Microporous Cellulose Research Articles

Preparation and characterization of a composite PDMS membrane on CA support

AbstractPolydimethylsiloxane (PDMS) is the most commonly used membrane material for the separation of condensable vapors from lighter gases. In this study, a composite PDMS membrane was prepared and its gas permeation properties were investigated at various upstream pressures. A microporous cellulose acetate (CA) support was initially prepared and characterized. Then, PDMS solution, containing crosslinker and catalyst, was cast over the support. Sorption and permeation of C3H8, CO2, CH4, and H2 in the prepared composite membrane were measured. Using sorption and permeation data of gases, diffusion coefficients were calculated based on solution‐diffusion mechanism. Similar to other rubbery membranes, the prepared PDMS membrane advantageously exhibited less resistance to permeation of heavier gases, such as C3H8, compared to the lighter ones, such as CO2, CH4, and H2. This result was attributed to the very high solubility of larger gas molecules in the hydrocarbon‐based PDMS membrane in spite of their lower diffusion coefficients relative to smaller molecules. Increasing feed pressure increased permeability, solubility, and diffusion coefficients of the heavier gases while decreased those of the lighter ones. At constant temperature (25°C), empirical linear relations were proposed for permeability, solubility, and diffusion coefficients as a function of transmembrane pressure. C3H8/gas solubility, diffusivity, and overall selectivities were found to increase with increasing feed pressure. Ideal selectivity values of 9, 30, and 82 for C3H8 over CO2, CH4, and H2, respectively, at an upstream pressure of 8 atm, confirmed the outstanding separation performance of the prepared membrane. Copyright © 2009 John Wiley & Sons, Ltd.

Control of Polyaniline Deposition on Microporous Cellulose Ester Membranes by in Situ Chemical Polymerization

Polyaniline (PANI) can be deposited either on the surface or in the bulk of a microporous membrane by various chemical oxidative polymerization techniques. Each technique has distinctive effects on the PANI site and extent of deposition on the base membrane. In the present study, mixed cellulose ester (ME) membranes with tortuous pore morphology were used as base membranes. The chemical oxidative polymerization techniques employed, included polymerization using an in-house-built two-compartment permeation cell. The resultant composite membranes have been characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR-ATR), and electrical conductivity measurements. The results showed that PANI was layered on the pore walls of the membrane using two-compartment permeation cell. Vapor-phase polymerization yielded a surface layer of PANI with little deposition in the bulk. A distorted PANI surface layer was achieved by solution-phase (dip) polymerization. Moreover, asymmetric PANI deposition within the membrane bulk was evidenced using two-compartment permeation cell. Composite membranes synthesized using two-compartment cell showed highest levels of conductivity (approximately 10(-2) S/cm) as compared to the membranes modified by single-step solution-phase polymerization. FTIR-ATR results indicated the extent of PANI coating and its oxidation state which was identified as doped emeraldine PANI, from all the employed techniques. Asymmetric deposition and extent have been explained in terms of the physical and chemical reaction steps involved in the heterogeneous aniline polymerization reactions in the two-compartment cell technique.

Protein adsorption in two-dimensional electrochromatography packed with superporous and microporous cellulose beads

Anion-exchange superporous cellulose (DEAE-SC) and microporous cellulose (DEAE-MC) adsorbents were packed in an electrochromatographic column, and the effect of external electric field (eEF) on the dynamic adsorption was investigated. The column was designed to provide longitudinal, transverse or 2-dimensional (2D) eEF. It was found that the electro-kinetic effect caused by the introduction of an electric field played an important role in the dynamic adsorption of bovine serum albumin to the adsorbents. The dynamic binding capacity (DBC) in the presence of 2D eEF was higher than in the presence of a one-dimensional eEF. The effect of flow velocity on the DBC of the two adsorbents was also demonstrated. It was found that the effect of electric field on the DEAE-MC column was more remarkable than that on the DEAE-SC column at the same flow rate, whereas the DEAE-SC column showed higher DBC and adsorption efficiency (AE) than the DEAE-MC column. With increasing flow rate, the DEAE-SC column could still offer high DBC and AE in the presence of the 2D eEF. For example, a DBC of 21.4 mg/mL and an AE of 57.7% were obtained even at a flow rate as high as 900 cm/h. The results indicate that the 2D electrochromatography packed with the superporous cellulose adsorbent is promising for high-speed protein chromatography.

Fabrication and characterization of superporous cellulose bead for high-speed protein chromatography

Novel superporous cellulose (SC) matrix has been fabricated by water-in-oil emulsification–thermal regeneration using granules of calcium carbonate as porogenic agents. As a control, microporous cellulose (MC) bead was fabricated in the absence of calcium carbonate. Simultaneously, double cross-linking was applied to enhance the mechanical strength of the particles. The photographs by scanning electron microscopy of the SC bead illustrated that there were more “craters” of several microns scattering on the surface of the beads. It led to a higher water content and effective porosity of the SC medium. The two beads were then modified with diethylaminoethyl (DEAE) group to prepare anion exchangers. The dynamic uptake results of bovine serum albumin (BSA) exhibited that the pore diffusivity of BSA in the DEAE-SC bead was two to three times larger than that in the DEAE-MC bead. In addition, the column packed with the DEAE-SC showed lower backpressure, higher column efficiency and dynamic binding capacity than the column packed with the DEAE-MC at a flow rate range of 150–900 cm/h. Moreover, the column efficiency of the DEAE-SC column was independent of flow velocity up to a flow rate of 1200 cm/h. All the results exhibited the superior characteristics of the SC bead as a potential medium for high-speed protein chromatography.

Immobilization and electrochemical behavior of gold nanoparticles modified leukemia K562 cells and application in drug sensitivity test

A new strategy for immobilization of tumor cells on electrode surface and accelerating electron transfer between electrode and the immobilized cells was proposed to study the electrochemical behavior of cells and the effect of antitumor drug on cell viability. The leukemia K562 cells immobilized in a microporous cellulose membrane were firstly modified with colloidal gold nanoparticles to retain efficiently the activity of immobilized living tumor cells and promote electron transfer between electroactive centers of the cells and the electrode, exhibiting a well-defined anodic peak of guanine at +0.830 V at 50 mV s −1. The electrochemical response could be used to describe cell growth and evaluate the effectiveness of antitumor drug methotrexate on tumor cells. The proposed method offered potential advantages for drug sensitivity test with little usage of cells. It could be developed as a convenient means for the study of the tumor cells growth and the cytotoxicity of antitumor drugs.

Preparation and properties of microporous cellulose membranes from novel cellulose/aqueous sodium hydroxide solutions

AbstractMicroporous cellulose membranes were prepared from novel cellulose/aqueous sodium hydroxide solutions by coagulation with aqueous H2SO4 solutions. The free and glass‐contacting surface morphology of the microporous cellulose membranes showed an asymmetric porous structure. The morphological structure, tensile properties, and permeability of the microporous cellulose membranes could be controlled by changes in the coagulation conditions such as the coagulant concentration and the coagulation time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 920–926, 2006

Formation of cellulose acetate membranes using a supercritical fluid assisted process

Microporous cellulose acetate membranes have been prepared from polymer–acetone solutions using a supercritical fluid phase inversion process in which CO 2 acts as the non-solvent. Series of experiments were performed at various polymer concentrations, temperatures and pressures. The structure of the resulting membranes was analysed using scanning electron microscopy. We operated with polymer concentrations ranging between 5 and 40% (w/w) in acetone obtaining different pore dimensions and membrane structures. Increasing the percentage of polymer in the solution, the structure of the membranes changed from beads-like structure to cellular structure. Polymer concentration also influenced the mean diameter of the pores that ranged from 2 to 50 μm for polymer concentrations from 40 to 5% (w/w). We also tested membrane formation pressures between 100 and 200 bar and at temperature between 45 and 65 °C. Pressure influences the change in membrane structure from cellular to beads-like, whereas temperature has a minor influence on pore size: both the effects can be partially related to CO 2 density. Cellulose acetate membrane formation mechanisms have also been discussed.

Effect of an electric field on the transport of Th(IV) in the presence of Eu(III) and U(VI) through supported liquid membrane containing di‐2‐ethylhexylphosphoric acid

AbstractThis paper investigates the transport of Th(IV) ions in nitric acid media through a supported liquid membrane (SLM) impregnated with di‐2‐ethylhexylphosphoric acid (HDEHP) in kerosene using an electric field. The transport was carried out in a three compartment cell fitted with microporous cellulose nitrate (SLM) and cation exchange membrane (Nafion). The effect of different parameters including nitric acid concentration in the feed solution, HDEHP concentration in the membrane, and HCl concentration were studied. The optimal conditions for Th(IV) transport were 0.1 mol dm−3 HDEHP, 10−3 mol dm−3 HNO3 in the feed solution, 1 mol dm−3 HCl in compartment 2 and 1 mol dm−3 HCl in compartment 3 at 25 °C. Under the optimal conditions of Th(IV) transport the recovery factor after 90 min was 0.25 without applying an electrostatic field, compared with 0.9 when the electric field was applied. The effect of electric current on the flux of Th(IV) through the membrane was also studied. The flux increased as the current density increased from 10 to 30 mA cm−2 to reach a maximum value at 30 mA cm−2 (8 × 10−9 g eq cm−2 s−1). The transport percentages of 0.3 g dm−3 Th(IV) in the presence of 0.1 g dm−3 Eu(III) and 1 g dm−3 U(VI) were 66, 84 and 15%, respectively. The determined selectivities of U(VI)–Th(IV) and Th(IV)–Eu(III) were 0.12 and 0.3, respectively, after 90 min. Therefore, the order of selectivity of this system is Eu(III) > Th(IV) > U(VI).© 2001 Society of Chemical Industry

Development of a specific immunoadsorbent containing immobilized synthetic peptide of acetylcholine receptor for treatment of myasthenia gravis. 1993.

INTRODUCTION Guest Editor's Introduction: The most specific adsorption of antibody can be achieved by the application of antigen‐antibody binding. The antibody is specific for a particular part of antigen called epitope rather than for the whole antigen molecules. Therefore, the immobilized epitope for target antibody could be used as the ligand of the adsorbent. Kuraray Co. developed a specific adsorbent for the anti‐acetylcholine receptor antibody. The adsorbent consists of microporous cellulose beads for the base material which immobilized a synthetic peptide as the epitope ligand. This paper describes the basic design and in vitro characteristics of the adsorbent. This paper was printed in Therapeutic Plasmapheresis, vol 12, page 573–576 (1993), and reprinted here with permission.

Development of selective low-density lipoprotein (LDL) apheresis system: immobilized polyanion as LDL-specific adsorption for LDL apheresis system. 1996.

Abstract: Guest Editor's Introduction: The binding site of the human LDL receptor is rich in anionic amino acids, and interacts with apolipoprotein‐B by the electrostatic force. Therefore, anionic ligands could be used for the selective adsorption of LDL without HDL adsorption. Based upon this concept, Kaneka Co. developed LDL adsorbent. The adsorbent named Loposorber consists of microporous cellulose beads which immobilized dextrane sulfate with a molecular weight of several thousands. This paper describes the basic study for the selection of polyanions, in vitro adsorption characteristics, and the references of initial clinical applications. This paper was printed in Artificial Organs, vol. 20, page 922–929 (1996), and reprinted here with permission.Low‐density lipoprotein (LDL) is widely recognized as one of the major risk factors for developing coronary heart diseases. Despite intensive development of LDL‐lowering drugs, there still exist those patients with refractory hyperlipidemia whose plasma LDL levels are not sufficiently lowered by drugs. LDL apheresis, direct removal of plasma LDL from circulating blood, is thought to be the most promising treatment for such refractory patients. Various techniques, such as the use of an immunoadsorbent utilizing an anti‐LDL antibody, have been used in an attempt to achieve the selective removal of LDL. However, none were widely used because of complications, poor selectivity, and so forth. To establish a safe and effective LDL apheresis system, we chose a synthetic affinity adsorbent as the LDL‐removing device. Synthetic polyanion compounds were used as the affinity ligands for LDL adsorbent to simulate the anion‐rich sequence of LDL binding sites in the human LDL receptor. Among various polyanion compounds, those polyanions with sulfate or sulfonate groups and hydrophilic backbone were found to have a strong affinity for LDL. In contrast, polyanions with carboxyl groups showed poor affinity. Dextran sulfate (DS) was selected as the affinity ligand of LDL adsorbent for its high affinity and low toxicity. The influence of its charge density and molecular weight on its affinity for LDL was suitable. The affinity rapidly increased as the charge density increased, then, reached a constant value. Little affinity was found for either the DS monomer (glucose sulfate) or DS with a molecular weight higher than 104 daltons whereas DS with molecular weights in the midrange showed strong affinity. DS with a midrange molecular weight was immobilized on cellulose hard gel to give LDL adsorbent clinical application. The adsorbent demonstrated an excellent selectivity for LDL and very low density lipoprotein (VLDL) in vitro. Adsorption of high‐density lipoprotein and major plasma proteins was almost negligible. Additional study of the LDL‐binding mechanism revealed that DS directly interacts with positively charged sites on LDL, which demonstrates that the nature of the interaction is the same as that of the LDL receptor. An LDL adsorption column (Liposorber) packed with an LDL adsorbent and polysulfone hollow‐fiber plasma separator (Sulflux) was developed as an efficient LDL apheresis system. Clinical investigation proved that this system is capable of intensively lowering the plasma LDL level without affecting major plasma components.

Role of polyethylene glycol in formation and structure of regenerated cellulose microporous membrane

Porous formation and supermolecular structure of regenerated cellulose (RC) microporous membranes prepared by coagulating mixture solution of cellulose cuoxam and polyethylene glycol (PEG400, PEG2000, PEG6000 and PEG20000) were investigated. SEM showed that the cellulose cuoxam/PEG mixture solution formed a homogeneous blend, and the miscibility between cellulose and PEG decreased with increasing molecular weight ( M w) of PEG. The mixture solutions exhibited homogeneous particles in aqueous 10 wt.% NaOH solution, and a smooth surface of RC membrane was observed after immersing in 5 wt.% H 2SO 4, suggesting that a new molecular architecture of cellulose is formed during the H 2SO 4 coagulation process. With an increase in M w of PEG, crystallinity χ c slightly decreased, while ( 1 1 ̄ 0 ) plane orientation parameter f //( 1 1 ̄ 0 ) of the membranes increased. The 13C CP/MAS NMR spectra indicated that the PEG molecules as pore former were completely removed from the membranes mixed with PEG400, while only 4 wt.% PEG remained in the membranes mixed with PEG2000, PEG6000 and PEG20000. The results of a spin-lattice relaxation suggested that intra-molecular hydrogen bonds of cellulose molecules in the membranes decreased, and inter-molecular hydrogen bonds increased, when M w of PEG increased. M w of PEG plays an important role in the morphology, structure and the pore size of the microporous cellulose membranes.

Photoelectrochemistry of polyaniline supported in a microporous cellulose acetate membrane

We studied the photoelectrochemical response of polyaniline dispersed in a microporous membrane structure. Films of the composite were obtained by electropolymerization of aniline on a platinum electrode coated with a microporous cellulose acetate membrane. They were characterized by UV—Visible spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy. We compared the results with a electrochemically synthesized polyaniline and a composite film prepared by casting. The photocurrent response of polyaniline is enhanced by its dispersion in the pores of the membrane. Depending on the potential applied to the electrode, we observe in both cases an n- or p-type semiconductor photoresponse.

刺激応答伸縮性ゲルを用いた微孔性セルロース膜のチャンネルゲーティング

刺激応答伸縮性ゲルを用いた微孔性セルロース膜のチャンネルゲーティング

Purification of Aspartase by Aqueous Two-Phase System and Affinity Membrane Chromatography in Sequence

Abstract A simple and rapid scheme which coupled aqueous two-phase extraction with affinity membrane chromatography for the recovery of aspartase from Escherichia coli was developed. The aspartase was recovered and purified from cell homogenate by three successive polyethylene glycol-phosphate aqueous two-phase extractions with high activity yield. During the extraction steps, cell debris, nucelic acids, and most contaminating proteins were removed. The aspartase was recovered in the phosphate-rich phase. The enzyme was further purified by affinity chromatography in which the regenerated microporous cellulose membrane and L-aspartate were used as support and ligand, respectively. The aspartase solution was forced to flow convectively through the pores in which ligand L-aspartate was immobilized on the surface. The affinity membrane chromatography carried out under a high flow rate resulted in a productivity of 17 L/L/h. The overall purification scheme yielded aspartase with a specific activity of 27.3 units/mg, a 32-fold increase in purity, and a 72% recovery yield. SDS-PAGE showed little contaminating proteins were presented in the purified aspartase.

Membrane affinity chromatography of alkaline phosphatase

A method for the preparation of a microporous cellulose membrane is described. The triazine dyes Cibacron Blue F3GA and Active Red K2BP were immobilized as affinity ligands. Up to 90 mg of Active Red K2BP can be coupled to 1 g of membrane matrix. A membrane cartridge containing red affinity membranes was also prepared. The flux of the cartridge containing 80 sheets of membrane can reach 5.0 ml min with a pressure drop of 0.1 MPa. On this cartridge, the chromatography of alkaline phosphatase was performed with a 60% recovery of activity and a 40-fold purification.

Design and application of NMR-compatible bioreactor circuits for extended perfusion of high-density mammalian cell cultures.

MR spectroscopy of cultured cells allows non-invasive analyses of the metabolism of cells with specific phenotypes under defined conditions. This technique can be used to investigate the intracellular metabolism of cells or extended to critically evaluate phenomena observed by in vivo MRS. In this paper, a cell maintenance system is described which allows MR analyses with unparalleled spectral resolution, S/N and stability. This system consists of a 25 mm diameter hollow fiber bioreactor and a supporting circuit. The hollow fiber reactor was chosen because it yields a large filling factor which can be perfused through defined volumes. The fibers were 300 microns diameter microporous (0.2 micron) cellulose acetate/cellulose nitrate membranes with high porosity, which allow bulk convective flow throughout the extracapillary space. This flow (Starling flow) is necessary to disrupt steady-state gradients in substrates and waste products. In many respects, the design of the supporting circuit is more important than the bioreactor itself, since it provides the reactor with the proper chemical and physical environment. Hence, this circuit can be applied to a variety of bioreactor configurations. The circuit consists of a hollow fiber oxygenator and a bleed-and-feed system housed in a temperature-controlled cabinet. Culture of mammalian cells in this reactor yields 31P spectra which have excellent spectral and temporal resolution. At confluence, endogenous 31P line widths were typically < 10 Hz (at 162 MHz) and well resolved spectra were obtained in < 30 s.

Plasma polymerization of octafluorocyclobutane and hydrophobic microporous composite membranes for membrane distillation

AbstractIn this paper, hydrophilic microporous cellulose nitrate membranes have been surface‐modified by plasma polymerization of octafluorocyclobutane (OFCB). The microporous composite membranes with a hydrophilic layer sandwiched between two hydrophobic layers have been obtained. The obtained composite membranes have been used in a membrane distillation (MD) process and have exhibited good performance. The effects of polymerization conditions, such as glow‐discharge power and deposition time, on the structures and MD performances of the obtained composite membranes have been investigated by SEM, X‐ray microscopical analysis, and XPS. The polymerization conditions should be as mild as possible in order to prepare the hydrophobic composite membrane with good MD performance. The typical MD behaviors of the obtained hydrophobic composite membranes are in agreement with that of hydrophobic membranes directly prepared from hydrophobic polymeric materials, like PVDF, PTFE, or PP.

Formulation and optimization of a modified microporous cellulose acetate latex coating for osmotic pumps.

A cellulose acetate (CA) latex was modified for use as a microporous coating for osmotic devices. Potassium chloride core tablets were coated with a CA latex formulation containing a plasticizer (triacetin) and a pore-forming agent (urea). To promote the coalescence of the cellulose acetate latex beads into a film on the surface of the tablet, it was necessary to cure the coated tablets, hereafter referred to as devices, at elevated temperatures. The objectives were to determine the effect of four formulation variables (plasticizer level, pore former level, cure time, and cure temperature) on the in vitro KCl release rate and coat burst strength using a full 2(4) factorial experimental design. Burst strength was measured as the number of grams force a depleted device could support before bursting. The results indicated that urea content was the most important variable, followed by triacetin content and cure time. Cure temperature did not influence the results. Response surfaces generated with the experimental values were used to predict a formulation which would have both a high release rate and a high burst strength. This formulation was prepared and tested both in vitro and in vivo in dogs. The in vitro release rate and burst strength results agreed with those predicted by the model. The in vitro and in vivo release rates were not statistically significantly different as determined by ALQ analysis.

The Particle Size Of Hepatitis C Virus Estimated By Filtration Through Microporous Regenerated Cellulose Fibre

To estimate the particle size of hepatitis C virus (HCV), a major causative agent of post-transfusion non-A, non-B hepatitis, we filtered plasma or serum samples through microporous cellulose fibres with different pore sizes. The amount of HCV particles in samples before and after filtration was determined by a quantitative reverse transcriptase polymerase chain reaction (PCR) method. Since there is no quantitative biological assay for HCV, except for that in chimpanzees, the HCV titre obtained from the PCR method was used in an equation constructed previously for application to filtration experiments with a flavivirus which is distantly related to HCV. The particle was estimated to be between 30 and 38 nm in diameter, although the possibility remained that larger HCV particles or HCV aggregates with a diameter of more than 39 nm might exist. Double-step filtration through microporous cellulose fibres with a pore size of 35 nm reduced the HCV content to below levels detectable by our PCR method, indicating that it is possible to eliminate HCV particles by simple filtration techniques.

The solubility-modulated osmotic pump: in vitro/in vivo release of diltiazem hydrochloride.

A generalized method was investigated for conversion of controlled-porosity osmotic pump release profiles from first-order to zero-order kinetics using diltiazem.HCl as a model drug. Diltiazem.HCl has an aqueous solubility greater than 590 mg/ml (37 degrees C) and was released from controlled-porosity osmotic pump devices with first-order kinetics. This high solubility was markedly reduced (155 mg/ml; 37 degrees C) in the presence of NaCl (1 M). Based on theory for osmotically actuated drug release, this reduced solubility would be expected to result in a zero-order release profile of greater than 80% of an initial diltiazem.HCl load. Devices were prepared with cores that contained diltiazem.HCl and sufficient NaCl granules coated with a microporous cellulose acetate butyrate 381-20 film to maintain a 1 M NaCl concentration within the drug compartment over a 16-hr period. This resulted in release of approximately 75% of the initial diltiazem.HCl load with zero-order kinetics over a 14- to 16-hr period. The in vivo performance of these devices in beagle dogs was analyzed. The in vivo percentage diltiazem absorbed profiles were superimposable with the in vitro release profile. These results suggest that diltiazem release and absorption from the solubility modulated osmotic pump occur throughout the GI tract in a fashion predictable from in vitro dissolution data.