Crosslinked Chitosan Membranes Research Articles

3-Aminopropyltriethoxysilane-aided cross-linked chitosan membranes for gas separation: grand canonical Monte Carlo and molecular dynamics simulations.

Molecular simulations were performed to consider the structural and transport properties of chitosan/3-aminopropyltriethoxysilane (APTEOS) mixed matrix membranes (MMMs). In order to consider the presence of APTEOS content on the performances of membrane, various amounts of APTEOS were added to the polymeric matrix as a cross-linker. Structural characterizations such as radial distribution function (RDF), fractional free volume (FFV) and X-ray diffraction (XRD) were carried out on the simulated cells. Self-diffusivity and solubility of membranes were calculated using mean square displacement (MSD) and adsorption isotherms, respectively. Additionally, permeability and permselectivity of CO2 and N2 gases were calculated by grand canonical Monte Carlo and molecular dynamics methods. The system temperature was set to 298K using a Nose-Hoover thermostat. According to the results, upon increasing APTEOS loading, CO2 permeability increases until 10wt.% loading. Then, by adding 20wt.% of APTEOS, CO2 permeability decreases, which could be related to higher crystallinity. XRD graphs indicated that the crystallinity decreased when adding 10wt.% APTEOS, while higher APTEOS content (up to 20wt.%) led to higher crystallinity percentage, consistent with permeability results. Compared to literature reports, the present simulation indicated higher accuracy for defining the structural and transport properties of APTEOS cross-linked chitosan MMMs. Graphical abstract 3-Aminopropyltriethoxysilane-aided cross-linked chitosan membranes for gasseparation.

Ionically Crosslinked Chitosan Membranes Used as Drug Carriers for Cancer Therapy Application.

The aim of this paper was to prepare, by the freeze-drying method, ionically crosslinked chitosan membranes with different contents of pentasodium tripolyphosphate (TPP) and loaded with 1,4-naphthoquinone (NQ14) drug, in order to evaluate how the physical crosslinking affects NQ14 release from chitosan membranes for cancer therapy application. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), swelling degree, and through in vitro drug release and cytotoxicity studies. According to the results, the molecular structure, porosity and hydrophilicity of the chitosan membranes were affected by TPP concentration and, consequently, the NQ14 drug release behavior from the membranes was also affected. The release of NQ14 from crosslinked chitosan membranes decreased when the cross-linker TPP quantity increased. Thus, depending on the TPP amount, the crosslinked chitosan membranes would be a potential delivery system to control the release of NQ14 for cancer therapy application. Lastly, the inhibitory potential of chitosan membranes ionically crosslinked with TPP and loaded with NQ14 against the B16F10 melanoma cell line was confirmed through in vitro cytotoxicity studies assessed via MTT assay. The anti-proliferative effect of prepared membranes was directly related to the amount of cross-linker and among all membranes prepared, such that one crosslinked with 0.3% of TPP may become a potential delivery system for releasing NQ14 drug for cancer therapy.

Characterization of Chitosan Membranes Crosslinked by Sulfuric Acid

Development of novel biomaterials and its practical application have been the subject of much research in the field of scaffolds for tissue engineering, providing the success of producing scaffolds biomaterials that facilitate tissue growth and provide structure support for cells. Due to its biocompatibility and biodegradability, chitosan has been the focus of several researches in recent years to be applied in the biomedical field and chemical modifications of chitosan through crosslinks can produce materials with a wide variety of properties. The objective of this study was to obtain and characterize, chemically and biologically, ionically crosslinked chitosan membranes. Chitosan membranes were prepared by solvent evaporation and the crosslinks were introduced by reaction with sulfuric acid solution. The cross-linked membranes were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Dispersive Energy Spectroscopy (EDX) and contact angle measurements. The biological assays of the membranes were performed with NIH 3T3 cells in two steps: evaluation of cytotoxicity by indirect contact of the cells with the extracts of the chitosan membranes and finally with the direct contact of the cells on the filaments of chitosan to obtain adhesion and cell proliferation information. Non-crosslinked membranes of chitosan were used as controls for all assays. With the physicochemical tests, it was possible to observe an effective crosslinking reaction in chitosan. Biological assays have revealed that the membranes are non-cytotoxic but must still be modified to provide cell adhesion and proliferation.

Comparing homogeneous and heterogeneous routes for ionic crosslinking of chitosan membranes

H2SO4 — ionically crosslinked chitosan membranes were prepared via homogeneous and heterogeneous routes. The control variable in homogeneous crosslinking was the SO42−/NH3+ molar ratio (1:4 e 1:6) while for heterogeneous crosslinking it was the immersion time of pure chitosan membrane in H2SO4 0.5M aqueous solution (5 and 30min). FTIR-ATR suggested lower crosslinking degree for homogeneous crosslinking, corroborated by XRD analysis that indicated the maintenance of the crystalline structure for such membranes. Thermal analysis showed very similar degradation processes for homogeneous and pure chitosan but quite different for heterogeneous: not only in terms of degradation temperature but also in amount and signal of heat involved. Swelling index results were very dependent on pH of medium. Particularly in acidic medium, homogeneous crosslinked membranes, presented a higher swelling capacity than the heterogeneous ones. Mechanical properties revealed that both methodologies render membranes with lower tensile strength and elongation but with Young modulus about four times higher, due to the interactions of SO42− groups of H2SO4 with NH3+ of chitosan. Finally, AFM images showed dramatic changes on surface topology, with reduction of roughness for heterogeneous and an increase for the homogeneous one.

Chitosan Nanocomposite Mesoporous Membranes: Mechanical and Barrier Properties as a Function of Temperature

This work investigates the influence of the type and wt.% of nanofillers on the tensile strength behaviour and barrier properties of fabricated chitosan (CS) mesoporous membranes and their nanocomposites using graphene (G) and fullerene (F) nanofillers. Non cross-linked chitosan (NCLCS) as well as cross-linked chitosan (CLCS) solutions with sodium tripolyphosphate (TPP) were both mixed with G and F nanofillers with different wt.%. NCLCS membranes displayed yield tensile strength of 24MPa while the CLCS membranes displayed a much lower yield tensile strength of 2.87MPa. The addition of G and F nanofiller enhanced the yield tensile strength of the CS membranes up to 45MPa. However, the increase in % elongation for CLCS membranes was 75% higher than that for NCLCS ones. Furthermore, the results revealed that there was a significant effect of the operating temperature on the membrane pore size, which decreased the tensile strength and the barrier of the produced membranes. The enhancement of the tensile properties of polymer nanocomposites membranes (PNC) membranes is crucial to avoid film fracture or delamination. Moreover, the addition of nanofillers improve the barrier properties of PNC membranes, thus the membranes are used in packaging and current filtration techniques. In this work, experimental as well as statistical analysis of the fabricated CS membranes and their yield tensile strength and % elongation data are presented. This study presents the effect of the filler type, the filler content and the cross-linking of CS membranes on tensile strength behaviour both experimentally as well as theoretically.

The Study of Ethanol/Water Vapors Permeation through Sulfuric Acid Cross-Linked Chitosan Magnetic Membranes

Sulfuric acid cross-linked chitosan membranes filled with a different amount of magnetite, were prepared. The permeation behavior of ethanol and water vapors in vapor permeation experiments were studied. Permeation rates were measured. Mass transport coefficients were evaluated. The study has been carried out to determine the influence of magnetic powder dispersed inside of the chitosan membrane on ethanol-water separation. The diffusion, fluxes, and permeation coefficients increased with greater amount of magnetite content. The separation factor increased with increasing flux and the best results were achieved for the membrane containing 15% w/w magnetite. The research allows optimizing the preparation procedure of chitosan magnetic membranes cross-linked by sulfuric acid with the best permeation properties.

Novel macroporous palladium cation crosslinked chitosan membranes for heterogeneous catalysis application

A novel palladium supported on chitosan porous membrane heterogeneous catalyst has been prepared by freeze-drying of Pd2+-crosslinked chitosan gel solution. The prepared membrane catalyst has three-dimensional porous structure (porosity: >70%). The crosslinking effects of Pd2+ to chitosan were good for the improvement of the mechanical properties and thermal stabilities. Pd2+ cations have been shown not only as the crosslinker, but also as the catalytic active sites. The reductive palladium species of the recycled membrane catalysts was found in the nanometer scale (20–40nm). Excellent cross-coupling yields were achieved using as low as 0.12mol% palladium catalyst loading for the Heck-type reaction of aromatic halides with acrylates. The catalyst could be recycled six times without obvious decreased conversion.

Preparation and characterization of chitosan composite membranes crosslinked by carboxyl-capped poly(ethylene glycol)

In this study a series of chemically crosslinked chitosan/poly(ethylene glycol) (CS/PEG) composite membranes were prepared with PEG as a crosslinking reagent other than an additional blend. First, carboxyl-capped poly(ethylene glycol) (HOOC-PEG-COOH) was synthesized. Dense CS/PEG composite membranes were then prepared by casting/evaporation of CS and HOOC-PEG-COOH mixture in acetic acid solution. Chitosan was chemically crosslinked due to the amidation between the carboxyl in HOOC-PEG-COOH and the amino in chitosan under heating, as confirmed by FTIR analysis. The hydrophilicity, water-resistance and mechanical properties of pure and crosslinked chitosan membranes were characterized, respectively. The results of water contact angle and water absorption showed that the hydrophilicity of chitosan membranes could be significantly improved, while no significant difference of weight loss between pure chitosan membranes and crosslinked ones was detected, indicating that composite membranes with amidation crosslinking possess excellent water resistanance ability. Moreover, the tensile strength of chitosan membranes could be significantly enhanced with the addition of certain amount of HOOC-PEG-COOH crosslinker, while the elongation at break didn’t degrade at the same time. Additionally, the results of swelling behaviors in water at different pH suggested that the composite membranes were pH sensitive.

Water state in chemically and physically crosslinked chitosan membranes

ABSTRACTChemically and physically crosslinked chitosan membranes were prepared by treating chitosan (Ch) with glutaraldehyde (GA) and sulfuric acid (SA). FTIR and XRD results were employed to confirm the formation of covalent and ionic crosslinks between Ch, GA, and SA. The states of water in non‐crosslinked and covalently and ionically crosslinked chitosan membranes containing different amount of water were investigated by low temperature differential scanning calorimetry measurements. The equilibrium swelling in water was examined gravimetrically. Two types of water were found in the polymer samples, i.e., freezing water and non‐freezing water. The effect of crosslinking process on water state and water uptake was analyzed. The water uptake decreased after chitosan crosslinking with GA, but significantly increased after later crosslinking with SA. The amount of non‐freezing water was generally smaller in crosslinked membranes. An impact of molecular and supermolecular structure on water uptake and state of water in non‐crosslinked and crosslinked chitosan membranes was discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1707–1715, 2013

Hydrophilic and hydrophobic interactions in cross-linked chitosan membranes

Chitosan membranes with different cross-linking density were prepared by modifying cross-linking time. Sodium tripolyphosphate was the cross-linking agent. A pulsed nuclear magnetic resonance study was performed on uncross-linked and cross-linked membranes. Different fraction of water molecules were identified in different zones within the membranes. The ratio of water molecules per chitosan repeating unit were calculated. A maximum of twelve water molecules were tightly coordinated to the chitosan repeating unit. Also, a very small water molecule fraction was identified but it was mobile enough as not to contribute to the dipolar interactions. The cross-linking reaction could lead to the formation of hydrophilic and hydrophobic interactions. These two types of interactions could result in the coexistence of a network formed by hydrophilic and hydrophobic micropores. This knowledge could be useful for the interpretation of results of hydrophobic drugs permeation across hydrophilic membranes. For example, the increment of estradiol fluxes across chitosan membranes with an increase in cross-linking density.

Adsorption of Copper(II) and Mercury(II) Ions onto Chemically-Modified Chitosan Membranes: Equilibrium and Kinetic Properties

Cross-linked chitosan was synthesized with glutaraldehyde (chitosan–GLA) and epichlorohydrin (chitosan–ECH). The structures of these matrices were characterized by elemental analysis, Fourier-transform infrared spectrometry (FT-IR), the degree of de-acetylation and the surface topography as determined via scanning electron microscopy (SEM). After promoting interaction with the metal ion, the adsorbent was also studied using FT-IR and energy dispersive X-ray spectroscopy (EDXS). Adsorption studies for Cu(II) and Hg(II) ions were carried out in a batch process. The adsorption kinetics were tested using three models, viz. pseudo-first-order, pseudo-second-order and intra-particle diffusion. The experimental kinetic data were best fitted by the pseudo-second-order model for Cu(II) ions (R2≥ 0.98) and for Hg(II) ions (R2= 0.99). Higher rate constants (k2) were obtained for the adsorption of Cu(II) ions onto chitosan–GLA [1.40 g/(mmol h)] and for Hg(II) ions onto raw chitosan [5.65 g/(mmol h)]. The adsorption rate depended on the concentration of Cu(II) and Hg(II) ions on the adsorbent surface and on the quantity of ions adsorbed at equilibrium. At 293 K, the Langmuir–Freundlich model provided a better fit to the adsorption isotherms on both raw and cross-linked chitosan membranes. The maximum adsorption capacity for Cu(II) ions was obtained with the chitosan–GLA matrix (2.7 mmol/g). A maximum adsorption capacity of 3.1 mmol/g was attained for Hg(II) ions onto the chitosan–ECH matrix.

Transferable crosslinked chitosan membranes for human melanocyte culture

Development of transferable biocompatible membranes, which can be used for melanocyte culture and transplantation, is considered a feasible approach to increase the success rate for vitiliginous treatment. In this study, a crosslinked chitosan membrane (CCM) was produced via physical crosslinking of chitosan with sodium sulfate. The physical and mechanical properties as well as growth and phenotype expression of melanocytes on the CCM were investigated. The CCM supported growth and proliferation of melanocytes with the existence of melanin granules in the cytoplasm. The melanocytes remained active after transplantation. The CCM absorbed water approximately doubled from its original weight and permitted ∼2400 g/m² per day of water vapor transmission, suggesting that the CCM can function as an efficient wound dressing. Dynamic mechanical and tensile measurement results showed that the CCM possessed favorable wet strength for cell culture, separation, transfer, and transplantation application. This transferable CCM has the potential to be applied for vitiligo treatment.

Chitosan hydrogel membranes for pervaporative dehydration of alcohols

In the present study chitosan was crosslinked with glutaraldehyde. Crosslinked (CHI-GL) and non-crosslinked chitosan (CHI) membranes were prepared by solvent evaporation method. FT-IR, AFM and TG/DTG were used to characterize the physicochemical properties of membranes. It was found that crosslinking of the CHI membranes with glutaraldehyde did not influence the surface morphology and thermal stability of membranes. Effect of alcohols (methanol, ethanol, 2-propanol) in aqueous alcohol/water mixtures on the swelling behavior and dehydration by pervaporation were examined. It was found that both membranes possessed hydrophilic properties in contact with alcohol/water mixture. The results demonstrated also that crosslinked chitosan membranes showed a higher permeation flux but a lower selectivity in contact with alcohol/water mixtures.

In Vitro Response of Retinal Pigment Epithelial Cells Exposed to Chitosan Materials Prepared with Different Cross-Linkers

The interaction between cells and biopolymers is the evaluation indicator of the biocompatibility of materials. The purpose of this work was to examine the responses of retinal pigment epithelial (RPE) cells to genipin (GP) or glutaraldehyde (GTA) cross-linked chitosan by means of cell viability assays, cytokine expression analyses, and apoptosis assays. Evaluations of non-cross-linked chitosan were conducted simultaneously for comparison. Both GP and GTA treated samples with the same extent of cross-linking (around 80%) were prepared by varying cross-linking time. Our results showed that GP cross-linking was carried out by either radical polymerization of the monomers or SN2 nucleophilic substitution reaction involving the replacement of the ester group on the monomer with a secondary amide linkage. On the other hand, GTA could react with free amino groups of chitosan, leading to the formation of either the Schiff bases or the Michael-type adducts with terminal aldehydes. The biocompatibility of non-cross-linked chitosan membranes was demonstrated by the absence of any signs of toxicity or inflammation reaction. The present study showed that the ARPE-19 cells exposed to GTA cross-linked chitosan membranes had significantly higher cytotoxicity, interleukin-6 levels, and number of TUNEL-positive nuclei than did those exposed to GP treated samples. In addition, the materials modified with GTA trigger apoptosis at an early stage and may induce toxicity in the RPE cells later. The findings suggest that while the chitosan molecules bridged by GP are satisfactorily cytocompatible, the counterparts treated by GTA do not seem to be tolerated. In terms of material safety, the GP cross-linked chitosan may be compatible with human RPE cells and may have a potential application as delivery carriers in the treatment of posterior segment diseases.

Dynamic adsorption of chromium ions onto natural and crosslinked chitosan membranes for wastewater treatment

Water pollution with heavy metals is a matter of major concern for public health and also for natural resource management. The present study investigated the effect of chemical modifications on biopolymeric adsorbents (based on chitosan membranes) for chromium removal using fixed-bed dynamic adsorption technique. Parameters such as flow rate, initial concentration and crosslinking agents were evaluated, from a practical point-of-view, in order to optimize the adsorption capacity of natural, glutaraldehyde and epichlorohydrin crosslinked chitosan membranes. The adsorption capacity of natural and epiclorohydrin-crosslinked chitosan membranes were very close to each other; however, glutaraldehyde-crosslinked chitosan membranes presented nearly twice the adsorption capacity compared to the other membranes, being the most promising adsorbent in such mass-transfer systems.

Theoretical studies of ionic conductivity of crosslinked chitosan membranes

Ionic conductivity of crosslinked chitosan membranes was studied using techniques of molecular modeling and simulation. The COMPASS force field was used. The simulation allows the description of the mechanism of ionic conductivity along the polymer matrix. The theoretical results obtained are compared with experimental results for chitosan membranes. The analysis suggests that the conduction mechanism is portrayed by the overlapping large Polaron tunneling model. In addition, when the chitosan membrane was crosslinked with an appropriate degree of crosslinking its ionic conductivity, at room temperature, was increased by about one order of magnitude. The chitosan membranes can be used as electrolytes in solid state batteries, electric double layer capacitors and fuel cells.

Ionic interactions between sulfuric acid and chitosan membranes

Treatment of chitosan with crosslinking agents is a common strategy for improving the performance of chitosan membranes in industrial applications. The preparation of sulfuric acid–crosslinked chitosan membranes was studied by infrared spectroscopy, elemental analysis, and X-ray diffraction, to better understand the mechanism of sulfuric acid treatment. The results indicated that first H 2SO 4 protonated the chitosan amine groups, then the SO 4 2 - anions slowly interacted with chitosan NH 3 + groups to form ionic bridges between the polymer chains. Kinetic analysis showed that protonation was the rate-limiting factor in the adsorption of sulfuric acid by the membrane. The strong interactions between chitosan NH 3 + groups and SO 4 2 - anions were related to changes in membrane crystallinity. Protonation of 10-μm-thick chitosan membranes by 0.01 M sulfuric acid was accomplished within 5 min and complete ionic crosslinking required 30 min. The results of this study suggest better guidelines for treating chitosan membranes with divalent and multivalent acids.

Adsorption and desorption of binary mixtures of copper and mercury ions on natural and crosslinked chitosan membranes

Copper and mercury ion adsorption on chitosan membranes was investigated in batch systems (with both single and binary solutions). The Langmuir model and its extensions (extended Langmuir, Jain-Snoeyink, and Langmuir-Freundlich models) were tested for the modeling of experimental data. Chitosan membranes presented more affinity for Hg ions than for Cu ions. The decrease of the amount of metal adsorbed on natural chitosan in binary systems (compared to single-metal solutions) showed the competition effects between the two metal ions. For glutaraldehyde-crosslinked chitosan and epichlorohydrin-crosslinked chitosan, the mixture effect was present, producing unexpected result such as higher adsorption capacities, when compared to the monocomponent solution of each metal. The desorption of the metals was also investigated, and copper and mercury ions could be selectively recovered using a combined process by using NaCl and H2SO4 as eluant.

Surface characteristics of ionically crosslinked chitosan membranes

AbstractIn this study, homogenous dense chitosan membranes were prepared by solution‐casting procedure. Then the membranes were ionically crosslinked by sulfuric acid. The surfaces of chitosan membranes before and after crosslinking were characterized by using FTIR‐ATR, X‐ray photoelectron spectroscopy (XPS), and atomic‐force microscopy (AFM) techniques. The XPS data suggest that the surface composition of crosslinked membrane does not change significantly with respect to uncrosslinked membrane and the most important evidence is a certain amount of sulfur, coming from the crosslinker. The result from FTIR‐ATR data shows the effectiveness of the crosslinking procedure by the shift in amide I and amide II bands. The investigation of membrane surfaces by AFM indicates that the crosslinking procedure modifies the surface morphology of chitosan. After crosslinking, the surface topography becomes more homogenous and relatively flat. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Trimesoyl chloride crosslinked chitosan membranes for CO 2/N 2 separation and pervaporation dehydration of isopropanol

Crosslinked chitosan membranes were prepared from interfacial crosslinking of chitosan membranes in trimesoyl chloride (TMC)/hexane. A higher degree of swelling was observed for the membrane with a higher degree of crosslinking when swollen in water at room temperature. Membranes were characterized with DSC and TGA, and a two-stage thermal decomposition mechanism was proposed. Pure gas permeation was performed with CO 2 and N 2 at room temperature, and CS-TMC-2 membrane had the best selectivity towards CO 2/N 2, with CO 2 permeability of ∼163 Barrers and the ideal separation factor of ∼42. Pervaporation was carried out for dehydration of isopropanol with the unconditioned and conditioned membranes, and CS-TMC-3 membrane showed the best pervaporation properties. The crosslinking-induced changes in the relaxation behavior and mobility/packing properties of polymer matrices were attributed to the changes in pervaporation and gas separation performances.