Albumin separation with Cibacron Blue carrying macroporous chitosan and chitin affinity membranes

Cibacron Blue F3GA, Procion Red HE-3B and Procion Blue MX-R were immobilized on macroporous chitosan and chitin membranes with concentrations as high as 10–200 μmol/ml membrane. These dyed membranes were chemically and mechanically stable, could be reproducibly prepared, and operated at high flow rates. Human serum albumin (HSA) and bovine serum albumin (BSA) were selected as model proteins, and their adsorption on and desorption from the dyed chitosan membranes investigated. The Cibacron Blue F3GA membranes had a higher protein adsorption capacity, much greater for HSA than BSA, than the other dyed membranes. About 8.4 mg HSA/ml membrane were adsorbed at saturation by Cibacron Blue F3GA–chitosan membranes from a 0.05 M Tris–HCl/0.05 M NaCl, pH 8 solution. The chitin membranes had a lower dye content and hence a lower protein adsorption capacity than the chitosan membranes. The effects of important operation parameters (flow rate, protein concentration and loading) were also investigated. Cibacron Blue F3GA–chitosan membranes were employed for the separation of HSA from human plasma and high purity HSA thus obtained. This suggests that these membranes could be used for large-scale plasma fractionation.     

The Effects of Demineralization Process on Diameter,Tensile Properties and Biodegradation of Chitosan Fiber

Chitosan fiber is one of the potential fibers that can be used as absorbable monofilament suture in biomedical application. In chitosan synthesis, aside from deproteination and deacetylation, demineralization is a crucial step where the major minerals within crustacean shells are removed. This demineralization process is carried out with two parameters, i.e. time and temperature. This research studies the influence of demineralization time on the diameter, tensile properties and biodegradability of chitosan fibers. Chitosan was synthesized from shrimp shells using 1 × 2 h and 3 × 2 h demineralization process. Chitosan fibers were produced by means of wet spinning. The chemical properties of chitosan fibers were characterized by means of Fourier Transform Infrared (FTIR) spectroscopy and X-Ray Diffractometry (XRD) technique. Physical properties characterization was carried out to measure the fibers’ diameter, density and viscosity. Tensile properties were evaluated by means of tensile test. The results were compared to standard of absorbable suture from the United States Pharmacopoeia (USP). Furthermore, in vitro degradation testing was also performed for analyzing biodegradation properties. Chitosan fibers were successfully made with diameter and maximum tensile force of chitosan fibers in a range of 364 - 460 μm and 5.6 - 8.3 N, respectively. The results of this research pointed that adding demineralization time would increase the diameter of chitosan fiber. However, the degradation occurred in prolonged demineralization process broke the bonds within the fiber which lead to a decrease in fiber's density. It is due to the degradation of chitosan occurred during extended demineralization process, which leads to degree of crystallinity reduction. Extensive demineralization process has been found to lower fibers’ tensile strength from 80.4 MPa to 38.4 MPa (52.2%), but increase their biodegradability by 17% and maximum elongation from 6.9% to 16.2% (136%). Despite that extensive demineralization process lowered chitosan fiber's tensile strength, both fibers made could still fit the standard for synthetic absorbable suture from USP number 0 and 1.     

Chemical modification of cellulose extracted from sugarcane bagasse: Preparation of hydroxyethyl cellulose

Cellulose was extracted from sugarcane bagasse by alkaline extraction with sodium hydroxide followed by delignification/bleaching using sodium chlorite/hexamethylenetetramine system. Factors affecting extraction process, including sodium hydroxide concentration, hexamethylenetetramine concentration and temperature were studied and optimum conditions for alkaline extraction were found to be boiling finely ground bagasse under reflux in 1 N sodium hydroxide solution and then carrying out the delignification/bleaching treatment at 95 °C using 5 g/l sodium chlorite together with 0.02 g/l hexamethylenetetramine. The extracted cellulose was used in the preparation of hydroxyethyl cellulose through reaction with ethylene oxide in alkaline medium. Factors affecting the hydroxyethylation reaction, like sodium hydroxide concentration during the alkali formation step, ethylene oxide concentration, reaction temperature and reaction duration were studied. Optimum conditions for hydroxyethylation reaction were using 20% NaOH solution and 200% ethylene oxide (based on weight of cellulose), carrying out the reaction at 100 °C for 60 min.     

Physicochemical and functional characteristics of radiation-processed shrimp chitosan

The effects of gamma irradiation on chitosan samples were determined in terms of physicochemical and functional properties. Shrimp chitosan was extracted from shell using a chemical process involving demineralization, deproteinization, decolorization and deacetylation. Commercial snow chitosan was also used. Samples (in a solid state) were given irradiation dose of 25 kGy at a dose rate of 1.1013 kGy/h in air and 0 kGy samples were used as controls. Results showed that moisture contents were between 8.690% and 13.645%. There were no significant differences (P>0.05) in the degree of deacetylation of the chitosan samples. Significant differences (P<0.05) were observed in the viscosity and viscosity-average molecular weight of the chistosan samples. Viscosity and molecular weight decreased when the samples were given the irradiation dose of 25 kGy. Chitosan samples had low antioxidant activity compared with BHT. Water binding capacity ranged from 582.40% to 656.75% and fat binding capacity was between 431.00% and 560.55%. Irradiation had a major effect on the viscosity and the viscosity-average molecular weight of the chitosan samples.     

Amperometric biosensing of glutamate using carbon nanotube based electrode

Amperometric biosensing of glutamate using nanobiocomposite derived from multiwall carbon nanotube (CNT), biopolymer chitosan (CHIT), redox mediator meldola’s blue (MDB) and glutamate dehydrogenase (GlDH) is described. The CNT composite electrode shows a reversible voltammetric response for the redox reaction of MDB at −0.15 V; the composite electrode efficiently mediates the oxidation of NADH at −0.07 V, which is 630 mV less positive than that on an unmodified glassy carbon (GC) electrode. The CNTs in the composite electrode facilitates the mediated electron transfer for the oxidation of NADH. The CNT composite electrode is highly sensitive (5.9 ± 1.52 nA/μM) towards NADH and it could detect as low as 0.5 μM of NADH in neutral pH. The CNT composite electrode is highly stable and does not undergo deactivation by the oxidation products. The electrode does not suffer from the interference due to other anionic electroactive compounds such as ascorbate (AA) and urate (UA). Separate voltammetric peaks have been observed for NADH, AA and UA, allowing the individual or simultaneous determination of these bioanalytes. The glutamate biosensor was developed by combining the electrocatalytic activity of the composite film and GlDH. The enzymatically generated NADH was electrocatalytically detected using the biocomposite electrode. Glutamate has been successfully detected at −0.1 V without any interference. The biosensor is highly sensitive, stable and shows linear response. The sensitivity and the limit of detection of the biosensor was 0.71 ± 0.08 nA/μM and 2 μM, respectively.     

Novel two-ply composite membranes of chitosan and sodium alginate for the pervaporation dehydration of isopropanol and ethanol

Novel two-ply dense composite membranes were prepared using successive castings of sodium alginate and chitosan solutions for the pervaporation dehydration of isopropanol and ethanol. Preparation and operating parameters namely polymer types facing to the feed stream, NaOH treatment for the regeneration of chitosan, and crosslinking system types were investigated using the factorial design method. It was shown that these parameters were all critical to the performance of the membrane in the form of the main and interaction effects. The pervaporation performance of the two-ply membrane with its sodium alginate layer facing the feed side and crosslinked or insolubilized in sulfuric acid solution was compared with the pure sodium alginate and the chitosan membranes in terms of the flux and separation factors. It was shown that although its flux was lower than that of the pure sodium alginate and chitosan membranes, the separation factors at various alcohol concentrations were in between values for the two pure membranes. For the dehydration of 90 wt% isopropanol–water mixtures the performance of the two-ply membrane which was moderately crosslinked in formaldehyde was found to match the high performance of the pure sodium alginate membrane. This two-ply membrane had fluxes of 70 g/m² h at 95% EtOH, 554 g/m² h at 90% PrOH and separation factors of 1110 at 95% EtOH, 2010 at 90% PrOH and its mechanical properties were better than that of the pure sodium alginate membrane.     

Macroporous chitin affinity membranes for wheat germ agglutinin purification from wheat germ

Macroporous chitin membranes of controlled porosity and pore sizes have been prepared. They have good mechanical properties and allow high flow rates of protein solutions at low pressure drops. Because of the numerous N-acetyl-D-glucosamine (GlcNAc) moieties they contain, the chitin membranes can be used for the separation of some valuable proteins both as affinity ligands and support matrix, without further modification. Due to their high porosity and high adsorption surface area, the chitin membranes provide a larger number of accessible binding sites for the wheat germ agglutinin than the chitin beads do. The adsorption capacity for wheat germ agglutinin (180 mg/g chitin membrane) is about 20 times larger than that of chitin beads. Because of the numerous binding sites, multiple-point bindings are involved in the protein adsorption. For this reason, a strong eluant, namely a 1 M acetic acid aqueous solution, had to be used to efficiently recover the wheat germ agglutinin from the membrane. The wheat germ agglutinin was extracted from wheat germ with 0.05 M HCl, precipitated with ammonium sulfate, dialyzed against 0.01 M Tris–HCl buffer (pH 8.5), and purified on the chitin membrane. A high purity (>99%) wheat germ agglutinin with high yield (∼50 mg/100 g wheat germ) was obtained.     

Oxygen reduction at the silver/hydroxide-exchange membrane interface

A solid-state cell is used to study the electrocatalysis of oxygen reduction at the silver/hydroxide-exchange membrane interface. The catalyst/membrane interface exhibits improved performance in comparison to a catalyst/aqueous sodium hydroxide interface. Surprisingly, the half-wave potential for oxygen reduction is shown to shift 185 mV higher at the silver/hydroxide-exchange membrane interface than for the silver/aqueous hydroxide solution interface, and the exchange current density is significantly higher at 1.02 × 10⁻⁶ A m⁻². On a cost per performance basis, silver electrocatalysts in a hydroxide-exchange membrane fuel cell may provide better performance than platinum in a proton-exchange membrane fuel cell.     

Squid chitin as a potential alternative chitin source: Deacetylation behavior and characteristic properties

β-Chitin was isolated from squid pens, and the characteristic chemical and physical properties were elucidated in comparison with those of shrimp chitin, α-chitin. Deacetylation behavior of the squid chitin was first studied to look into the reactivity of β-chitin and also to establish an efficient procedure for preparing squid chitosan. The squid chitin proved to show much higher reactivity in alkaline deacetylation than shrimp chitin. Although it was deacetylated quite easily, the product assumed a dark brown color under the ordinary reaction conditions for shrimp chitosan. Squid chitosan was successfully prepared by repeated alkaline treatments under mild conditions, particularly with high concentration alkali at low temperatures, without appreciable discoloration. The structural characteristics of the squid chitin were discussed on the basis of the IR and x-ray analysis data. The crystalline structure of squid chitin was destroyed easily on deacetylation compared to that of shrimp chitin, and moreover, the resulting squid chitosan was amorphous unlike crystalline shrimp chitosan. The squid chitin was characterized by the remarkable affinity for organic solvents and water. Squid chitin and chitosan also showed much higher hygroscopicity and retention of the absorbed water than shrimp chitin and chitosan and are considered to be useful as highly hydrophilic materials. © 1993 John Wiley & Sons, Inc.     

(Vapor + liquid) equilibria for the {water + poly(ethylene glycol diacetyl ether) (PEGDAE) and methanol + PEGDAE} systems

We measured binary (vapor + liquid) equilibrium data for the {water + poly(ethylene glycol diacetyl ether) (PEGDAE) and methanol + PEGDAE} systems at pressures up to 400 kPa and temperatures from 333 K to 393 K. A static apparatus was used in this study. The measured data were correlated by the Peng–Robinson equation of state using the Wong–Sandler mixing rules with NRTL as the excess Gibbs free energy model.     

Solubilities of imidazolium-based ionic liquids in aqueous salt solutions at 298.15 K

The solubilities of ionic liquids in the ternary systems (ionic liquid + H₂O + inorganic salt) were reported at 298.15 K and atmospheric pressure. The examined ionic liquids are [C₄mim][PF₆] (1-n-butyl-3-methylimidazolium hexafluorophosphate), [C₈mim][PF₆] (1-n-octyl-3-methylimidazolium hexafluorophosphate), and [C₈mim][BF₄] (1-n-octyl-3-methylimidazolium tetrafluoroborate). The examined inorganic salts are the chloride-based salts (sodium chloride, lithium chloride, potassium chloride, and magnesium chloride) and the sodium-based salts (sodium thiocyanate, sodium nitrate, sodium trifluoroacetate, sodium bromide, sodium iodide, sodium perchlorate, sodium acetate, sodium hydroxide, sodium dihydrogen phosphate, sodium phosphate, sodium tetrafluoroborate, sodium sulfate, and sodium carbonate). The effects of the cations and the anions of the ionic liquids and of the inorganic salts on the solubility of the ionic liquids in the ternary solutions were systematically compared and discussed.     

Simultaneous determination of ibuprofen and paracetamol using derivatives of the ratio spectra method

Simple, rapid and accurate new method is described for the simultaneous determination of ibuprofen (IB) and paracetamol (PA) in two components mixture and Cetofen tablets. The method depends on the derivative of the ratio spectra DD by measurement of the amplitude of ¹DD at 225.6 nm and the amplitude of ²DD at 238.9 nm for IB and PA. Calibration graphs are linear in the range 2–32 (LOD 0.53) and 2–24 (LOD 0.57) μg/ml IB and PA, respectively. The proposed method is successfully applied for simultaneous determining IB and PA in authentic mixtures and Cetofen tablets.     

Papain incorporated chitin dressings for wound debridement sterilized by gamma radiation

Wound debridement is essential for the removal of necrotic or nonviable tissue from the wound surface to create an environment conducive to healing. Nonsurgical enzymatic debridement is an attractive method due to its effectiveness and ease of use. Papain is a proteolytic enzyme derived from the fruit of Carica papaya and is capable of breaking down a variety of necrotic tissue substrates. The present study was focused on the use of gamma radiation for sterilization of papain dressing with wound debriding activity. Membranes with papain were prepared using 0.5% chitin in lithium chloride/dimethylacetamide solvent and sterilized by gamma radiation. Fluid absorption capacity of chitin–papain membranes without glycerol was 14.30±6.57% in 6 h. Incorporation of glycerol resulted in significant (p<0.001) increase in the absorption capacity. Moisture vapour transmission rate of the membranes was 4285.77±455.61 g/m²/24 h at 24 h. Gamma irradiation at 25 kGy was found suitable for sterilization of the dressings. Infrared (IR) spectral scanning has shown that papain was stable on gamma irradiation at 25–35 kGy. The irradiated chitin–papain membranes were impermeable to different bacterial strains and also exhibited strong bactericidal action against both Gram-positive and Gram-negative bacteria. The fluid handling characteristics and the antimicrobial properties of chitin–papain membranes sterilized by gamma radiation were found suitable for use as wound dressing with debriding activity.     

Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m² day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1–5 kGy) and it was revealed that PS values were reduced significantly (p≤0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1–1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1–5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p≤0.05) with the rise of radiation dose.     

Equilibrium solubility of sodium 3-sulfobenzoate in binary (sodium chloride + water), (sodium sulfate + water), and (ethanol + water) solvent mixtures at temperatures from (278.15 to 323.15) K

The solubility of sodium 3-sulfobenzoate in binary (sodium chloride + water), (sodium sulfate + water), and (ethanol + water) solvent mixtures was measured at elevated temperatures from (278.15 to 323.15) K by a steady-state method. The results of these experiments were correlated by a modified Apelblat equation. The dissolution enthalpy and entropy of sodium 3-sulfobenzoate in aqueous solutions of different mole fraction were obtained.     

Deoxyribonucleic acid modified poly(dimethylsiloxane) microfluidic channels for the enhancement of microchip electrophoresis

In this paper, deoxyribonucleic acid (DNA) was employed to construct a functional film on the PDMS microfluidic channel surface and apply to perform electrophoresis coupled with electrochemical detection. The functional film was formed by sequentially immobilizing chitosan and DNA to the PDMS microfluidic channel surface using the layer-by-layer assembly. The polysaccharide backbone of chitosan can be strongly adsorbed onto the hydrophobic PDMS surface through electrostatic interaction in the acidic media, meanwhile, chitosan contains one protonatable functional moiety resulting in a strong electrostatic interactions between the surface amine group of chitosan and the charged phosphate backbone of DNA at low pH, which generates a hydrophilic microchannel surface and reveals perfect resistance to nonspecific adsorption of analytes. Aminophenol isomers (p-, o-, and m-aminophenol) served as a separation model to evaluate the effect of the functional PDMS microfluidic chips. The results clearly showed that these analytes were efficiently separated within 60 s in a 3.7 cm long separation channel and successfully detected on the modified microchip coupled with in-channel amperometric detection mode at a single carbon fiber electrode. The theoretical plate numbers were 74,021, 92,658 and 60,552 N m^?1 at the separation voltage of 900 V with the detection limits of 1.6, 4.7 and 2.5 μM (S/N = 3) for p-, o-, and m-aminophenol, respectively. In addition, this report offered an effective means for preparing hydrophilic and biocompatible PDMS microchannel surface, which would facilitate the use of microfluidic devices for more widespread applications.     

One-step fabrication of chitosan–hematite nanotubes composite film and its biosensing for hydrogen peroxide

This work reports on a novel chitosan–hematite nanotubes composite film on a gold foil by a simple one-step electrodeposition method. The hybrid chitosan–hematite nanotubes (Chi–HeNTs) film exhibits strong electrocatalytic reduction activity for H₂O₂. Interestingly, two electrocatalytic reduction peaks are observed at −0.24 and −0.56 V (vs SCE), respectively, one controlled by surface wave and the other controlled by diffusion process. The Chi–HeNTs/Au electrode shows a linear response to H₂O₂ concentration ranging from 1 × 10⁻⁶ to 1.6 × 10⁻⁵ mol L⁻¹ with a detection limit of 5 × 10⁻⁸ mol L⁻¹ and a sensitivity as high as 1859 μA μM⁻¹ cm⁻².     

Systematic fabrication of chitosan nanoparticle by gamma irradiation

The present investigation is mainly focused on the systematic preparation of chitosan nanoparticle in the potential range 1–100 nm using γ-ray irradiation. The effect of irradiation conditions in terms of physical form of chitosan, i.e. flake, colloidal and acidic solution, and γ-ray dose was studied. The molecular weights of chitosan were 10, 25, and >1000 times reduced when irradiated with the γ-ray dose as high as 100 kGy in Chi-flake, Chi-colloid, and Chi-acid, respectively. The particle size reduced to 70 nm after being irradiated to only 10 kGy γ-rays and it showed a tendency to decrease when the γ-ray doses were increased. The γ-rays effectively induced the reduction of chitosan particle size to <100 nm with narrow size distribution. The effective size reduction was particularly observed in Chi-colloid. Heterogeneous chemical conjugation of deoxycholic acid onto 10 kGy irradiated Chi-colloid resulted in narrow particle size as small as 50 nm.     

Effects of gamma irradiation on chemical,microbial quality and shelf life of shrimp

In the present study the combined effect of gamma irradiation (1, 3 and 5 kGy) and storage at two temperatures: refrigeration (+4 °C) and frozen (?18 °C), on the shelf-life extension of fresh shrimp meat was investigated. The study was based on microbiological and physicochemical changes occuring in the shrimp samples. Total volatile base nitrogen values and trimethylamine values for irradiated shrimp samples were significantly lower than non-irradiated samples at both storage temperatures, and the rate of decrease was more pronounced in samples irradiated at the higher dose (p<0.05). Thiobarbituric acid values for irradiated shrimp samples were significantly higher than non-irradiated samples at both storage temperatures (p<0.05). pH values of shrimp samples were affected significantly by both irradiating dose and storage temperatures (p<0.05). Microbial counts for non-irradiated shrimp samples were higher than the respective irradiated samples at both storage temperatures (p<0.05). The results revealed that irradiation at high dose (5 kGy) might enhance lipid oxidation, although the growth of microorganisms and protein oxidation was inhibited.