Study of synthesis parameters and active layer morphology of interfacially polymerized polyamide-polysulfone membranes

Thin film composite (TFC) polyamide membranes were prepared on a polysulfone support membrane and the effect of various synthesis conditions on the active layer morphology, the physicochemical properties and the membrane performance was investigated. The support membrane porosity factor had a significant effect on the TFC membrane performance. A polyamide top layer was formed within 15 s of reaction. Prolonging the reaction time, although resulting in a thicker active layer, only had a minor influence on the membrane performance. This highlights the importance of the incipient layer of the polyamide structure on its performance. The addition of both a surfactant and a base to the amine solution resulted in a change of the active layer morphology and an improved performance. The effect of additives was attributed to changes in the polymerization mechanism. In addition, it was demonstrated that curing at 50°C resulted in an improved membrane performance, due to more cross-linking of the active layer. Curing at higher temperatures deteriorated the structure of the support membrane. This research shows that the TFC membrane performance is well correlated with the changes in the active layer morphology, measured using SEM, AFM and TEM; whereas only minor changes in the physicochemical characteristics of the membranes were detected by zeta potential and ATR-FTIR spectroscopy when the same synthesis parameters were varied.status: publishe

Dynamic response of ultrathin highly dense ZIF-8 nanofilms

Ultrathin ZIF-8 nanofilms are prepared by facile step-by-step dip coating. A critical withdrawal speed allows for films with a very uniform minimum thickness. The high refractive index of the films denotes the absence of mesopores. The dynamic response of the films to CO2 exposure resembles behaviour observed for nonequilibrium organic polymers

Solvent-resistant nanofiltration for product purification and catalyst recovery in Click chemistry reactions

The quickly developing field of "click" chemistry Would undoubtedly benefit from the availability of an easy and efficient technology for product purification to reduce the potential health risks associated with the presence of copper in the final product. Therefore. solvent-resistant nanofiltration (SRNF) membranes have been developed to selectively separate "clicked" polymers from the copper catalyst and solvent. By using these solvent-stable cross-linked polyimide membranes in diafiltration, up to 98% of the initially present copper could be removed through the membrane together with the DMF solvent, the polymer product being almost completely retained. This paper also presents the first SRNF application in which the catalyst permeates through the membrane and the reaction product is retained

Pituitary tumors contain a side population with tumor stem cell-associated characteristics

Pituitary adenomas cause significant endocrine and mass-related morbidity. Little is known about the mechanisms that underlie pituitary tumor pathogenesis. In the present study, we searched for a side population (SP) in pituitary tumors representing cells with high efflux capacity and potentially enriched for tumor stem cells (TSCs). Human pituitary adenomas contain a SP irrespective of hormonal phenotype. This adenoma SP, as well as the purified SP (pSP) that is depleted from endothelial and immune cells, is enriched for cells that express ‘tumor stemness’ markers and signaling pathways, including epithelial–mesenchymal transition (EMT)-linked factors. Pituitary adenomas were found to contain self-renewing sphere-forming cells, considered to be a property of TSCs. These sphere-initiating cells were recovered in the pSP. Because benign pituitary adenomas do not grow in vitro and have failed to expand in immunodeficient mice, the pituitary tumor cell line AtT20 was further used. We identified a SP in this cell line and found it to be more tumorigenic than the non-SP ‘main population’. Of the two EMT regulatory pathways tested, the inhibition of chemokine (C-X-C motif) receptor 4 (CXCR4) signaling reduced EMT-associated cell motility in vitro as well as xenograft tumor growth, whereas the activation of TGFβ had no effect. The human adenoma pSP also showed upregulated expression of the pituitary stem cell marker SOX2. Pituitaries from dopamine receptor D2 knockout (Drd2−/−) mice that bear prolactinomas contain more pSP, Sox2+, and colony-forming cells than WT glands. In conclusion, we detected a SP in pituitary tumors and identified TSC-associated characteristics. The present study adds new elements to the unraveling of pituitary tumor pathogenesis and may lead to the identification of new therapeutic targets.Fil: Mertens, Freya. Ku Leuven University (University of Leuven). Research Unit of Stem Cell Research; BélgicaFil: Gremeaux, Lies. Ku Leuven University (University of Leuven). Research Unit of Stem Cell Research; Bélgica; BélgicaFil: Chen, Jianghai. Huazhong University of Science and Technology. Tongji Medical College Union Hospital; China. Ku Leuven University (University of Leuven). Research Unit of Stem Cell Research; BélgicaFil: Fu, Qiuli. Ku Leuven University (University of Leuven). Research Unit of Stem Cell Research; Bélgica. Zhejiang Provincial Key Laboratory of Ophthalmology; China. Medical College of Zhejiang University. Eye Center of the 2nd Affiliated Hospital; ChinaFil: Willems, Christophe. Ku Leuven University (University of Leuven). Research Unit of Stem Cell Research; BélgicaFil: Roose, Heleen. Ku Leuven University (University of Leuven). Research Unit of Stem Cell Research; BélgicaFil: Govaere, Olivier. KU Leuven. Department of Imaging and Pathology; BélgicaFil: Roskams, Tania. KU Leuven. Department of Imaging and Pathology; BélgicaFil: Cristina, Silvia Carolina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires; ArgentinaFil: Becu Villalobos, Damasia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Joriseen, Mark. University Hospitals Leuven. Unit Head and Neck Oncology; BélgicaFil: Vander Poorten, Vincent. University Hospitals Leuven. Research Group Experimental Oto-Rhino-Laryngology, ; BélgicaFil: Bex, Marie. University Hospitals Leuven. Unit Clinical and Experimental Endocrinology; BélgicaFil: Van Loon, Johannes. University Hospitals Leuven. Research Group Experimental Neurosurgery and Neuroanatomy; BélgicaFil: Vankelecom, Hugo. Ku Leuven University (University of Leuven). Research Unit of Stem Cell Research; Bélgic

Synthesis and Characterization of Micro-Patterned Thin Film Composite (TFC) Membranes for Water Treatment

Thin film composite (TFC) membranes, mostly used in reverse osmosis and nanofiltration are critical for water treatment and provide clean and desalinated water to millions on daily basis. The two main limitations: fouling and low permeance of these membranes greatly affect their performance and sustainability. Several measures have been taken for membrane fouling mitigation including chemical, physical and hydrodynamic methods. Recently, patterned membranes have been evolved as an innovative tool for fouling mitigation. However, the synthesis procedure for patterned membranes has not been developed at a scale-up level. Lately, Prof. Vankelecom’s research group (KU Leuven) has introduced a non-solvent spray assisted phase inversion (s-NIPS) as an efficient synthesis procedure for patterned membranes. s-NIPS makes the use of a patterned casting knife combined with modified non-solvent spray assisted phase inversion process. It overcomes the limitations of previously used methods such as phase separation micromolding (PSμM) and imprinting lithography (IL) as phase separation induces from the pattern side and no reduction in pore size is observed. Previous studies for patterned TFC membranes have only managed to create a top selective layer above patterned UF supports with heights in the range of 160 nm to 5 μm which limits the potential advantages of such membranes. s-NIPS patterned supports can significantly enhance the intrinsic low permeance of such NF/RO membranes by producing UF supports with higher pattern heights up to 180 μm. Hence, in this study, a defect-free thin film polyamide layer was developed over s-NIPS micro-patterned supports through interfacial polymerization (IP). In order to achieve this, several parameters were explored including effect of monomer concentrations, effect of pattern height, removal of excess monomer solution from the valleys before IP, effect of UF polymer support and spin assisted layer by layer thin film deposition. It was found that the 1, 2 and 3 layered TFC membrane could give a maximum of ca. 85, 96 and 97 % MgSO4 retention respectively at enhanced permeance. Furthermore, 2 layered spin assisted IP with 2 wt% MPD and 0.1 wt% TMC concentration was found to be optimum for PSf500 supports (polysulfone supports prepared using casting knife with pattern height 500 μm) with 94% MgSO4 retention at the permeance of 1.66 LMH/bar.<br /

Significant Quantitative and Qualitative Transition in Pituitary Stem / Progenitor Cells Occurs during the Postnatal Development of the Rat Anterior Pituitary

We reported recently that a pituitary-specific transcription factor PROP1 is present in SOX2-positive cells and disappears at the early stage of the transition from progenitor cell to committed cell during the embryonic development of the rat pituitary. In the present study, we examined the localisation and identification of SOX2-positive and PROP1/SOX2-positive cells in the neonatal and postnatal rat pituitaries by immunohistochemistry. Quantitative analysis of immunoreactive cells demonstrated that SOX2-positive pituitary stem/progenitor cells are not only predominantly localised in the marginal cell layer, but also are scattered in the parenchyma of the adult anterior lobe. In the marginal cell layer, the number of PROP1/SOX2-positive cells significantly decreased after postnatal day 15, indicating that a significant quantitative transition is triggered in the marginal cell layer during the first postnatal growth wave of the anterior pituitary. By contrast, other phenotypes of SOX2-positive stem/progenitor cells that express S100β appeared in the postnatal anterior pituitary. These data suggested that quantitative and qualitative transition occurs by acquisition of a novel mechanism in terminal differentiation in the postnatal development of the anterior pituitary

Immunohistochemical, morphological and ultrastructural resemblance between dendritic cells and folliculo-stellate cells in normal human and rat anterior pituitaries

Immunolabeling of cryo-sections of human anterior pituitaries obtained at autopsy, and of cryo-sections of freshly prepared rat anterior pituitaries, with a panel of monoclonal antibodies against markers of the monocyte/dendritic cell/macrophage lineage, reveals in both species a characteristic pattern of immunopositive cells, among which many cells with dendritic phenotype are found. Cells characterized by marker expression of MHC-class II determinants and a dendritic morphology are present in both human and rat anterior pituitary. Markers characteristic of dendritic cells such as the L25 antigen and the OX62 antigen were present in anterior pituitaries from human and rat respectively. The population of MHC-class II expressing dendritic cells of the rat anterior pituitary is compared at the ultrastructural level with the folliculo-stellate cell population, which cell type has been previously characterized by its distinctive ultrastructure and immunopositivity for the S100 protein. Using immune-electron microscopy of rat anterior pituitaries fixed with periodate-lysine-paraformaldehyde, we were able to distinguish non-granulated cells expressing MHC-class II determinants, whereas no MHC-class II expression was found in the granulated endocrine cells. Using double immunolabeling of cryo-sections of these rat AP with 25 nm and 15 nm gold labels, we demonstrated an overlap between the populations of MHC-class II-expressing and S100 protein-expressing cells. Furthermore, MHC-class II-expressing and S100-positive cells showed ultrastructural characteristics that have been previously ascribed to folliculo-stellate cells. At the light microscopical level in the rat AP, a proportion of 10 to 20% of the S100-positive cells was found immunopositive for the MHC-class II marker OX6. In the hu

Applicability of organic carbonates as green solvents for membrane preparation

Common polar aprotic solvents, like N,N-dimethylformamide (DMF), 1,4-dioxane, N,N-dimethylacetamide (DMA) and tetrahydrofuran (THF), are excellent for membrane preparation. However, due to their toxicity or volatile nature, it would be useful to replace them by “greener” solvents for environmental and health reasons. In this work, organic carbonates, obtainable through carbon dioxide fixation, were selected as green solvents to find possible use in membrane preparation. Polymer solubility experiments were performed to screen their applicability in the phase inversion process to create porous membrane with appropriate structures and selectivities. Hansen solubility parameters were used to rationalize the solubility results. Membrane morphology and pore structure were characterized using scanning electron microscopy (SEM), while the performance of the membrane was determined by applying a 35 μM aqueous feed solution of rose bengal (RB, MW = 1017 Da) to screen the potential of these polymer/organic carbonate systems toward nanofiltration application

Tools and techniques for solvent selection: green solvent selection guides

Driven by legislation and evolving attitudes towards environmental issues, establishing green solvents for extractions, separations, formulations and reaction chemistry has become an increasingly important area of research. Several general purpose solvent selection guides have now been published with the aim to reduce use of the most hazardous solvents. This review serves the purpose of explaining the role of these guides, highlighting their similarities and differences. How they can be used most effectively to enhance the greenness of chemical processes, particularly in laboratory organic synthesis and the pharmaceutical industry, is addressed in detail