Overview of PES biocompatible/hemodialysis membranes: PES–blood interactions and modification techniques

Preparation of an anticoagulant polyethersulfone membrane by immobilizing FXa inhibitors with a polydopamine coating

Anticoagulation treatment for patients with high bleeding risk during hemodialysis is challenging. Contact between the dialysis membrane and the blood leads to protein adsorption and activation of the coagulation cascade reaction. Activated coagulation Factor X (FXa) plays a central role in thrombogenesis, but anticoagulant modification of the dialysis membrane is rarely targeted at FXa. In this study, we constructed an anticoagulant membrane using the polydopamine coating method to graft FXa inhibitors (apixaban and rivaroxaban) on the membrane surface. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the membranes. The apixaban- and rivaroxaban-modified membranes showed lower water contact angles, decreased albumin protein adsorption, and suppressed platelet adhesion and activation compared to the unmodified PES membranes. Moreover, the modified membranes prolonged the blood clotting times in both the intrinsic and extrinsic coagulation pathways and inhibited FXa generation and complement activation, which suggested that the modified membrane enhanced biocompatibility and antithrombotic properties through the inhibition of FXa. Targeting FXa to design antithrombotic HD membranes or other blood contact materials might have great application potential.

Simulation-based assessment of zwitterionic pendant group variations on the hemocompatibility of polyethersulfone membranes

In the realm of hemodialysis, Polyethersulfone (PES) membranes dominate due to their exceptional stability and mechanical properties, capturing 93% of the market. Despite their widespread usage, the hydrophobic nature of PES introduces complications in hemodialysis, potentially leading to severe adverse reactions in patients with end-stage renal disease (ESRD) through protein fouling. Addressing this issue, our study focused on enhancing hemocompatibility by modifying PES surfaces with zwitterionic materials, known for their hydrophilicity and biological membrane compatibility. We investigated the functionalization of PES membranes utilizing various zwitterions in different ratios. Utilizing molecular docking, we examined the interactions of three zwitterionic ligands-carboxybetaine methacrylate (CBMA), sulfobetaine methacrylate (SBMA), and (2-(methacryloyloxy)ethyl) phosphorylcholine (MPC)-with human serum proteins. Our analysis revealed that a 1:1 ratio of phosphobetaine and sulfobetaine exhibits the lowest affinity energy towards serum proteins, denoting an optimal hemocompatibility without the limitations associated with increased zwitterion ratios. This pivotal finding offers a new pathway for developing more efficient and safer hemodialysis membranes, promising improved care for ESRD patients.

Supplementary information

The online version contains supplementary material available at 10.1186/s42252-024-00062-6.

Comparative Study of Autogenic and Allogenic Chondrocyte Transplants on Polyethersulfone Scaffolds for Cartilage Regeneration

The aim of this study was to evaluate the chondrogenic potential of chondrocyte transplants cultured in vitro on polyethersulfone (PES) membranes. Forty-eight rabbits (96 knee joints) were used in the project. The synthetic, macro-porous PES membranes were used as scaffolds. Fragments of articular cartilage were harvested from non-weight-bearing areas of the joints of the animals. Chondrocytes were isolated and then cultivated on PES scaffolds for 3 weeks. The animals were divided into four groups. All the lesions in the articular cartilage were full thickness defects. In Group I, autogenic chondrocytes on PES membranes were transplanted into the defect area; in Group II, allogenic chondrocytes on PES membranes were transplanted into the defect area; in Group III, pure PES membranes were transplanted into the defect area; and in Group IV, lesions were left untreated. Half of the animals from each group were terminated after 8 weeks, and the remaining half were terminated 12 weeks postoperatively. The samples underwent macroscopic evaluation using the Brittberg scale and microscopic evaluation using the O'Driscoll scale. The best regeneration was observed in Groups II and I. In Group I, the results were achieved with two surgeries, while in Group II, only one operation was needed. This indicates that allogenic chondrocytes do not require two surgeries, highlighting the importance of further in vivo studies to better understand this advantage. The success of the study and the desired properties of PES scaffolds are attributed mainly to the presence of sulfonic groups in the structure of the material. These groups, similar to chondroitin sulfate, which naturally occurs in hyaline cartilage, likely enable mutual affinity between the scaffold and cells and promote scaffold colonization by the cells.

Preparation and Hemocompatibility of Novel Antioxidant-Modified Polyethersulfone Membranes as Red Blood Cell Thrombosis Inhibitors

The contact between the dialysis membrane and blood can induce oxidative stress and thrombosis, causing oxidative organ damage and impaired toxin clearance. To date, the selection of anticoagulants has focused on mechanisms inhibiting white, but not red (erythrocytes) thrombus formation. In the present study, polyethersulfone (PES) membranes are modified with the antioxidant drug tiopronin; the physicochemical properties and dialysis performance of the Tio-PES membranes are evaluated. The effects on erythrocyte thrombosis are evaluated in terms of erythrocyte morphology, prothrombotic properties (adhesion, aggregation, viscosity, sedimentation, and hemolysis), and fibrinogen (FIB)-erythrocyte interactions. The regular anticoagulant and antiplatelet properties are also assessed. Superoxide dismutase, malondialdehyde, plasma protein, and complement C3a are further determined. Finally, the biosafety of the Tio-PES membranes is evaluated both in vitro and in vivo. The Tio-PES membranes exhibit excellent physicochemical properties and improved dialysis performance. It is found that the Tio-PES membranes stabilize erythrocyte morphology, reduce erythrocyte prothrombotic properties, decrease FIB adsorption, and prevent red thrombus formation. In addition, the Tio-PES membranes exhibit excellent antioxidant properties and show biosafety in primary toxicity studies. Thus, Tio-PES membranes hold promise as novel, safe, and effective dialysis materials for potential clinical application.

Aminolysis-Based Zwitterionic Immobilization on Polyethersulfone Membranes for Enhanced Hemocompatibility: Experimental, Computational, and Ex Vivo Investigations

Dialysis membranes are not hemocompatible with human blood, as the patients are suffering from the blood-membrane interactions' side effects. Zwitterionic structures have shown improved hemocompatibility; however, their complicated synthesis hinders their commercialization. The goal of the study is to achieve fast functionalization for carboxybetaine and sulfobetaine zwitterionic immobilization on PES membranes while comparing the stability and the targeted hemocompatibility. The chemical modification approach is based on an aminolysis reaction. Characterization, computational simulations, and clinical analysis were conducted to study the modified membranes. Atomic force microscopy (AFM) patterns showed a lower mean roughness for carboxybetaine-modified (6.3 nm) and sulfobetaine-modified (7.7 nm) membranes compared to the neat membrane (52.61 nm). The pore size of the membranes was reduced from values above 50 nm for the neat PES to values between 2 and 50 nm for zwitterionized membranes, using Brunauer-Emmett-Teller (BET) analysis. More hydrophilic surfaces led to a growth equilibrium water content (EWC) of nearly 6% for carboxybetaine and 10% for sulfobetaine-modified membranes. Differential scanning calorimetry (DSC) measurements were 12% and 16% stable water for carboxybetaine- and sulfobetaine-modified membranes, respectively. Sulfobetaine membranes showed better compatibility with blood with respect to C5a, IL-1a, and IL-6 biomarkers. Aminolysis-based zwitterionization was found to be suitable for the improvement of hemodialysis membranes. The approach introduced in this paper could be used to modify the current dialysis membranes with minimal change in the production facilities.

Polyethersulfone Polymer for Biomedical Applications and Biotechnology

Polymers stand out as promising materials extensively employed in biomedicine and biotechnology. Their versatile applications owe much to the field of tissue engineering, which seamlessly integrates materials engineering with medical science. In medicine, biomaterials serve as prototypes for organ development and as implants or scaffolds to facilitate body regeneration. With the growing demand for innovative solutions, synthetic and hybrid polymer materials, such as polyethersulfone, are gaining traction. This article offers a concise characterization of polyethersulfone followed by an exploration of its diverse applications in medical and biotechnological realms. It concludes by summarizing the significant roles of polyethersulfone in advancing both medicine and biotechnology, as outlined in the accompanying table.

Synthesis and Characterization of Phenazine-Based Redox Center for High-Performance Polymer Poly(aryl ether sulfone)-5,10-Diphenyl-dihydrophenazine

Phenazine-based redox-active centers are capable of averting chemical bond rearrangements by coupling during the reaction process, leading to enhanced stabilization of the material. When introduced into a high-performance polymer with excellent physicochemical properties, they can be endowed with electrochemical properties and related prospective applications while maintaining the capabilities of the materials. In this study, a facile C-N coupling method was chosen for the synthesis of serial poly(aryl ether sulfone) materials containing phenazine-based redox-active centers and to explore their electrochemical properties. As expected, the cyclic voltammetry curves of PAS-DPPZ-60, which basically overlap after thousands of cycles, indicate the stability of the electrochemical properties. As an electrochromic material, the transmittance change in PAS-DPPZ-60 exhibits only a slight attenuation after as long as 600 cycles. Meanwhile, as an organic battery cathode material, PAS-DPPZ has a theoretical specific capacity of 126 mAh g-1, and the capacity retention rate is 82.6% after 100 cycles at a 0.1 C current density. The perfect combination of advantageous features between phenazine and poly(aryl ether sulfone) is considered to be the reason for the favorable electrochemical performance of the material series.

Immobilization of carbonic anhydrase on modified PES membranes for artificial lungs

The introduction of carbonic anhydrase (CA) onto an extracorporeal membrane oxygenation (ECMO) membrane can improve the permeability of carbon dioxide (CO2). However, existing CA-grafting methods have limitations, and the hemocompatibility of current substrate membranes of commercial ECMO is not satisfactory. In this study, a 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC)/N-hydroxy succinimide (NHS) activation method is adopted to graft CA with CO2-catalyzed conversion activity onto a polyethersulfone (PES) membrane, which is prepared by a phase inversion technique after in situ crosslinking polymerization of 1-vinyl-2-pyrrolidone (VP) and acrylic acid (AA) in PES solution. The characterization results reveal that CA has been grafted onto the modified PES membrane successfully and exhibits catalytic activity. The kinetic parameters of esterase activity verify that the grafted amount of active CA increases with an increase in the concentration of the CA incubation solution. The CA-grafted membrane (CA-M) can accelerate the conversion of bicarbonate to CO2 in water and blood, which demonstrates the special catalytic activity towards bicarbonate of CA. Finally, blood compatibility tests prove that the CA-M does not lead to hemolysis, shows suppressed protein adsorption and increased coagulation time, and is suitable for application in ECMO. This work demonstrates a green and efficient method for preparing bioactive materials and has practical guiding significance for subsequent pulmonary membrane research and ECMO applications.

Sulfonated Polyether Ketone Membranes Embedded with Nalidixic Acid-An Emerging Controlled Drug Releaser

The effective administration of medication has advanced over decades, but the medical community still faces significant demand. Burst release and inadequate assimilation are major drawbacks that affect wound healing efficiency, leading to therapy failure. The widespread application of polymers in biomedical research is significant. The polyether ether ketone (PEEK) family is known for its biocompatibility, inertness, and semi-crystalline thermoplastic properties. In our present studies, we have chosen a member of this family, polyether ketone (PEK), to explore its role as a drug carrier. The PEK backbone was subjected to sulfonation to increase its hydrophilicity. The response surface methodology (RSM) was used to optimize the sulfonation process based on the time, degree of sulfonation, and temperature. The PEK polymer was sulfonated using sulfuric acid at 150 °C for 6 h; back titration was performed to quantify the degree of sulfonation, with 69% representing the maximum sulfonation. SPEK and nalidixic sodium salt were dissolved in dichloroacetic acid to create a thin membrane. The physiological and morphological properties were assessed for the SPEK membrane. The studies on drug release in distilled water and a simulated body fluid over the course of 24 h revealed a controlled, gradual increase in the release rate, correlating with a mathematical model and demonstrating the zero-order nature of the drug release. Hemolysis on the SPEK membrane revealed lower toxicity. The SPEK membrane's biocompatibility was established using in vitro cytotoxicity tests on the Vero (IC50: 137.85 g/mL) cell lines. These results confirm that the SPEK membranes are suitable for sustained drug release.

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

Scaffolds for Cartilage Tissue Engineering from a Blend of Polyethersulfone and Polyurethane Polymers

In recent years, one of the main goals of cartilage tissue engineering has been to find appropriate scaffolds for hyaline cartilage regeneration, which could serve as a matrix for chondrocytes or stem cell cultures. The study presents three types of scaffolds obtained from a blend of polyethersulfone (PES) and polyurethane (PUR) by a combination of wet-phase inversion and salt-leaching methods. The nonwovens made of gelatin and sodium chloride (NaCl) were used as precursors of macropores. Thus, obtained membranes were characterized by a suitable structure. The top layers were perforated, with pores over 20 µm, which allows cells to enter the membrane. The use of a nonwoven made it possible to develop a three-dimensional network of interconnected macropores that is required for cell activity and mobility. Examination of wettability (contact angle, swelling ratio) showed a hydrophilic nature of scaffolds. The mechanical test showed that the scaffolds were suitable for knee joint applications (stress above 10 MPa). Next, the scaffolds underwent a degradation study in simulated body fluid (SBF). Weight loss after four weeks and changes in structure were assessed using scanning electron microscopy (SEM) and MeMoExplorer Software, a program that estimates the size of pores. The porosity measurements after degradation confirmed an increase in pore size, as expected. Hydrolysis was confirmed by Fourier-transform infrared spectroscopy (FT-IR) analysis, where the disappearance of ester bonds at about 1730 cm−1 wavelength is noticeable after degradation. The obtained results showed that the scaffolds meet the requirements for cartilage tissue engineering membranes and should undergo further testing on an animal model.

Surface Engineering of a Bioartificial Membrane for Its Application in Bioengineering Devices

Membrane technology is playing a crucial role in cutting-edge innovations in the biomedical field. One such innovation is the surface engineering of a membrane for enhanced longevity, efficient separation, and better throughput. Hence, surface engineering is widely used while developing membranes for its use in bioartificial organ development, separation processes, extracorporeal devices, etc. Chemical-based surface modifications are usually performed by functional group/biomolecule grafting, surface moiety modification, and altercation of hydrophilic and hydrophobic properties. Further, creation of micro/nanogrooves, pillars, channel networks, and other topologies is achieved to modify physio-mechanical processes. These surface modifications facilitate improved cellular attachment, directional migration, and communication among the neighboring cells and enhanced diffusional transport of nutrients, gases, and waste across the membrane. These modifications, apart from improving functional efficiency, also help in overcoming fouling issues, biofilm formation, and infection incidences. Multiple strategies are adopted, like lysozyme enzymatic action, topographical modifications, nanomaterial coating, and antibiotic/antibacterial agent doping in the membrane to counter the challenges of biofilm formation, fouling challenges, and microbial invasion. Therefore, in the current review, we have comprehensibly discussed different types of membranes, their fabrication and surface modifications, antifouling/antibacterial strategies, and their applications in bioengineering. Thus, this review would benefit bioengineers and membrane scientists who aim to improve membranes for applications in tissue engineering, bioseparation, extra corporeal membrane devices, wound healing, and others.

In-situ synchrotron quantitative analysis of competitive adsorption tendency of human serum proteins on polyether sulfone clinical hemodialysis membrane

Comprehensive understanding of protein adsorption phenomenon on membrane surface during hemodialysis (HD) is one of the key moments for development of hemocompatible HD membrane. Though many mechanisms and kinetics of protein adsorption on some surface have been studied, we are still far away from complete understanding and control of this process, which results in a series of biochemical reactions that causes severe complications with health and even the death among HD patients. The aim of this study is to conduct quantitative analysis of competitive adsorption tendency of human serum protein on polyether sulfone (PES) clinical dialysis membrane. In situ synchrotron radiation micro-computed tomography (SR-µCT) imaging available at the Canadian Light Source (CLS) was conducted to assess human serum proteinbinding and undertake the corresponding quantitative analysis.The competitive adsorption of Human protein albumin (HSA), fibrinogen (FB) and transferrin (TRF) were tested from single and multiple protein solution. Furthermore, in-vitro human serum protein adsorption on clinical dialyzers was investigated using UV-Visible to confirm the competitive adsorption tendency. Results showed that when proteins were adsorbed from their mixture, FB content (among proteins) in the adsorbed layer increased from 3.6% mass (content in the initial solution) to 18% mass and 12%, in case of in situ quantitative and invitro analysis, respectively. The increase in FB content was accompanied by the decrease in the HSA content, while TRF remained on approximately on the same level for both cases. Overall, the percentage of HSA adsorption ratio onto the HD membrane has dropped approximately 10 times when HSA was adsorbed in competition with other proteins, compared to the adsorption from single HSA solution. The substitution of HSA with FB was especially noticeable when HSA adsorption from its single solution was compared with the case of the protein mixture. Moreover, SR-µCT has revealed that FB when adsorbed from a protein mixture solution is located predominately in the middle of the membrane, whereas the peak of the distribution is shifted to membrane bottom layers when adsorption from FB single solution takes place. Results showed that HSA FB and TRF adsorption behavior observations are similar on both in-situ small scale and clinical dialyzer of the PES membrane.

Selectively mixed matrix hemodialysis membrane for adequate clearance of p-cresol by the incorporation of imprinted zeolite

The adequacy in uremic toxin removal upon hemodialysis treatment is essential in patients with kidney failure diseases as poor removal leads to heart failure, hypertension, and stroke. The combination of adsorption and diffusion processes has become very advantageous for hemodialysis membranes. By this mechanism, water-soluble uremic toxins (WSUTs) and protein-bounded uremic toxins (PBUTs) could be removed at one time. Therefore, this study aimed to develop a novel imprinted zeolite by p-cresol (IZC) and then incorporated it into polyethersulfone (PES) and poly(vinyl pyrrolidone) (PVP) to produce hollow fiber mixed matrix membrane (HF-MMM). The IZC proved to be sensitive in attracting the adsorbate, classifying it as having a strong adsorption behavior. Accordingly, IZC is very promising to be applied as an adsorbent in the hemodialysis treatment. In this study, IZC as p-cresol's adsorbent was incorporated into a PES-based polymeric membrane with a small addition of PVP to produce HF-MMM using a dry/wet spinning process. The effect of air gap distance between the spinneret and coagulant bath and percentage loading for PES, PVP, and IZC were studied and optimized to obtain the best performance of HF-MMM. The 40 cm of air gap distance, 16 wt% of PES, 2 wt% of PVP, and 1 wt% of IZC loading were able to produce a superior hemodialysis membrane. These optimized parameters showed sufficient uremic toxin removal, i.e., 60.74% of urea, 52.35% of p-cresol in the phosphate buffer saline solution, and 66.29% of p-cresol in bovine serum albumin solution for 4 h permeation using the dialysis system. These HF-MMMs also achieved pure water flux of 67.57 L m^-2 h^-1 bar^-1 and bovine serum albumin rejection of 95.05%. Therefore, this membrane has proven to be able to clean up WSUT and PBUT through a one-step process. Moreover, as compared to the neat PES membrane, MMM was able to remove p-cresol at 186.22 times higher capability.

Investigation on Human Serum Protein Depositions Inside Polyvinylidene Fluoride-Based Dialysis Membrane Layers Using Synchrotron Radiation Micro-Computed Tomography (SR-μCT)

Hemodialysis (HD) membrane fouling with human serum proteins is a highly undesirable process that results in blood activations with further severe consequences for HD patients. Polyvinylidene fluoride (PVDF) membranes possess a great extent of protein adsorption due to hydrophobic interaction between the membrane surface and non-polar regions of proteins. In this study, a PVDF membrane was modified with a zwitterionic (ZW) polymeric structure based on a poly (maleic anhydride-alt-1-decene), 3-(dimethylamino)-1-propylamine derivative and 1,3-propanesultone. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and zeta potential analyses were used to determine the membrane's characteristics. Membrane fouling with human serum proteins (human serum albumin (HSA), fibrinogen (FB), and transferrin (TRF)) was investigated with synchrotron radiation micro-computed tomography (SR-μCT), which allowed us to trace the protein location layer by layer inside the membrane. Both membranes (PVDF and modified PVDF) were detected to possess the preferred FB adsorption due to the Vroman effect, resulting in an increase in FB content in the adsorbed protein compared to FB content in the protein mixture solution. Moreover, FB was shown to only replace HSA, and no significant role of TRF in the Vroman effect was detected; i.e., TRF content was nearly the same both in the adsorbed protein layer and in the protein mixture solution. Surface modification of the PVDF membrane resulted in increased FB adsorption from both the protein mixture and the FB single solution, which is supposed to be due to the presence of an uncompensated negative charge that is located at the COOH group in the ZW polymer.

Recent advancement challenges with synthesis of biocompatible hemodialysis membranes

The focus of this study is to enhance the protein fouling resistance, hydrophilicity, biocompatibility, hemocompatibility and ability of the membranes and to reduce health complications like chronic pulmonary disease, peripheral vascular disease, cerebrovascular disease, and cardiovascular disease after dialysis, which are the great challenges in HD applications. In the current study, the PSF-based dialysis membranes are studied broadly. Significant consideration has also been provided to membrane characteristics (e.g., flowrate coefficient, solute clearance characteristic) and also on commercially available polysulfone HD membranes. PSF has gained a significant share in the development of HD membranes, and continuous improvements are being made in the process to make high flux PSF-based dialysis membranes with enhanced biocompatibility and improved protein resistance ability as the major issue in the development of membranes for HD application is biocompatibility. There has been a great increase in the demand for novel biocompatible membranes that offer the best performances during HD therapy, for example, low oxidative stress and low change ability of blood pressure.

Preparation and blood compatibility of polyethersulfone dialysis membrane modified by apixaban as coagulation factor Xa inhibitor

Blood purification therapy is widely used in the treatment of critically ill patients. However, most dialysis membranes are prone to thrombosis. Activated coagulation factor X (FXa) functions at the intersection of intrinsic, extrinsic, and common coagulation pathways and plays a central role in thrombogenesis. To date, few dialysis membranes that directly inhibit FXa have been reported. We modified a polyethersulfone(PES) membrane using apixaban as an FXa inhibitor and investigated the performance of this membrane (AMPES). The contact angle of the modified membrane was reduced. PWF and retention rates of BSA were increased, demonstrating good hydrophilicity and dialysis performance. Albumin adsorption was reduced from 141.8 ± 15.5 to 114.1 ± 6.9 μg cm^-2. Reduced protein adsorption, especially targeted anti-FXa effect, inhibited the activation of intrinsic, extrinsic, and common coagulation pathways, as evidenced by significant prolongations of activated partial thromboplastin time, prothrombin time, and thrombin time by 145.04, 46.84 and 11.46 s, respectively. Furthermore, we determined the FXa concentration of each group, and found that the modified membrane had better anticoagulant performance through the inhibition of FXa. Favorable antiplatelet activity was also demonstrated. Thromboelastogram was used to comprehensively evaluate the anticoagulant and antithrombotic activities of the modified membrane. The R value was increased by 43.1 min, while the reduction in α angle was 42.5°. The coagulation comprehensive index reduction was 34.3. In addition, C3a and C5a were decreased by 15.3 % and 30.4 %, respectively. Furthermore, in vitro cytotoxicity and erythrocyte stability testing as well as in vivo murine experiments demonstrated the biosafety of the modified membrane. These results indicate that the AMPES dialysis membrane has an excellent potential for clinical applications.

Dual Optimized Sulfonated Polyethersulfone and Functionalized Multiwall Carbon Tube Based Composites High Fouling Resistance Membrane for Protein Separation

Commercial grade sulfonated-Polyethersulfone (S-PES) and functionalized multiwall carbon nanotube (f-MWCNT)/polyvinylpyrrolidone (PVP) nanocomposites (NCs) were used to enhance and optimize the antifouling, protein resistance and protein separation properties of the S-PES ultrafiltration membranes. The polarities of sulfonic groups of S-PES, carbonyl carbon of pyrrolidone, hydroxyl and carboxyl groups of f-MWCNT in the membrane composition helped to strongly bind each other through hydrogen bonding, as shown by Fourier-transform infrared spectroscopy (FTIR). These binding forces greatly reduced the leaching of NCs and developed long finger-like projection, as confirmed by elution ratio and cross-sectional studies of the membranes via field emission scanning electron microscope (FESEM). The contact angle was reduced up to 48% more than pristine PES. Atomic force microscopy (AFM) was employed to study the various parameters of surface roughness with 3d diagrams, while grain analysis of membrane surface provided a quantitative estimation about volume, area, perimeter, length, radius and diameter. The NCs/S-PES enhanced the flux rate with an impressive (80–84%) flux recovery ratio and (58–62%) reversible resistance (R_r) value in situ, with 60% and 54.4% lesser dynamic and static protein adsorption. The best performing membrane were reported to remove 31.8%, 66.3%, 83.6% and 99.9% for lysozyme-(14.6 kDa), trypsin-(20 kDa), pepsin-(34.6 kDa) and bovine serum albumin (BSA-66 kDa), respectively.

Insights from molecular dynamics simulations of albumin adsorption on hydrophilic and hydrophobic surfaces

Protein adsorption at the surface affects the material biocompatibility directly as it is the first reaction that happens when a foreign material comes in contact with blood. In this study, the mechanism of albumin adsorption on hydrophilic and hydrophobic surfaces is investigated. Although it is studied extensively and has been of keen interest for decades, the adsorptive nature of albumin is still not fully understood with contradicting reported studies. This problem results from previous works focusing on mostly qualitative and quantitative adsorption properties of albumin, rather than the specific interaction mechanisms. The variable local surface properties across albumin can significantly impact adsorption and must be explored. In this work, the effect of hydration is found to significantly increase adsorption with minor reductions. The adsorption of albumin on hydrophilic or hydrophobic surfaces is dependent on albumin orientation, which is dictated by local charge effects. Based on these findings, an optimized material surface is proposed to minimize albumin adsorption using functional groups to limit surface availability for hydrophobic interactions while inhibiting excess electrostatic effects at hydrophilic sites. The extent of albumin adsorption and shape change are characterized herein using the heat capacity. Current study identifies interaction mechanisms previously missing in literature, which are responsible for inconsistent adsorption results.

Hydrophilized Ultrafiltration Membranes Synthesized from Acrylic Acid Grafted Polyethersulfone for Downstream Processing of Therapeutic Insulin and Cobalamin

The present study focuses on synthesis of novel high-performance acrylic acid (AA) grafted polyethersulfone (PES) ultrafiltration (UF) membranes for purification of small therapeutic biomolecules such as urea, insulin, and cobalamin. The membranes were indigenously synthesized by adding polyethylene glycol (PEG) of 6 kDa M.Wt. as a pore former and subsequent grafting of AA using 2 to 6 wt.% concentrations under UV-induced photo grafting. Scanning electron microscopy reveals that the PEG additive profoundly influences the pore density on the membrane surface. FTIR spectra confirm the graft polymerization of AA with the PES substrate. Separation performance of the grafted membranes was evaluated to establish the trade-off between the degree of grafting and MWCO. From the experimental results, the pure water flux (PWF) of 6% grafted PES membrane was enhanced from 8.5 (PES [0] [6]) to 18.20 l m^-2 h^-1 (PES [6 +] [6]) in the presence of PEG pore former, respectively. The grafting concentration window of 2-6% resulted in selective membranes to altogether remove uremic toxins into the permeate with retention of high molecular size proteins. Hence, 5 and 6 wt.% AA grafted membranes exhibited > 90% rejection for insulin and cobalamin biomolecules along with 24.5 and 23.8 l m^-2 h^-1 bar^-1 permeability towards urea, respectively. The process results correlate well with the MWCO values of membranes ranging from 1 to 10 kDa. This work provides the efficacy of these grafted membranes for potential application in the downstream processing of therapeutic biomolecules such as insulin and cobalamin.

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.

Fabrication and performance evaluation of polymeric membrane using blood compatible hydroxyapatite for artificial kidney application

In the current study, a phase inversion scheme was employed to fabricate hydroxyapatite (HA)/polysulfone (PSF)-based asymmetric membranes using a film applicator with water as a solvent and nonsolvent exchanging medium. Fourier Transform Infrared (FTIR) and X-ray diffraction (XRD) spectroscopic studies were conducted to confirm the bonding chemistry and purity of filler. The inherent thick nature of PSF generated sponge-like shape while the instantaneous demixing process produced finger-like pore networks in HA/PSF-based asymmetric membranes as exhibited by scanning electron microscope (SEM) micrographs. The FTIR spectra confirmed noncovalent weak attractions toward the polymer surface. The leaching ratio was evaluated to observe the dispersion behavior of HA filler in membrane composition. Hydrophilicity, pore profile, pure water permeation (PWP) flux, and molecular weight cutoff (MWCO) values of all formulated membranes were also calculated. Antifouling results revealed that HA modified PSF membranes exhibited 43% less adhesion of bovine serum albumin (BSA) together with >86% recovery of flux. Membrane composition showed 74% total resistance, out of which 60% was reversible resistance. Biocompatibility evaluation revealed that the modified membranes exhibited prothrombin time (PT), and thrombin time (TT) comparable with typical blood plasma, whereas proliferation of living cells over membrane surface proved its nontoxic behavior toward biomedical application. The urea and creatinine showed effective adsorption aptitude toward HA loaded PSF membranes.

Resveratrol as a plant type antioxidant modifier for polysulfone membranes to improve hemodialysis-induced oxidative stress

Resveratrol (RES) is a plant extract with excellent antioxidant, biocompatibility, anti-inflammatory and inhibition of platelet aggregation. RES-modified polysulfone (PSF) hemodialysis membranes have been fabricated using an immersion phase transformation method. The antioxidant properties of the blend membranes were evaluated in terms of their 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS⁺), reactive oxygen species (ROS) free radicals scavenging, total antioxidant capacity (T-AOC) of serum and lipid peroxidation inhibition. The observed results of decreasing DPPH and ABTS⁺ levels, scavenging ROS, significant inhibition of lipid peroxidation and improving the T-AOC of serum all contribute to the recovery of oxidative balance and the use of RES as an antioxidant modifier. The antioxidant stability of PSF/RES blend membranes was also studied. Moreover, the results of blood compatibility experiments showed that the addition of RES improved the blood compatibility of PSF membrane, inhibited the adhesion of red blood cells and platelets; inhibited complement activation; and reduced the blood cells deformation rate. The dialysis simulation experiment indicated that PSF/RES membrane (M-3) can clear 90.33% urea, 89.50% creatinine, 74.60% lysozyme and retention 90.47% BSA. All these results showed the new PSF/RES blend membranes have potential to be used in the field of hemodialysis to improve oxidative stress status in patients.

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 case study of poly (aryl ether sulfone) hemodialysis membrane interactions with human blood: Molecular dynamics simulation and experimental analyses

Patients with end-stage renal diseases (ESRD) require specific health cares as the accumulation of toxins due to the lack of kidney functionality would affect their lives. However, the mortality rate is still high due to cardiovascular diseases, socks, etc. A majority of patients with chronic kidney disease (CKD) require hemodialysis services. Blood purifying membranes, as the main component of hemodialysis setups, however, still suffer from lack of optimum biocompatibility, which results in morbidity and mortality of hemodialysis service receiving patients. The goal of the present case study is to have an in-depth understanding of the current blood-hemodialysis membrane interactions occurring during hemodialysis sessions using poly (aryl ether sulfone)-poly (vinyl pyrrolidone) (PAES-PVP) membrane. Attenuated total reflectance-Fourier transmission infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, and solid-state nuclear magnetic resonance (SSNMR) spectroscopy were used to assess the initial chemical structure of the PAES-PVP membrane along with the variations after with the infections with human blood. Furthermore, scanning electron microscopy (SEM) and Transition electron microscopy (TEM) were used to visualize the structural variation of the membrane, blood aggregations, and blood clots on the membrane surface. Besides, Molecular dynamics (MD) simulation was used to assess the interaction of PAES-PVP with major human blood proteins, in terms of interaction energy, which is a novel contribution to the area. The macromolecules (human serum albumin (HSA), human serum transferrin (TRF), and human fibrinogen (HFG)) were chosen from the plasma protein component. These protein structures were chosen based on their different molecular size. Three advanced spectroscopy techniques and two advanced visualization techniques were used for the assessment of the membranes. Spectroscopy studies revealed amine related peak displacement and intensity shifts as indices for attachment of biological species to the polymeric membrane surfaces. Raman peaks around 370, 798, and 1299 cm^-1, which experienced significant shifts that were related to carbon-nitrogen and sulfur-oxygen bonds due to protein adhesion. Visualization techniques illustrated blood protein fouling patterns and extracellular vesicles' presence in the pore structures into membranes. The findings highlight the importance of whole structure biocompatibility improvement, rather than only focusing on surface modifications of hemodialysis membranes. Molecular dynamics simulation assessment showed various interaction behaviors for different proteins suggesting molecular weight and active residues of the protein macromolecules play an important role in interacting with polymeric structure. FB had the highest interaction (4,274,749.07 kcal/mol) and binding (10,370.90 kcal/mol) energy with the PAES-PVP structure. TRF owned the lowest interaction energy with respect to its lower molecular weight and fewer active residue count.

Review of Synthetic and Hybrid Scaffolds in Cartilage Tissue Engineering

Cartilage tissue is under extensive investigation in tissue engineering and regenerative medicine studies because of its limited regenerative potential. Currently, many scaffolds are undergoing scientific and clinical research. A key for appropriate scaffolding is the assurance of a temporary cellular environment that allows the cells to function as in native tissue. These scaffolds should meet the relevant requirements, including appropriate architecture and physicochemical and biological properties. This is necessary for proper cell growth, which is associated with the adequate regeneration of cartilage. This paper presents a review of the development of scaffolds from synthetic polymers and hybrid materials employed for the engineering of cartilage tissue and regenerative medicine. Initially, general information on articular cartilage and an overview of the clinical strategies for the treatment of cartilage defects are presented. Then, the requirements for scaffolds in regenerative medicine, materials intended for membranes, and methods for obtaining them are briefly described. We also describe the hybrid materials that combine the advantages of both synthetic and natural polymers, which provide better properties for the scaffold. The last part of the article is focused on scaffolds in cartilage tissue engineering that have been confirmed by undergoing preclinical and clinical tests.

Ex vivo evaluation of the blood compatibility of mixed matrix haemodialysis membranes

The patients with end stage kidney disease need haemodialysis therapies, using an artificial kidney. Nevertheless, the current therapies cannot remove a broad range of uremic toxins compared to the natural kidney. Adsorption therapies, using sorbent-based columns, can improve the clearance of uremic toxins, but the sorbent particles often require polymeric coatings to improve their haemocompatibility leading to mass transfer limitations and to lowering of their performance. Earlier, we have developed a dual layer Mixed Matrix fiber Membrane (MMM) based on polyethersulfone/polyvinylpyrrolidone (PES/PVP) polymer blends. There, the sorbent activated carbon particles are embedded in the outer membrane layer for achieving higher removal whereas the inner blood contacting selective membrane layer should achieve optimal blood compatibility. In this work, we evaluate in detail the haemocompatibility of the MMM following the norm ISO 10993-4. We study two generations of MMM having different dimensions and transport characteristics; one with low flux and no albumin leakage and another with high flux but some albumin leakage. The results are compared to those of home-made PES/PVP single layer hollow fiber and to various control fibers already applied in the clinic. Our results show that the low flux MMM successfully avoids contact of blood with the activated carbon and has good haemocompatibility, comparable to membranes currently used in the clinic. STATEMENT OF SIGNIFICANCE: Haemodialysis is a life-sustaining extracorporeal treatment for renal disease, however a broad range of uremic toxins cannot still be removed. In our previous works we showed that a double layer Mixed Matrix Membrane (MMM) composed of polyethersulfone/polyvinylpyrrolidone and activated carbon can achieve higher removal of uremic toxics compared to commercial haemodialysers. In this work we evaluate the haemocompatibility profile of the MMM in order to facilitate its clinical implementation. The lumen particle-free layer of the MMM successfully avoids the contact of blood with the poorly blood-compatible activated carbon. Moreover, thanks to the high amount of polyvinylpyrrolidone and to the smoothness of the lumen layer, the MMM has very good haemocompatibility, comparable to membranes currently used in the clinic.

A High Cell-Bearing Capacity Multibore Hollow Fiber Device for Macroencapsulation of Islets of Langerhans

Macroencapsulation of islets of Langerhans is a promising strategy for transplantation of insulin-producing cells in the absence of immunosuppression to treat type 1 diabetes. Hollow fiber membranes are of interest there because they offer a large surface-to-volume ratio and can potentially be retrieved or refilled. However, current available fibers have limitations in exchange of nutrients, oxygen, and delivery of insulin potentially impacting graft survival. Here, multibore hollow fibers for islets encapsulation are designed and tested. They consist of seven bores and are prepared using nondegradable polymers with high mechanical stability and low cell adhesion properties. Human islets encapsulated there have a glucose induced insulin response (GIIS) similar to nonencapsulated islets. During 7 d of cell culture in vitro, the GIIS increases with graded doses of islets demonstrating the suitability of the microenvironment for islet survival. Moreover, first implantation studies in mice demonstrate device material biocompatibility with minimal tissue responses. Besides, formation of new blood vessels close to the implanted device is observed, an important requirement for maintaining islet viability and fast exchange of glucose and insulin. The results indicate that the developed fibers have high islet bearing capacity and can potentially be applied for a clinically applicable bioartificial pancreas.

Strong Hydration at the Poly(ethylene glycol) Brush/Albumin Solution Interface

Albumin molecules are extensively used as biocompatible coatings, and poly(ethylene glycol) (PEG) materials are widely used for antifouling. PEG materials have excellent antifouling property because of their strong surface hydration. Our previous research indicates that hydration at the PEG/bovine serum albumin solution interface is stronger than that at the PEG/water interface. This research shows that this observation is general for different types of albumin molecules. Different albumins including bovine, porcine, rat, rabbit, and sheep serum albumins were studied in this research. It was found that the hydration at the PEG methacrylate (pOEGMA)/albumin solution interface is always stronger than that at the pOEGMA/water interface. Here, we define "strong interfacial hydration" as "ordered strongly hydrogen-bonded interfacial water". We believe that such a strong hydration is because of the strong hydration on the albumin surface, leading to its biocompatible property. All of the albumin molecules demonstrated stronger hydration on the pOEGMA surface compared to other protein molecules such as lysozyme and fibrinogen. The strong hydration on albumin molecules is related to the high surface coverage of glutamic acid and lysine with similar amounts.

Recent Progress of Microfluidic Devices for Hemodialysis

Microfluidic hemodialysis techniques have recently attracted great attention in the treatment of kidney disease due to their advantages of portability and wearability as well as their great potential for replacing clinical hospital-centered blood purification with continuous in-home hemodialysis. This Review summarizes the recent progress in microfluidic devices for hemodialysis. First, the history of kidney-inspired hemodialysis is introduced. Then, recent achievements in the preparation of microfluidic devices and hemodialysis nanoporous membrane materials are presented and categorized. Subsequently, attention is drawn to the recent progress of nanoporous membrane-based microfluidic devices for hemodialysis. Finally, the challenges and opportunities of hemodialysis microfluidic devices in the future are also discussed. This Review is expected to provide a comprehensive guide for the design of hemodialysis microfluidic devices that are closely related to clinical applications.

Recent advances in heparinization of polymeric membranes for enhanced continuous blood purification

Continuous blood purification technology such as hemodiafiltration has been used worldwide for saving patients suffering from severe diseases or organ function failure, especially in the intensive care unit and emergency setting. The filters as core devices are commonly made of polymer materials as hollow fiber membranes. However, the membrane is often inductively blocked by blood clot formation due to its interactions with blood components. Heparin is the anticoagulant often used in clinical practice for anti-coagulation. Recently, heparin is also employed to modify the hollow fiber membranes either chemically or physically to improve the filtration performance. This review summarizes recent advances in methodology for surface heparinization of such hollow fiber membranes, and their filtration performance improvement. The review also provides expert opinions for further research in this rapidly expanding field.

New perspectives on development of polysulfones/cellulose derivatives based ionic-exchange membranes: Dielectric response and hemocompatibility study

Due to the increasing need from the membrane technologies for diverse applications, development of new generation of materials with electroactive properties and significant impact on the future technological systems was imposed. An innovative way of designing the membrane materials with long-term stable hydrophilicity, enhanced workability, porosity, and good biocompatibility, has been adopted by blending of quaternized polysulfone (PSFQ) with a cellulose derivative (cellulose acetate phthalate, CAP). Moreover, the quaternization effect has significantly improved the electrical performances, in terms of the ionic conductivity, electron interactions, and dielectric properties, required by target applications, i.e., ionic-exchange membranes, IEMs. Results derived from dielectric spectroscopy confirm the enhanced dielectric quality, reflected by a low dielectric constant and dielectric loss at high frequency. Additionally, the relationship between the resulted dielectric properties and response at the blood-biomaterial interface, have confirmed their excellent performance, constituting the preliminary basis for future tests concerning their functionality as IEMs in hemodialysis.