A novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) artificial lung membrane for enhanced gas transport and excellent hemo-compatibility

Agarose modification on PDMS/PES composite membrane for improved hemocompatibility and anti-fouling performance

Agarose, the natural hydrophilic polysaccharide with good biocompatibility, low immunogenicity and low cost which has been widely used in tissue engineering and regenerative medicine but not in biomedical equipment, was employed to modify the potential oxygenation membrane, the core component for blood oxygenation ex vivo in the artificial lung machine. The oxidized agarose was successfully coated onto the hydrophobic polydimethylsiloxane (PDMS) surface forming a hydrophilic layer via intermolecular chemical bonding as well as physical interactions based on characterization and analyses from SEM, HNMR, FTIR, XPS and water contact angle measurement. The agarose modification significantly improved the hemocompatibility, reducing protein adsorption by 50-60 % and hemolysis rate from ∼0.45 % to ∼0.2 %, elongating the plasma recalcification time and blood clotting time, as well as alleviating platelet adhesion, and the antibacterial performance of the membrane, which would reduce the contamination of the membrane thus prolonging the membrane service life as well as blood clotting, blood damage and blood fouling. Meanwhile, the CO2/O2 gas selectivity was promoted to ∼9, an 64 % increase in comparison to that of unmodified membranes, which would significantly enhance the gas exchange efficiency of the oxygenation membrane. Moreover, the membrane modified with agarose exhibited long-term stability against platelet adhesion and blood leakage. This agarose modification strategy is simple yet effective, providing new ideas for oxygenation membrane synthesis and improvement.

Anticoagulant Sulfonate Polyamide/Poly(ether sulfone) Membrane Barrier for Efficient Blood Oxygenation

Extracorporeal membrane oxygenation (ECMO) is the most important support for patients with severe cardiopulmonary failure. As the key component, the oxygenation membrane has suffered the risk of blood coagulation and plasma leakage in the long term. Herein, we prepare a sulfonate polyamide film on poly(ether sulfone) (PES) support via interfacial polymerization modulated by a sulfonate amine monomer. The pore diameter of the prepared polyamide film is ∼3.67 Å (exactly a little smaller than the water molecule, the base of plasma). By such size repulsion effect, the polyamide film demonstrates remarkable plasma leakage resistance (confirmed by human plasma circulation). Moreover, the introduction of the sulfonate amine monomer effectively enhances the anticoagulation performance (activated partial thromboplastin time (aPTT) prolongation >10 s). In addition, the PES support used for interfacial polymerization is modified and realizes improved porosity, hydrophilicity, and positive charge potential, resulting in lower mass transfer resistance and improved interfacial strength between the support and polyamide film. ECMO-simulated circulation tests prove the facilitation effect on gas exchange derived from the support modification and interfacial polymerization modulation. This work provides a composite membrane simultaneously with significant plasma leakage resistance and anticoagulation properties for efficient blood oxygenation.

Sulfonated covalent organic frameworks (COF)/polyethersulfone (PES) membrane with enhanced hemocompatibility for blood oxygenation

In extracorporeal membrane oxygenation (ECMO) treatment, designing membrane with self-anticoagulant properties can solve problems resulting from the adverse effect of anticoagulants. In this study, 2,4,6-Triformylphloroglucinol (Tp) and 2,5-Diaminobenzenesulfonic acid (Pa-SO3H) were applied to grow a sulfonated COF film in situ on the polyethersulfone (PES) membrane. The introduction of sulfonic groups increased the hydrophilicity and electronegativity of the TpPa COF film, improved its anti-protein adhesion properties, maintained the normal morphology of blood cells, and endowed the COF film with antithrombotic properties. In the porcine blood circulation test, the duration to increase So2 (O2 saturation) from ∼75-95 % in TpPa-SO3H COF/PES membrane (M-TpPa-SO3H) was 70 min shorter than that in TpPa COF/PES membrane (M-TpPa). This preparation method is applicable to the preparation of not only flat membranes, but also hollow fiber membranes. These findings emphasize the potential of M-TpPa-SO3H in ECMO applications, providing superior antithrombotic property and CO2 efflux potential.

Characterization of anisotropic pore structure and dense selective layer of capillary membranes for long-term ECMO by cross-sectional ion-milling method

Since the COVID-19 pandemic of 2020-2023, extracorporeal membrane oxygenator (ECMO) has attracted considerable attention worldwide. It is expected that ECMO with long-term durability is put into practical use in order to prepare for next emerging infectious diseases and to facilitate manufacturing for novel medical devices. Polypropylene (PP) and polymethylpentene (PMP) capillary membranes are currently the mainstream for gas exchange membrane for ECMO. ECMO support days for COVID-19-related acute hypoxemic respiratory failure have been reported to be on average for 14 or 24 days. It is necessary to improve opposing functions such that promoting the permeation of oxygen and carbon dioxide and inhibiting the permeation of water vapor or plasma to develop sufficient durability for long-term use. For this purpose, accurately controlling the anisotropy of the pore structure of the entire cross section and functions of capillary membrane is significant. In this study, we focused on the cross-sectional ion-milling (CSIM) method, to precisely clarify the pore structure of the entire cross section of capillary membrane for ECMO, because there is less physical stress on the porous structure applied during the preparation of cross-sectional samples of porous capillary membranes. We attempted to observe the cross sections of commercially available PMP membranes using the CSIM method. As a result, we succeeded in fabricating fine-scale flat cross-sectional samples of PMP capillary membranes. The pore structures and the degree of anisotropy of the cross sections are quantitatively clarified. The achievements and the approaches of this study are being applied to the development of next-generation gas exchange membranes.

Stability Study of Anticoagulant Hydrogel Coatings Toward Long-Term Cardiovascular Devices

Implantable cardiovascular devices have revolutionized the treatment of cardiovascular diseases, yet their long-term functionality without causing thrombosis is a persistent challenge. Although the surface modification of anticoagulant coating has greatly improved the biocompatibility of the devices, its long-term stability in complex physiological environments still remains questionable. Herein, the stability of three anticoagulant hydrogel coatings, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(sodium 2-acryloyl-2-methylpropanesulfonate) (PAMPS), and poly(4-styrenesulfonate sodium) (PSS), is studied. The fabrication of these coatings onto device surfaces is validated by using X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. In vitro anticoagulation assays confirm the coatings' significant anticoagulant effects. Among all three coatings, the PSS coating demonstrated superior chemical and mechanical stability in the comprehensive tests, showing great potential for improving the long-term anticoagulant performance of implantable cardiovascular devices.

An endothelium membrane mimetic antithrombotic coating enables safer and longer extracorporeal membrane oxygenation application

Thrombosis and plasma leakage are two of the most frequent dysfunctions of polypropylene (PP) hollow fiber membrane (PPM) used in extracorporeal membrane oxygenation (ECMO) therapy. In this study, a superhydrophilic endothelial membrane mimetic coating (SEMMC) was constructed on polydopamine-polyethyleneimine pre-coated surfaces of the PPM oxygenator and its ECMO circuit to explore safer and more sustainable ECMO strategy. The SEMMC is fabricated by multi-point anchoring of a phosphorylcholine and carboxyl side chained copolymer (PMPCC) and grafting of heparin (Hep) to form PMPCC-Hep interface, which endows the membrane superior hemocompatibility and anticoagulation performances. Furthermore, the modified PPM reduces protein adsorption amount to less than 30 ng/cm2. More significantly, the PMPCC-Hep coated ECMO system extends the anti-leakage and non-clotting oxygenation period to more than 15 h in anticoagulant-free animal extracorporeal circulation, much better than the bare and conventional Hep coated ECMO systems with severe clots and plasma leakage in 4 h and 8 h, respectively. This SEMMC strategy of grafting bioactive heparin onto bioinert zwitterionic copolymer interface has great potential in developing safer and longer anticoagulant-free ECMO systems. STATEMENT OF SIGNIFICANCE: A superhydrophilic endothelial membrane mimetic coating was constructed on surfaces of polypropylene hollow fiber membrane (PPM) oxygenator and its ECMO circuit by multi-point anchoring of a phosphorylcholine and carboxyl side chain copolymer (PMPCC) and grafting of heparin (Hep). The strong antifouling nature of the PMPCC-Hep coating resists the adsorption of plasma bio-molecules, resulting in enhanced hemocompatibility and anti-leakage ability. The grafted heparin on the zwitterionic PMPCC interface exhibits superior anticoagulation property. More significantly, the PMPCC-Hep coating achieves an extracorporeal circulation in a pig model for at least 15 h without any systemic anticoagulant. This endothelial membrane mimetic anticoagulation strategy shows great potential for the development of safer and longer anticoagulant-free ECMO systems.

Polyimide as a biomedical material: advantages and applications

Polyimides (PIs) are a class of polymers characterized by strong covalent bonds, which offer the advantages of high thermal weight, low weight, good electronic properties and superior mechanical properties. They have been successfully used in the fields of microelectronics, aerospace engineering, nanomaterials, lasers, energy storage and painting. Their biomedical applications have attracted extensive attention, and they have been explored for use as an implantable, detectable, and antibacterial material in recent years. This article summarizes the progress of PI in terms of three aspects: synthesis, properties, and application. First, the synthetic strategies of PI are summarized. Next, the properties of PI as a biological or medical material are analyzed. Finally, the applications of PI in electrodes, biosensors, drug delivery systems, bone tissue replacements, face masks or respirators, and antibacterial materials are discussed. This review provides a comprehensive understanding of the latest progress in PI, thereby providing a basis for developing new potentially promising materials for medical applications.

Biomimetic nanoporous oxygenation membranes with high hemocompatibility and fast gas transport property

Membrane technology holds great potential for separation applications and also finds critical needs in biomedical fields, such as blood oxygenation. However, the bottlenecks in gas permeation, plasma leakage, and especially hemocompatibility hamper the development of membrane oxygenation. It remains extremely challenging to design efficient membranes and elucidate underlying principles. In this study, we report biomimetic decoration of asymmetric nanoporous membranes by ultrathin FeIII-tannic acid metal-ligand networks to realize fast gas exchange with on plasma leakage and substantially enhance hemocompatibility. Because the intrinsic nanopores facilitate gas permeability and the FeIII-catechol layers enable superior hydrophilicity and electronegativity to original surfaces, the modified membranes exhibit high transport properties for gases and great resistances to protein adsorption, platelet activation, coagulation, thrombosis, and hemolysis. Molecular docking and density functional theory simulations indicate that more preferential adsorption of metal-ligand networks with water molecules than proteins is critical to anticoagulation. Moreover, benefiting from the better antiaging property gave by biomimetic decoration, the membranes after four-month aging present gas permeances similar to or even larger than those of pristine ones, despite the initial permeation decline. Importantly, for blood oxygenation, the designed membranes after aging show fast O2 and CO2 exchange processes with rates up to 28-17 and 97-47 mL m-2 min-1, respectively, accompanied with no detectable thrombus and plasma leakage. We envisage that the biomimetic decoration of nanoporous membranes provide a feasible route to achieve great biocompatibility and transport capability for various applications.

3D porous structure imaging of membranes for medical devices using scanning probe microscopy and electron microscopy: from membrane science points of view

The evolution of hemodialysis membranes (dialyzer, artificial kidney) was remarkable, since Dow Chemical began manufacturing hollow fiber hemodialyzers in 1968, especially because it involved industrial chemistry, including polymer synthesis and membrane manufacturing process. The development of hemodialysis membranes has brought about the field of medical devices as a major industry. In addition to conventional electron microscopy, scanning probe microscopy (SPM), represented by atomic force microscopy (AFM), has been used in membrane science research on porous membranes for hemodialysis, and membrane science contributes greatly to the hemodialyzer industry. Practical studies of membrane porous structure-function relationship have evolved, and methods for analyzing membrane cross-sectional morphology were developed, such as the ion milling method, which was capable of cutting membrane cross sections on the order of molecular size to obtain smooth surface structures. Recently, following the global pandemic of SARS-CoV-2 infection, many studies on new membranes for extracorporeal membrane oxygenator have been promptly reported, which also utilize membrane science researches. Membrane science is playing a prominent role in membrane-based technologies such as separation and fabrication, for hemodialysis, membrane oxygenator, lithium ion battery separators, lithium recycling, and seawater desalination. These practical studies contribute to the global medical devices industry.

Evolutions of extracorporeal membrane oxygenator (ECMO): perspectives for advanced hollow fiber membrane

Hollow fiber membrane is incorporated into an extracorporeal membrane oxygenator (ECMO), and the function of the membrane determines the ECMO's functions, such as gas transfer rate, biocompatibility, and durability. In Japan, the membrane oxygenator to assist circulation and ventilation is approved for ECMO support. However, in all cases, the maximum use period has been only 6 h, and so-called 'off-label use' is common for ECMO support of severely ill COVID-19 patients. Under these circumstances, the HLS SET Advanced (Getinge Group Japan K.K.) was approved in 2020 for the first time in Japan as a membrane oxygenator with a two-week period of use. Following this membrane oxygenator, it is necessary to establish a domestic ECMO system that is approved for long-term use and suitable for supporting patients. Looking back on the evolution of ECMO so far, Japanese researchers and manufacturers have also contributed to the developments of ECMO globally. Currently, excellent membrane oxygenators and systems have been marketed by Japanese manufacturers and some of them are globally acclaimed, but in fact, most of the ECMO membranes are not made in Japan. Fortunately, Japan has led the world in the fields of membrane separation technology and hollow fiber membrane production. In the wake of this pandemic, from the perspective of medical and economic security, the practical use of purely domestic hollow fiber membranes and membrane oxygenators for long-term ECMO is imperative in anticipation of the next pandemic.

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.

Asymmetric Triple-Functional Janus Membrane for Blood Oxygenation

The oxygenation membrane, a core material of extracorporeal membrane oxygenation (ECMO), is facing challenges in balancing anti-plasma leakage, gas exchange efficiency, and hemocompatibility. Here, inspired by the asymmetric structural features of alveolus pulmonalis, a novel triple-functional membrane for blood oxygenation with a Janus architecture is proposed, which is composed of a hydrophobic polydimethylsiloxane (PDMS) layer to prevent plasma leakage, an ultrathin polyamide layer to enhance gas exchange efficiency with a CO2 :O2 permeance ratio of ≈10.7, and a hydrophilic polyzwitterionic layer to improve the hemocompatibility. During the simulated ECMO process, the Janus oxygenation membrane exhibits excellent performance in terms of thrombus formation and plasma leakage prevention, as well as adequate O2 transfer rate (17.8 mL min-1 m-2 ) and CO2 transfer rate (70.1 mL min-1 m-2 ), in comparison to the reported oxygenation membranes. This work presents novel concepts for the advancement of oxygenation membranes and demonstrates the application potential of the asymmetric triple-functional Janus oxygenation membrane in ECMO.

Heparin-Mimetic Chitooligosaccharides-Based Monoliths Obtained from C/W Emulsions: Hemocompatibility and Toxin Removal Ability

Hemoperfusion (HP) is one of the most prominent therapies for treating uremia, hyperbilirubinemia, and acute drug toxicity. The comprehensive performance of currently used porous HP adsorbents needs to be improved due to the impediment to their synthesis strategy. Herein, green carbon dioxide-in-water high internal phase emulsions (C/W HIPEs) were utilized and emulsified with poly(vinyl alcohol) (PVA) for the formation of a heparin-mimetic chitosan oligosaccharides/poly(acrylamide-co-sodium 4-styrenesulfonate) [COS/P(AM-co-SSS)] monolith, which exhibited good mechanical properties, stable swelling performance, hydrophilic properties, anticoagulant effect, and low hemolysis. It showed a strong toxin adsorption capacity (415.2 mg/g for creatinine, 199.3 mg/g for urea, 279.5 mg/g for bilirubin, and 160 mg/g for tetracycline). The adsorption process of porous COS/P(AM-co-SSS) followed the pseudo-second-order kinetic and Langmuir isotherm models. Moreover, the porous materials had a strong electrostatic force on creatinine. The removal of creatinine by simulated in vitro blood perfusion was 80.2% within 30 min. This work provides a green preparation strategy for developing novel HP materials, highlighting their potential application value in blood and environmental purification.

Fast Blood Oxygenation through Hemocompatible Asymmetric Polymer of Intrinsic Microporosity Membranes

Membrane technology has attracted considerable attention for chemical and medical applications, among others. Artificial organs play important roles in medical science. A membrane oxygenator, also known as artificial lung, can replenish O2 and remove CO2 of blood to maintain the metabolism of patients with cardiopulmonary failure. However, the membrane, a key component, is subjected to inferior gas transport property, leakage propensity, and insufficient hemocompatibility. In this study, we report efficient blood oxygenation by using an asymmetric nanoporous membrane that is fabricated using the classic nonsolvent-induced phase separation method for polymer of intrinsic microporosity-1. The intrinsic superhydrophobic nanopores and asymmetric configuration endow the membrane with water impermeability and gas ultrapermeability, up to 3,500 and 1,100 gas permeation units for CO2 and O2, respectively. Moreover, the rational hydrophobic-hydrophilic nature, electronegativity, and smoothness of the surface enable the substantially restricted protein adsorption, platelet adhesion and activation, hemolysis, and thrombosis for the membrane. Importantly, during blood oxygenation, the asymmetric nanoporous membrane shows no thrombus formation and plasma leakage and exhibits fast O2 and CO2 transport processes with exchange rates of 20 to 60 and 100 to 350 ml m-2 min-1, respectively, which are 2 to 6 times higher than those of conventional membranes. The concepts reported here offer an alternative route to fabricate high-performance membranes and expand the possibilities of nanoporous materials for membrane-based artificial organs.

Polymeric Membranes for Biomedical Applications

Polymeric membranes are selective materials used in a wide range of applications that require separation processes, from water filtration and purification to industrial separations. Because of these materials' remarkable properties, namely, selectivity, membranes are also used in a wide range of biomedical applications that require separations. Considering the fact that most organs (apart from the heart and brain) have separation processes associated with the physiological function (kidneys, lungs, intestines, stomach, etc.), technological solutions have been developed to replace the function of these organs with the help of polymer membranes. This review presents the main biomedical applications of polymer membranes, such as hemodialysis (for chronic kidney disease), membrane-based artificial oxygenators (for artificial lung), artificial liver, artificial pancreas, and membranes for osseointegration and drug delivery systems based on membranes.