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Membranes (Basel) ; 11(3)2021 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-33652896


Forward osmosis (FO) modules currently suffer from performance efficiency limitations due to concentration polarisation (CP), as well as pressure drops during operation. There are incentives to further reduce CP effects, as well as optimise spacer design for pressure drop improvements and mechanical support. In this study, the effects of applying transmembrane pressure (TMP) on FO membrane deformation and the subsequent impact on module performance was investigated by comparing experimental data to 3D computational fluid dynamics (CFD) simulations for three commercial FO modules. At a TMP of 1.5 bar the occlusion of the draw-channel induced by longitudinal pressure hydraulic drop was comparable for the Toray (16%) and HTI modules (12%); however, the hydraulic perimeter of the Profiera module was reduced by 46%. CFD simulation of the occluded channels indicated that a change in hydraulic perimeter due to a 62% increase in shear strain resulted in a 31% increase in the Reynolds number. This reduction in channel dimensions enhanced osmotic efficiency by reducing CP via improved draw-channel hydrodynamics, which significantly disrupted the external concentration polarization (ECP) layer. Furthermore, simulations indicated that the Reynolds number experienced only modest increases with applied TMP and that shear strain at the membrane surface was found to be the most important factor when predicting flux performance enhancement, which varied between the different modules. This work suggests that a numerical approach to assess the effects of draw-spacers on pressure drop and CP can optimize and reduce investment in the design and validation of FO module designs.

Membranes (Basel) ; 10(5)2020 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-32466224


In an effort to improve performances of forward osmosis (FO) systems, several innovative draw spacers have been proposed. However, the small pressure generally applied on the feed side of the process is expected to result in the membrane bending towards the draw side, and in the gradual occlusion of the channel. This phenomenon potentially presents detrimental effects on process performance, including pressure drop and external concentration polarization (ECP) in the draw channel. A flat sheet FO system with a dot-spacer draw channel geometry was characterized to determine the degree of draw channel occlusion resulting from feed pressurization, and the resulting implications on flow performance. First, tensile testing was performed on the FO membrane to derive a Young's modulus, used to assess the membrane stretching, and the resulting draw channel characteristics under a range of moderate feed pressures. Membrane apex reached up to 67% of the membrane channel height when transmembrane pressure (TMP) of 1.4 bar was applied. The new FO channels considerations were then processed by computational fluid dynamics model (computational fluid dynamics (CFD) by ANSYS Fluent v19.1) and validated against previously obtained experimental data. Further simulations were conducted to better assess velocity profiles, Reynolds number and shear rate. Reynolds number on the membrane surface (draw side) increased by 20% and shear rate increased by 90% when occlusion changed from 0 to 70%, impacting concentration polarisation (CP) on the membrane surface and therefore FO performance. This paper shows that FO draw channel occlusion is expected to have a significant impact on fluid hydrodynamics when the membrane is not appropriately supported in the draw side.

IEEE Rev Biomed Eng ; 13: 261-279, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31395552


Globally, around 2.6 million people receive renal replacement therapy (RRT), and a further 4.9-9.7 million people need, but do not have access to, RRT [1]. The next generation RRT devices will certainly be in demand due to the increasing occurrence of diabetes, atherosclerosis and the growing population of older citizens. This review provides a comprehensive, yet concise overview of the cleared and remaining hurdles in the development of artificial kidneys to move beyond traditional dialysis technology-the current baseline of renal failure treatment. It compares and contrasts the state-of-the-art in 'cell-based' and 'non-cell-based' approaches. Based on this study, a new engineering perspective on the future of artificial kidneys is described. This review suggests that stem-cell-based artificial kidneys represent a long-term, complete solution but it can take years of development due to the limitations of current cell seeding technology, viability and complicated behaviour control. Alternatively, there is much potential for near- and medium- term solutions with the development of non-cell-based wearable and implantable devices to support current therapies. Based on recent fundamental advances in microfluidics, membranes and related research, it may be possible to integrate these technologies to enable implantable artificial kidneys (iAK) in the near future.

Rins Artificiais , Membranas Artificiais , Microfluídica , Animais , Humanos , Ratos , Terapia de Substituição Renal
Thromb Haemost ; 103(1): 103-13, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20062921


Both long- and short-term (1-2 hours) exposure to particulate matter (PM) are associated with morbidity and mortality caused by cardiovascular diseases. One of the underlying mechanisms may be due to changes to blood coagulability upon exposure to PM. We investigated this possibility by measuring differences in blood clots formed in the presence of particulate matter in vitro. Total (T)PM increased the permeation of clots in a dose-dependant manner. Filtered (F)PM (17 microg/ml) also produced a significant increase in permeation. Turbidity measured as maximum optical density (ODmax) was increased in a dose-dependant manner with increasing concentration of TPM and FPM. Turbidity measurements also showed a significantly faster rate of polymerisation in the presence of 68 microg/ml FPM. Laser scanning confocal microscopy (LSCM) showed a decrease in fibre density without a significant increase in fibre diameter. However, LSCM showed increased clot heterogeneity due to fibre clustering, creating areas of denser fibrin network surrounded by looser network. The presence of reactive oxygen species (ROS) scavenger mannitol inhibited the effects on fibre clustering. Our data show that TPM and FPM cause alterations in fibrin clot structure, likely through the formation of ROS. These changes in fibrin clot structure may play a role in thromboembolic events upon PM exposure.

Coagulação Sanguínea/efeitos dos fármacos , Fibrina/metabolismo , Material Particulado/toxicidade , Trombose/induzido quimicamente , Emissões de Veículos/toxicidade , Relação Dose-Resposta a Droga , Fibrina/ultraestrutura , Sequestradores de Radicais Livres/farmacologia , Humanos , Cinética , Manitol/farmacologia , Microscopia Confocal , Nefelometria e Turbidimetria , Tamanho da Partícula , Porosidade , Multimerização Proteica , Espécies Reativas de Oxigênio/metabolismo , Trombose/sangue
Mutagenesis ; 25(2): 125-32, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19948595


The increasing use of single cell gel electrophoresis (the comet assay) highlights its popularity as a method for detecting DNA damage, including the use of enzymes for assessment of oxidatively damaged DNA. However, comparison of DNA damage levels between laboratories can be difficult due to differences in assay protocols (e.g. lysis conditions, enzyme treatment, the duration of the alkaline treatment and electrophoresis) and in the end points used for reporting results (e.g. %DNA in tail, arbitrary units, tail moment and tail length). One way to facilitate comparisons is to convert primary comet assay end points to number of lesions/10(6) bp by calibration with ionizing radiation. The aim of this study was to investigate the inter-laboratory variation in assessment of oxidatively damaged DNA by the comet assay in terms of oxidized purines converted to strand breaks with formamidopyrimidine DNA glycosylase (FPG). Coded samples with DNA oxidation damage induced by treatment with different concentrations of photosensitizer (Ro 19-8022) plus light and calibration samples irradiated with ionizing radiation were distributed to the 10 participating laboratories to measure DNA damage using their own comet assay protocols. Nine of 10 laboratories reported the same ranking of the level of damage in the coded samples. The variation in assessment of oxidatively damaged DNA was largely due to differences in protocols. After conversion of the data to lesions/10(6) bp using laboratory-specific calibration curves, the variation between the laboratories was reduced. The contribution of the concentration of photosensitizer to the variation in net FPG-sensitive sites increased from 49 to 73%, whereas the inter-laboratory variation decreased. The participating laboratories were successful in finding a dose-response of oxidatively damaged DNA in coded samples, but there remains a need to standardize the protocols to enable direct comparisons between laboratories.

Ensaio Cometa , Dano ao DNA/efeitos da radiação , DNA-Formamidopirimidina Glicosilase/metabolismo , Laboratórios/estatística & dados numéricos , Laboratórios/normas , Monócitos/metabolismo , Estresse Oxidativo/efeitos da radiação , Células Cultivadas , Processamento Eletrônico de Dados , Raios gama , Guanina/análogos & derivados , Guanina/metabolismo , Humanos , Monócitos/citologia , Monócitos/efeitos da radiação , Variações Dependentes do Observador , Padrões de Referência , Estudos de Validação como Assunto