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At least 19 recordsLinked to original sources
PubMed2002

Nasal delivery of insulin using novel chitosan based formulations: a comparative study in two animal models between simple chitosan formulations and chitosan nanoparticles.

PURPOSE: To investigate whether the widely accepted advantages as sociated with the use of chitosan as a nasal drug delivery system might be further improved by application of chitosan formulated a nanoparticles. METHODS: Insulin-chitosan nanoparticles were prepared by the ionotropic gelation of chitosan glutamate and tripolyphosphate pentasodium and by simple complexation of insulin and chitosan. The nasal absorption of insulin after administration in chitosan nanoparticle formulations and in chitosan solution and powder formulations wa evaluated in anaesthetised rats and/or in conscious sheep. RESULTS: Insulin-chitosan nanoparticle formulations produced a pharmacological response in the two animal models, although in both cases the response in terms of lowering the blood glucose levels was less (to 52.9 or 59.7% of basal level in the rat, 72.6% in the sheep than that of the nasal insulin chitosan solution formulation (40.1% in the rat, 53.0% in the sheep). The insulin-chitosan solution formulation was found to be significantly more effective than the complex and nanoparticle formulations. The hypoglycaemic response of the rat to the administration of post-loaded insulin-chitosan nanopar ticles and insulin-loaded chitosan nanoparticles was comparable. As shown in the sheep model, the most effective chitosan formulation for nasal insulin absorption was a chitosan powder delivery system with a bioavailability of 17.0% as compared to 1.3% and 3.6% for the chitosan nanoparticles and chitosan solution formulations, respectively. CONCLUSION: It was shown conclusively that chitosan nanoparticles did not improve the absorption enhancing effect of chitosan in solution or powder form and that chitosan powder was the most effective for mulation for nasal delivery of insulin in the sheep model.

Administration, Intranasal↗
PubMed2003

Antimicrobial activity of native chitosan, degraded chitosan, and O-carboxymethylated chitosan.

The antimicrobial activity of native chitosan was compared to that of lipase-degraded chitosan. The effects of O-carboxymethylated (O-CM) substitution on native (molecular weight, 120; degree of deacetylation, 84.71%) and lipase-degraded chitosans were also investigated. The antimicrobial activity of native chitosan was more extensive than that of lipase-degraded chitosan; however, lipase-degraded chitosan was still highly effective and more water-soluble. O-CM chitosan derived from degraded chitosan was more effective than O-CM chitosan derived from native chitosan. O-CM substitution enhanced lipase-degraded chitosan's antimicrobial activity without reducing its solubility.

Acetylation↗
PubMed2004

Improved chitosan-mediated gene delivery based on easily dissociated chitosan polyplexes of highly defined chitosan oligomers.

Nonviral gene delivery systems based on conventional high-molecular-weight chitosans are efficient after lung administration in vivo, but have poor physical properties such as aggregated shapes, low solubility at neutral pH, high viscosity at concentrations used for in vivo delivery and a slow dissociation and release of plasmid DNA, resulting in a slow onset of action. We therefore developed highly effective nonviral gene delivery systems with improved physical properties from a series of chitosan oligomers, ranging in molecular weight from 1.2 to 10 kDa. First, we established structure-property relationships with regard to polyplex formation and in vivo efficiency after lung administration to mice. In a second step, we isolated chitosan oligomers from a preferred oligomer fraction to obtain fractions, ranging from 10 to 50-mers, of more homogeneous size distributions with polydispersities ranging from 1.01 to 1.09. Polyplexes based on chitosan oligomers dissociated more easily than those of a high-molecular-weight ultrapure chitosan (UPC, approximately a 1000-mer), and released pDNA in the presence of anionic heparin. The more easily dissociated polyplexes mediated a faster onset of action and gave a higher gene expression both in 293 cells in vitro and after lung administration in vivo as compared to the more stable UPC polyplexes. Already 24 h after intratracheal administration, a 120- to 260-fold higher luciferase gene expression was observed compared to UPC in the mouse lung in vivo. The gene expression in the lung was comparable to that of PEI (respective AUCs of 2756+/-710 and 3320+/-871 pg luciferase x days/mg of total lung protein). In conclusion, a major improvement of chitosan-mediated nonviral gene delivery to the lung was obtained by using polyplexes of well-defined chitosan oligomers. Polyplexes of oligomer fractions also had superior physicochemical properties to commonly used high-molecular-weight UPC.

Animals↗
PubMed1995

[Pharmacological properties of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent (I). Effect of chitosan DAC in normal rats].

The effects of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent of urea and ammonia, were examined in an in vitro adsorption study and in normal rats. Chitosan DAC showed high adsorption capacity for urea and ammonia in an in vitro study using the diluted supernatant of rat gastrointestinal fluid. In contrast, Kremezin, an oral charcoal adsorbent (AST-120), had little influence on these substances. In normal rats fed diets containing chitosan DAC (1, 2, 3, 4, 5, 7, and 10% content) for three weeks, increases in fecal wet weight, fecal dry weight and fecal water content were observed in a dose-dependent manner. In addition, chitosan DAC feeding increased fecal excretion of nitrogen and electrolytes (sodium, potassium and chloride ions) and decreased the apparent protein ratio in a dose-dependent manner. There were no obvious effects in serum parameters except that increased levels of protein and albumin and decreased levels of blood urea nitrogen, cholesterol and glucose were observed in rats fed a high concentration of chitosan DAC. In conclusion, these findings suggest the possibility that chitosan DAC treatment might be effective for improving chronic renal failure.

Administration, Oral↗
PubMed1995

[Pharmacological properties of chitosan-coated dialdehyde cellulose (chitosan DAC), a newly developed oral adsorbent (II). Effect of chitosan DAC on rats with chronic renal failure induced by adriamycin].

The effects of chitosan-coated dialdehyde cellulose (Chitosan DAC), a newly developed oral adsorbent of urea and ammonia, were examined in rats with progressive chronic renal failure (CRF) induced by adriamycin. CRF rats induced by repeated injections of adriamycin were fed a diet containing chitosan DAC (5% content) or Kremezin (5% content), an oral charcoal adsorbent (AST-120) under strict paired-feeding for four months. CRF rats that received both a normal diet and Kremezin showed progressive azotemia, hyperphosphatemia, hyperlipidemia, proteinuria, and anemia, and began to die from 9 weeks after feeding started. In contrast, chitosan DAC-treatment showed marked prolongation of the survival period and decreases in blood urea nitrogen, serum creatinine, and serum phosphate. In addition, chitosan DAC-treatment ameliorated anemia in CRF rats, although hyperlipidemia and proteinuria were not improved. Furthermore, fecal weight, fecal water content, fecal nitrogen and fecal sodium were markedly increased, and the apparent protein ratio was decreased in CRF rats fed a diet containing chitosan DAC for 9 weeks. In contrast, none of these effects were observed in CRF rats receiving Kremezin. These observations suggest the further possibility of using oral adsorbent therapy for CRF patients.

Administration, Oral↗
PubMed2003

Uptake of chitosan and associated insulin in Caco-2 cell monolayers: a comparison between chitosan molecules and chitosan nanoparticles.

PURPOSE: To evaluate the uptake of chitosan molecules (fCS) and nanoparticles (fNP), and their ability to mediate insulin transport in Caco-2 cell monolayers. METHODS: Cell-associated fCS and fNP were evaluated by fluorometry, trypan blue quenching, and confocal microscopy using FITC-labeled chitosan. Chitosan-mediated transport of FITC-labeled insulin was studied in Caco-2 cell monolayers cultured on permeable inserts. RESULTS: Caco-2 cells showed twofold higher association with fNP than fCS after 2-h incubation with 1 mg/ml samples. fNP uptake was a saturable (Km 1.04 mg/ml; Vmax 74.15 microg/mg/h), concentration- and temperature-dependent process that was inhibited by coadministered chlorpromazine. fCS uptake was temperature dependent, but was less sensitive to concentration and was inhibited by filipin. Postuptake quenching with 100 microg/ml of trypan blue suggests a significant amount of intracellular fNP, although the bulk of fCS was extracellular. Internalized fNP were located by confocal microscopy at 15 microm from the apical membrane, but there was no apparent breaching of the basal membrane. This might explain the failure of the nanoparticles to mediate significant insulin transport across the Caco-2 cell monolayer. CONCLUSIONS: Formulation of chitosan into nanoparticles transforms its extracellular interactions with the Caco-2 cells to one of cellular internalization via clathrin-mediated endocytosis.

Caco-2 Cells↗
PubMed2006

Characteristics of vitamin C encapsulated tripolyphosphate-chitosan microspheres as affected by chitosan molecular weight.

In this paper, the effect of chitosan molecular weight on the characteristics (size, encapsulation efficiency, zeta potential, surface morphology and release rate) of vitamin C encapsulated tripolyphosphate cross-linked chitosan (TPP-chitosan) microspheres. The molecular weight of chitosan had a noticeable influence on the size, encapsulation efficiency, zeta potential, surface morphology and controlled release behaviour of the vitamin C encapsulated TPP-chitosan microspheres. The mean particle size and encapsulation efficiencies of TPP-chitosan microspheres were 3.1, 4.9 and 6.7 microm and 67.25, 60.43 and 52.74% for the microspheres prepared using low, medium and high molecular weight chitosan, respectively. All the TPP-chitosan microspheres (low, medium and high molecular weight) had positive charge on their surface. The zeta potential of the TPP-chitosan microspheres prepared using low, medium and high molecular weight chitosan was 41.25, 40.84 and 39.13 mV, respectively. The particle sizes of TPP-chitosan microspheres increased with increases in chitosan molecular weight. Molecular weight of chitosan did not affect significantly the % yield of TPP-chitosan microspheres prepared by spray-drying. The influence of chitosan molecular weight on the surface morphology of vitamin C encapsulated TPP-chitosan microspheres was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that, as the molecular weight of chitosan increases, TPP-chitosan microspheres with uniform spherical shape could be obtained. The physical state of vitamin C (amorphous or crystalline) in TPP-chitosan matrix was studied by X-ray diffraction (XRD) and it was found that vitamin C is dispersed at the molecular level (amorphous) in the TPP-chitosan matrix. Release rate of the vitamin C from TPP-chitosan microspheres was significantly affected by the chitosan molecular weight. The release rate decreased with increase in the chitosan molecular weight. The release of vitamin C from TPP-chitosan microspheres followed Fick's law of diffusion.

Ascorbic Acid↗
PubMedDate not supplied

Chitosan-cholesterol and chitosan-stearic acid interactions at the air-water interface.

We report in this work the isotherms of cholesterol and stearic acid at the air-water interface modified by different chitosans (chitosan chloride, hydrophobic modified chitosan, and medium and high molecular weight chitosans) in the aqueous subphase. The Langmuir-Blodgett films of the complexes cholesterol-chitosan and stearic acid-chitosan are analyzed by atomic force microscopy (AFM), and a molecular simulation was performed to visualize the chitosan-lipid interactions. Strong modifications are obtained in the isotherms as a result of the chitosan interactions with cholesterol and stearic acid at the air-water interface. These modifications were dependent on the type and concentration of chitosan. Severe modifications of all phases were noticed with larger molecular areas, and the observed changes in the compressional modulus were dependent on the type of chitosan used. The complexes of chitosan-stearic acid were more flexible than the ones of chitosan-cholesterol. The AFM images demonstrated that chitosan was disaggregated by the cholesterol and stearic acid interactions producing more homogeneous surfaces in some cases. The hydrophobic chitosan showed more affinity with stearic acid, while both medium and high molecular weight chitosans produced homogeneous surfaces with cholesterol. The simulated chitosan chains interacting with cholesterol and stearic acid demonstrated the possibility of specific sites of electrostatic bonds between these molecules. Adsorption of cholesterol on the different powdered chitosans, performed by HPLC, showed that the medium and high molecular weight chitosans could retain higher proportions of cholesterol compared with the other analyzed samples.

Adsorption↗
PubMedDate not supplied

Chitosan nanocapsules as carriers for oral peptide delivery: effect of chitosan molecular weight and type of salt on the in vitro behaviour and in vivo effectiveness.

We have recently reported preliminary data showing the efficacy of chitosan nanocapsules as carriers for oral peptide delivery. In the present work, our aim was to investigate the influence of some chitosan properties, such as the molecular weight and type of salt, on the interaction of these nanocapsules with the Caco-2 cells and also on their in vivo effectiveness. Chitosan nanocapsules were prepared by the solvent displacement technique using high (450 kDa) and medium (160 kDa) molecular weight chitosan glutamate as well as high molecular weight chitosan hydrochloride (270 kDa). The results indicated that the size of the nanocapsules was dependent on the chitosan molecular weight, whereas the zeta potential and the association efficiency of salmon calcitonin were not affected by the chitosan properties. Upon incubation with the Caco-2 cells, chitosan nanocapsules exhibited a dose-dependent cellular viability, which was hardly affected by, either the chitosan molecular weight or, the type of salt. In addition, it was observed that the transepithelial electrical resistance of the Caco-2 monolayer was not significantly modified upon their exposure to chitosan nanocapsules. The results of the in vivo studies, following oral administration to rats, indicated that chitosan nanocapsules were able to reduce significantly the serum calcium levels, and to prolong this reduction for at least 24 hours, irrespective of the type of chitosan salt and molecular weight of chitosan. Consequently, the performance of chitosan nanocapsules as oral carriers for salmon calcitonin was not affected by the characteristics of chitosan.

Administration, Oral↗
PubMed2004

Kinetics and thermodynamics of the adsorption of some dyestuffs and p-nitrophenol by chitosan and MCM-chitosan from aqueous solution.

The effect of initial concentration, temperature, and shaking rate on the adsorption of three dyestuffs [orange II (O-II), crystal violet (CV), and reactive blue 5 (RB5)] and an ideal adsorbate, p-nitrophenol (PNP), by chitosan (Sigma C-3646) and the effect of temperature on the adsorption of O-II and CV by monocarboxymethylated chitosan (MCM-chitosan) were investigated. Kinetic data obtained for the adsorption of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan at different temperatures were applied to the Lagergren equation, and adsorption rate constants (k(ads)) at these temperatures were determined. These rate constants related to the adsorption of O-II and RB5 by chitosan and of O-II by MCM-chitosan were applied to the Arrhenius equation, and activation energies (E(a)) were determined. In addition, the isotherms for adsorption, at different temperatures, of each dyestuff and PNP by chitosan and of O-II and CV by MCM-chitosan were also determined. These isothermal data were applied to linear forms of isotherm equations that they fit, and isotherm constants were calculated. Because the isotherm curves obtained for the adsorption of O-II and CV by chitosan and of CV by MCM-chitosan fit the Langmuir adsorption isotherm, b constants were applied to thermodynamic equations, and thermodynamic parameters (delta G, delta H, and delta S) were calculated. Lastly, chitosan and MCM-chitosan were compared with respect to the ability to take up the dyestuffs and PNP.

Adsorption↗
PubMed1998

Microcapsules of alginate-chitosan--I. A quantitative study of the interaction between alginate and chitosan.

The binding of chitosan to alginate beads was studied quantitatively by using radioactive labelled fractions of chitosan. The alginate-chitosan capsules were made either by dropping a solution of sodium alginate into a solution containing chitosan or by incubating calcium alginate beads in a solution of chitosan. The first procedure yielded a binding of 0.015 microg chitosan per mm2 of capsule surface, while the latter procedure yielded over 2 microg mm(-2). The maximum obtained weight ratio of chitosan to alginate in a microcapsule after 24 h was 0.40. The binding of chitosan was markedly increased by reducing the number average molecular weight of chitosan below 20000 Da and by increasing the porosity of the alginate gel. The porosity was increased by producing homogeneous gels, and by adding calcium chloride to the chitosan solution during the membrane forming stage. The effect of calcium ions on the porosity of the gel was studied by experiments involving release of blue dextran from calcium alginate beads. The binding of chitosan was also found to increase with decreasing fraction of N-acetylations, FA, on chitosan in the range of FA = 0.3 to FA = 0, and with increasing pH in the range from pH 4 to 6. Capsules with a diameter of 500 microm had a higher weight ratio of chitosan to alginate after 24 h of binding than the capsules with the larger diameter of 1500 microm.

Acetylation↗
PubMed1998

Comparison of the effect of different chitosan salts and N-trimethyl chitosan chloride on the permeability of intestinal epithelial cells (Caco-2).

A partially quaternized chitosan derivative, N-trimethyl chitosan chloride (TMC) (degree of quaternization 12.28%), was synthesized and the effects of this novel polymer on the permeability of intestinal epithelial cells, using Caco-2 cell monolayers, were investigated and compared with those of chitosan hydrochloride and chitosan glutamate. Transepithelial electrical resistance (TEER) measurements at pH 6.20 revealed that all these polymers (0.25-1.5% w/v) caused an immediate and pronounced lowering in TEER values in the order chitosan hydrochloride (84% reduction after 2 h incubation) > chitosan glutamate (60% reduction) > TMC (24% reduction) at 0.25% w/v concentrations. At higher concentrations (up to 2.5% w/v), TMC was able to decrease the TEER further. Similar results were obtained in transport studies, using the hydrophilic radioactive markers, [14C]-mannitol (MW 182.2) and [14C]-polyethylene glycol 4000 (PEG-4000, MW 4000). Large increases in the permeation of these markers were found. The transport of [14C]-mannitol was increased 34-fold (chitosan hydrochloride), 25-fold (chitosan glutamate) and 11-fold (TMC) at 0.25% w/v concentrations. Further increases in the permeation of both markers were found at higher concentrations of TMC. Due to its quaternary structure, TMC is better soluble than the other chitosan salts, and its higher solubility may compensate for its lesser effectivity at similar concentrations. It is also soluble at pH 7.40, where the chitosan salts are insoluble and therefore ineffective. No deleterious effects to the cells could be demonstrated with trypan blue exclusion studies and confocal laser scanning microscopy (CLSM). CLSM confirmed that these polymers increase the transport of large hydrophilic compounds (using the fluorescent markers FD-4, MW 4400 and FD-20, MW 19,600) through opening of tight junctions to allow for paracellular transport. It is concluded from this study that the charge, charge density and the structural features of chitosans and chitosan derivatives are important factors determining their potential use as absorption enhancers.

Biological Transport↗
PubMedDate not supplied

Structural analysis of chitosan mediated DNA condensation by AFM: influence of chitosan molecular parameters.

Chitosan is a nontoxic and biodegradable polysaccharide that has recently emerged as a promising candidate for gene delivery. Here the ability of various chitosans, differing in the fractional content of acetylated units (F(A)) and the degree of polymerization (DP), to compact DNA was studied. Polyplexes made from mixing plasmid DNA with chitosan yielded a blend of toroids and rods, as observed by AFM. The ratios between the fractions of toroids and rods were observed to decrease with increasing F(A) of the chitosan, indicating that the charge density of chitosan, proportional to (1 - F(A)), is important in determining the shape of the compacted DNA. The amount of chitosan required to fully compact DNA into well-defined toroidal and rodlike structures were found to be strongly dependent on the chitosan molecular weight, and thus its total charge. A higher charge ratio (+/-) was needed for the shorter chitosans, showing that an increased concentration of the low DP chitosan could compensate for the reduced interaction strength of the individual ligands with DNA. Employing chitosans with different molecular parameters offers the possibility of designing DNA-chitosan polyplexes with various geometries, reflecting various chitosan-DNA interaction strengths, which is necessary for the evaluation of efficient gene delivery vehicles.

Chitosan↗
PubMed2002

Antibacterial activity of chitosans and chitosan oligomers with different molecular weights.

Antibacterial activities of six chitosans and six chitosan oligomers with different molecular weights (Mws) were examined against four gram-negative (Escherichia coli, Pseudomonas fluorescens, Salmonella typhimurium, and Vibrio parahaemolyticus) and seven gram-positive bacteria (Listeria monocytogenes, Bacillus megaterium, B. cereus, Staphylococcus aureus, Lactobacillus plantarum, L. brevis, and L. bulgaricus). Chitosans showed higher antibacterial activities than chitosan oligomers and markedly inhibited growth of most bacteria tested although inhibitory effects differed with Mws of chitosan and the particular bacterium. Chitosan generally showed stronger bactericidal effects with gram-positive bacteria than gram-negative bacteria in the presence of 0.1% chitosan. The minimum inhibitory concentration (MIC) of chitosans ranged from 0.05% to >0.1% depending on the bacteria and Mws of chitosan. As a chitosan solvent, 1% acetic acid was effective in inhibiting the growth of most of the bacteria tested except for lactic acid bacteria that were more effectively suppressed with 1% lactic or formic acids. Antibacterial activity of chitosan was inversely affected by pH (pH 4.5-5.9 range tested), with higher activity at lower pH value.

Anti-Bacterial Agents↗
PubMed1984

Proteinase inhibitor synthesis in tomato leaves : induction by chitosan oligomers and chemically modified chitosan and chitin.

Soluble chemical derivatives of chitin and chitosan including ethylene glycol chitin, nitrous acid-modified chitosan, glycol chitosan, and chitosan oligomers, produced from chitosan by limited hydrolysis with HCl, were found to possess proteinase inhibitor inducing activities when supplied to young excised tomato (Lycopersicon esculentum var Bonnie Best) plants. Nitrous acid-modified chitosans and ethylene glycol chitin exhibited about 2 to 3 times the activity of acid hydrolyzed chitosan and 15 times more activity than glycol chitosan. The parent chitin and chitosans are insoluble in water or neutral buffers and cannot be assayed. Glucosamine and its oligomers from degree of polymerization = 2 through degree of polymerization = 6 were purified from acid-fragmented chitosan and assayed. The monomer was inactive and dimer and trimer exhibited weak activities. Tetramer possessed higher activity and the larger pentamer and hexamer oligomers were nearly as active as the total hydrolyzed mixture. None of the fragments exhibited more than 2% acetylation (the limits of detection). The contents of the acid-fragmented mixture of oligomers was chemically N-acetylated to levels of 13% and 20% and assayed. The N-acetylation neither inhibited nor enhanced the proteinase inhibitor inducing activity of the mixture. These results, along with recent findings by others that chitinases and chitosanases are present in plants, provide further evidence for a possible role of soluble chitosan fragments as signals to activate plant defense responses.

Journal Article↗
PubMed2004

Glycosaminoglycan destabilization of DNA-chitosan polyplexes for gene delivery depends on chitosan chain length and GAG properties.

Chitosan-based gene delivery systems are promising candidates for non-viral gene therapy. A wide range of chitosans has been studied to optimize the properties of the DNA-chitosan complexes to yield high transfection efficiencies. An important parameter to control is the polyplex stability to allow transport towards the cells, subsequent internalization and release of DNA intracellularly. The stability of the DNA-chitosan complexes was here studied after exposure to heparin and hyaluronic acid (HA) using atomic force microscopy (AFM) and ethidium bromide (EtBr) fluorescence assay. To study the effect of polycation chain length on the polyplex stability, chitosans with a degree of polymerization (DP) varying from approximately 10 to approximately 1000 were employed for DNA compaction. Whereas HA was unable to dissociate the complexes, the degree of dissociation caused by heparin depended on both the chitosan chain length and the amount of chitosan used for complexation. When increasing the chitosan concentration, larger heparin concentrations were required for polyplex dissociation. Furthermore, increasing the chitosan chain length yielded more stable complexes. Varying the chitosan chain length thus provides a tool for controlling the ability of the polyplex to deliver therapeutic gene vectors to cells.

Chitosan↗
PubMed2005

Effect of molecular weight and degree of deacetylation of chitosan on the formation of oil-in-water emulsions stabilized by surfactant-chitosan membranes.

The objective of this study was to establish the influence of polyelectrolyte characteristics (molecular weight and charge density) on the properties of oil-in-water emulsions containing oil droplets surrounded by surfactant-polyelectrolyte layers. A surfactant-stabilized emulsion containing small droplets (d32 approximately 0.3 microm) was prepared by homogenizing 20 wt% corn oil with 80 wt% emulsifier solution (20 mM SDS or 2.5 wt% Tween 20, 100 mM acetate buffer, pH 3) using a high-pressure valve homogenizer. This primary emulsion was then diluted with various chitosan solutions to produce secondary emulsions with a range of chitosan concentrations (3 wt% corn oil, 0-1 wt% chitosan). The influence of the molecular characteristics of chitosan on the properties of these emulsions was examined by using chitosan ingredients with different molecular weights (MW approximately 15, 145, and 200 kDa) and degree of deacetylation (DDA approximately 40, 77, and 92%). The electrical charge and particle size of the secondary emulsions were then measured. Extensive droplet aggregation occurred when the chitosan concentration was below the amount required to saturate the droplet surfaces, but stable emulsions could be formed at higher chitosan concentrations. The zeta-potential and mean diameter (d32) of the particles in the secondary emulsions was not strongly influenced by chitosan MW, however the chitosan with the lowest DDA (40%) produced droplets with smaller mean diameters and zeta-potentials than the other two DDA samples examined. Interestingly, we found that stable multilayer emulsions could be formed by mixing medium or high MW chitosan with an emulsion stabilized by a non-ionic surfactant (Tween 20) due to the fact the initial droplets had some negative charge. The information obtained from this study is useful for preparing emulsions stabilized by multilayer interfacial layers.

Chitosan↗
PubMed2005

Rate studies on the adsorption of some dyestuffs and p-nitrophenol by chitosan and monocarboxymethylated(mcm)-chitosan from aqueous solution.

In this study, the effect of temperature on the adsorption of some dyestuffs [orange II (O-II), crystal violet (CV) and reactive blue 5 (RB5)] and p-nitrophenol (PNP) by chitosan and of O-II and CV by modified chitosan [monocarboxymethylated(mcm)-chitosan] from aqueous solution was investigated. Kinetical data related to the adsorptions of each dyestuff and PNP by chitosan and of O-II and CV by mcm-chitosan were applied to Lagergren and Weber-Morris equations, and adsorption rate constants (kads) and pore diffusion rate constants (kp) were determined, respectively. In addition, Langmuir isotherm constants with experimental data related to the adsorptions of O-II and CV by chitosan and of CV by mcm-chitosan were applied to McKay et al. equation, and external mass transfer coefficients (kf) were also determined. Lastly, chitosan and mcm-chitosan were compared according to their dyestuffs and PNP uptake capabilities. It was seen that mcm-chitosan removed more O-II (99.2%) and RB5 (34.9%) but less CV (3.1%) and PNP (0.9%).

Adsorption↗