Assessing the contact‐activation of coagulation during hemodialysis with three different polysulfone filters: A prospective randomized cross‐over trial

Introduction: During hemodialysis (HD) the interaction of the blood with the dialyzer triggers both an inflammatory reaction and an activation of the coagulation cascade. An accepted parameter to quantify the extent of coagulation activation during HD is not available. This study aims to evaluate its amplitude, comparing dialyzers made of different polysulfone polymers, by measuring D‐dimers in the filter‐rinsing fluids (Frf) and to test whether Frf D‐dimers are suitable candidate markers to assess contact coagulation activation during HD. Methods: In a prospective, cross‐over study 41 hemodialysis patients were randomly allocated to nine HD sessions with three types of polysulfone membranes: Filter A: Poliflux®RevaclearMAX; Filter B: Helixone®Fx80, Filter C: Polyflux®H210. Findings: A total of 117 HD sessions were studied. The mean (SD) filter (Frf) D‐dimers were 0.19 µg/L (0.56) for Filter A; 0.66 µg/L (2.81) for Filter B; 0.33 µg/L (1.13) for Filter C. Significant differences were found: A vs. B (P < 0.01), A vs. C (P = 0.01); B vs. C not significant. A large between‐patient variability of D‐dimer filter levels was found. D‐Dimers in blood showed a similar trend but differences were not significant. Discussion: The contact activation of coagulation during HD may also vary among filters made up with similar polysulfones. D‐dimer in the filter rinsing fluid but not in the blood can be considered a candidate marker for the evaluation of thrombogenicity during HD. Further studies are needed to elucidate the mechanism(s) and to confirm the usefulness of filter rinsing fluid D‐Dimers as a clotting activation marker during HD.     

Catalytic Behaviour of Lipase Free and Immobilized in Biphasic Membrane Reactor with Different Low Water-Soluble Substrates

The catalytic activity and reaction rate of lipase have been studied using the biocatalyst free in an organic/aqueous emulsion and immobilized in a biphasic organic/aqueous membrane reactor. The first reaction system was realized in a stirred tank reactor. The other was obtained by immobilizing the enzyme in the sponge layer of an asymmetric capillary membrane and recirculating the two phases along the two separate circuits of the membrane module. The performance of the reactors has been studied using two different low water-soluble substrates: triglycerides present in commercial olive oil and (R,S)-cyanomethyl-[2-(4-isobutylphenyl)propionate] (CNE). The effects of substrate viscosity and flow dynamics conditions, such as organic phase flow rate, on the biphasic membrane reactor performance have been evaluated on the basis of observed reaction rate and catalytic activity of free and immobilized lipase for both substrates. It has been observed that free lipase showed higher catalytic activity with olive oil, while immobilized lipase showed higher catalytic activity with CNE which has a lower viscosity than olive oil. The increase of organic phase flow rate negatively affected the reactor performance, with a minor effect when using CNE rather than olive oil. The influence of temperature on the biocatalyst performance with the two substrates has also been investigated. The optimal temperature value of lipase was different for the two substrates: 28°C with CNE and 40°C with olive oil. © 1997 SCI.     

Multifunctional membranes based on natural polymers: preparation,characterization and in vitro performance evaluation

The aim of this study was to synthesize new multifunctional biopolymers via esterification of hemp fibres with two reagents: meso‐2,3‐dimercaptosuccinic acid and ethylenediaminetetraacetic acid. The obtained biopolymers were characterized using infrared spectroscopy. The antibacterial activity of the derivative containing ethylenediaminetetraacetic acid moiety was evaluated by assessing the growth inhibition of Pseudomonas aeruginosa in Petri dishes. The results suggest that this biomaterial exhibits an excellent in vitro antibacterial activity. The antioxidant activity of the biopolymer from meso‐2,3‐dimercaptosuccinic acid was tested in rat liver microsomal membranes in the presence of tert‐butylhydroperoxide as free radical source. Results suggest that this material inhibits lipid peroxidation induced by the free radical species. Both derivatives were used to prepare multifunctional membranes that were characterized and tested indicating the maintenance of biopolymer functionalized properties. Moreover, these functionalized biopolymers interact with metal ions due to their chelating functional groups. The absorption capacity for a selected metal ion, Cd(II), was investigated in aqueous solutions at pH = 0.65, 4.1 and 7.0 using optical emission spectroscopy. This study demonstrates that these new materials are very effective in chelating cadmium ions showing maximum efficiency at pH = 7.0. © 2014 Society of Chemical Industry     

Process intensification in lactic acid production: A review of membrane based processes

Lactic acid the most widely occurring hydroxy-carboxylic acid has traditionally been used as food preservative and acidulent. So long, it has been produced through either chemical synthesis route or fermentation route the latter being the dominating one. Despite its tremendous potential for large scale production and use in a wide variety of applications, cost-effective production of high purity lactic acid has remained a challenge for decades, mainly due to high downstream processing cost. In the recent years, possibility of integration of highly selective membranes with the conventional fermentors has opened a golden opportunity for full commercial exploitation of the tremendous application potential of this wonder chemical. This paper discusses recent developments of such membrane-based processes representing process intensification in production of monomer grade lactic acid while suggesting a very promising production scheme.     

Galactose derivative immobilized glow discharge processed polyethersulfone membranes maintain the liver cell metabolic activity

New strategies aimed to surface modification of polymeric membranes are crucial to optimise cell-biomaterial interactions in vivo and in vitro biohybrid systems. In this paper, we investigated the surface modification of Polyethersulfone (PES) membranes by plasma polymerisation of acrylic acid monomers (PES-pdAA) and by immobilization of galactonic acid through a hydrophilic "spacer arm" molecule (PES-pdAA-SA-GAL). The modification steps were characterised by high resolution X-ray photoelectron spectroscopy. The performance of modified and unmodified membranes was evaluated by assessing the expression of liver specific biotransformation functions of pig and human hepatocytes. Human liver cells cultured on PES-pdAA-SA-GAL membranes displayed an enhanced albumin production, urea synthesis and protein secretion for 24 days of culture. The immobilisation of galactose derivative units on the membrane allowed specific interactions with hepatocytes biomimicking the cellular microenvironment and produced an improvement of the long-term maintenance and differentiation of human hepatocytes.