Intervening oxidative stress integrated with an excellent biocompatibility of hemodialysis membrane fabricated by nucleobase-recognized co-immobilization strategy of tannic acid, looped PEtOx brush and heparin

Antifouling Polymer Coatings for Bioactive Surfaces

Bioactive surfaces play a pivotal role in biomedical applications by enabling precise biological interactions through immobilized functional molecules. However, their performance is often hindered by nonspecific protein adsorption and cell adhesion. Antifouling polymer coatings have emerged as an effective solution, creating hydration barriers to preserve functionality and reduce biofouling. This review provides an overview of the recent advances in the development of antifouling polymer coatings for bioactive surfaces, with particular focus on nonionic polymers, such as polyethylene glycol (PEG), and zwitterionic polymers like poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). Among them, zwitterionic polymers, with their unique charge-balanced structures, exhibit exceptional hydration, protein resistance, and stability, making them particularly promising for biomedical applications. In addition, key applications of these bioactive surfaces, including their use in anticoagulant materials, antibacterial coatings, and biosensor interfaces, are also discussed. The discussion concludes with an address of the field's challenges and future directions, highlighting the need for innovative materials that balance antifouling properties, biocompatibility, and long-term stability for both clinical and industrial use. This review aims to review the latest advancements in antifouling polymer coatings for bioactive surfaces and provide insights into optimizing multifunctional bioactive surfaces to meet the evolving and dynamic demands of the biomedical field.

Antifouling and Antioxidant Properties of PVDF Membrane Modified with Polyethylene Glycol Methacrylate and Propyl Gallate

In this study, molecules of propyl gallate (PG) and polyethylene glycol methacrylate (PEGMA) were covalently bonded via a transesterification reaction and subsequently grafted onto polyvinylidene fluoride substrates using a homogeneous radiation grafting technique. The enhancement of the membranes' hydrophilicity with the increment of the grafting rate was corroborated by scanning electron microscopy imaging and measurements of the water contact angle. At a grafting degree of 10.1% and after a duration of 4 min, the water contact angle could decrease to as low as 40.1°. Cyclic flux testing demonstrated that the membranes modified in this manner consistently achieved a flux recovery rate exceeding 90% across varying degrees of grafting, indicating robust anti-fouling capabilities. Furthermore, these modified membranes exhibited significant antioxidant ability while maintaining antifouling performance over 30 days. The ability of the modified membranes to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS+) free radicals remained nearly unchanged after being stored in pure water for 30 days, and the flux recovery rate remained above 95% after immersion in sodium hypochlorite solution for 30 days. Among the tested membranes, the PVDF-g-PEGMAG modified membrane with a grafting degree of 7.2% showed the best antioxidant effect.

Overcoming the structure deficiency of nanodrug coated with tannic acid shell through phenolic hydroxyl protection strategy for Alzheimer's disease combination treatment

Tannic acid (TA) shell is of great interest for nanodrug design due to its versatile application such as antioxidant, antibacterial, anti-inflammatory. However, evidence is emerging that TA air oxidation in storage stage and unfavorable interactions of TA with electrolyte or protein in drug delivery could bring great challenge for the structure stability of nanodrug. In this study, a smart TA shell of nanomicelles was constructed through phenolic hydroxyl protection strategy, and the antioxidant capacity of nanomicelles maintain stable after 24 days storage. The phenolic hydroxyl protective tannic acid micelles (PHPTA micelles) show excellent performance for combination delivery of azoramide (Azo), dantrolene (Dan), Trazodone (Tra) in accelerated senescence (SAMP8) mice. This study may pave the way for the fabrication of nanodrugs with stable and smart TA shell for oxidative stress relevant diseases.

Alleviation of Oxidative Stress during Hemodialysis Sessions by Hemodialysis Membrane Innovation: A Multidisciplinary Perspective

Oxidative stress is prevalent in end-stage kidney disease patients receiving chronic hemodialysis and is associated with heavy cardiovascular disease burdens and increased mortality risks. Hemoincompatible hemodialysis membranes per se contribute to the activation of oxidative reactions and the generation of oxygen free radicals. Since the early 1990s, vitamin E-coated membranes have been extensively used in hemodialysis patients to reduce oxidative stress during hemodialysis sessions. However, the beneficial effects of vitamin E-coated membranes versus unmodified synthetic membranes on long-term patient-centered outcomes, such as survival, quality of life, and prevalence of cardiovascular diseases, remain controversial. Accordingly, novel antioxidant hemodialysis membranes were prepared to replace the use of vitamin E-coated membranes despite the translational research on these membranes unfortunately coming to a standstill. In this review, we first summarize the state-of-the-art on the use of vitamin E-coated membranes in hemodialysis patients to highlight their strengths and limitations. Then, we discuss the latest advances in fabricating antioxidant hemodialysis membranes and provide perspectives to bridge knowledge gaps between laboratorial investigations and clinical practice in fabricating antioxidant hemodialysis membranes.

Two-Dimensional Theoretical Analysis and Experimental Study of Mass Transfer in a Hollow-Fiber Dialysis Module Coupled with Ultrafiltration Operations

This research theoretically and experimentally develops a hollow-fiber dialysis module coupled with ultrafiltration operations by introducing a trans-membrane pressure during the membrane dialysis process, which can be applied to the waste metabolic end products in the human body for improving the dialysis efficiency. The solutes were transported by both diffusion and convection from the concentration driving-force gradient between retentate and dialysate phases across the membrane, compared to the traditional dialysis processes by diffusion only. A two-dimensional modeling of such a dialysis-and-ultrafiltration system in the hollow-fiber dialysis module was formulated and solved using the stream function coupled with the perturbation method to obtain the velocity distributions of retentate and dialysate phases, respectively. The purpose of the present work is to investigate the effect of ultrafiltration on the dialysis rate in the hollow-fiber dialyzer with ultrafiltration operations. A highest level of dialysis rate improvement up to about seven times (say 674.65% under Va=20 mL/min) was found in the module with ultrafiltration rate Vw=10 mL/min and membrane sieving coefficient θ=1, compared to that in the system without operating ultrafiltration. Considerable dialysis rate improvements on mass transfer were obtained by implementing a hollow-fiber dialysis-and-ultrafiltration system, instead of using the hollow-fiber dialyzer without ultrafiltration operation. The experimental runs were carried out under the same operating conditions for the hollow-fiber dialyzers of the two experimental runs with and without ultrafiltration operations for comparisons. A very reasonable prediction by the proposed mathematical model was observed.

Device Performance of a Tubular Membrane Dialyzer Incorporating Ultrafiltration Effects on the Dialysis Efficiency

Membrane dialysis is one of the membrane contactors applied to wastewater treatment. The dialysis rate of a traditional dialyzer module is restricted because the solutes transport through the membrane only by diffusion, in which the mass-transfer driving force across the membrane is the concentration gradient between the retentate and dialysate phases. A two-dimensional mathematical model of the concentric tubular dialysis-and-ultrafiltration module was developed theoretically in this study. The simulated results show that the dialysis rate improvement was significantly improved through implementing the ultrafiltration effect by introducing a trans-membrane pressure during the membrane dialysis process. The velocity profiles of the retentate and dialysate phases in the dialysis-and-ultrafiltration system were derived and expressed in terms of the stream function, which was solved numerically by the Crank-Nicolson method. A maximum dialysis rate improvement of up to twice that of the pure dialysis system (Vw=0) was obtained by employing a dialysis system with an ultrafiltration rate of Vw=2 mL/min and a constant membrane sieving coefficient of θ=1. The influences of the concentric tubular radius, ultrafiltration fluxes and membrane sieve factor on the outlet retentate concentration and mass transfer rate are also illustrated.

Preparation and surface modification of ultrahigh throughput tannic acid coblended polyethersulfone ultrafiltration membranes for hemodialysis

Low dialysis and blood incompatibility efficiency are key issues to be addressed for polymeric hemodialysis membranes. To improve the comprehensive performance of hemodialysis membranes, polyethersulfone (PES)/tannic acid (TA) coblended ultrafiltration membranes were prepared and modified with a heparin‐like functionalized TA coating. The coblended TA improved the pore structure of the PES ultrafiltration membrane. And it could also undergo π‐π conjugation with the heparin‐like functionalized TA in the modified solution, resulting in a greater abundance of modified groups loaded on the membrane surface and pores close to the surface. The modified coating further improved the membrane performance. The physicochemical properties, solute filtration, and blood compatibility properties of the membrane were tested. The effect of TA on the pore structure of the membrane and the presence of modified layers were demonstrated by morphological and chemical structure analyses. The final modified membrane had an ultrahigh water flux (1053 L/m2·h), improved dialysis performance (BSA retention >99%, Lysozyme clearance >30% and Urea clearance >90%), and excellent hemocompatibility (The hemolysis rate was 1.31%, and APTT, PT, and TT values were increased by 40.8%, 74.2%, and 85.9%, respectively). This study shows that TA has great potential for improving the pore structure of polymeric membranes.

A high-protein retained PES hemodialysis membrane with tannic acid as a multifunctional modifier

A high protein retention polyethersulfone (PES) membrane was prepared by nonsolvent-induced phase separation and surface coating, which exhibited enhanced hemocompatibility and antioxidant stress performance. The cross-linked network was constructed by tannic acid (TA) and alpha-lipoic acid (α-LA) on the surface of the membrane, which controlled the pores to a reasonable size. The enrichment of heparin-like groups on the membrane surface, implemented by "hydrophobic interaction" and "click reaction", confers anticoagulant properties; the presence of a large number of phenolic hydroxyl groups from TA and the introduction of α-LA allows the modified membranes to intervene in oxidative stress. The hemocompatibility characterizations included plasma recalcification time (PRT), activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT) and hemolysis rate (HR). Additionally, the DPPH ABTS radical scavenging capacity was tested to evaluate the antioxidant performance. The results show that the modified membrane presents an outstanding protein retention rate (99.3%) along with permeability. In addition, the PRT is prolonged to 341.7 s, and the DPPH• scavenging ability reaches 0.74 µmol•cm-2. The membranes can be easily prepared and present excellent comprehensive performance. This work provides a simple and facile strategy for the fabrication of hemodialysis membranes with controllable pore sizes.

Membranes for the life sciences and their future roles in medicine

Since the global outbreak of COVID-19, membrane technology for clinical treatments, including extracorporeal membrane oxygenation (ECMO) and protective masks and clothing, has attracted intense research attention for its irreplaceable abilities. Membrane research and applications are now playing an increasingly important role in various fields of life science. In addition to intrinsic properties such as size sieving, dissolution and diffusion, membranes are often endowed with additional functions as cell scaffolds, catalysts or sensors to satisfy the specific requirements of different clinical applications. In this review, we will introduce and discuss state-of-the-art membranes and their respective functions in four typical areas of life science: artificial organs, tissue engineering, in vitro blood diagnosis and medical support. Emphasis will be given to the description of certain specific functions required of membranes in each field to provide guidance for the selection and fabrication of the membrane material. The advantages and disadvantages of these membranes have been compared to indicate further development directions for different clinical applications. Finally, we propose challenges and outlooks for future development.

Chemistry and engineering of brush type polymers: Perspective towards tissue engineering

In tissue engineering, it is imperative to control the behaviour of cells/stem cells, such as adhesion, proliferation, propagation, motility, and differentiation for tissue regeneration. Surfaces that allow cells to behave in this way are critical as support materials in tissue engineering. Among these surfaces, brush-type polymers have an important potential for tissue engineering and biomedical applications. Brush structure and length, end groups, bonding densities, hydrophilicity, surface energy, structural flexibility, thermal stability, surface chemical reactivity, rheological and tribological properties, electron and energy transfer ability, cell binding and absorption abilities for various biological molecules of brush-type polymers were increased its importance in tissue engineering applications. In addition, thanks to these functional properties and adjustable surface properties, brush type polymers are used in different high-tech applications such as electronics, sensors, anti-fouling, catalysis, purification and energy etc. This review comprehensively highlights the use of brush-type polymers in tissue engineering applications. Considering the superior properties of brush-type polymer structures, it is believed that in the future, it will be an effective tool in structure designs containing many different biomolecules (enzymes, proteins, etc.) in the field of tissue engineering.