Zwitterionic Material Research Articles

Enhanced Mg2+/Li+ separation performance of polyelectrolyte multilayers nanofiltration membranes modified by trimethylamine N-oxide zwitterions

Polyelectrolyte multilayer nanofiltration (NF) membranes have garnered attention for their potential in Mg2⁺/Li⁺ separation applications, particularly due to their positively charged nature and the versatility offered by the layer-by-layer (LbL) self-assembly technique. However, these membranes often face significant challenges in balancing high ion selectivity with adequate water permeability. Addressing these limitations, this study introduces a novel approach by grafting a zwitterionic material, trimethylamine N-oxide (TMAO), onto polyacrylamide hydrochloride (PAH), creating a new cationic polyelectrolyte (TPAH). By cyclically depositing sodium polystyrene sulfonate (PSS) and TPAH onto a polyethersulfone (PES) substrate, we have successfully fabricated a high-performance NF membrane (i.e., (PSS/TPAH)n) that demonstrates enhanced Mg2⁺/Li⁺ selectivity with high water permeability. TMAO features shorter distances between its positive and negative charge groups and smaller dipoles compared to other zwitterions. These characteristics enhance its ability to resistance to salt effects and transfer charge from amine oxide to water molecule. Furthermore, the grafting of TMAO enhanced the hydrophilicity of TPAH and regulated the charge distribution of the polyelectrolyte. Compared to the control membrane (PSS/PAH)n, the optimized membrane (PSS/TPAH)n showed reduced rejection of LiCl from 60.9 ± 2.7 % to 35.9 ± 1.5 %, while that of MgCl2 increased from 94.3 ± 1.6 % to 96.1 ± 0.7 %. Additionally, water permeability improved from 9.2 ± 0.9 LMH/bar to 16.1 ± 0.5 LMH/bar. Notably, the membranes exhibited an improved selectivity for Mg2+/Li+ ions in synthetic saline, reaching a maximum of 30.5 ± 1.5, highlighting its potential for practical separation applications. Density functional theory simulations indicate that TMAO not only enhances Donnan effect and intensify ion dehydration of polyelectrolyte multilayers NF membranes but also increases their hydrophilicity. In general, these polyelectrolyte multilayers NF membranes exhibit considerable promise for multiple applications, such as seawater pretreatment, groundwater softening and lithium extraction.

Comparative Evaluation of Zwitterionic Material, Self-assembling Peptide, and Bioactive Glass Incorporated with MI Varnish for Fluoride, Calcium, and Phosphorus Ion Release, Enamel Remineralization, and Microhardness.

White spot lesions occur when the pathogenic bacteria have broken through the enamel layer. White spot lesions (WSLs) can be treated using a complex approach. The most crucial step is to stop demineralization and biofilm formation and use assorted strategies for remineralization of lesions, thinning, microabrasion, erosion infiltration, adhesive composite resin restorations, and the bonded facets. To evaluate and compare the fluoride, calcium, and phosphorus ion release, remineralizing efficacy, and microhardness of zwitterionic material, self-assembling peptide, and bioactive glass (BGA) incorporated with MI Varnish. The original study was conducted on 60 extracted premolars; the sample size calculated was 10 per group. All samples were divided into four groups-group A, MI Varnish (control), group B, MI Varnish + zwitterionic material, group C, MI Varnish + self-assembling peptide, and group D, MI Varnish + BGA. All these groups were further evaluated and compared for fluoride, calcium, and phorphorus ion release, remineralizing efficacy, and surface microhardness (SMH). Zwitterionic material, when incorporated with MI Varnish showed high fluoride and calcium ion release and high remineralizing efficacy under polarized light microscopy (PLM). BGA, when incorporated with MI Varnish showed high phosphorus ion release and higher values in the evaluation of SMH, followed by zwitterionic material and self-assembling peptide. MI varnish alone had remineralizing properties of WSLs, but when novel materials like zwitterionic ion, self-assembling peptide, and BGA are incorporated, its efficacy increases. Among all zwitterionic ions showed superior results for fluoride and calcium ion release and remineralization and BGA for phosphorus ion release and SMH. Patil SV, Gugwad SC, Devendrappa SN, et al. Comparative Evaluation of Zwitterionic Material, Self-assembling Peptide, and Bioactive Glass Incorporated with MI Varnish for Fluoride, Calcium, and Phosphorus Ion Release, Enamel Remineralization, and Microhardness. Int J Clin Pediatr Dent 2024;17(S-1):S37-S42.

Zwitterionic functional layer modified electrospun polyurethane nanofiber membrane incorporating silver nanoparticles for enhanced antibacterial applications

Nanofiber materials, with their porous nature and high specific surface area, can effectively adsorb and capture bacteria. Additionally, their antibacterial properties can be enhanced by incorporating substances with antibacterial effects and by surface modification with special chemical functional groups. Therefore, this study uses the electrospinning method to prepare polyurethane (PU) nanofiber antimicrobial membranes. Silver nanoparticles (AgNPs) will be incorporated into the PU nanofiber membranes through a green reduction method, followed by atmospheric plasma treatment to graft the zwitterionic material (2-methacryloyloxyethyl phosphorylcholine, MPC) with quaternary ammonium functional groups onto the surface. This process will result in the production of PMPC@PU/AgNPs nanofiber antimicrobial membranes. The results show that MPC grafted onto the surface of PU/AgNPs nanofiber membranes exhibits better antibacterial capability against Escherichia coli than the pristine PU/AgNPs nanofiber antimicrobial membranes, with an antibacterial efficiency reaching 99.68 ± 0.07 %. This is attributed to the synergistic effect provided by the combination of AgNPs within the PU nanofibers and the surface grafting of zwitterionic materials, leading to an antibacterial effectiveness close to 100 %. Therefore, the prepared PMPC@PU/AgNPs nanofiber antimicrobial membrane demonstrates the potential for applications in public health, specifically in areas such as food packaging materials, membrane filters and the biomedical field.

Synthesis of (5-Iminio-4,5-dihydro-1,3,4-oxadiazol-2-yl)tetrazol-1-ide: A Zwitterionic Compound Containing a Tetrazole Anion as a Promising Blunt Energetic Material

Abstract(5-Iminio-4,5-dihydro-1,3,4-oxadiazol-2-yl)tetrazol-1-ide is the first zwitterionic energetic material containing tetrazole as an anion and 1,3,4 oxadiazole as a cation. Its low mechanical sensitivity (IS >40 J, FS >360 N) and high gas volume after detonation at standard temperature and pressure (767.0 dm3/kg) make it a prime example of a novel type of blunt energetic material with promising applications.

Zwitterionic materials for nucleic acid delivery and therapeutic applications

Nucleic acid therapeutics have demonstrated substantial potential in combating various diseases. However, challenges persist, particularly in the delivery of multifunctional nucleic acids. To address this issue, numerous gene delivery vectors have been developed to fully unlock the potential of gene therapy. The advancement of innovative materials with exceptional delivery properties is critical to propel the clinical translation of nucleic acid drugs. Cationic vector materials have received extensive attention, while zwitterionic materials remain relatively underappreciated in delivery. In this review, we outline a diverse range of zwitterionic material nucleic acid carriers, predominantly encompassing zwitterionic lipids, polymers and peptides. Their respective chemical structures, synthesis approaches, properties, advantages, and therapeutic applications are summarized and discussed. Furthermore, we highlight the challenges and future opportunities associated with the development of zwitterionic vector materials. This review will aid to understand the zwitterionic materials in aiding gene delivery, contributing to the continual progress of nucleic acid therapeutics.

Continuous Ultrathin Zwitterionic Covalent Organic Framework Membrane Via Surface-Initiated Polymerization Toward Superior Water Retention.

Efficient construction of proton transport channels in proton exchange membranes maintaining conductivity under varied humidity is critical for the development of fuel cells. Covalent organic frameworks (COFs) hold great potential in providing precise and fast ion transport channels. However, the preparation of continuous free-standing COF membranes retaining their inherent structural advantages to realize excellent proton conduction performance is a major challenge. Herein, a zwitterionic COF material bearing positive ammonium ions and negative sulphonic acid ions is developed. Free-standing COF membrane with adjustable thickness is constructed via surface-initiated polymerization of COF monomers. The porosity, continuity, and stability of the membranes are demonstrated via the transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) characterization. The rigidity of the COF structure avoids swelling in aqueous solution, which improves the chemical stability of the proton exchange membranes and improves the performance stability. In the higher humidity range (50-90%), the prepared zwitterionic COF membrane exhibits superior capability in retaining the conductivity compared to COF membrane merely bearing sulphonic acid group. The established strategy shows the potential for the application of zwitterionic COF in the proton exchange membrane fuel cells.

Zwitterionic material for construction of an antifouling polyamide thin film composite membrane

Zwitterionic materials containing equal proportions of positively and negatively charged groups have been used to provide membranes with antifouling capabilities. This study focuses on the modification of a commercially available polyamide thin-film composite membrane with a zwitterionic material and investigates its effectiveness in fouling mitigation. The zwitterionic material, sulfobetaine vinylimidazole (SBVI), was synthesized by reacting 1,3-propane sulfone with 1-vinyl imidazole. A NF90 polyamide membrane functionalized with propagyl bromide was modified by the polymerization of SBVI on its surface. Various techniques were used to verify the successful modification of membranes. The water flux and salt rejection of the pristine and modified membranes were measured under comparable stabilization conditions, and showed an increase in salt rejection and a decrease in permeability for the modified membrane because of additional membrane resistance. However, fouling tests conducted with a wide range of foulants in cross-flow filtration mode showed a lower fouling ratio and higher recovery ratio for the modified membrane than for the pristine membrane. The enhancement in the antifouling characteristics of the modified membrane was mainly attributed to the improvement in hydrophilicity resulting from the zwitterionic brushes. Our results demonstrated the fouling resistance is further reinforced in an ionic environment through the “salting-in” effect.

Preparation and characterization of zwitterion-substituted lignin/Nafion composite membranes

In this study, a novel zwitterion-substituted lignin (ZL) containing amino and sulfonic acid groups was synthesized, and ZL/Nafion composite membranes were fabricated as proton exchange membranes. Kraft lignin was modified using an aminosilane and 1,3-propanesultone via a continuous grafting reaction to provide zwitterionic moieties. Chemical structural analyses confirmed the successful introduction of the zwitterion moiety into lignin. In particular, the surface charge of ZL is positive in an acidic medium and negative in a basic medium, suggesting that ZL is a zwitterionic material. ZL was incorporated into a Nafion membrane to enhance its ion exchange capacity, thermal stability, and hydrophilicity. The proton conductivity of ZL/Nafion 0.5 %, 151.0 mS/cm, was 55.3 % higher than that of unmodified ML (methanol-soluble lignin)/Nafion 0.5 % (97.2 mS/cm), indicating that the zwitterion moiety of ZL enhances the proton transport ability. In addition, oxidative stability evaluation confirmed that ZL/Nafion 2 % was chemically more durable than pure Nafion. This confirmed that using lignin as a membrane additive yielded positive results in terms of chemical durability and oxidation stability in Nafion. Therefore, ZL is expected to be utilized as a multifunctional additive and exhibits the potential for fuel cell applications.

Morph-genetic biomimetic multiscale porous hydrogels for high-efficient solar evaporation from seawater

Huge seawater resources are of utmost importance in addressing the increasing and severe water shortage worldwide. However, high-efficiently and sustainably extracting fresh water from seawater through solar evaporation remains a challenging task. Herein, we propose a novel approach based on the morph-genetic biomimetic concept, utilizing a cuttlebone-templated directional porous hydrogel (CTDPH). By etching away the cuttlebone (CaCO3) in the hydrogel network, we have developed a zwitterionic material that exhibits high-efficiency photo-thermal conversion, resistance to salt deposition, and super hydrophilicity, enabling high-efficiency solar evaporation. The resultant CTDPH demonstrates a high level of photo-thermal conversion efficiency, thanks to the incorporation of MXene (Ti3C2Tx) 2D nanosheets. By introducing polyzwitterions into the hydrogel matrix, the CTDPH achieves superhydrophilicity, greatly enhancing the transport of seawater. More importantly, the CTDPH possesses a penetrating oriented macro-porous structure, enabling rapid seawater transportation while effectively preventing salt crystallization. This prevents salt deposition on the surface of the hydrogel even during continuous 12-hour 1.0 sun irradiation. As a result, compared with the MXene-free gels and cuttlebone-reserved gels, this CTDPH can largely increase the seawater evaporating rate from 0.73 or 1.75 to 3.11 kg m-2h−1 under 1.0 sun irradiation. Furthermore, even after undergoing 10 cycles of seawater evaporation, the CTDPH still maintains 91.6% of its original solar evaporation rate (2.85 kg m-2h−1). The CTDPH emerges as a promising contender, offering both high efficiency and sustainability for solar evaporation from seawater, while simultaneously paving the way for innovative approaches to explore other materials and systems in the realm of solar evaporation.

Immobilization of horseradish peroxidase with zwitterionic polymer material for industrial phenolic removal.

Horseradish peroxidase (HRP) is a hemoglobin composed of a single peptide chain that catalyzes the oxidation of various substrates such as phenol and aniline in the presence of hydrogen peroxide via its iron-porphyrin catalytic center. This enzyme is widely used in industrial phenol removal, food additives, biomedicine, and clinical test reagents due to its rapid reaction rate and obvious reaction outcomes. However, the large-scale use of HRP in industrial applications still faces numerous challenges, including activity, stability, and sustainability. This study demonstrates that when peroxidase is immobilized in zwitterionic polymer hydrogels, polycarboxybetaine (PCB) and polysulfobetaine (PSB), the properties of the enzyme are improved. PCB and PSB-embedded HRP exhibit a 6.11 and 1.53 times increase in Kcat/Km value, respectively, compared to the free enzyme. The immobilized enzyme also experiences increased activity over a range of temperatures and better tolerance to extreme pH and organic solvents, including formaldehyde. In addition, immobilized HRP exhibits excellent performance in storage and reproducibility. Remarkably, PCB-HRP still retains 80% of the initial activity after a 6-week storage period and can still attain the initial catalytic level of the free enzyme after six repeated cycles. It also removes 90% of phenol within 12 min, surpassing the current pharmacy on the market. These experimental results indicated that we have successfully designed a set of stable and efficient support substrates for horseradish peroxidase, which enhances its suitability for deployment in industrial applications.

Membrane surface coated with zwitterions for fouling mitigation in membrane bioreactor: Performance and mechanism

Zwitterionic surface engineering is an effective strategy to improve membrane antifouling ability. In this present study, zwitterions were introduced onto hollow-fiber (HF) membrane via a simple flow-through coating method using zwitterionic organosilica material, and then the membrane was incorporated into a membrane bioreactor (MBR) to demonstrate improvement in fouling control. Zwitterions endowed the membrane with superior fouling resistance in the MBR; the critical flux of the membrane was improved from 25 LMH to 35 LMH, which signified higher allowable operation flux; the transmembrane pressure (TMP) development was greatly retarded, which resulted in fouling cycle extended by approximately 2 times (from 32 d to 66 d) and less cleaning frequency. Batch fouling experiments with key foulants found that zwitterion-coated membrane had superior resistance to extracellular polymeric substances (EPS) and soluble microbial polymer (SMP) adsorption. In particular, it presented exceptionally high resistance against protein adsorption. Interfacial free energy analysis revealed that zwitterions substantially altered interfacial interaction between the membrane and the EPS/SMP; the Lifshitz-van der Waals and Lewis acid-base attractive forces were obviously attenuated. As a result, the energy barrier for foulants attaching on membrane surface was greatly elevated. Our study provided a deeper insight into the antifouling mechanism of zwitterion-coated membrane and demonstrated its good potential for improving fouling control in MBR.

Preparation of a CAB-GO/PES Mixed Matrix Ultrafiltration Membrane and Its Antifouling Performance.

Serious membrane fouling has limited the development of ultrafiltration membrane technology for water purification. Synthesis of an ultrafiltration membrane with prominent anti-fouling ability is of vital importance. In this study, CAB-GO composite nanosheets were prepared by grafting graphene oxide (GO) with a zwitterionic material cocamidopropyl betaine (CAB) with strong antifouling properties. Anti-fouling CAB-GO/PES mixed matrix ultrafiltration membrane (CGM) was prepared by the phase inversion method with polyethersulfone (PES). Due to its electrostatic interaction, the interlayer distance between CAB-GO nanosheets was increased, and the dispersibility of GO was improved to large extent, thereby effectively avoiding the phenomenon of GO agglomeration in organic solvents. Based on the improvement of the surface porosity and surface hydrophilicity of the CAB-GO/PES mixed matrix membrane, the pure water flux of CGM-1.0 can reach 461 L/(m2·h), which was 2.5 times higher than that of the original PES membrane, and the rejection rates toward BSA and HA were above 96%. Moreover, when the content of CAB-GO was 0.1 wt%, the prepared CAB-GO/PES membrane exhibited very high BSA (99.1%) and HA (98.1%) rejection during long-term operation, indicating excellent anti-fouling ability.

Zwitterionic surface modification of polyethylene via atmospheric plasma-induced polymerization of (vinylbenzyl-)sulfobetaine and evaluation of antifouling properties

Zwitterionic polymer brushes were grafted from bulk polyethylene (PE) by air plasma activation of the PE surface followed by radical polymerization of the zwitterionic styrene derivative (vinylbenzyl)sulfobetaine (VBSB). Successful formation of dense poly-(VBSB)-brush layers was confirmed by goniometry, IR spectroscopy, XPS and ToF-SIMS analysis. The resulting zwitterionic layers are about 50–100 nm thick and cause extremely low contact angles of 10° (water) on the material. Correspondingly we determined a high density of > 1.0 × 1016 solvent accessible zwitterions/cm2 (corresponding to 2,0 *10-8 mol/cm2) by a UV-based ion-exchange assay with crystal violet. The elemental composition as determined by XPS and characteristic absorption bands in the IR spectra confirmed the presence of zwitterionic sulfobetaine polymer brushes. The antifouling properties of the resulting materials were evaluated in a bacterial adhesion test against gram-positive bacteria (S. aureus). We observed significantly reduced cellular adhesion of the zwitterionic material compared to pristine PE. These microbiological tests were complemented by tests in natural seawater. During a test period of 21 days, confocal microscopy revealed excellent antifouling properties and confirmed the operating antifouling mechanism. The procedure reported herein allows the efficient surface modification of bulk PE with zwitterionic sulfobetaine polymer brushes via a scalable approach. The resulting modified PE retains important properties of the bulk material and has excellent and durable antifouling properties.

A Novel Zwitterionic Hydrogel Incorporated with Graphene Oxide for Bone Tissue Engineering: Synthesis, Characterization, and Promotion of Osteogenic Differentiation of Bone Mesenchymal Stem Cells.

Zwitterionic materials are widely applied in the biomedical field due to their excellent antimicrobial, non-cytotoxicity, and antifouling properties but have never been applied in bone tissue engineering. In this study, we synthesized a novel zwitterionic hydrogel incorporated with graphene oxide (GO) using maleic anhydride (MA) as a cross-linking agent by grafted L-cysteine (L-Cys) as the zwitterionic material on maleilated chitosan via click chemistry. The composition and each reaction procedure of the novel zwitterionic hydrogel were characterized via X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FT-IR), while the morphology was imaged by scanning electron microscope (SEM). In vitro cell studies, CCK-8 and live/dead assay, alkaline phosphatase activity, W-B, and qRT-CR tests showed zwitterionic hydrogel incorporated with GO remarkably enhanced the osteogenic differentiation of bone mesenchymal stem cells (BMSCs); it is dose-dependent, and 2 mg/mL GO is the optimum concentration. In vivo tests also indicated the same results. Hence, these results suggested the novel zwitterionic hydrogel exhibited porous characteristics similar to natural bone tissue. In conclusion, the zwitterionic scaffold has highly biocompatible and mechanical properties. When GO was incorporated in this zwitterionic scaffold, the zwitterionic scaffold slows down the release rate and reduces the cytotoxicity of GO. Zwitterions and GO synergistically promote the proliferation and osteogenic differentiation of rBMSCs in vivo and in vitro. The optimal concentration is 2 mg/mL GO.

The Effect of Sulfobetaine Coating in Inhibiting the Interaction between Lyotropic Liquid Crystalline Nanogels and Proteins.

The injective lyotropic liquid crystalline nanogels (LLCNs) were widely used in drug delivery systems. But when administered in vivo, LLCNs exposed to the biological environment interact with proteins. Recently, it has been shown that nanoparticles coated with zwitterions can inhibit their interaction with proteins. Thus, in this study, the interaction between proteins and LLCNs coated with the zwitterionic material sulfobetaine (GLLCNs@HDSB) was investigated using bovine serum albumin (BSA) as a model protein. Interestingly, it was found that GLLCNs@HDSB at higher concentrations (≥0.8 mg/mL) could block its interaction with BSA, but not at lower concentrations (<0.8 mg/mL), according to the results of ultraviolet, fluorescence, and circular dichroism spectra. In the ultraviolet spectra, the absorbance of GLLCNs@HDSB (0.8 mg/mL) was 1.9 times higher than that without the sulfobetaine coating (GLLCNs) after incubation with protein; the fluorescence quenching intensity of GLLCNs@HDSB was conversely larger than that of the GLLCNs; in circular dichroism spectra, the ellipticity value of GLLCNs@HDSB was significantly smaller than that of the GLLCNs, and the change in GLLCNs@HDSB was 10 times higher than that of the GLLCNs. Generally, nanoparticles coated with sulfobetaine can inhibit their interaction with proteins, but in this study, LLCNs showed a concentration-dependent inhibitory effect. It could be inferred that in contrast to the surface of nanoparticles covered with sulfobetaine in other cases, the sulfobetaine in this study interacted with the LLCNs and was partially inserted into the hydrophobic region of the LLCNs. In conclusion, this study suggests that coating-modified nanoparticles do not necessarily avoid interacting with proteins, and we should also study coating-modified nanoparticles interacting with proteins both in vitro and in vivo. In the future, finding a coating material to completely inhibit the interaction between LLCNs and proteins will generate a great impetus to promote the clinical transformation of LLCNs.

A zwitterionic polymer-inspired material mediated efficient CRISPR-Cas9 gene editing

The type II prokaryotic CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR/Cas9) adaptive immune system is a cutting-edge genome-editing toolbox. However, its applications are still limited by its inefficient transduction. Herein, we present a novel gene vector, the zwitterionic polymer-inspired material with branched structure (ZEBRA) for efficient CRISPR/Cas9 delivery. Polo-like kinase 1 (PLK1) acts as a master regulator of mitosis and overexpresses in multiple tumor cells. The Cas9 and single guide sgRNA (sgRNA)-encoded plasmid was transduced to knockout Plk1 gene, which was expected to inhibit the expression of PLK1. Our studies demonstrated that ZEBRA enabled to transduce the CRISPR/Cas9 system with large size into the cells efficiently. The transduction with ZEBRA was cell line dependent, which showed ∼10-fold higher in CD44-positive cancer cell lines compared with CD44-negative ones. Furthermore, ZEBRA induced high-level expression of Cas9 proteins by the delivery of CRISPR/Cas9 and efficient gene editing of Plk1 gene, and inhibited the tumor cell growth significantly. This zwitterionic polymer-inspired material is an effective and targeted gene delivery vector and further studies are required to explore its potential in gene delivery applications.

Long-circulation zwitterionic dendrimer nanodrugs for phototherapy of tumors

The development of stealth and effective antitumor nanodrugs has been drawing great attention. Herein, generation five poly(amide amine) dendrimer (G5 PAMAM) was modified by zwitterionic material carboxybetaine methacrylamide (CBMAA) on its surface to prepare zwitterionic dendrimer (G5-CBMAAn). The results showed that G5-CBMAA30 had the longest blood circulation time due to its thickest zwitterionic layer, and its residual rate after injection into mice at 2 and 12 h was as high as 47.22 % and 14.37 %, respectively. Nanodrug G5-CBMAA30-ICG was prepared by containing indocyanine green (ICG) in the cavity of G5-CBMAA30. G5-CBMAA30-ICG had better tumor targeting ability and antitumor effect than free ICG in mice after laser irradiation, and the tumor inhibition rate was 96.6 % after 14 days’ treatment. The prepared G5-CBMAA30-ICG has great potential applications in the field of antitumor by phototherapy.

Engineering sterilization-resistant and fouling-resistant porous membranes by the vapor-induced phase separation process using a sulfobetaine methacrylamide amphiphilic derivative

The in-situ modification of polyvinylidene fluoride (PVDF)-based membranes with zwitterionic copolymers for environmental applications remains challenging because of the large polarity difference between PVDF and zwitterionic materials. Besides, common zwitterionic units such as sulfobetaine methacrylate fail when exposed to elevated temperatures, limiting their range of applications in biomedical engineering. We designed an amphiphilic copolymer containing sulfobetaine methacrylamide (SBAA), styrene and ethylene glycol methyl ether methacrylate (EGMA) groups. Once the appropriate composition determined, membranes were prepared by vapor-induced phase separation (VIPS), a process permitting fine control over formation mechanisms, hence over the matrix structure. Sorption, mapping FT-IR and DSC tests indicated that even a low proportion of SBAA (< 10 mol%) in the P(S-r-EGMA-r-SBAA) copolymer significantly increases the proportion of non-freezable water and enhances the strength of the hydration layer, compared to a system containing styrene and EGMA groups only, P(S-r-EGMA). The modification also resulted in a large increase in membrane hydration capacity (> 550 mg/cm3 vs. < 25 mg/cm3 for the virgin membrane). Consequently, the zwitterionic copolymer could efficiently mitigate biofouling by fibrinogen (76% drop), Escherichia coli (99% decrease) or whole blood (82% reduction), even after a steam sterilization process, while the control zwitterionic sulfobetaine methacrylate material failed at maintaining its performances. Separation tests carried out with bacterial solutions revealed the ability of the zwitterionic copolymer to significantly decrease irreversible fouling (27%), compared to a commercial membrane (47%). All in all, their porous structure, hydration capacity and their ability to withstand steam sterilization make these novel porous zwitterionic membranes ideal candidates for biomedical (blood filtration) or environmental applications (water treatment).

Simulated preparation and hydration property of a new-generation zwitterionic modified PVDF membrane

Improving the surface hydrophilicity of the membrane can effectively deal with the membrane fouling problem in the water treatment process. In this work, the molecular dynamics (MD) simulation method was adopted to simulate the vapor induced phase separation (VIPS) process in the preparation of trimethylamine oxide-derived zwitterionic polymer-grafted polyvinylidene fluoride (PVDF-g-PTMAO) membrane. PTMAO is a new-generation zwitterionic material with zero-length carbon spacer length (CSL), which exclude the hydrophobic effect of the CSL. The hydration properties of the formed zwitterionic membrane were investigated. The effect of grafting ratio of PTMAO:PVDF on the membrane surface morphology and hydration ability were explored. The simulation results show that the zwitterionic segments are enriched at membrane surface due to the attraction of water vapor and a stable hydration layer is formed on the membrane surface. As the grafting ratio increases from 5% to 15%, the number of hydrogen bonds between membrane and water molecules boosts and their interaction is strengthened, while water diffusion along the membrane surface is reduced, as a result of significantly enhanced hydration of PVDF-g-PTMAO membrane. This work helps investigate the migration behavior of the zwitterionic polymer in a PVDF-based membrane during the VIPS process and provides a better understanding of the antifouling mechanism of zwitterionic membrane as well as gives a guidance for designing new antifouling materials.

A Biofouling Resistant Zwitterionic Polysulfone Membrane Prepared by a Dual-Bath Procedure.

This study introduces a zwitterionic material to modify polysulfone (PSf) membranes formed by a dual bath procedure, in view of reducing their fouling propensity. The zwitterionic copolymer, derived from a random polymer of styrene and 4-vinylpyrridine and referred to as zP(S-r-4VP), was incorporated to the PSf solution without any supplementary pore-forming additive to study the effect of the sole copolymer on membrane-structuring, chemical, and arising properties. XPS and mapping FT-IR provided evidence of the modification. Macrovoids appeared and then disappeared as the copolymer content increased in the range 1–4 wt%. The copolymer has hydrophilic units and its addition increases the casting solution viscosity. Both effects play an opposite role on transfers, and so on the growth of macrovoids. Biofouling tests demonstrated the efficiency of the copolymer to mitigate biofouling with a reduction in bacterial and blood cell attachment by more than 85%. Filtration tests revealed that the permeability increased by a twofold factor, the flux recovery ratio was augmented from 40% to 63% after water/BSA cycles, and irreversible fouling was reduced by 1/3. Although improvements are needed, these zwitterionic PSf membranes could be used in biomedical applications where resistance to biofouling by cells is a requirement.