Enhancing oil-water emulsion separation via synergistic filtration using graphene oxide-silver oxide nanocomposite-embedded polyethersulfone membrane.

This study introduces an innovative approach for enhancing oil-water emulsion separation using a polyethersulfone (PES) membrane embedded with a nanocomposite of graphene oxide (GO) and silver oxide (AgO). The composite membrane, incorporating PES and polyvinyl chloride (PVC), demonstrates improved hydrophilicity, structural integrity and resistance to fouling. Physicochemical characterization confirms successful integration of GO and AgO, leading to increased tensile strength, porosity and hydrophilicity. Filtration tests reveal substantial improvements in separating various oils from contaminated wastewater, with the composite membrane exhibiting superior efficiency and reusability compared to pristine PES membranes. This research contributes to the development of environmentally friendly oil-water separation methods with broad industrial applications.

The effect of adding concentrated cheese whey prepared by ultrafiltration on the quality of Syrian bread.

The objective of this study is to evaluate the effect of adding two types cheese whey (W) contaning 0.9% protein and concentrated cheese whey (CW) containing 7.61% protein on the physical, chemical and sensory properties of Syrian bread. Concentrated whey samples were prepared using a UF membrane unit of 15 KDa at 25 °C and 4 bars. Both W and CW samples were added to wheat flour (72% extraction rate) at dilution level: 0, 25, 50, 75, and 100% levels. The effects of W and CW on dough rheology were evaluated using farinograph and alveograph parameters. The addition of 25% W or 50% CW improved the dough stability in the farinogram, as well as pressure and energy values in the alveogram. Significant increases were observed in ash, minerals (Ca, K, Mg, and P), and protein content (13.8%) when 50% CW was added to the dough. The results of sensory analysis showed that Syrian bread containing 25% whey (W) or 50% whey concentrate (CW) has achieved highest overall acceptability scores than control.

Membrane surface roughness promotes rapid initial cell adhesion and long term microalgal biofilm stability.

In biofilm membrane photobioreactors development, conscientious works revolving around the effect of external environment factors on microalgal biofilm growth were assessed but more comparative research about the role of carrier surfaces properties such as surface roughness is necessary. Thus, commercial polyethersulfone (PES) membranes with two different molecular-weight-cut-offs (1 kDa and 30 kDa) were selected as the main representatives of surface roughness in a 20 days long-term biofilm cultivation experiment under dynamic flow condition for the biofilm evolvement of three benthic diatoms (Amphora coffeaeformis, Cylindrotheca fusiformis and Navicula incerta). Results depicted that rougher 30 kDa PES enable higher cell attachment degree for C. fusiformis (25.85 ± 2.75 × 109 cells m-2), followed by A. coffeaeformis (11.86 ± 2.76 × 109 cells m-2) and N. incerta (10.10 ± 0.65 × 109 cells m-2). Bounded extracellular polymeric substances (bEPS) gathered were relatively higher than soluble EPS (sEPS) while bEPS accumulated at least 10% higher on smooth 1 kDa PES than rough 30 kDa PES for the purpose of enhancing the biofilm disruption resistivity under liquid flow. Moreover, cell adhesion mechanism was proposed via computational fluid dynamics in parallel with EPS analysis. Copious amount of asperities and stagnant zones present on rough 30 kDa surfaces accelerated biofilm development and the consistency of the results have a great valence for interpretation of microalgal biofilm lifestyle on porous surfaces.

Stationary photocurrent generation from bacteriorhodopsin-loaded lipo-polymersomes in polyelectrolyte multilayer assembly on polyethersulfone membrane.

Vesicles constructed of either synthetic polymers alone (polymersomes) or a combination of polymers and lipids (lipo-polymersomes) demonstrate excellent long-term stability and ability to integrate membrane proteins. Applications using lipo-polymersomes with integrated membrane proteins require suitable supports to maintain protein functionality. Using lipo-polymersomes loaded with the light-driven proton pump bacteriorhodopsin (BR), we demonstrate here how the photocurrent is influenced by a chosen support. In our study, we deposited BR-loaded lipo-polymersomes in a cross-linked polyelectrolyte multilayer assembly either directly physisorbed on gold electrode microchips or cross-linked on an intermediary polyethersulfone (PES) membrane covalently grafted using a hydrogel cushion. In both cases, electrochemical impedance spectroscopic characterization demonstrated successful polyelectrolyte assembly with BR-loaded lipo-polymersomes. Light-induced proton pumping by BR-loaded lipo-polymersomes in the different support constructs was characterized by amperometric recording of the generated photocurrent. Application of the hydrogel/PES membrane support together with the polyelectrolyte assembly decreased the transient current response upon light activation of BR, while enhancing the generated stationary current to over 700 nA/cm2. On the other hand, the current response from BR-loaded lipo-polymersomes in a polyelectrolyte assembly without the hydrogel/PES membrane support was primarily a transient peak combined with a low-nanoampere-level stationary photocurrent. Hence, the obtained results demonstrated that by using a hydrogel/PES support it was feasible to monitor continuously light-induced proton flux in biomimetic applications of lipo-polymersomes. Graphical abstract.

Optimization of membrane modification using SiO2 for robust anti-fouling performance with calcium-humic acid feed in membrane distillation.

The goal of this study was to prepare a robust anti-wetting and anti-fouling polyethersulfone (PES) membrane for the rejection of a highly saline (NaCl and CaCl2·2H2O) feed solution containing humic acid (HA) in direct contact membrane distillation (DCMD). Response surface methodology (RSM) was used to determine the optimum formulation of the used materials. The variable factors selected were polydimethyl siloxane (PDMS) and silica (SiO2); liquid entry pressure (LEP) and contact angle (CA) were selected as responses. Scanning electron microscopy (SEM) analysis confirmed the SiO2 deposition and Fourier-transform infrared spectroscopy (FTIR) test evidenced the new functional groups i.e., Si-OH, siloxane, and C-F bond vibrations at 3446, 1099 cm-1, and 1150-1240 cm-1 respectively on the membrane surface. The average roughness (Ra) was increased four times for the coated membranes (0.202-0.242 µm) as compared to that for pristine PES membrane (0.053 µm). The optimum PES-13 membrane exhibited consistent flux of 12 LMH and salt rejection (> 99%) with anti-fouling characteristic in DCMD using the feed solution of 3.5 wt% NaCl + 10 mM CaCl2·2H2O + 10 mg L-1 HA. The PES-13 membrane may therefore be a key membrane for application in DCMD against CaCl2·2H2O-containing salty solutions with HA.

Asymmetric triacetate membrane keeps high water flux during ultrafiltration: in vitro study.

Membrane fouling is a primary challenge encountered during the administration of hemodialysis (HD) and hemodiafiltration (HDF). A high-flux membrane is suitable for dialyzer reuse, since it is used repeatedly. Water flux is a benchmark used to assess the effectiveness of the dialysis membrane during treatment and it is usually evaluated to determine whether membrane fouling has occurred. Polysulfone (PS) membrane has good biocompatibility and solute permeability; however, polyethersulfone (PES) is often used as a hemodiafilter membrane because of better hydrophilicity compared to PS. We evaluated water flux across hemodiafilters using newly developed asymmetric triacetate (ATA) and PES as conventional membranes in vitro. Water flux of across ATA and PES membranes significantly decreased 30 min after the start of the experiments and thereafter showed stabilization. Water flux across the ATA membrane consistently showed significantly higher values of greater than 100 mL/m2/h/mmHg, compared to lower values observed across the PES membrane. These results suggest that the ATA membrane has a potential use not only for HDF, but also for long-time therapies of HD and HDF.

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.

Polydopamine-functionalized polyethersulfone membrane: A paradigm advancement in the field of α-amylase stability and immobilization.

Biocatalytic membranes have great potential in various industrial sectors, with the immobilization of enzymes being a crucial stage. Immobilizing enzymes through covalent bonds is a complex and time-consuming process for large-scale applications. Polydopamine (PDA) offers a more sustainable and eco-friendly alternative for enzyme immobilization. Therefore, surface modification with polydopamine as mussel-inspired antifouling coatings has increased resistance to fouling. In this study, α-amylase enzyme was covalently bound to a bioactive PDA-coated polyethersulfone (PES) membrane surface using cyanuric chloride as a linker. The optimal activity of α-amylase enzyme immobilized on PES/PDA membrane was obtained at temperature and pH of 55°C and 6.5, respectively. The immobilized enzyme can be reused up to five reaction cycles with 55% retention of initial activity. Besides, it maintained 60% of its activity after being stored for five weeks at 4°C. Additionally, the immobilized enzyme demonstrated increased Michaelis constant and maximum velocity values during starch hydrolysis. The results of the biofouling experiment of various membranes in a dead-end cell demonstrated that the PES membrane's water flux increased from 6722.7 Lmh to 7560.2 Lmh after PDA modification. Although α-amylase immobilization reduced the flux to 7458.5 Lmh due to enhanced hydrophilicity, compared to unmodified membrane. The findings of this study demonstrated that the membrane produced through co-deposition exhibited superior hydrophilicity, enhanced coating stability, and strong antifouling properties, positioning it as a promising candidate for industrial applications.

Preparation and Characterization of Polyethersulfone/Activated Carbon Composite Membranes for Water Filtration.

Ultrafiltration membrane technology holds promise for wastewater treatment, but its widespread application is hindered by fouling and flux reduction issues. One effective strategy for enhancing ultrafiltration membranes involves incorporating activated carbon powder. In this study, composite polyethersulfone (PES) ultrafiltration membranes were fabricated to include activated carbon powder concentrations between 0 and 1.5 wt.%, with carbon size fixed at 200 mesh. The ultrafiltration membranes were evaluated in terms of membrane morphology, hydrophilicity, pure water flux, equilibrium water content, porosity, average pore size, protein separation, and E-coli bacteria removal. It was found that the addition of activated carbon to PES membranes resulted in improvements in some key properties. By incorporating activated carbon powder, the hydrophilicity of PES membranes was enhanced, lowering the contact angle from 60° to 47.3° for composite membranes (1.0 wt.% of activated carbon) compared to the pristine PES membrane. Water flux tests showed that the 1.0 wt.% composite membrane yielded the highest flux, with an improvement of nearly double the initial value at 2 bar, without compromising bovine serum albumin rejection or bacterial removal capabilities. This study also found that the inclusion of activated carbon had a minor impact on the membrane's porosity and equilibrium water content. Overall, these insights will be beneficial in determining the optimal concentration of activated carbon powder for PES ultrafiltration membranes.

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.

Construction of novel antiplatelet modified polyethersulfone membrane and study into its blood compatibility.

Blood purification therapy is widely used in patients with renal insufficiency and severe infections, where membrane-associated thrombosis is a side effect. How to improve the hemocompatibility of dialysis membranes and reduce thrombosis is a focus of current research, in which platelets play a key role. However, few dialysis membranes that directly inhibit platelets have been developed to date. In this study, a polyethersulfone (PES) membrane was modified with ticagrelor, a platelet P2Y12 receptor inhibitor, and detailed characterization was performed. The ticagrelor modified PES membrane (TMPES) showed good hydrophilicity and anti-protein adsorption and significantly inhibited platelet adhesion, aggregation, and activation, which demonstrated good antithrombotic properties. In addition, the membrane had excellent red blood cell (RBC) compatibility, anticoagulant, and antiinflammatory effects, which demonstrated superior biosafety in cell and animal experiments. Therefore, the TMPES dialysis membrane could have potential in clinical applications.

Fabrication of a Modified Polyethersulfone Membrane with Anti-Fouling and Self-Cleaning Properties from SiO2-g-PHEMA NPs for Application in Oil/Water Separation.

To prepare anti-fouling and self-cleaning membrane material, a physical blending modification combined with surface grafting modification has been carried out; first, poly (2-hydroxyethyl methacrylate) grafted silica nanoparticles (SiO2-g-PHEMA NPs) were synthesized using surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and used as a blending modifier to fabricate a polyethersulfone (PES)/SiO2-g-PHEMA organic-inorganic membrane by the phase-inversion method. During the membrane formation process, hydrophobic PES segments coagulated immediately to form a membrane matrix, and the hydrophilic SiO2-g-PHEMA NPs migrated spontaneously to the membrane surface in order to reduce interfacial energy, which enhanced the hydrophilicity and anti-fouling properties of the PES/SiO2-g-PHEMA membrane. Importantly, the membrane surface contained abundant PHEMA segments, which provided active sites for further surface functionalization. Subsequently, the carboxyl-terminated fluorocarbon surfactant (fPEG-COOH) composed of hydrophilic polyethyleneglycol segments and low-surface-energy perfluorinated alkyl segments was synthesized via the esterification of fPEG with succinic anhydride. Lastly, the PES/SiO2-g-PHEMA/fPEG membrane was prepared by grafting fPEG-COOH onto surface of the PES/SiO2-g-PHEMA. Thus, a versatile membrane surface with both fouling-resistant and fouling-release properties was acquired. The PES/SiO2-g-PHEMA/fPEG membrane has a large oil-water flux (239.93 L·m-2·h-1), almost 21 times that of PES blank membrane and 2.8 times of the PES/SiO2-g-PHEMA membrane. Compared with the unmodified PES membrane, the flux recovery ratio increased from 45.75% to 90.52%, while the total flux decline ratio decreased drastically from 82.70% to 13.79%, exhibiting outstanding anti-fouling and self-cleaning properties. Moreover, the grafted fPEG segments on the membrane surface show excellent stability due to the presence of stable chemical bonds. The grafted segments remain at the surface of the membrane even after a long shaking treatment. This suggests that this PES/SiO2-g-PHEMA/fPEG membrane material has potential for application in oil/water separation.

Structure and properties of lipase activated by cellulose-silica polyethersulfone membrane for production of pentyl valerate.

Herein, this study extracted nanocrystalline cellulose (NC) and silica (SiO2) from raw oil palm leaves (OPL), and employed as nanofillers in polyethersulfone (PES) to produce NC-SiO2-PES as support to immobilize Candida rugosa lipase (CRL) (NC-SiO2-PES/CRL). XRD, TGA-DTG and FTIR-ATR data affirmed that NC and SiO2 were isolated from OPL with corresponding crystallinity indices of 68 % and 70 %. A 0.02 cm membrane size with 5% (w/v) of NC-SiO2 without PVP K30 was optimal for membrane fabrication. CRL immobilized on the Glut-AP-NC-SiO2-PES membrane gave a higher conversion of pentyl valerate (PeVa) (91.3 %, p < 0.05) compared to Glut-NC-SiO2-PES (73.9 %) (p < 0.05). Characterization of the NC-SiO2-PES/CRL biocatalyst verified the presence of CRL. Hence, raw OPL is a proven good source of NC and SiO2, as reinforcement nanofillers in PES. The overall findings envisage the promising use of NC-SiO2-PES/CRL to catalyze an expedient and high yield of PeVa, alongside the suitability of NC-SiO2-PES for activating other enzymes.

Localized surface plasmon resonance (LSPR) biosensor based on thermally annealed silver nanostructures with on-chip blood-plasma separation for the detection of dengue non-structural protein NS1 antigen.

Early diagnosis of dengue biomarkers by employing a technology that is less labor- and time-intensive and offers higher sensitivity and lower limits of detection would find great significance in the developing world. Here, we report the development of a biosensor that exploits the localized surface plasmon resonance (LSPR) effect of silver nanostructures, created via thermal annealing of thin metal film, to detect dengue NS1 antigen, which appears as early as the onset of infection. The biosensor integrates membrane-based blood-plasma separation to develop lab-on-chip device that facilitates rapid diagnosis (within 30 min) of dengue NS1 antigen from a small volume (10 µL) of whole blood. The refractive index (RI) sensitivity of the LSPR biosensor was verified by using aqueous glycerol (0-100 wt%) which showed that it is sufficiently sensitive to detect 10-3 change in RI, which is comparable to that observed with protein-protein interaction. The RI sensitivity was utilized to demonstrate protein binding by using bovine serum albumin and detection of antibody-antigen immune reaction by binding human chorionic gonadotropin antigen to immunoglobulin antibody immobilized in our LSPR biosensor. Next, we demonstrated the detection of NS1 in plasma obtained via centrifugation and in plasma separated on-chip. From 10 µL of whole blood spiked with NS1 antigen, our biosensor reliably detects 0.06 µg/mL of NS1, which lies within the clinical limit observed during the first seven days of infection, with a sensitivity of 9 nm/(µg/mL). These results confirm that the proposed LSPR biosensor can potentially be used in point-of-care dengue diagnostics.

Optimization of transglutaminase (TG) immobilization on the surface of polyethersulfone ultrafiltration membrane and its characteristics in a membrane reactor.

The process of microbial transglutaminase (TG) covalent immobilization on an ultrafiltration membrane surface, the optimum immobilization conditions and the characteristics of the enzymatic membrane in a reactor were investigated. The process of TG immobilization on polyethersulfone (PES) membrane surfaces was analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. The optimal condition for TG immobilization was in pH 5.0 phosphate buffer containing TG (20 U/mL). The immobilized TG had a high affinity for the substrate according to the kinetic parameters and retained 50% activity until the twentieth day. Water contact angle and antifouling tests showed that the hydrophilicity of immobilized-transglutaminase membrane was improved compared with pure PES membrane. The enzyme could maintain relatively high activity under a transmembrane pressure of 0.15 MPa. Moreover, the enzymatic membrane had higher relative membrane flux at 0.15 MPa in a membrane reactor, and could retain its activity in pH 5.0 phosphate buffer and catalysis under 40 °C.

Comparative Extractables Study of Autoclavable Polyethersulfone Filter Cartridges for Sterile Filtration.

Sterile filters are ubiquitous in biopharmaceutical manufacturing processes. Because such filters are in direct contact with the process fluid, profiling of the extractables is of utmost importance. The work presented here reveals the extractables profile from filter cartridges for sterilizing-grade filtration, which were obtained from six different vendors. All filters contain a 0.2 µm polyethersulfone membrane for sterile filtration combined with a polyethersulfone pre-filter with retention rates spanning from 0.4 to 0.6 µm. These filter cartridges are designed for use in stainless steel housings which allow for in-line steam sterilization. A combination of different analytical techniques such as (headspace) gas chromatography-mass spectrometry, ultra-performance liquid chromatography-high-resolution mass spectrometry (electrospray ionization), inductively coupled plasma mass spectrometry, total organic carbon, non-volatile residue, conductivity, and pH value were applied to develop a comprehensive extractables profile on a qualitative and semi-quantitative basis. Pure ethanol and purified water were used as extraction media. The extractables profile consisted of various polyolefin-related extractables, additives such as antioxidants and degradation products thereof, hydrocarbons, and processing aids in addition to membrane-related extractables.LAY ABSTRACT: Filter cartridges or other filter products for sterile filtration are currently most commonly made of polymeric materials such as polypropylene, and a filter membrane material such as polyethersulfone. These materials will usually release chemical substances upon extraction in the laboratory (extractables), or upon application in biopharmaceutical processing (leachables). Potential extractables and leachables are additives used to tailor the physicochemical properties and to protect the polymeric materials, or degradants of these substances, or they arise from substances used during the manufacturing of the filter cartridges. Multiple analytical techniques were applied here to investigate the concentration and chemical nature of extractables obtained upon application of two distinct extraction solvents. Typical extractables found were antioxidants or releasing agents in addition to compounds originating from the polyethersulfone membrane.

Impact of feed water pH and membrane material on nanofiltration of perfluorohexanoic acid in aqueous solution.

Nanofiltration was thought to be a good option for the recovery of perfluorohexanoic acid (PFHxA) from industrial wastewater. In this study, two commercially available nanofiltration (NF) membranes (NF 270 and NTR-7450) were tested to concentrate the PFHxA in aqueous solution. Filtration test was conducted in crossflow filtration mode. Membrane flux and PFHxA rejection rate were monitored throughout the filtration test. The impact of initial feed water pH on membrane performance was investigated. Results demonstrated that the two NF membranes showed different response to the change of initial feed water pH, which was caused by the intrinsic properties of membrane material. The flux performance of NF 270 was stable, while its rejection rate of PFHxA was very sensitive to the change of initial feed water pH. Opposite result was obtained with NTR-7450. It had a very good stability on rejection rate, while its flux was very sensitive to the change of initial feed water pH. The mechanisms behind these phenomena were also discussed. The results obtained in this study should be very useful for the process design in practical engineering.

Characterization of Polyethersulfone Membranes for Tear Fluid Collection.

BACKGROUND: The sampling of tear fluids is essential for the reproducibility of tear assays. But, an operable, efficient and stable method for tear collection has not been widely established. This study evaluated the utility of polyethersulfone membranes (PESms) for tear collection and compared it with two frequently employed approaches: the use of Schirmer test paper (STP) and capillary tube (CaT). METHODS: STP and PESms (0.45 and 0.65 µm) were examined using scanning electron microscopy(SEM), applied to soak up water, bovine albumin and cellular lysates, and employed to collect tear fluids from rabbits. The proteins in the cellular lysates and tear fluid were characterized through band profiling of SDS-polyacrylamide electrophoresis (PAGE) gels. Western blot analyses with antibodies against vinculin and lysozyme C were used to compare rabbit tear fluids sampling with CaT, STP and PESm. Rabbit ocular surfaces and eye blinking were evaluated under different conditions. RESULTS: The SEM examination showed that PESms exhibited much smoother surfaces and smaller pores than STP. PESm65 exhibited the highest water absorption and water recovery in vitro. Although SDS-PAGE revealed no obvious differences in the cellular or tear protein band patterns, the highest Dice's similarity coefficient and lowest variance in the differences in peak heights(i.e. band intensities) were observed in the PESm65 samples. The Western blot showed that the band intensities of vinculin protein in tear fluids obtained using CaT, STP and PESm65 are in order of CaTPESm65>STP. PESm65 exhibited less blinks and conjunctival injuries than STP during sampling-rabbit tears. CONCLUSION: Tear collection using PESm has less variance in protein components and is easily operable than traditional STP. PESm possesses the potential for clinical utilization in diagnostic tear assays.

Biofouling prevention using silver nanoparticle impregnated polyethersulfone (PES) membrane: E. coli cell-killing in a continuous cross-flow membrane module.

Biofouling significantly decreases membrane performance. So silver nanoparticle (Ag-NP) was impregnated selectively on a sulfonated polyethersulfone (SPES) membrane and its efficacy was tested in a continuous, cross-flow membrane module. The main challenges are: (i) to prevent biofouling on the membrane surface, (ii) achieve zero bacterial cell (E. coli) count in the permeate water, (iii) maintain Ag concentration in the permeate stream within the permissible limit of drinking water and (iv) maintain a high tensile strength of the membrane to prevent mechanical failure. Addressing these factors would ensure a long and productive service-life of the membrane. To this end, 104CFU/ml of E. coli cell-suspension was passed through the Ag-SPES membrane of 150µm total thickness, which has a narrow (1.74µm thickness), upper surface of Ag-NPs. We achieved zero E. coli cell-count and a minimum (10µg/L) Ag concentration in the permeate stream; simultaneously increasing the tensile strength from 2.78MPa to 3.92MPa due to Ag-NP impregnation. Thus, for a continuous inlet flow of E. coli contaminated water, the membrane module could deliver an almost constant permeate flow rate of 3.45L per hour, due to complete E. coli cell-killing. Simultaneously, Ag concentration in permeate stream is well-below the WHO's recommended limit of 100µg/L, for potable quality water. Therefore, the Ag-SPES membrane can be used as an anti-biofouling membrane in a continuous operational mode.