyme/Cytochrome, <8 % of negative BSA/Myoglobin; ≤0.5 g/L) at extremely high flow rates (>3.000 hL/h*MPa*m2), but also their desorption (>97 %) and re-equilibration (using NaCl) with flux recovery (>80 %). Such efficiency was achieved with up to 5 consecutive filtering cycles. The high permeability (>87 %) of the spherical and negatively surface charged microparticles (used as models) also suggests the likelihood of removing larger microbial species, which, while retaining relatively smaller and positively charged proteins, further increases their potential in biopharma applications.

Recent development and application of membrane chromatography

Membrane chromatography is mainly used for the separation and purification of proteins and biological macromolecules in the downstream processing process, also applications in sewage disposal. Membrane chromatography is recognized as an effective alternative to column chromatography because it significantly improves chromatography from affinity, hydrophobicity, and ion exchange; the development status of membrane chromatography in membrane matrix and membrane equipment is thoroughly discussed, and the applications of protein capture and intermediate purification, virus, monoclonal antibody purification, water treatment, and others are summarized. This review will provide value for the exploration and potential application of membrane chromatography.

Negatively Charged Composite Nanofibrous Hydrogel Membranes for High-Performance Protein Adsorption

Nanofibrous materials are considered as promising candidates for fabricating high-efficiency chromatography media, which are urgently needed in protein pharmaceuticals purification and biological research, yet still face several bottlenecks. Herein, novel negatively charged composite nanofibrous hydrogel membranes (NHMs) are obtained by a facile combination of electrospinning and surface coating modification. The resulting NHMs exhibit controllable morphologies and chemical structures. Benefitting from the combined effect of the stable framework of silicon dioxide (SiO₂) nanofiber and the function layer of negatively charged hydrogel, as well as good pore connectivity among nanofibers, NHMs exhibit a high protein adsorption capacity of around 1000 mg g^-1, and are superior to the commercial cellulose fibrous adsorbent (Sartobind^®) and the reported nanofibrous membranous adsorbents. Moreover, due to their relatively stable physicochemical and mechanical properties, NHMs possess comprehensive adsorption performance, favorable resistance to acid and solvents, good selectivity, and excellent regenerability. The designed NHMs composite adsorbents are expected to supply a new protein chromatography platform for effective protein purification in biopharmaceuticals and biochemical reagents.

Electrospun Hydrophobic Interaction Chromatography (HIC) Membranes for Protein Purification

Responsive membranes for hydrophobic interaction chromatography have been fabricated by functionalizing poly(N-vinylcaprolactam) (PVCL) ligands on the substrate of electrospun regenerated cellulose nanofibers. Both static and dynamic binding capacities and product recovery were investigated using bovine serum albumin (BSA) and Immunoglobulin G (IgG) as model proteins. The effects of ligand chain length and chain density on static binding capacity were also studied. A static binding capacity of ~25 mg/mL of membrane volume (MV) can be achieved in optimal ligand grafting conditions. For dynamic binding studies, protein binding capacity increased with protein concentration from 0.1 to 1.0 g/L. Dynamic binding capacity increased from ~8 mg/mL MV at 0.1 g/L BSA to over 30 mg/mL at 1.0 g/L BSA. However, BSA recovery decreased as protein concentration increased from ~98% at 0.1 g/L BSA to 51% at 1 g/L BSA loading concentration. There is a clear trade-off between binding capacity and recovery rate. The electrospun substrate with thicker fibers and more open pore structures is superior to thinner fibrous membrane substrates.

An EVOH nanofibrous sterile membrane with a robust and antifouling surface for high-performance sterile filtration via glutaraldehyde crosslinking and a plasma-assisted process

Constructing a sterile membrane with a robust and antifouling surface is a powerful means to improve the sterile filtration efficiency of sterile membranes. In this work, a robust EVOH nanofibrous sterile membrane was facilely fabricated by the method of in situ crosslinking with glutaraldehyde and surface plasma treatment. The resultant EVOH nanofibrous sterile membrane possessed a carboxylated-crosslinked surface, with high hydrophilicity, which generated high chemical stability, high-temperature steam resistance, and an ultrahigh antifouling performance against bovine serum albumin, ribonucleic acid and nanoparticle pollutants. Moreover, the membrane also exhibited a reasonably high primary water permeance (4522.2 LMH bar^-1 at 0.2 MPa), as well as an absolute interception rate (100%) of Escherichia coli, Staphylococcus aureus cells and Brevundimonas diminuta superior to the state-of-the-art sterile membrane. Moreover, the modified membrane packed syringe-driven filter presented 100% interception (LRV ≥ 7) to Brevundimonas diminuta and high permeation flux (from 10.8 to 41.8 L·h^-1) in a wide operating pressure range of 0.1 MPa to 0.6 MPa, indicating its potential in real bio-separation applications. This work provides a facile strategy for the preparation of a high-performance sterile membrane for biological drug product sterilization.

Cationic microcrystalline cellulose - Montmorillonite composite aerogel for preconcentration of inorganic anions from dairy wastewater

Development of efficient adsorbents to inorganic anions as a solid phase extraction (SPE) material is highly desirable for chromatographic analysis and pollution control. In this work we developed a new hybrid cationic microcrystalline cellulose aerogel composite. Cationic cetylpyridinium imbedded montmorillonite (CPC-MT) was uniformly entrapped in microcrystalline cellulose (MCC) to enhance anionic adsorption efficiency and mechanical stability. The developed CPC-MT@MCC aerogel was used as an SPE adsorbent for anions from dairy wastewater by coupling with ion-column chromatography. Further quaternized CPC-MT@MCC aerogel (CPC-MT@QMCC) showed unique low density (10.6 mg cm^-3), large specific surface area (320 m² g^-1), porosity 70%, 800 mg g^-1 nitrate adsorption capacity within 60 min and ease of elution in alkaline solutions. The CPC-MT@QMCC aerogel showed efficient regeneration and reuse performances for up to 10 cycles. More importantly, a dynamic binding efficiency of 710 mg g^-1 highlights its excellent performance for practical applications. 96% of nitrate anion from environmental manure wastewater samples were adsorbed with 98.7% recovery. A good linear relationship was obtained in the range of 0.01-10 mg L^-1 and the limits of detection was 0.5 mg L^-1 using CPC-MT@QMCC aerogel as a preconcentration column. The successful synthesis of such intriguing and economic CPC-MT@QMCC aerogel may provide a promising matrix for high-performance and high efficiency chromatographic media.

De Novo Ion-Exchange Membranes Based on Nanofibers

The unique functions of nanofibers (NFs) are based on their nanoscale cross-section, high specific surface area, and high molecular orientation, and/or their confined polymer chains inside the fibers. The introduction of ion-exchange (IEX) groups on the surface and/or inside the NFs provides de novo ion-exchangers. In particular, the combination of large surface areas and ionizable groups in the IEX-NFs improves their performance through indices such as extremely rapid ion-exchange kinetics and high ion-exchange capacities. In reality, the membranes based on ion-exchange NFs exhibit superior properties such as high catalytic efficiency, high ion-exchange and adsorption capacities, and high ionic conductivities. The present review highlights the fundamental aspects of IEX-NFs (i.e., their unique size-dependent properties), scalable production methods, and the recent advancements in their applications in catalysis, separation/adsorption processes, and fuel cells, as well as the future perspectives and endeavors of NF-based IEMs.

Bisphosphonated-immobilized porous cellulose monolith with tentacle grafting by atom transfer radical polymerization for selective adsorption of lysozyme

Here, a m-xylene bisphosphonate immobilized tentacle-type cellulose monolith (BP-PCM) is prepared by atom transfer radical polymerization for lysozyme purification. In the preparation, the m-xylene bisphosphonate was anchored glycidyl methacrylate and then polymerized to enhance the flexibility of the ligands to improve lysozyme adsorption capacity, and glycerol monomethacrylate serves as spacer to further optimize the layers structure and ligands density of the grafted tentacles for satisfactory adsorption capacity. The maximum static and dynamic adsorption capacity (10% breakthrough) of BP-PCM reach to 169.6 and 102.6 mg mL-1, respectively. Moreover, BP-PCM displays weak nonspecific adsorption and is able to successfully enrich lysozyme from diluted chicken egg white, indicating the excellent selectivity. The results demonstrated that BP-PCM is promising for use as high-capacity protein chromatography.

Iminodiacetic Acid (IDA) Cation-Exchange Nonwoven Membranes for Efficient Capture of Antibodies and Antibody Fragments

There is strong need to reduce the manufacturing costs and increase the downstream purification efficiency of high-value therapeutic monoclonal antibodies (mAbs). This paper explores the performance of a weak cation-exchange membrane based on the coupling of IDA to poly(butylene terephthalate) (PBT) nonwoven fabrics. Uniform and conformal layers of poly(glycidyl methacrylate) (GMA) were first grafted to the surface of the nonwovens. Then IDA was coupled to the polyGMA layers under optimized conditions, resulting in membranes with very high permeability and binding capacity. This resulted in IgG dynamic binding capacities at very short residence times (0.1–2.0 min) that are much higher than those achieved by the best cation-exchange resins. Similar results were obtained in the purification of a single-chain (scFv) antibody fragment. As is customary with membrane systems, the dynamic binding capacities did not change significantly over a wide range of residence times. Finally, the excellent separation efficiency and potential reusability of the membrane were confirmed by five consecutive cycles of mAb capture from its cell culture harvest. The present work provides significant evidence that this weak cation-exchange nonwoven fabric platform might be a suitable alternative to packed resin chromatography for low-cost, higher productivity manufacturing of therapeutic mAbs and antibody fragments.

Fabrication of polydopamine-based NIR-light responsive imprinted nanofibrous membrane for effective lysozyme extraction and controlled release from chicken egg white

The development of highly efficient performance matrix for protein adsorption and scalable throughput adsorbent is highly desired, especially in pharmaceuticals and food industries. In this work, we present a simple methodology to prepare a nanofibrous membrane based surface molecular imprinted matrix (MIP) for selective separation of lysozyme. The MIP was developed by coating carboxylated poly (vinyl alcohol-co-ethylene) nanofibrous mat (EVOH-CCA NFM) with a near infrared (NIR)-light responsive polydopamine (PDA) layer. The open porous nanofibrous structure and a thin PDA layer endowed the MIPs with adsorption capacity (500 mg.g-1) within 150 min. The developed surface MIPs not only showed imprinting factor (IF = 4) with reusability upon 5 cycles, but also capability of extracting lysozyme from egg-white directly. The MIPs showed controlled release of extracted lysozyme triggered by the NIR-light responsive property of the PDA layer. Moreover, the released lysozyme possesses good bioactivity, evidenced by efficient decomposition of micrococcus bacterial cell wall.

Effective tetracycline removal from liquid streams of dairy manure via hierarchical poly (vinyl alcohol-co-ethylene)/polyaniline metal complex nanofibrous membranes

Antibiotic residues from animal wastes enter underground and surface water streams, posing high risks to public health. Novel technologies capable of removing the residues from the matrix of concern such as animal waste should be developed. This research investigates the development of nanofiber absorbent for removing tetracycline (TC) antibiotic residues from liquid streams of dairy manure produced in a typical dairy farm. Hierarchically structured nanofibrous adsorbent was developed through growing a uniform polyaniline (PAni) nanodots on poly (vinyl alcohol-co-ethylene) (EVOH) nanofiber membrane (NFM). Moreover, Cu²⁺ ions were chelated on the developed EVOH/PAni-Cl NFM to improve TC adsorption efficiency and selectivity. The TC adsorption capacities of EVOH/PAni-Cl-Cu²⁺ and EVOH/PAni-Cl) NFM were 1100 mg g^-1 and 600 mg g^-1 within 120 min., respectively. The NFMs adsorption efficiency was investigated using dairy wastewater. Initial TC concentrations in dairy wastewater sample varied between 20 and 50 ppm. The EVOH/PAni-Cl-Cu²⁺ NFM showed TC removal of 86% from dairy manure samples at 25 ppm initial TC concentration within 60 min. during batch mode treatment. Results showed that the dynamic binding efficiency of 450 mg g^-1 can be achieved at an initial TC concentration of 50 ppm. Furthermore, the NFM displayed efficient chemical and physical stability even after 8 cycles of reusing without significant changes in its performance or hazardous Cu²⁺ leaching.

Rapid removal of nitrate from liquid dairy manure by cationic poly (vinyl alcohol-co-ethylene) nanofiber membrane

Elevated levels of nitrate in surface water is a leading concern, which impacts human and animal health, and controlling it requires improved and sustainable methods capable of removing nitrate anions from source waste water to reduce nitrate anions transport to environment. In liquid dairy manure, nitrogen content can vary from 200 to 600 ppm and the transport of manure nitrogen into ambient water through hydrologic processes has a potential to exceed the maximum contaminant level limit (10 ppm) of nitrate nitrogen for regulated public water systems. Dairy manure is considered as a reservoir of nitrate. This research investigates on the determination of optimal designing of nanofiber membrane to remove nitrate anions from liquid dairy manure. A cationic poly (vinyl alcohol-co-ethylene) nanofiber membrane (EVOH) NFM was grafted via UV with 2-(methacryloyloxy) ethyl trimethylammonium chloride (DMAC) monomers. The adsorption efficiency of nitrate by the membrane was determined on liquid manure of dairy lagoons located in Central Valley of California. Initial nitrate concentrations in dairy manure varied from 75 to 100 ppm. Results showed that nitrate in dairy water was removed by 70% in 40 min. Tortuous structure and chemical stability of membrane resulted in nitrate dynamic binding capacity of 40 mg g^-1. Furthermore, it exhibits efficient reusability without significant changes in its performance using 0.5 M sodium hydroxide solution for nitrate desorption. Results showed that change in pH, and multi-anion conditions had limited effects on nitrate removal efficiency, and EVOH NFM can be a viable option to remove nitrate of liquid manure. This could be used for mitigating transport of excess nitrate from manure to environment. Overall, the results suggest that EVOH-g-DMAC NFM is efficient, low-cost (13 USD/m³) and recyclable material for sustainable removal of nitrate from dairy manure wastewater without requiring any ionic strength or pH adjustment.

Electrospun Nanofibers for Chemical Separation

The separation and purification of specific chemicals from a mixture have become necessities for many environments, including agriculture, food science, and pharmaceutical and biomedical industries. Electrospun nanofiber membranes are promising materials for the separation of various species such as particles, biomolecules, dyes, and metals from liquids because of the combined properties of a large specific surface, light weight, high porosity, good connectivity, and tunable wettability. This paper reviews the recent progress in the design and fabrication of electrospun nanofibers for chemical separation. Different capture mechanisms including electrostatic, affinity, covalent bonding, chelation, and magnetic adsorption are explained and their distinct characteristics are highlighted. Finally, the challenges and future aspects of nanofibers for membrane applications are discussed.

Electrospun Weak Anion-exchange Fibrous Membranes for Protein Purification

Membrane based ion-exchange (IEX) and hydrophobic interaction chromatography (HIC) for protein purification is often used to remove impurities and aggregates operated under the flow-through mode. IEX and HIC are also limited by capacity and recovery when operated under bind-and-elute mode for the fractionation of proteins. Electrospun nanofibrous membrane is characterized by its high surface area to volume ratio and high permeability. Here tertiary amine ligands are grafted onto the electrospun polysulfone (PSf) and polyacrylonitrile (PAN) membrane substrates using UV-initiated polymerization. Static and dynamic binding capacities for model protein bovine serum albumin (BSA) were determined under appropriate bind and elute buffer conditions. Static and dynamic binding capacities in the order of ~100 mg/mL were obtained for the functionalized electrospun PAN membranes whereas these values reached ~200 mg/mL for the functionalized electrospun PSf membranes. Protein recovery of over 96% was obtained for PAN-based membranes. However, it is only 56% for PSf-based membranes. Our work indicates that surface modification of electrospun membranes by grafting polymeric ligands can enhance protein adsorption due to increased surface area-to-volume ratio.

An Innovative Nanobody-Based Electrochemical Immunosensor Using Decorated Nylon Nanofibers for Point-of-Care Monitoring of Human Exposure to Pyrethroid Insecticides

A novel ultrasensitive nanobody-based electrochemical immunoassay was prepared for assessing human exposure to pyrethroid insecticides. 3-Phenoxybenzoic acid (3-PBA) is a common human urinary metabolite for numerous pyrethroids, which broadly served as a biomarker for following the human exposure to this pesticide group. The 3-PBA detection was via a direct competition for binding to alkaline phosphatase-embedded nanobodies between free 3-PBA and a 3-PBA-bovine serum albumin conjugate covalently immobilized onto citric acid-decorated nylon nanofibers, which were incorporated on a screen-printed electrode (SPE). Electrochemical impedance spectroscopy (EIS) was utilized to support the advantage of the employment of nanofibrous membranes and the success of the immunosensor assembly. The coupling between the nanofiber and nanobody technologies provided an ultrasensitive and selective immunosensor for 3-PBA detection in the range of 0.8 to 1000 pg mL-1 with a detection limit of 0.64 pg mL-1. Moreover, when the test for 3-PBA was applied to real samples, the established immunosensor proved to be a viable alternative to the conventional methods for 3-PBA detection in human urine even without sample cleanup. It showed excellent properties and stability over time.

Preparation and Protein Separation Properties of the Porous Polystyrene/Ethylene-Vinyl Acetate Copolymer Blend Nanofibers Membranes

To date, the preparation of a novel ultrafiltration membrane and the efficient separation and purification of protein solutions have gradually attracted widespread attention of many researchers. In this study, a hollow porous polystyrene/ethylene-vinyl acetate copolymer blend nanofibrous membrane (PS/EVA-BNM) was generated by electrospinning and chemical modification and then used to separate and purify proteins in solution. The BNM was characterized by scanning electron microscopy and specific surface area and pore size analyses. The membrane separation system was assembled using the BNM, which was overlaid to form the reaction layer. The optimal conditions for protein separation were determined by adjusting the operating pressure, filtration time, and pH. The results showed that the rejection rate of serum albumin and the membrane flux could reach 94.35% and 2.04 L/(m2 min), respectively, under the following conditions: the operating pressure was 0.10 MPa and the processing time was 1.5 h. By comparing the parameters of the polyethersulfone commercial ultrafiltration membrane with the PS/EVA-BNM system, it could be inferred that the rejection rate of the latter decreased slightly, whereas its transport flux improved several times. At the same time, the experimental results indicated that the PS/EVA-BNM possessed excellent reusability and mechanical properties. Additionally, the BNM could retain its nanofibrous morphological structure after the separation of serum albumin several times in an aqueous environment.

Shapeable, Underwater Superelastic, and Highly Phosphorylated Nanofibrous Aerogels for Large-Capacity and High-Throughput Protein Separation

Developing nanofibrous aerogels with high porosity, robust underwater mechanical strength, and rich adsorption ligands, has been considered as one of the most promising strategies for preparing the next generation of high-efficiency and high-throughput chromatographic media; yet great challenges still remain. Herein, a novel type of highly phosphorylated nanofibrous aerogels (PNFAs) is fabricated, for the first time, by combining electrospinning, cryogenic induced phase separation regulation, and in situ phosphorylation modification. The PNFAs exhibit outstanding underwater superelasticity and excellent compression fatigue resistance (∼0% plastic deformation after 1000 compression cycles), as well as favorable shape-memory property. Besides, the PNFAs also can be bent and compressed even in the ultracold liquid nitrogen without obvious plastic deformation, further highlighting their robust structural stability. Benefiting from the superelastic, interconnected, and highly phosphorylated 3D nanofibrous frameworks, the PNFAs possess a superb protein adsorption capability of 3.3 × 10³ mg g^-1 and a large liquid flux of 1.5 × 10⁴ L m^-2 h^-1, which are superior to the commercial and previously reported fiber-based chromatographic media. Moreover, the PNFAs also exhibit superior performance stability, easy assembly, and outstanding applicability, highlighting their potential actual application. The successful preparation of such fascinating PNFAs may not only provide a new option for the current protein adsorption and purification engineering, but also could open up some new perspectives for further design and development of next-generation nanofibrous aerogel-based chromatographic media for various bioseparation applications.

Amphiphilic Oxygenated Amorphous Carbon-Graphite Buckypapers with Gas Sensitivity to Polar and Non-Polar VOCs

To precisely control the emission limit of volatile organic compounds (VOCs) even at trace amounts, reactive nanomaterials of, e.g., carbon are demanded. Particularly, considering the polar/non-polar nature of VOCs, amphiphilic carbon nanomaterials with a huge surface area could act as multipurpose VOC sensors. Here, for the first time, a buckypaper sensor composed of oxygenated amorphous carbon (a-CO_x)/graphite (G) nanofilaments is developed. Presence of the oxygen-containing groups rises the selectivity of the sensor to polar VOCs, such as ethanol and acetone through formation of hydrogen bonding, affecting the electron withdrawing ability of the group, the hole carrier density, and, thus, the resistivity. On the other hand, the electrostatic interactions between the toluene aromatic ring and the π electrons of the graphitic crystals cause a formation of charge-transfer complexes, which could be the main mechanism of high responsiveness of the sensor towards non-polar toluene. To the best of my knowledge, an amphiphilic carbon nanofilamentous buckypaper has never been reported for gas sensing, and my device sensing polar/non-polar VOCs is state of the art for environmental control.

A magnetic nanofiber-based zwitterionic hydrophilic material for the selective capture and identification of glycopeptides

High-performance affinity materials are highly required in the sample preparation process in mass spectrometry-based glycoproteomics studies. In this research, a novel magnetic nanofiber-based zwitterionic hydrophilic material is prepared for glycopeptide enrichment and identification. The one-dimensional hydroxyapatite nanofiber (HN) acted as the supporting substance for immobilizing both Fe3O4 nanoparticles and Au nanoparticles, following the surface modification with a zwitterionic tripeptide l-glutathione (GSH) via the affinity interactions between the thiol group in GSH and both Au and Fe3O4 to form the magHN/Au-GSH nanofiber. Owing to the unique structural features, excellent hydrophilicity, abundant zwitterionic molecules, and strong magnetic responsiveness, the as-prepared magHN/Au-GSH nanofiber possesses satisfactory specificity for glycopeptide enrichment. As a result, the magHN/Au-GSH nanofiber demonstrated great detection sensitivity (2 fmol), satisfying enrichment recovery (89.65%), large binding capacity (100 mg g-1), and high enrichment selectivity (1 : 100) toward glycopeptides. Furthermore, 246 N-glycosylated peptides corresponding to 104 N-glycosylated proteins were identified from only 1 μL human serum, revealing the great potential of this affinity nanofiber for glycopeptide enrichment and glycoproteomics research.

Fabrication of Water Absorbing Nanofiber Meshes toward an Efficient Removal of Excess Water from Kidney Failure Patients

Excellent water-absorbing nanofiber meshes were developed as a potential material for removing excess fluids from the blood of chronic renal failure patients toward a wearable blood purification system without requiring specialized equipment. The nanofiber meshes were successfully fabricated from poly(acrylic acid) (PAA) under various applied voltages by appropriately setting the electrospinning conditions. The electrospun PAA nanofibers were thermally crosslinked via heat treatment and then neutralized from their carboxylic acid form (PAA) to a sodium carboxylate form poly(sodium acrylate) (PSA). The PSA nanofiber meshes exhibited a specific surface area 393 times that of the PSA film. The PSA fiber meshes showed a much faster and higher swelling than its corresponding film, owing to the higher capillary forces from the fibers in addition to the water absorption of the PSA gel itself. The proposed PSA fibers have the potential to be utilized in a new approach to remove excess water from the bloodstream without requiring specialized equipment.

A highly selective and reversible turn-off fluorescent chemosensor for Cu2+ based on electrospun nanofibrous membrane modified with pyrenecarboxaldehyde

A fluorescent nanofibrous membrane (NFM) was successfully fabricated by functionalizing electrospun ethylene-vinyl alcohol copolymer (EVOH) NFM with 4‑aminobenzoic acid (PABA) and 1‑pyrenecarboxaldehyde (Py-CHO) for fast and selective determination of Cu²⁺ in aqueous solution. The effective grafting of PABA and Py-CHO on the surface of EVOH NFM was confirmed by FTIR and XPS spectra. Benefiting from the integrated merits of electrospun EVOH NFM, PABA and Py-CHO, the as-appeared EVOH-PABA-Py NFM exhibited high sensitivity and selectivity towards Cu²⁺ detection. The quenching efficiency was 91.7% when the concentration of Cu²⁺ reached 5 × 10^-3 M, while the detectable fluorescence response of the NFM was still observed when the concentration of Cu²⁺ was 1 × 10^-9 M. The fluorescence quenching caused by Cu²⁺ was hardly affected by other commonly co-existent metal ions. More importantly, the fluorescent NFM exhibited fast response and high reversibility towards Cu²⁺ detection. The "off-on" fluorescence switching process via alternating addition of Cu²⁺ and Na₂EDTA occurred in 3 min, and the quenching efficiency of the NFM kept relatively stable values within 10 cycles. This work may provide a new insight into the development of rapid, portable, stable and reusable fluorescent sensor based on electrospun nanofibers that can satisfy the requirements of practical metal ions detection.

Multifunctional negatively-charged poly (ether sulfone) nanofibrous membrane for water remediation

Multifunctional materials, which can effectively and simultaneously remove various water-soluble contaminants like dyes and heavy metal ions, and separate oil from water, are urgent to meet increasing challenges on wastewater remediation. Herein, a cross-linked poly (acrylic acid) (PAA) modified poly (ether sulfone) nanofibrous membrane (NFM) was fabricated by a facile in-situ pre-reaction followed by electrospinning. The as-prepared NFM showed excellent hydrophilicity and underwater lipophobicity, therefore expressed excellent water permeability with high water flux (about 5142 L m² h^-1). As a result, under solely driven by gravity, the NFM was capable to separate emulsified oil/water emulsion and a wide range of oil/water mixtures. Moreover, repeating separation tests indicated that the NFM had great long-term sustainability even after ten separation cycles. In addition, due to the introduction of PAA and the large surface-to-volume ratio, the NFM also expressed rapid adsorption capacity for cationic dyes as well as heavy metal ions; thus could simultaneously remove these contaminants during the oil/water separation process. Furthermore, the NFM could be also decorated by Ag NPs to endow the membranes with remarkable antibacterial ability against both E. coli and S. aureus. Our findings strongly suggested that the multifunctional NFM may have great potential in treating complicated wastewater.