High performance thin-film nanofibrous composite hemodialysis membranes with efficient middle-molecule uremic toxin removal

Chitosan particles embedded bacterial nanocellulose flat membrane for hemodialysis

The development of bio-based hemodialysis membranes continues to be a challenge. Bacterial nanocellulose (BNC) membranes show potential in hemodialysis but can hardly retain beneficial proteins. Here, chitosan particles/bacterial nanocellulose (CSP/BNC) membranes were designed to efficiently remove uremic toxins and retain beneficial proteins. First, CSPs were synthesized in situ within a BNC membrane by ionic gelation following negative pressure impregnation. Subsequently, these membranes were thoroughly characterized. Compared with the BNC membrane, the pore volume and pore size of the 3 % CSP/BNC membrane decreased by 42.2 % and 32.1 %, respectively. The increased 22.2 times of Young's modulus and 88.9 % of tensile strength in the 3 % CSP/BNC membrane confirmed enhanced mechanical property. The sieving coefficient of bovine serum albumin decreased to 0.05 ± 0.03 in the 3 % CSP/BNC membrane. Moreover, the CSP/BNC membrane exhibited good hemocompatibility and cytocompatibility. The simulated dialysis results showed that the 3 % CSP/BNC membrane exhibited high clearance of urea (16.37 %/cm2) and lysozyme (3.54 %/cm2), while efficiently retaining bovine serum albumin (98.04 %/cm2). This is the first demonstration of the construction of a BNC-based hemodialysis membrane with in situ CSP formation to effectively regulate the pore properties of the membrane, making the CSP/BNC membrane a promising candidate for hemodialysis applications.

Biobased chitosan-derived self-nitrogen-doped porous carbon nanofibers containing nitrogen-doped zeolites for efficient removal of uremic toxins during hemodialysis

Highly efficient adsorbents are needed to remove uremic toxins and reduce the economic and societal burden of the current dialysis treatments in resource-limited environments. In this study, nanostructured porous carbon nanofibers with nitrogen-doped zeolites (NZ-PCNF) were prepared, by electrospinning zeolites with chitosan-poly(ethylene oxide) blends, followed by a one-step carbonization process, without further activation steps or aggressive chemical additives for N-doping. The results showed that N-zeolites were successfully integrated into an ultrafine carbon nanofiber network, with a uniform nanofiber diameter of approximately 25 nm, hierarchical porous structure (micro- and mesopores), and high specific surface area (639.29 m2/g), facilitating uremic toxin diffusion and adsorption. The self-N-doped structure in the NZ-PCNF removed more creatinine (∼1.8 times) than the porous carbon nanofibers when using the same weight of precursor materials. Cytotoxicity and hemolysis tests were performed to verify the safety of NZ-PCNF. This study provides a novel strategy for transforming chitosan-based materials into state-of-the-art porous carbon nanofiber/zeolite self-N-doped composites, affording an efficient bioderived adsorbent for the removal of uremic toxins in patients with chronic kidney disease.

Advances in Enhancing Hemocompatibility of Hemodialysis Hollow-Fiber Membranes

Hemodialysis, the most common modality of renal replacement therapy, is critically required to remove uremic toxins from the blood of patients with end-stage kidney disease. However, the chronic inflammation, oxidative stress as well as thrombosis induced by the long-term contact of hemoincompatible hollow-fiber membranes (HFMs) contribute to the increase in cardiovascular diseases and mortality in this patient population. This review first retrospectively analyzes the current clinical and laboratory research progress in improving the hemocompatibility of HFMs. Details on different HFMs currently in clinical use and their design are described. Subsequently, we elaborate on the adverse interactions between blood and HFMs, involving protein adsorption, platelet adhesion and activation, and the activation of immune and coagulation systems, and the focus is on how to improve the hemocompatibility of HFMs in these aspects. Finally, challenges and future perspectives for improving the hemocompatibility of HFMs are also discussed to promote the development and clinical application of new hemocompatible HFMs.

Graphical Abstract

Electrostatic Repulsive Features of Free-Standing Titanium Dioxide Nanotube-Based Membranes in Biofiltration Applications

This study presents the electrostatic repulsive features of electrochemically fabricated titanium dioxide nanotube (NT)-based membranes with different surface nanomorphologies in cross-flow biofiltration applications while maintaining a creatinine clearance above 90%. Although membranes exhibit antifouling behavior, their blood protein rejection can still be improved. Due to the electrostatically negative charge of the hexafluorotitanate moiety, the fabricated biocompatible, superhydrophilic, free-standing, and amorphous ceramic nanomembranes showed that about 20% of negatively charged 66 kDa blood albumin was rejected by the membrane with ∼100 nm pores. As the nanomorphology of the membrane was shifted from NTs to nanowires by varying fabrication parameters, pure water flux and bovine serum albumin (BSA) rejection performance were reduced, and the membrane did not lose its antifouling behavior. Herein, nanomembranes with different surface nanomorphologies were fabricated by a multi-step anodic oxidation process and characterized by scanning electron microscopy, atomic force microscopy, water contact angle analysis, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The membrane performance of samples was measured in 3D printed polyethylene terephthalate glycol flow cells replicating implantable artificial kidney models to determine their blood toxin removal and protein loss features. In collected urine mimicking samples, creatinine clearances and BSA rejections were measured by the spectrophotometric Jaffe method and high-performance liquid chromatography.

Influence of Modified Carbon Black on Nylon 6 Nonwoven Fabric and Performance as Adsorbent Material

The number of chronic kidney disease (CKD) persons continues to rise in Mexico. They require renal replacement therapy, and in the absence of it, hemodialysis is the major option for their survival. The uremic toxins present in the blood are removed by hemodialysis, which involve membranes. In this study, nonwoven fabrics with modified carbon black nanoparticles in a matrix polymer of Nylon 6 were obtained and evaluated as an adsorbent material of uremic toxins. All nonwoven fabrics were characterized by FTIR, XRD, TGA, SEM, and contact angle measurements and were evaluated as an adsorbent material for the urea toxin and as an albumin retainer. The findings suggest their potential application as a hemodialysis membrane. Nanocomposites had a higher hydrophilic characteristic compared to pure Nylon 6. The average diameter size of the fibers was in the range of 5 to 50 μm. All nanocomposites nonwoven fabrics showed high removal percentages of inulin in a range of 80-85% at 15 min of contact. Most Ny6 Zytel/CB nanocomposites showed a high percentage of urea removal (80 to 90%).

Hierarchically structural layered double oxides with stretchable nanopores for highly effective removal of protein-bound uremic toxins

The global outbreak and prevalence of coronavirus disease 2019 (COVID-19) has triggered an urgent demand for family hemodialysis equipment. It is particularly vital to design and apply superior adsorbents to adsorb toxins for reducing the usage of dialysate. In this work, hierarchically structural MgAl layered double oxides (LDO) with stretchable nanopores were exploited through a facile one-pot trisodium citrate (TSC) assistant hydrothermal reaction followed by calcination treatment for effectively adsorbing protein-bound uremic toxins such as hippuric acid (HA) or indoxyl sulfate (IS). The optimized MgAl LDO possessed flower-like spherical morphology, ultrahigh specific surface area (187.3 m²/g) and uniquely stretchable nanopores, which were more conducive to incorporating anions due to their unique memory effect endowing them with promising adsorption capacities for HA or IS. And the adsorption data could be better conformed to pseudo-second-order kinetic model and Langmuir isotherm determining that the maximum adsorption capacity of HA and IS was 129.8 mg/g and 63.1 mg/g, respectively. Furthermore, the computation of molecular size paired with the analysis of adsorption mechanism accurately revealed that high-efficiency toxin capture was mainly attributed to electrostatic interaction for internal intercalation and surface adsorption. Therefore, the application of such delicate LDO as new premium adsorbent would facilitate the development and popularization of family hemodialysis equipment.

Manufacturing and Separation Characteristics of Hemodialysis Membranes to Improve Toxin Removal Rate

With the recently growing interest in health care, hemodialysis is being performed not only to treat patients with renal disease but also to improve blood circulation. At present, filters used for hemodialysis are manufactured only in certain countries, and all other countries must rely on imports. In this study, polyethersulfone (PES), which has excellent blood compatibility, was used as the main material to develop hemodialysis membranes for hemodialysis filters, and these hemodialysis membranes were prepared by adding a hydrophilic polymer, polyvinylpyrrolidone (PVP), and varying the type of nonsolvent during the manufacturing process to improve the toxin removal rate and biocompatibility. The addition of PVP was confirmed through attenuated total reflection Fourier transform infrared (ATR-FTIR), and the structure of the membranes depending on the nonsolvent was analyzed through scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. The contact angle results indicated that the hydrophilicity of the membrane surface was improved as the concentration of PVP increased. The results of the toxin filtration efficiency experiment using urea, creatinine, and bovine serum albumin (BSA) confirmed removal rates of 58.8% and 56.87%, respectively, and a protein loss of less than 8%. Also, cell viability was over 90% at the PVP concentration of 2% or higher. A preliminary study was conducted on the improvement of toxin filtration efficiency and the development potential of these hemodialysis membranes with excellent biocompatibility.

Dialysis Membranes for Acute Kidney Injury

Mortality and morbidity rates among critically ill septic patients having acute kidney injury (AKI) are very high, considering the total number of deaths after their admission. Inappropriate selection of the type of continuous renal replacement therapy and inadequate therapy become the immediate causes of these issues. Dialysis is a commonly used treatment intended to prolong the life of AKI patients. Dialysis membranes, which are the core of dialysis treatment, must be properly selected to ensure fair treatment to the patients. The accumulation of certain types of molecules must be dealt with using the right membrane. Whether it is low-flux, high-flux, or adsorptive type, the dialysis membrane should be chosen depending on the condition of the patients. The selection of dialysis membranes should also be based on their effect on the treatment outcomes and well-being. All these options are needed to serve the patients of different clinical settings. The use of dialysis membranes is not restricted to conventional haemodialysis, but rather they can be employed in haemoperfusion, haemofiltration, haemodiafiltration, or a combination of any two of them. This review focuses in-depth on different types of dialysis membranes, their characteristics, and approaches in addressing the issues encountered in patients having AKI with sepsis and/or multiorgan failure in intensive care units.

High-performance TFNC membrane with adsorption assisted for removal of Pb(II) and other contaminants

Rapid and thorough removal of heavy metal ions in wastewater is critical for the urgent need of clean water. Herein, we prepared a high-performance thin film nanofibrous composite (TFNC) membrane consisting of a polyacrylonitrile (PAN)-UiO-66-(COOH)₂ composite nanofibrous substrate (CPAN) and a calcium alginate (CaAlg) skin layer. Owing to abundant adsorption sites of UiO-66-(COOH)₂ MOF, the optimal CPAN-2 nanofibrous substrate showed excellent adsorption capacity for lead ions. The maximum Pb²⁺ adsorption capacity of CPAN-2 substrate calculated by Langmuir isotherm model was 254.5 mg/g. Meanwhile, due to the relatively loose structure of CaAlg skin layer, this TFNC membrane showed high water permeate flux about 50 L m^-2h^-1 at 0.1 MPa, and the rejection for dyes was higher than 95%. Therefore, CaAlg/CPAN TFNC membranes were appropriate for dynamic adsorption/filtration to remove Pb²⁺. Compared with original CaAlg/PAN membrane, the optimal CaAlg/CPAN TFNC membrane showed much better ability to treat Pb(II)-containing wastewater and had good recyclability. Most importantly, the CaAlg/CPAN TFNC membrane could treat 7659 L m^-2 wastewater containing single lead ions under WHO drinking water standard, and effectively deal with more simulated lead-containing wastewater. This work could provide a substitutable solution for effective removal of heavy metal ions and other various contaminants in wastewater.

A photo-responsive membrane for tailored drug delivery with spatially and temporally controlled release

Accurate delivery of therapeutics to tumor regions and effective sparing of normal tissue structures are important principles for the treatment of widespread metastases or malignant lesions in close proximity to vital organs. However, the currently available drug delivery techniques do not support precise drug release within the identified disease margins. We propose a tailored drug delivery strategy that utilizes a photo-responsive material in combination with tumor margin imaging for automated and tailored release of therapeutics. As a proof of concept, a poly(ethylene oxide)-b-PSPA (PEO-b-PSPA) diblock copolymer is synthesized by spiropyran (SP) polymerization. A photo-responsive membrane (PRM) is formed and irradiated with light sources of different wavelengths. Switching irradiation between ultraviolet light (UV) and green light (Vis) controls the permeability of the PRM in coincidence with the programmed irradiation patterns. The dynamic process of photo-switchable drug permeation through the PRM is modeled and compared with the experimental results. The strategy of tailored drug release is verified using both regular geometric shapes and metastatic cancer images. The therapeutic effect of this tailored drug release strategy is demonstrated in vitro in human breast cancer cells. Our pilot study implies the technical potential of using photo-responsive carriers for image-guided chemotherapy with precisely controlled drug release patterns.

A Review of Commercial Developments and Recent Laboratory Research of Dialyzers and Membranes for Hemodialysis Application

Dialyzers have been commercially used for hemodialysis application since the 1950s, but progress in improving their efficiencies has never stopped over the decades. This article aims to provide an up-to-date review on the commercial developments and recent laboratory research of dialyzers for hemodialysis application and to discuss the technical aspects of dialyzer development, including hollow fiber membrane materials, dialyzer design, sterilization processes and flow simulation. The technical challenges of dialyzers are also highlighted in this review, which discusses the research areas that need to be prioritized to further improve the properties of dialyzers, such as flux, biocompatibility, flow distribution and urea clearance rate. We hope this review article can provide insights to researchers in developing/designing an ideal dialyzer that can bring the best hemodialysis treatment outcomes to kidney disease patients.

Nano architectured cues as sustainable membranes for ultrafiltration in blood hemodialysis

Membranes with zeolites are encouraging for performing blood dialysis because zeolites can eliminate uremic toxins through molecular sieving. Although the addition of various pore-gen and adsorbent in the membrane can certainly impact the membrane production along with creatinine adsorption, however, it is not directed which pore-gen along with zeolite leads to better performance. The research was aimed at reducing the adsorption of protein-bound and uremic toxins by using mordenite zeolite as an adsorbent while polyethylene glycol and cellulose acetate as a pore generating agent. Membranes were cast by a phase-inversion technique which is cheap and easy to handle as compared to the electro-spinning technique. Through this strategy, the ability to adsorb creatinine and solute rejection percentage were measured and compared against the pristine PSU, when only PEG was used as a pore-modifier and when PEG along with CA was used as a pore-modifier along with a different concentration of zeolite. The experiments revealed that PEG membranes can give a better solute rejection percentage (93%) but with a low creatinine adsorption capacity that is 7654 μg/g and low bio-compatibility (PRT 392 s, HR 0.46%). However, PEG/CA membranes give maximum creatinine adsorption that is 9643 μg/g and also better bio-compatibility (PRT 490 s, HR 0.37%) but with a low BSA rejection (72%) as compared to the pristine PSU and PEG membranes. The present study finds that the concentration of mordenite zeolite affects the membrane performance because its entrapment and large pore size of the membrane decreases solute rejection but increases creatinine uptake level along with the better bio-compatibility.

Fabrication of Zwitterion TiO2 Nanomaterial-Based Nanocomposite Membranes for Improved Antifouling and Antibacterial Properties and Hemocompatibility and Reduced Cytotoxicity

Although zwitterion nanomaterials exhibit outstanding antifouling property, hemocompatibility, and antibacterial activity, their poor solubility in organic solvents limits their practical applications. In the present study, natural lysine (amino acids) was surface-grafted onto one-dimensional (1D) TiO2 nanofibers (NFs) through an epoxy ring opening in which the 3-glycidyloxypropyl (dimethoxy) methyl silane was used as a coupling agent. Chemical binding and morphological studies, such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, were conducted to confirm the successful grafting of lysine onto the TiO2 NFs. The lysine-grafted TiO2 NF-polyethersulfone (PES) membrane induced electrostatic interactions and increased the surface charges from -28 to 16 mV in ζ-potential analysis. The lysine exhibited zwitterion characteristics owing to the presence of amino (cations) and carboxyl (anions) functional groups. Moreover, the modified TiO2-PES zwitterion membranes exhibited good water flux performances compared to the pristine membrane. ZT-4 membrane displayed the highest water fluxand bovine serum albumin (BSA) rejection of 137 ± 1.8 L m-2 h-1 and 94 ± 1%, respectively. The cell viability results revealed that the zwitterion PES membrane had excellent biocompatibility with peripheral blood mononuclear cells. The present work offers a convenient strategy to improve the hydrophilicity, antifouling property, and hemocompatibility of modified TiO2-PES zwitterion membranes for their biomedical and blood-contacting applications such as hemodialysis.

Zeolite Composite Nanofiber Mesh for Indoxyl Sulfate Adsorption toward Wearable Blood Purification Devices

A nanofiber mesh was prepared for the adsorption of indoxyl sulfate (IS), a toxin associated with chronic kidney disease. Removing IS is highly demanded for efficient blood purification. The objective of this study is to develop a zeolite composite nanofiber mesh to remove IS efficiently. Eight zeolites with different properties were used for IS adsorption, where a zeolite with a pore size of 7 Å, H+ cations, and a silica to aluminum ratio of 240 mol/mol exhibited the highest adsorption capacity. This was primarily attributed to its suitable silica to aluminum ratio. The zeolites were incorporated in biocompatible poly (ethylene-co-vinyl alcohol) (EVOH) nanofibers, and a zeolite composite nanofiber mesh was successfully fabricated via electrospinning. The nanofiber mesh exhibited an IS adsorption capacity of 107 μg/g, while the adsorption capacity by zeolite increased from 208 μg/g in powder form to 386 μg/g when dispersed in the mesh. This also led to an increase in cell viability from 86% to 96%. These results demonstrated that this zeolite composite nanofiber mesh can be safely and effectively applied in wearable blood purification devices.

Cellulose acetate-polyvinyl alcohol blend hemodialysis membranes integrated with dialysis performance and high biocompatibility

Hemodialysis considered as therapy of end-stage renal disease (ESRD) for the separation of protein and uremic toxins based on their molecular weights using semi-permeable membranes. Cellulose Acetate (CA) hemodialysis membrane has been widely used in the biomedical field particularly for hemodialysis applications. The main issue of CA membrane is less selectivity and hemocompatibility. In this study, to enhance the filtration capability and biocompatibility of CA hemodialysis membrane modified by using Polyvinyl Alcohol (PVA) and Polyethylene Glycol (PEG) as additives. CA-PVA flat sheet membranes were cast by phase inversion method, and separation was done by dead-end filtration cell. The synthesized membranes were described in terms of chemical structure using Fourier Transform Infrared Spectroscopy (FTIR) and morphology by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), pure water flux, solute permeation, and protein retention. Biocompatibility of the membranes was tested by the platelet adherence, hemolysis ratio, thrombus formation, and plasma recalcification time. SEM images exposed that the CA-PVA membrane has a uniform porous structure. 42.484 L/m² h is the maximum pure water flux obtained. The CA-PVA rejected up to 95% of bovine serum albumin (BSA). A similar membrane separated 93% of urea and 89% of creatinine. Platelet adhesion and hemolysis ratio of casted membranes were less than the pure CA membrane. Increased clotting time and less thrombus formation on the membrane's surface showed that the fabricated membrane is biocompatible. CA-PVA hemodialysis membranes are more efficient than conventional reported hemodialysis membranes. It revealed that CA-PVA is high performing biocompatible hemodialysis membrane.

A review on surface modification methods of poly(arylsulfone) membranes for biomedical applications

Considerable methods have so far been used for the surface modification of biomedical membranes. Several reviews and articles have been published on the improvements achieved in the field of poly(arylsulfone) membranes subjected to various surface modification methods and used in biomedical applications. This review concentrates on the surface modification, biological applications and future perspective of the poly(arylsulfone) biomedical membranes. Different surface modification procedures employed for the poly(arylsulfone) membranes have been classified, studied and compared. Diverse surface modification techniques include surface coating, chemical modification and immobilization/cross-linking, grafting, surface zwitterionicalization, mussel-inspired coating and layer-by-layer assembly. Furthermore, we review the recent research studies performed on the surface modification of the poly(arylsulfone) biomedical membranes. Meanwhile, the properties of biomedical membranes are also discussed in each section. At last, the future perspective and challenges of the strategies utilized for the surface modification of poly(arylsulfone) biomedical membranes are presented.

A novel anticoagulant affinity membrane for enhanced hemocompatibility and bilirubin removal

Affinity membrane is widely employed to promote specific adsorption of toxins and reduce the blood purification therapeutic time. However, it suffers from insufficient toxin binding and low hemocompatibility. Herein, a novel anticoagulant affinity membrane (AAM) was developed to clear bilirubin from human blood in a pore-flow-through way. Firstly, a nylon net membrane with a regularly arranged pore as the matrix was coated with poly(pyrrole-3-carboxylic acid) via chemical vapor deposition (CVD) method. Then, poly(L-arginine) (PLA) as a highly specific ligand of bilirubin, was immobilized onto the surface of the composited membrane after the modification of heparin. Owing to the 3-dimensional molecular architecture of PLA, up to 86.1 % of bilirubin was efficiently cleared. Besides, the AAM exhibited effective anticoagulant activity in the measurement of clotting time, with suppressed thrombus formation, low hemolysis ratio, minimized platelet and leukocyte adhesion, and excellent biosafety. Therefore, the AAM has enormous potential in blood purification therapy for enhancing hemocompatibility and bilirubin removal.

Case studies of clinical hemodialysis membranes: influences of membrane morphology and biocompatibility on uremic blood-membrane interactions and inflammatory biomarkers

End stage renal disease (ESRD) patients depend on hemodialysis (HD) as a life-sustaining treatment, but HD membrane properties play a critical role in blood activation during HD and can lead to severe patient outcomes. This study reports on a series of investigations on the common clinical HD membranes available in Canadian hospitals to explore the key reasons behind their susceptibility to blood activation and unstable cytokine. Clinical HD membranes composed of cellulose triacetate (CTA) and polyvinylpyrrolidone: polyarylethersulfone (PAES: PVP) were thoroughly characterized in terms of morphology and chemical composition. Membrane-surface interactions with uremic blood samples after HD treatment were probed using Fourier Transform Infra-Red (FTIR) and Raman spectroscopic techniques in order to understand changes in chemistry on membrane fibers. In addition, as part of this innovative study, we utilized Molecular Modeling Docking to examine the interactions of human blood proteins and membrane models to gain an in-depth understanding of functional group types responsible for perceived interactions. In-vitro adsorption of fibrinogen on different clinical HD membranes was compared at similar clinical operating conditions. Samples were collected from dialysis patients to ascertain the extent of inflammatory biomarkers released, before, during (30 and 90 min) and after dialysis (4 h). Collected blood samples were analyzed using Luminex assays for the inflammatory biomarkers of Serpin/Antithrombin-III, Properdin, C5a, 1L-1α, 1L-1β, TNF-α, IL6, and vWF. We have likewise incubated uremic blood in vitro with the two membrane materials to determine the impact that membrane materials pose in favor of activation away from the hydrodynamics influences. The results of our morphological, chemical, spectroscopic, and in vitro incubation analyses indicate that CTA membranes have a smoother surface and higher biocompatibility than PAES: PVP membranes, however, it has smaller pore size distribution, which results in poor clearance of a broad spectrum of uremic toxins. However, the rougher surface and greater hydrophilicity of PAES: PVP membranes increases red blood cell rupture at the membrane surface, which promotes protein adsorption and biochemical cascade reactions. Molecular docking studies indicate sulfone functional groups play an important role in the adsorption of proteins and receptors. PAES: PVP membranes result in slower but greater adsorption of fibrinogen, but are more likely to experience reversible and irreversible fouling as well as backfiltration. Our major finding is that a single dialysis session, even with a more biocompatible membrane such as CTA, increases the levels of complement and inflammation factors, but to a milder extent than dialysis with a PAES membrane.

Hierarchical Surface Architecture of Hemodialysis Membranes for Eliminating Homocysteine Based on the Multifunctional Role of Pyridoxal 5'-phosphate

Patients with end-stage renal disease are prone to developing a complication of hyperhomocysteinemia, manifesting as an elevation of the homocysteine (Hcy) concentration in human plasma. However, Hcy as a protein-bound toxin is barely removed by conventional hemodialysis membranes. Here, we report a novel hemodialysis membrane by preparing a bioactive coating of pyridoxal 5'-phosphate (PLP) and adding biocompatible hyperbranched polyglycerol (HPG) brushes to achieve Hcy removal. The dip-applied PLP coating, a coenzyme with a role in Hcy metabolism, dramatically promoted a decrease in the Hcy concentration in human plasma. Moreover, the aldehyde group of PLP had an intrinsic chemical reactivity toward the terminal amino group to immobilize the HPG brushes on the hemodialysis membrane surface. The hierarchical PLP-HPG layer-functionalized membranes had a high efficacy for eliminating Hcy, with a concentration from the initial stage of 150 μmol/L reduced to a nearly normal level of 20 μmol/L in simulated dialysis. By analyzing the impact of HPG brushes with various chain lengths, we found that HPG brushes with a medium length enabled the PLP coating with the bioactive function of Hcy conversion to additionally protect Hcy-attacked target cells by providing excellent hydrophilicity and a dense enough chain volume overlap of the hyperbranched architecture. Simultaneously, the densely packed HPG brushes generated a maximal steric and hydration barrier that significantly improved biofouling resistance against blood proteins. The optimally functionalized membranes showed a clearance of 83.1% urea and 49.6% lysozyme and a rejection of 96.0% bovine serum albumin. The diversely functionalized PLP-HPG layers demonstrate a potential route for a more integrated hemodialysis membrane that can cope with the urgent issue of hyperhomocysteinemia in clinical hemodialysis therapy.

Transparent Polyurethane Nanofiber Air Filter for High-Efficiency PM2.5 Capture

Fine particulate matter (PM) has seriously affected human life, such as affecting human health, climate, and ecological environment. Recently, many researchers use electrospinning to prepare nanofiber air filters for effective removal of fine particle matter. However, electrospinning of the polymer fibers onto the window screen uniformly is only achieved in the laboratory, and the realization of industrialization is still very challenging. Here, we report an electrospinning method using a rotating bead spinneret for large-scale electrospinning of thermoplastic polyurethane (TPU) onto conductive mesh with high productivity of 1000 m²/day. By changing the concentration of TPU in the polymer solution, PM2.5 removal efficiency of nanofiber-based air filter can be up to 99.654% with good optical transparency of 60%, and the contact angle and the ventilation rate of the nanofiber-based air filter is 128.5° and 3480 mm/s, respectively. After 10 times of filtration, the removal efficiency is only reduced by 1.6%. This transparent air filter based on TPU nanofibers has excellent filtration efficiency and ventilation rate, which can effectively ensure indoor air quality of the residential buildings.

Carbon Nanotube/Conducting Polymer Hybrid Nanofibers as Novel Organic Bioelectronic Interfaces for Efficient Removal of Protein-Bound Uremic Toxins

Protein-bound uremic toxins (PBUTs) can cause noxious effects in patients suffering from renal failure as a result of inhibiting the transport of proteins and inducing their structural modification. They are difficult to remove through standard hemodialysis (HD) treatment. Herein, we report an organic bioelectronic HD device system for the effective removal of PBUTs through electrically triggered dissociation of protein-toxin complexes. To prepare this system, we employed electrospinning to fabricate electrically conductive quaternary composite nanofiber mats-comprising multiwalled carbon nanotubes (MWCNTs), poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), poly(ethylene oxide) (PEO), and (3-glycidyloxypropyl)trimethoxysilane (GOPS)-on conventional polyethersulfone (PES) dialysis membranes. These composite nanofiber platforms exhibited (i) long-term water resistance (due to cross-linking among PSS, PEO, and GOPS), (ii) high adhesion strength on the PES membrane (due to GOPS functioning as an adhesion promoter), (iii) enhanced electrical properties [due to the MWCNTs and PEDOT:PSS promoting effective electrical stimulation (ES) operation in devices containing bioelectronic interfaces (BEI)], and (iv) good anticoagulant ability and negligible hemolysis of red blood cells. We employed this organic BEI electronic system as a novel single-membrane HD device to study the removal efficiency of four kinds of uremic toxins [p-cresol (PC), indoxyl sulfate, and hippuric acid as PBUTs; creatinine as a non-PBUT] as well as the effects of ES on lowering the protein binding ratio. Our organic BEI devices provided a high rate of removal of PC with low protein loss after 4 h of a simulated dialysis process. It also functioned with low complement activation, low contact activation levels, and lower amounts of platelet adsorption, suggesting great suitability for use in developing next-generation bioelectronic medicines for HD.

Impact of three-dimensional tortuous pore structure on polyethersulfone membrane morphology and mass transfer properties from a manufacturing perspective

We examined typical commercial poly(ethersulfone) (PESf) hemodialysis and hemoconcentration membranes successfully used in manufacturing, and employed scanning probe microscope (SPM) to achieve a structural observation of the pores in the inner membrane surfaces, as well as measure the pore diameters and their distribution, verifying the relationship between the typical mass transfer properties. We focused on the differences between the PESf membranes which were expected to further improve the advanced pore structure control and functional design for various medical uses. The three-dimensional tortuous capillary pores on the inner surface of hollow fiber hemodialysis and hemoconcentrator membranes were investigated using dynamic force microscopy (DFM), and the pore diameter and distribution were measured through a line analysis. Compared with PUREMA-A, PES-Sα hemodialysis membranes have smaller three-dimensional tortuous capillary pore diameters and pore areas, as well as a smaller pore diameter distribution and pore area distribution, which make the accurate measurements of the pore diameter using FE-SEM impossible. These PESf membranes are almost the same in pure water permeability, but greatly differ in pore diameter and pore diameter distribution. By comparing and verifying as above, we may gain insight into the flexibility, versatility, and superior structural and functional controllability of PESf membrane pore structures, which could advance the development of pore structure control. Pending issues include the fact that, using a line analysis software of SPM devices, it is very difficult to measure hundred pores which clearly reflects the poor quality of pore size distributions obtained in this study, measurement accuracy must be improved further.