Billions of people rely solely on groundwater for drinking and daily use. In the last few decades, groundwater was shown to be contaminated with arsenic in high concentrations, especially in Asian countries such as Bangladesh. Arsenic (As) is ranked the first among 20 toxic substances by the Agency for Toxic Substances and Disease Registry (ATSDR) and United States Environmental Protection Agency (USEPA). Because many diseases and deaths were linked to consumption of arsenic-contaminated groundwater, the world health organization (WHO) reduced the arsenic standard level for drinking water from 50 to 10 µg L-1. Urgent demands for safe drinking water lead to developing potential technologies for removal of arsenic from groundwater. Arsenic is mainly present as uncharged As(III) in groundwater, which makes it difficult to be efficiently removed by conventional treatment methods. Therefore, membrane technology could be a promising potential solution. Because membrane technology has not been widely tested for arsenic removal, a novel in-house defect-free interfacially-polymerized (IP) cross-linked polyamide thin-film composite (TFC) nanofiltration membrane, namely, PIP-KRO1, was tested in this research. Two commercial TFC membranes, namely Dow NF270 and Sepro RO4, were also tested and compared to PIP-KRO1. The membranes were tested at four different pH conditions (4, 6, 8, and 10) in a cross-flow flat sheet membrane unit. The experiments were divided into two parts: (i) the membranes were tested for water permeance and salt (NaCl) removal and (ii) tested for As(III) removal in the presence of 250 ppm NaCl. The results in this study showed strong size sieving rejection for RO4 and a combination of size sieving and charge exclusion mechanisms for PIP-KRO1 and NF270. In general, the rejection trend was RO4 > PIP-KRO1 > NF270 for both NaCl and As(III). In contrast, the trend for water permeance was NF270 > PIP-KRO1 > RO4. The minimum and maximum salt rejection at pH 4 and pH 10, respectively, were 85 and 98.8% for RO4, 57 and 89% for PIP-KRO1, and 34 and 76.8% for NF270. In addition, the TFC membranes demonstrated a maximum As(III) rejection of 98.7, 69.5, and 46.3% for RO4, PIP-KRO1, and NF270, respectively. Based on the characterizations of the membranes, PIP-KRO1 had the highest cross-linking (N/O ratio) followed by RO4 and NF270, respectively. The same trend was observed for the thickness of the polyamide selective layer (PIP-KRO1 > RO4 > NF270). The zeta potential for NF270 was slightly higher than that for PIP-KRO1; RO4 had much lower membrane surface charge. In terms of surface roughness, the following trend was observed: RO4 > PIP-KRO1 > NF270.

This research work examines the process of block copolymer membrane fabrication by self-assembly combined by non-solvent induced phase separation. Self-assembly takes place from the preparation of the primordial solution until the moment of immersion in a non-solvent bath. These mechanisms are driven thermodynamically but are limited by kinetic factors. It is shown in this work how the ordering of the assembly of micelles is improved by the solution parameters such as solvent quality and concentration of block copolymer. Order transitions are detected, yielding changes in the morphology. The evaporation of the solvents after casting is demonstrated to be essential to reach optimum membrane structure. The non-solvent bath stops the phase separation at an optimum evaporation time.

Separating oil/water emulsions is significant for the ecosystem and the petroleum and processing industry. To this end, we prepared an underwater superoleophobic membrane inspired by unique wettability of the fish scales. This membrane was fabricated by a facile vacuum filtration process of sepiolite nanofibers and chitosan, and after the cross-linking via glutaraldehyde, a self-standing membrane was obtained. The as-prepared membrane exhibited excellent capability of separating both the surfactant-free and surfactant-stabilized oil-in-water emulsions with high efficiency. This sepiolite fibrous membrane offers a convenient, reliable and efficient way for the large-scale de-emulsification process.

This research study describes the gas separation performance of different sets of Polyethyleneoxide-block-Polysulfone-block-Polyethyleneoxide/poly(ether-block-amide) (PEO-b-PSU-b-PEO/Pebax) composite membranes for CO2 separation from N2 and CH4. Gas permeation properties of the membranes prepared were studied at ambient temperature (21oC) and 8bar. The dependence of gas flux and selectivity on pressure was explored for different pressures from 2.5 bar up to 19 bar also at ambient temperature. Pebax/PAN composite membranes have a range of CO2 permeance of 4467±274 GPU, 365±64 GPU for CH4 and 152±17 GPU for N2 with CO2/N2 and CO2/CH4selectivities ranges of 30 and 13 respectively. Improved CO2/N2 and CO2/CH4 selectivities coupled with flux reduction were obtained from the introduction of PEO-b-PSU-b-PEO films on Pebax/PAN composite membranes. The gas flux reduced to about one-tenth of Pebax/PAN membrane’s while the selectivities obtained for all the PEO-b-PSU-b- PEO/Pebax/PAN membrane range from 33 to 60 for CO2/N2 and 17 to 33 for CO2/CH4 as the thickness of PEO-b-PSU-b-PEO top layer increases.

We investigated the effects of angiotensinogen (Ang), angiotensin I (Ang I), and angiotensin II (Ang II) on the fluidity of phosphatidylcholine vesicles. Changes in fluidity were assessed by changes in anisotopy values calculated from fluorescence polarization measurements. All three compounds produced an increase in membrane fluidity when localized inside the phosphatidylcholine vesicles. When placed outside the vesicles. Ang II increased bilayer rigidity (decreased fluidity), whereas Ang and Ang I produced no effect. These results suggest the possibility that these peptides may alter the fluidity of cell membranes by a direct action on the phospholipid bilayer, which may in turn interfere with receptor-mediated effects.

In this work, we report a facile and robust surface membrane modification method via a simple coating of PVDF membrane using tannic acid (TA) followed by oxidation with sodium periodate (NaIO4). The modified membranes were investigated by SEM, AFM, XPS, FTIR, and a water contact angle measurement. The Contact angle measurement shows that the TA modified membrane exhibits superhydrophilicity and underwater oleophobicity. Results from FTIR and XPS indicate that the carboxylic groups were formed on the surface of the TA modified membrane due to the oxidation of quinone by NaIO4, which is the key to superhydrophilicity of the TA modified membrane surface. In addition, the modified membrane was tested for oil-in-water emulsion separation. A high TOC rejection of 99% was achieved for different kinds of surfactant-stabilized oil-in-water emulsions as well as the surfactant-free oil/water mixture. The modified membrane not only showed a good water flux and oil/water separation performance but also exhibited excellent recyclability and chemical stability. Also, the developed method is versatile and can be applied to the different types of substrate material. This robust, simple, and green approach gives great potential to fabricate large-scale material surfaces for the industrial oily wastewater treatment.

Les micropolluants d'origine pharmaceutique tels que les antibiotiques, les hormones, les anti-inflammatoires ou les médicaments anticancéreux sont généralement réfractaires aux procédés classiques de traitement des eaux et leur rejet dans l'environnement même à l'état de traces (< µg/L) pose de réels problèmes environnementaux et de santé publique. Le traitement de ces effluents par voie enzymatique semble être une alternative intéressante et ce d'autant plus si le biocatalyseur est immobilisé directement à la surface d'une membrane afin d'améliorer sa stabilité et permettre sa réutilisation. Le travail à réaliser dans le cadre de cette thèse vise la conception et l'optimisation de bioréacteurs destinés à la dégradation de micropolluants ciblés. Réalisé dans le cadre d'un contrat Européen (ENDETECH), ce travail est une collaboration avec d'autres équipes de recherche européennes en charge de sélectionner les biocatalyseurs et de mettre au point les méthodes analytiques de détection et de caractérisation des produits de la réaction. / Pharmaceutical micropollutants such as antibiotics, hormones, anti-inflammatory or anti-cancer drugs are usually reluctant to conventional wastewater treatment processes and their disposal in the environment, even at low concentrations (< µg/L) may have an impact on human health. The enzymatic treatment of these effluents seems a promising alternative if the biocatalyst is immobilized on a membrane to enhance its stability and to enable its reuse. This thesis work aims at designing and optimizing bioreactors for micropollutants degradation. It is a collaboration (ENDETECH project) with other European research teams in charge of selecting the biocatalysts and developing analytical methods for the detection and characterization of transformation products.

Indiana University-Purdue University Indianapolis (IUPUI) / The cell membrane serves as a barrier between the interior and exterior of a living cell. Its main structural component is the lipid bilayer, which is composed of various kinds of lipids that segregate into domains. These lipid domains, distinguished in composition and physical properties from the bulk lipids that surround them, are believed to modulate the function of resident proteins by providing an appropriate lipid environment. Polyunsaturated fatty acids (PUFA) are a type of fatty acid that contain multiple C=C double bonds. They have a lot of health benefits, which may originate in part due to their incorporation into lipids in the plasma membrane. Hypotheses that PUFA-containing lipids laterally separate into domains and/or modulate the structure of existing domains have been raised to explain the fundamental role played by PUFA. In our research, we use molecular dynamics (MD) simulations to simulate model membranes composed of PUFA-containing phospholipids and to investigate their interaction with cholesterol and vitamin E that are influential membrane constituents. The presumptive function for vitamin E in membranes is to protect PUFA against oxidation. Although the chemistry of the process is well established, the role played by the molecular structure that we address with atomistic molecular dynamics (MD) simulations remains controversial. We compared the behavior of vitamin E in lipid bilayers composed of 1-stearoyl-2-docosahexaenoylphosphatidylcholine (SDPC, 18:0-22-6PC) and 1-stearoyl-2-oleoylphosphatidylcholine (SOPC, 18:0-18:1PC) via all-atom MD simulations at 37° C. SDPC represents a PUFA-containing lipid, and SOPC serves as monounsaturated control. From the calculation of van der Waals energy of interaction between vitamin E and fatty acid (FA) chains, we found higher probability that the PUFA chains surround the chromanol head group on vitamin E. This is further demonstrated by probability density maps of acyl chains around vitamin E molecules. Also, an ability to more easily penetrate deep into the PUFA containing bilayer of vitamin E is detected by faster flip-flop rate of vitamin E observed in the SDPC bilayers. These results showed that the high disorder of polyunsaturated docosahexaenoic acid (DHA) chains allows vitamin E to easily tunnel down into the bilayer and often brings the PUFA chains up to the surface of the bilayer, improving the likelihood that the reactive (hydroxyl) group on vitamin E would encounter a lipid peroxyl radical and terminate the oxidation process. Thus, the simulations indicate that the molecular structure of vitamin E supports its role as an antioxidant in a PUFA-containing membrane. A subsequent study on the partitioning of vitamin E into PUFA-containing lipids was done by analyzing the binding energy of vitamin E in the corresponding lipid bilayer. The binding energy is obtained from the potential of mean force (PMF) profile of vitamin E alone the membrane normal direction (z), which is calculated from umbrella sampling MD simulations. We found the binding in SDPC is smaller in SOPC, indicating that vitamin E does not prefer PUFA-containing phospholipids. The flip-flop rate was also estimated from the PMF profile, confirming that vitamin E flip-flops across the SDPC bilayer more easily than the SOPC bilayer. From the simulations it was noted that the membrane deforms as vitamin E is pulled out, which suggests interactions between the phospholipids contribute to the binding energy of the vitamin E. In a final study, a comparison was made between the effect on membrane organization of the three types of long chain omega-3 (n-3) PUFA found in fish oils: eicosapentaenoic acid (EPA, 20:5), DHA (22:6) and docosapentaenoic acid (DPA, 22:5). MD simulations were run on lipid bilayers composed of 1-stearoyl-2-eicosapentaenoylphosphatidylcholine (EPA-PC, 18:0-20:5PC), 1-stearoyl-2-docosapentaenoylphosphatidylcholine (DPA-PC, 18:0-22:5PC), SDPC (DHA-PC, 18:0-22:6PC) and, as a monounsaturated control, SOPC (OA-PC, 18:0-18:1PC) in the absence and presence of cholesterol. By analyzing the physical properties such as membrane order and thickness, we found all three n-3 PUFAs disorder the membrane. The disordering is greatest with EPA and least with DPA. Unique among the n-3 PUFA-containing membranes, there is region of high order in the upper portion of the DPA chain. The PUFA-containing lipids were found to less favorably interact with cholesterol compared to the OA-containing lipid, which is caused by their disorder. We speculate that differences between DPA, DHA and EPA might potentially modulate their effect on lipid domain formation.

BACKGROUND: Epiretinal membranes are a common disease that can either be idiopathic, meaning no cause can be detected this is usually caused by aging, or secondary which is caused by injury disease or surgery. Despite current treatment methods, there are still persistence of this disease in some rare cases. Methotrexate although traditionally used to treat cancer and rheumatoid arthritis has been being explored as a treatment option in the field of ophthalmology for use against proliferative and migrating cellular diseases coupled with inflammation. Methotrexate has been reported in a few ocular diseases to reduce or stop cell migration and proliferation due to this finding a case study was conducted with this recurrent ERM patient to test its effectiveness against this disease. PURPOSE: To investigate a potential new treatment method for recurrent epiretinal membranes. After a visually significant epiretinal membrane develops there would be an epiretinal membrane (ERM) peel performed. Traditionally if there is recurrence of epiretinal membranes post ERM peeling the patient will be treated with an internal limiting membrane (ILM) peel. For most cases, this will resolve the issue. In the rare instances where an ILM peel doesn’t resolve recurrence, like in this case, we sought to test whether a series of methotrexate injections could help prevent ERM re-proliferation. CASE REPORT: Reporting on a case of a 65-year-old woman with a recurrent recalcitrant epiretinal membrane. This membrane was treated with a pars plana vitrectomy and ERM peeling. The membrane grew back and was met with an ILM peel in hopes of resolution. With continuing recurrence, the patient was treated with another ERM and ILM peel and 12 weekly intravitreal methotrexate (MTX) injections. METHODS: A patient with persistent recurrent epiretinal membranes underwent three surgeries in an attempt to cure the ERM. At every clinical visit, best corrected distance visual acuity was assessed with a Snellen Vision Test and the retina was imaged using optical coherence tomography. Measurements were taken using the machines built in analysis technology to measure retinal thickness and retinal volume at each visit. These were graphed alongside visual acuity to determine complimenting trends. RESULTS: At the first visit the patient began treatment at a visual acuity of 20/200 and a central macular thickness of 676. Seven months after the final methotrexate injection the patient was at a visual acuity of 20/80 and a central macular thickness of 328. The overall results were that visual acuity and central macular thickness significantly improved without ERM recurrence at seven months after treatment. CONCLUSION: When an ERM is significantly impacting the patient’s visual acuity surgery is usually performed in the form of an ERM peel or ILM peel. Although treatment of recurrent epiretinal membranes is well maintained by these procedures there are a small percentage of cases where recurrence is still found post ILM surgery. This case represents the first documented use of MTX to treat recurrent ERM and it suggests great potential for its use in otherwise treatment resistant cases. More research is required to better understand the true potential of this treatment option as well as associated risks.

A thesis submitted to the Faculty of Medicine. University of the Witwatersrand. Johannesburg, for the Degree of Doctor of Philosophy / Abnormal cell membrane function and altered cellular cation homeostasis have been implicated in the pathogenesis of essential hypertension. The role of these factors in the aetiology of malignant hypertension is unknown. (Abbreviation abstract) / Andrew Chakane 2019