Modified Chitosan Membranes Research Articles

Inhibition of Coliforms and Escherichia coli Bacterial Strains in Water by 3D Printed CS/GO/AgNP Filtration Membranes

The effect of 3D printed modified Chitosan membranes on bacterial strains by water filtration system was explored in this study. Specifically, it focused on the characterisation of 3D printed Chitosan–graphene oxide–silver nanoparticles (CS–GO–AgNP) composite membranes and the effects of Dimethylacetamide (DMAc) used as co-solvent on the performance of the CS–GO–AgNP nanocomposites. It also examined the impact of GO–AgNP on the CS matrix for inhibition of Fecal Coliforms, Total Coliforms and Escherichia coli (E. coli) bacterial strains in contaminated surface water. The increase in DMAc concentration and subsequent reduction in CS mole fraction within the ink formulation resulted to wider distribution of AgNP across membrane surface, improvement in mechanical strength and surface hydrophilicity of the modified CS membranes. Similarly, increase in GO–AgNP concentration effectively reduced the spread of the identified microorganisms. Sample B-12 with 79% CS, 21% DMAc and 1.2 ml of GO–AgNP exhibited the highest inhibition of the bacterial strains, with more than 95% of Fecal and Total Coliforms suppressed or inactivated, while 99.9% of the E. coli bacterial cells were completely prevented, indicating that our 3D printed modified CS membranes can effectively be used for water treatment.

Biofriendly chitosan-based high-efficiency dialysis membrane

Chitosan, a biofriendly material, has a wide range of applications owing to its biocompatibility and biodegradability. We successfully prepared super-adsorbent membranes by dip-coating filter paper in chemically and physically modified chitosan solutions, and compared the urea adsorption performances of the different chitosan membranes. Chemical modification was achieved by successfully introducing carboxyl and amine groups into chitosan by carboxylation and amination using chloroacetic acid (ClCH₂CO₂H) and ethylenediamine (C2H4(NH2)2), respectively. Physical modification was performed by attempting different crosslinking reactions using sodium tripolyphosphate and copper ions (Cu2+). The effects of the various physical and chemical modifications was determined on the urea reduction ratio (URR). At a urea concentration of 500 ppm, the modified chitosan membranes exhibited URRs of >80 % within 2 h, a 38 % decrease in the equilibrium swelling ratio, and a 600 % increase in the bursting strength. These results demonstrate the immense potential of these membranes for hemodialysis in biomedical research. Lastly, model fitting revealed that the mechanisms of urea adsorption onto chitosan were best described using the Freundlich adsorption isotherm and the pseudo-second-order kinetic model.

Modified electrospun chitosan membranes for controlled release of simvastatin.

Chitosan nanofibrous membranes have immense potential in tissue engineering and drug delivery applications because of their increased surface area, high degree of biocompatibility, and their ability to mimic the extracellular matrix. However, their use is often limited due to their extreme hydrophilic nature causing them to lose their nanofibrous structure in vivo. In the present study, chitosan membranes were modified either by acylation reactions using fatty acids of different chain lengths or tert-butyloxycarbonyl (tBOC) protecting groups to increase the hydrophobicity of the membranes and protect the nanofibrous structure. The modified membranes were characterized using scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, water contact angle and elemental analysis to confirm the addition of the modification groups. These membranes were then evaluated to control the release of a hydrophobic osteogenic drug-simvastatin (SMV). The interaction between SMV and the polymer was determined using molecular modeling. Pure SMV and SMV loaded membranes were examined for their in vitro cytotoxicity and osteogenic potential using preosteoblast mouse bone marrow stromal cells. From results, it was evident that as the fatty acid chain length increased from two to six methylene groups, the hydrophobicity of the membranes increased (59.2±8.2° to 94.3±8.5° water contact angle). The amount of drug released from the membranes could be controlled by changing the amount of initial drug loaded and/or the type of modifications. After 4 weeks, for a 500μg loading, the short chain fatty acid modified membranes released 17.8±3.2% of the drug whereas a long chain fatty acid released only 4.8±0.8%. Similarly, for a 50μg loading, short chain modified membranes released more (73.3±33.3%) of the loaded drug as compared to the long chain membranes (43.0±3.5%). The long chain fatty acid membranes released SMV for extended time periods of up to 90days. This data was further supported by molecular modeling, which revealed that SMV was more compatible with more hydrophobic membranes. Cell studies showed that pure SMV from 75 to 600ng/ml range possessed osteogenic potential in a dose dependent manner and the amount of SMV released from the most hydrophobic FA treated membranes was not cytotoxic and supported osteogenic differentiation. Therefore, this study demonstrates our ability to control the release of a hydrophobic drug from modified chitosan membranes as per the clinical need.

Synthesis and characterization of modified chitosan membranes for applications in electrochemical capacitor

Chitosan-based membranes were formed by a casting method from a CS (chitosan) acetic acid solution, and then modified. Sodium hydroxide (NaOH) and glutaraldehyde (GA) solutions were used as covalent or ionic crosslinking agents respectively. The physicochemical properties of crosslinked CS membranes were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Changes in surface hydrophilicity as a result of the crosslinking process were investigated by means of contact angle measurements. In addition, for both modified and unmodified CS membranes, tensile and electrolyte solution swelling ratio tests were performed. All of the obtained chitosan-based membranes were used in electric double layer capacitor (EDLC) cells to study their applicability as gel electrolytes and membranes. 2 M LiOAc (lithium acetate) water solution was used as an electrolyte in the EDLC cells. Electrochemical characteristics of EDLC cells containing chitosan membranes were determined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) methods. The results show that the CS crosslinking agent type may improve the mechanical properties and limit electrolyte absorption by the membranes. All tested EDLC cells with CS membranes exhibited very good electrochemical performance. The specific capacitances for EDLC cells with modified chitosan (CS) membranes are equal 106 F g−1 after the 10 000th discharge cycle for both CS/GA and CS/NaOH capacitor cells.

Removal of aqueous copper(II) by using crosslinked chitosan films

Chitosan films crosslinked with sulfuric acid were prepared by using two different methodologies named as homogeneous and heterogeneous. The Cu(II) adsorption capacity of the films was studied by means of kinetic and equilibrium experiments. Neat chitosan (CS) and homogeneously crosslinked samples (CSHA and CSHB) exhibited quite similar performances for aqueous Cu2+ removal (near to 80% for 14 ppm aqueous solutions); whereas the adsorption capacity of heterogeneous films (CSHtA and CSHtB) was significantly lower. The pseudo-second order model adequately reproduced the kinetics curves, while the Freundlich isotherm was preferable for modelling the equilibrium. The capability of the chitosan films for pressure-driven filtration of water solutions was explored by determining pure water permeability along with the flux and rejection of aqueous Cu2+ solutions. Water flux was thoroughly low in the order: CSHA ≥ CS > > CSHtA. The permeate flux observed for modified chitosan membranes during filtration experiments with aqueous Cu(II) solutions was steady, being significantly higher for the homogeneous samples. All the prepared films exhibited excellent antifouling properties and the crosslinked specimens also enhanced Cu2+ rejection potential (above 95%). The homogeneously crosslinked film CSHA appeared as a promising material for the treatment by adsorption and filtration of aqueous copper streams.

Formation of complexes between functionalized chitosan membranes and copper: A study by angle resolved XPS

Chitosan is a biopolymer with potential applications in various fields. Recently, it has been used for heavy metals removal like copper, due to the presence of amino and hydroxyl groups in its structure. Chitosan membranes were crosslinked with epichlorohydrin and bisoxirano and functionalized with chelating agents, such as iminodiacetic acid, aspartic acid and tris-(2-amino-ethyl) polyamine. These membranes were used for copper adsorption and the formed complexes were characterized. Thermal and crystalline properties of chitosan membranes were studied by TG-DCS and X-ray diffraction. Raman, XPS and FT-IR data confirmed that copper is linked to the modified chitosan membranes by the amino groups. The oxidation state of copper-chitosan membranes were also studied by angle resolved XPS, and by UV–Vis diffuse reflectance spectroscopy.

Enhanced attachment and growth of periodontal cells on glycine-arginine-glycine-aspartic modified chitosan membranes

Background: Chitosan, a polymeric carbohydrate derived from the exoskeleton of arthropod, has been suggested to be an excellent biomaterial for improving wound healing, especially for bones. To improve the periodontal cell attachment and growth, the cell adhesive peptide glycine-arginine-glycine-aspartic acid (Gly-Arg-Gly-Asp, GRGD) grafted chitosan membrane was introduced in this study. Materials and Methods: Two types of commercial chitosan, three types of primary cultured cells, and two established cell lines were used. Human gingival and periodontal fibroblasts (hGF and hPDL), human root derived cell (hRDC), and rat calvaria bone cell (rCalB) were cultured on the GRGD-fixed by ultraviolet light photochemical method on the chitosan membrane. With (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium) assay and propidium iodine (PI) staining, the cell adhesion and growth on GRGD-grafted chitosan were examined. Basal mRNA expressions of the receptors for GRGD, integrin αv (ITG αv) and ITG β3, in the human gingival fibroblast cell line and mouse osteoblast cell line (MC3T3-E1) were examined with real-time polymerase chain reaction. Results: Because the cell adhesion/growth patterns on two chitosan membranes were similar, the GRGD modification was performed on one membrane (Primex) only. For periodontal cells (hGFs, hPDLs, and hRDCs), the number of attached cells were increased on the membrane with the high concentration of GRGD than those on the membrane unmodified or modified with low concentration GRGD. For rCalBs cells, a different pattern was noted: GRGD modification did not enhance the calvaria cells attachment or growth. Moreover, mRNA expressions of ITG αv and β3 in AG09319 cells were significantly higher than those in MC3T3-E1 cells. Conclusions: With the limitation of this study, we suggested that GRGD-modified chitosan, especially at high concentration, could enhance the growth of various periodontal fibroblasts, but did not change those of osteoblasts. Therefore, chitosan might be an excellent biomaterial for periodontal use.

Sunlight mediated diesel degradation under saline conditions using ionic silver coated sand via nanoreduction: Use of impregnated form of thiourea modified chitosan membranes for ex situ application

The present research investigates the use of ionic silver coated sand dust (ISSD) for the sunlight mediated degradation of diesel under saline conditions. Sand dust was used as a template for reduction of silver ions by effective removal of chloride ions. Diesel degradation was estimated in terms of degradation (%), chloride removal, volume reduction and nanoparticle synthesis, respectively. The process was optimized using a 7-level Box–Behnken design. Among several factors, time (B), Tween 80 (C), ISSD dosage (D) and silver(I) concentration (F) were found to be most significant. Maximum diesel degradation 99.8% was obtained in a period of 14h which was analyzed by gas chromatography. XPS analysis confirmed silver reduction as the underlying phenomena. TEM analysis and albeit first approximation method confirmed that enhanced degradation occurred due to physical contact between diesel components and ISSD. First order kinetic model exhibited the best fit. Light microscopy results showed the various stages in diesel degradation by a reduction in bubble size. Ex situ application was carried out using ISSD impregnated thiourea modified chitosan/PVA membranes by surface floatation technique for the remediation of diesel contaminated sea water. Complete diesel degradation was noted after 48h of sunlight exposure.

Probing cellular behaviors through nanopatterned chitosan membranes

This paper describes a high-throughput method for developing physically modified chitosan membranes to probe the cellular behavior of MDCK epithelial cells and HIG-82 fibroblasts adhered onto these modified membranes. To prepare chitosan membranes with micro/nanoscaled features, we have demonstrated an easy-to-handle, facile approach that could be easily integrated with IC-based manufacturing processes with mass production potential. These physically modified chitosan membranes were observed by scanning electron microscopy to gain a better understanding of chitosan membrane surface morphology. After MDCK cells and HIG-82 fibroblasts were cultured on these modified chitosan membranes for various culture durations (i.e. 1, 2, 4, 12 and 24 h), they were investigated to decipher cellular behavior. We found that both cells preferred to adhere onto a flat surface rather than on a nanopatterned surface. However, most (> 80%) of the MDCK cells showed rounded morphology and would suspend in the cultured medium instead of adhering onto the planar surface of negatively nanopatterned chitosan membranes. This means different cell types (e.g. fibroblasts versus epithelia) showed distinct capabilities/preferences of adherence for materials of varying surface roughness. We also showed that chitosan membranes could be re-used at least nine times without significant contamination and would provide us consistency for probing cell–material interactions by permitting reuse of the same substrate. We believe these results would provide us better insight into cellular behavior, specifically, microscopic properties and characteristics of cells grown under unique, nanopatterned cell-interface conditions.

Using surfaces to modulate the morphology and structure of attached cells – a case of cancer cells on chitosan membranes

This paper describes the development of physically and/or chemically modified chitosan membranes to probe cellular behaviors and molecular-level structural responses of NIH-3T3 fibroblasts (normal cells) and Ha-ras-transformed cells (abnormal cells) adhered onto these modified membranes. To prepare chitosan membranes with nanometrically scaled physical features, we have demonstrated an inexpensive and easy-to-handle method that could be easily integrated with IC-based manufacturing processes with mass production potential. These physically or chemically modified chitosan membranes were examined via scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement, in order to gain a better understanding of chitosan membrane surface characteristics including surface morphology, stiffness, functional groups, and surface hydrophobicity/hydrophilicity. NIH-3T3 fibroblasts and their Ha-ras-transformed progeny were cultured on these modified chitosan membranes. After 12, 24 and 48 h of culture, these cells were investigated to decipher cellular behaviors. We found that NIH-3T3 fibroblasts and their Ha-ras-transformed progeny exhibited distinct structurally based responses attributable to chitosan membrane surface chemical or physical properties that we demonstrate as possibly applicable, for drug screening applications. Secondarily, but crucially to this study, we developed a chitosan-based micropatterning procedure that allowed us to re-arrange mammalian cells (i.e., HeLa cells in this study, for cancer drug screening) at the desired locations (with a single-cell array format). This procedure was based on cell affinity to different surface topographies of chitosan membranes that we prepared. This cell-based patterning approach has the potential for use in a wide range of applications including use as a promising platform for drug discovery, cytotoxicity studies, functional genomics, and investigations of cellular microenvironment. We believe that this study would provide further understanding of naturally derived biomaterials, lay the foundation for broadening the applications of chitosan, and facilitate the development of new biomedical devices (i.e., artificial stents, implantable artificial tissues, and sustainable implantable biosensors) with unique cell–material interface properties and characteristics, such as in vitro cell culture and diagnostic platforms.

Influence of varying surface hydrophobicity of chitosan membranes on the adsorption and activity of lipase

AbstractThe hydrophobic surface modification of chitosan membranes was performed using the amidating reaction of amino groups on a membrane surface with stearic acid activated by 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide hydrochloride (EDC) and N‐hydroxysuccinimide (NHS). The varying surface hydrophobicity of chitosan membranes was achieved by changing the degree of amidation and evaluated by the water contact angle analysis and the adsorption experiment of the hydrophobic dye, Rose Bengal. The effects of the surface hydrophobicity of chitosan membranes on the adsorption behaviors, activity and stability of Candida rugosa lipases were investigated. The experimental results suggested that the increased surface hydrophobicity of chitosan membranes improved the adsorption capacity and activity of the immobilized lipase. The modified chitosan membranes with 30.36% amidation exhibited the maximum activity retention of 83.87%. In addition, a desirable thermal stability was also achieved for the adsorbed lipase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Blood compatibility and mechanical properties of oxidized‐chitosan films

AbstractBy dipping chitosan films into saturated NO2–glacial acetic acid solution, the hydromethyl groups on the film surface could be oxidized to carboxyl groups and the blood compatibility of the films improved. Fourier transform infrared (FTIR) spectra indicated the presence of many COOH and COO− groups on the modified membrane surface. Scanning electron microscopy (SEM) showed that the surface of the modified membrane was rough, as compared with the chitosan film, which possessed a smooth surface. In the oxidation process, with increased dipping time of the films in saturated NO2–glacial acetic acid solution, the tensile strength of the films decreased slowly initially, and rapidly 10 h later. The swelling ratio of the modified chitosan film increased obvious noticeably as the degree of oxidation of the film increased. All antithrombosis and hemolysis tests and blood cell morphology observation with SEM revealed that the blood compatibility of modified chitosan membranes is superior to that of chitosan films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Ionic conductivity and tensile properties of hydroxyethyl and hydroxypropyl chitosan membranes

AbstractHydroxyethyl chitosan and hydroxypropyl chitosan were prepared through the reaction of alkali‐chitosan with 2‐chloroethanol and propylene epoxide, respectively. Fourier transform infrared and 13C NMR measurements were made to examine the substitution on the chitosan unit. According to a comparison of the peak areas between the modified chitosan and unmodified chitosan and the integration of peak areas of 1H NMR spectra, for both modified chitosans, the maximum degree of substitution was less than 25%. The ionic conductivity and mechanical properties of modified chitosan membranes were investigated. In comparison with the unmodified chitosan membrane, hydrated hydroxyethyl and hydroxypropyl chitosan membranes with a higher degree of substitution showed an increase in ionic conductivity of about one order of magnitude; moreover, the crystallinity of hydroxyethyl and hydroxypropyl chitosan membranes was remarkably reduced, and their swelling indices increased significantly. However, these modified membranes did not exhibit significant changes in their tensile strength and breaking elongation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1379–1397, 2004

Controlled release of glucose through modified chitosan membranes

Controlled release of glucose as a model compound through modified chitosan membranes was studied. The chitosan membranes were modified by graft copolymerization of 2-hydroxyethylmethacrylate (HEMA) onto chitosan films using 60 Co γ-ray irradiation. The release characteristics of glucose were studied as a function of degree of grafting. The permeability coefficient of glucose through grafted membranes was found to be in the order 10 −6–10 −7 cm 2/s. The effect of thickness of membranes on the permeability was also determined. Chitosan membranes showed a negligible boundary layer effect. The release of glucose was found to be pH dependent.

Hepatocyte attachment on biodegradable modified chitosan membranes: in vitro evaluation for the development of liver organoids.

Extracellular matrix structures including glycosaminoglycans play a critical role in cell attachment, differentiation, and morphogenesis. We evaluated chitosan ([1-->4] linked 2-amino-2-deoxy-beta-D-glucan) as a biomaterial for hepatocyte attachment because of its structural similarity to glycosaminoglycans. Freshly isolated rat and fetal porcine hepatocytes were seeded on chitosan membranes that had been previously blended with collagen, gelatin, or albumin to improve biocompatibility and surface roughness. The optimal cell density and attachment kinetics were quantified. The metabolic activity was investigated by measuring daily urea and total protein secretion by the cells for 2 weeks. While collagen blended-chitosan membranes provided a good attachment surface for rat hepatocytes, albumin and gelatin blended chitosan membranes were superior for fetal porcine hepatocyte attachment. The optimal attachment was maintained with membranes of medium molecular weight (Mr = 750,000 daltons) chitosan, at 3-4 x 10(4) cells/cm2 after 3 h of incubation. In vitro experiments demonstrated that fetal porcine hepatocytes survived at least 14 days when seeded on the chitosan-albumin matrix, demonstrating that this biomaterial can provide suitable cell attachment scaffolds for creating liver tissue organoids.

Pervaporation separation of water/alcohol mixtures through hydroxypropylated chitosan membranes

The present study investigated the pervaporation performance of novel hydroxypropylated chitosan (HPCS) membranes to separate water from an aqueous alcohol solution. Hydroxypropylated chitosan was prepared from the reaction of chitosan and propylene oxide. The results show that the separation factor decreases and the flux increases with increasing of the substitution degree of the hydroxypropylated chitosan membrane. Crosslinking with glutaraldehyde or treatment with Cu 2+ can improve the pervaporation performance of modified chitosan membrane grately. The performance data indicate that the crosslinking hydroxypropylated chitosan membrane treated with Cu 2+ is an excellent pervaporation membrane for the separation of alcohol-water mixtures, and one-stage separation is attainable for some alcohol-water mixtures such as an n-propanol-water and an isopropanol-water system, which has a good separation factor of 220 for the n-PrOH/water system and 240 for the i-PrOH/ water system using 85 wt % alcohol concentration at 60°C. The flux for both cases is around 0.5 kg m -2 h -1 . At the same time, the structure of the chemically modified chitosan membranes and their separation characteristics for aqueous alcohol solutions are also discussed.

Permeation of solutes through chemically modified chitosan membranes

AbstractChemically and mechanically stable chitosan and N‐acylchitosan were prepared. N‐Octanoylchitosan gives the pronounced decrease of water content, whereas N‐benzoylchitosan keeps a higher content of water. The equilibrium sorption of various sodium salts was determined and is explained by a dual mechanism, consisting of partition and Langmuir sorption. The characteristics of the membrances and the size of the salt anions clearly influence permeability as well as sorption. Permeation behavior was interpreted by the Teorell‐Meyer‐Sievers (TMS) theorem. The mobility of anions decreases with Stokes radius, decreasing in the order chitosan > N‐benzoylchitosan > N‐octanoylchitosan, indicating the effect of the polymer chain molecules, especially a steric obstruction effect on the ion transportation through the membranes. The introduction of the N‐acylated hydrophobic group to the charged chitosan membranes appears to enhance permselectivity. © 1995 John Wiley & Sons, Inc.

Phenyl alanine, tryptophan immobilized chitosan beads as adsorbents for selective removal of immunoproteins.

The use of adsorbents for the treatment of patients suffering from various immune diseases is still in its infancy. Therefore, the development of selective absorbents for the removal or decrease of immunoproteins from plasma is of great importance. In this study, chitosan, a natural polysaccharide having structural characteristics similar to glycosamino glycans, which is non-toxic and biocompatible, has been used for protein adsorption studies. Amino acids like phenyl alanine and tryptophan in different ratios are bonded to these polymers to observe immunoadsorption. Several layers of phenyl alanine or tryptophan have been coated covalently on chitosan beads using N2-plasma, carbodiimide or glutaraldehyde treatments. Scanning electron micrographs have revealed the surface morphological changes after such modifications. The surface modified chitosan beads have exhibited high binding affinity for gamma-globulin compared to bare beads. It is also observed that the amount of fibrinogen adsorption is reduced on modified substrate. A selective removal of IgG and IgM has also been observed with these modified matrix when tested with human plasma, using immuno diffusion methods. The modified chitosan membranes have demonstrated a reduction in platelet attachment, showing that these substrates have become more blood compatible. Hence, it appears that modified chitosan surfaces may be an excellent sorbent system for haemoperfusion due to their high binding affinity for immunoproteins and blood compatibility. Further studies are needed to determine the behaviour under clinical conditions.

Structure of chemically modified chitosan membranes and their characteristics of permeation and separation of aqueous ethanol solutions

The structure of chitosan membranes chemically modified with aldehydes, such as glutaraldehyde and n-butyl aldehyde, was analyzed. Characteristics of permeation and separation of aqueous ethanol solutions through the membranes were investigated by evapomeation. Chitosan membranes reacted with glutaraldehyde were cross-linked by Schiff base bonds and had no pendant structure. Density and crystallinity of the cross-linked chitosan membranes decreased with increasing glutaraldehyde content in the membranes. The permeation rate, separation factor for water permselectivity, and degree of swelling of the cross-linked chitosan membrane for aqueous ethanol solutions increased with increasing glutaraldehyde content in the chitosan membrane. The structure of the chemically modified chitosan membrane and the permeation and separation characteristics for aqueous ethanol solutions are discussed from the viewpoint of hydrogen bonds of the cross-linked membrane.

Solid‐phase modification of chitosan hydrogel membranes and permeability properties of modified chitosan membranes

AbstractA novel preparation method for modified chitosan membranes was developed. Chitosan hydrogel membranes were prepared by immersing an aqueous acetic acid solution of chitosan in KOH solution and modified with 3,3′‐dithiodipropionic acid (DTPA), which has a functional group that causes the thiol ⟷ disulfide transition through a redox reaction. It was smoothly modified with DTPA even in a solid‐phase modification when carbodiimides were used as the condensing reagents. The chitosan membrane modified with DTPA was reduced with tri‐n‐butyl phosphine (MSH membrane) and then oxidized with iodine (MSS membrane). Permeabilities of KCl, sucrose, and urea through these modified chitosan membranes were investigated. The permeability of urea was quite high and followed by KCl and sucrose in that order. The permeabilities of KCl and sucrose through the MSS membrane showed a decrease compared to those through the MSH membrane. The thiol ⟷ disulfide transition was responsible for changes in the permeabilities of KCl and sucrose. The permeability of urea was almost the same for both membrane systems, i.e., permeation of urea was not affected by the thiol ⟷ disulfide transition, probably due to the break of hydrogen bonding in the membranes. © 1993 John Wiley & Sons, Inc.