Chitosan-alginate Polyelectrolyte Complex Research Articles

Characterization and biodegradation of chitosan–alginate polyelectrolyte complexes

Polyelectrolyte complexes (PECs) have been the focus of an expanding number of studies for their wide use. This study investigated the characteristics and biodegradation of chitosan–alginate PECs prepared by freeze-drying a precipitate from sufficient mixtures of the two polymers. The analyses of X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) suggested that the partial protonated amine groups of chitosan reacted with the carboxylate groups of alginate and thus strong PECs were formed. After incubating in lysozyme solution, the PECs showed high ability of enzyme adsorption, and low degradation rate in spite of different degrees of deacetylation of chitosan, due to the strong interaction between chitosan and alginate and the hindrance of closely adsorbed lysozyme.

Reversed chitosan–alginate polyelectrolyte complex for stability improvement of alpha-amylase: Optimization and physicochemical characterization

The present work explores, using response surface methodology, the main and interaction effects of some process variables on the preparation of a reversed chitosan–alginate polyelectrolyte complex (PEC) with entrapped α-amylase for stability improvement. A 3 3 full factorial design was used to investigate the effect of the chitosan and alginate concentrations and hardening time on the percent entrapment, time required for 50% ( T 50) and 90% ( T 90) enzyme release, and particle size. The beads were prepared by dropping chitosan containing α-amylase into a sodium alginate solution without any salt. The in vitro enzyme release profile of the beads was fitted to various release kinetics models to study the release mechanism. A topographical characterization was carried out using scanning electron microscopy (SEM), and the entrapment was confirmed using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). Stability testing was carried out according to the International Conference on Harmonization (ICH) guidelines for zones III and IV. Beads prepared using 2.5% w/v chitosan and 3% w/v sodium alginate with a hardening time of 60 min had more than 90% entrapment and a T 90 value greater than 48 min. Moreover, the shelf-life of the enzyme-loaded beads was found to increase to 3.68 years, compared with 0.99 years for the conventional formulation. It can be inferred that the proposed methodology can be used to prepare a reversed PEC of chitosan and alginate with good mechanical strength, provided both the reactants are in a completely ionized form at the time of the reaction. Proper selection of the reaction pH, polymer concentration and hence charge density, and hardening time is important and determines the characteristics of the PEC.

Immobilization of urease by using chitosan–alginate and poly(acrylamide-co-acrylic acid)/κ-carrageenan supports

Jack bean urease (urea aminohydrolase, E.C. 3.5.1.5) was entrapped into chitosan-alginate polyelectrolyte complexes (C-A PEC) and poly(acrylamide-co-acrylic acid)/kappa-carrageenan (P(AAm-co-AA)/carrageenan) hydrogels for the potential use in immobilization of urease, not previously reported. The effects of pH, temperature, storage stability, reuse number, and thermal stability on the free and immobilized urease were examined. For the free and immobilized urease into C-A PEC and P(AAm-co-AA)/carrageenan, the optimum pH was found to be 7.5 and 8, respectively. The optimum temperature of the free and immobilized enzymes was also observed to be 55 and 60 degrees C, respectively. Michaelis-Menten constant (K(m)) values for both immobilized urease were also observed smaller than free enzyme. The storage stability values of immobilized enzyme systems were observed as 48 and 70%, respectively, after 70 days. In addition to this, it was observed that, after 20th use in 5 days, the retained activities for immobilized enzyme into C-A PEC and P(AAm-co-AA)/carrageenan matrixes were found as 55 and 89%, respectively. Thermal stability of the free urease was also increased by a result of immobilization.

Antibacterial activity of chitosan–alginate sponges incorporating silver sulfadiazine: Effect of ladder‐loop transition of interpolyelectrolyte complex and ionic crosslinking on the antibiotic release

AbstractHydrogel membranes prepared from polyelectrolyte complex (PEC) have been used for repair of wounds and controlled antibacterial release. A simple method, based on homogenizing interpolyelectrolyte complex, has been developed to prepare a chitosan–alginate sponge with high stability. The spongelike chitosan–alginate hydrogel can be used as a wound dressing for the sustained release of silver sulfadiazine (AgSD) in a controlled way. In this study, we evaluated the effect of electrolyteic properties of chitosan and alginate on the characteristics of the prepared chitosan–alginate PEC. All types of the spongelike chitosan–alginate hydrogels exhibited superabsorbent properties. However, only the chitosan–alginate hydrogel prepared by the interpolyelectrolyte complex of alginate with low pH of chitosan, and that prepared by the interpolyelectrolyte complex of chitosan with high pH of alginate, can keep their stability after swelling in PBS solution. FTIR analysis suggests that the protonated amino groups on chitosan and the ionized carboxylic groups on alginate should be responsible for the formation of a stable ladder‐type of chitosan–alginate PEC. Ionic crosslinking is helpful to increase the stability of the loop‐type of chitosan–alginate PEC. The release of AgSD from chitosan–alginate PEC sponges could be controlled by the variation of ladder‐loop structural transition of chitosan–alginate PEC and the ionic crosslinking of the chitosan–alginate complex. The antibacterial ability of AgSD‐incorporated PEC sponges was examined in agar plate against Pseudomonas aeruginosa and Staphylococcus aureus. The result suggests that the PEC sponges containing antimicrobial agents should effectively suppress bacterial proliferation to protect the wound from bacterial invasion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 538–549, 2005

Formation and stability of shark liver oil loaded chitosan/calcium alginate capsules

Calcium alginate capsules containing shark liver oil were prepared by ionotropic gelation of alginate solutions. Since the capsules were permeable to the oil, they were coated with a membrane of chitosan-alginate polyelectrolyte complex to reduce permeability. Encapsulation efficiencies (expressed as the percentage of shark liver oil entrapped) greater than 87% (w/w) were obtained by using 6% (w/v) alginate solution. The oil content in the capsules was higher than 65% (w/w) when the oil was dispersed in the alginate solution at 10% (v/v) or more. However, at the level of 15 or 20% (v/v) the oil was exuded after 48 h. Capsules were degraded in vitro by enzymes, with lipase being more effective than pancreatine. No release of oil from the capsules up to 4 h at pH 1.2 was observed, but after 4 h the capsules became very fragile when they were immersed in buffer solution at pH 7.4.

Drug release from chitosan–alginate complex beads reinforced by a naturally occurring cross-linking agent

Cross-linking reinforced chitosan–alginate complex beads were prepared by dropping chitosan droplets into alginate–cross-linker co-existing gelling solution. A novel, naturally occurring material — genipin was used as the cross-linking agent. Genipin and its related iridoid compounds, extracted from the Gardenia fruits, have been used in the traditional Chinese medicine for the treatments of jaundice and various inflammatory and hepatic diseases. The gelation of chitosan droplets in alginate–genipin mixed solution depends on both controlling factors: chitosan–alginate polyelectrolyte complex and chitosan cross-linked by genipin. The reaction of chitosan–alginate complex dominates the formation of skin layer on the surface of beads, but cross-linking of chitosan by genipin dominates the curing of inner core of beads. The swelling ratio of the cross-linking reinforced chitosan–alginate complex bead decreases as the pH or concentration of alginate in the gelling solution was decreased. The protonation of amine group of chitosan by hydrogen ions from acid or the shield of charge of ammonium group of chitosan by Cl− ions result in the decrease of cross-linking density due to the inhibition of nucleophilic attack on the dihydropyran ring of genipin. Contrary to the swelling properties, the rate of indomethacin releasing out of the chitosan–alginate complex beads increases with the decrease in pH or concentration of alginate in the gelling solution due to the decreased cross-linking density of the beads. The cytotoxic examination suggested that the chitosan–alginate beads cross-linked by genipin had a good cellular compatibility.

Chitosan-alginate films prepared with chitosans of different molecular weights.

Chitosan-alginate polyelectrolyte complex (CS-AL PEC) is water insoluble and more effective in limiting the release of encapsulated materials compared to chitosan or alginate. Coherent CS-AL PEC films have been prepared in our laboratory by casting and drying suspensions of chitosan-alginate coacervates. The objective of this study was to evaluate the properties of the CS-AL PEC films prepared with chitosans of different molecular weights. Films prepared with low-molecular-weight chitosan (Mv 1.30 x 10(5)) were twice as thin and transparent, as well as 55% less permeable to water vapor, compared to films prepared with high-molecular-weight chitosan (Mv 10.0 x 10(5)). It may be inferred that the low-molecular-weight chitosan reacted more completely with the sodium alginate (M(v) 1.04 x 10(5)) than chitosan of higher molecular weight. A threshold molecular weight may be required, because chitosans of Mv 10.0 x 10(5) and 5.33 x 10(5) yielded films with similar physical properties. The PEC films exhibited different surface properties from the parent films, and contained a higher degree of chain alignment with the possible formation of new crystal types. The PEC films exhibited good in vitro biocompatibility with mouse and human fibroblasts, suggesting that they can be further explored for biomedical applications.

PEC films prepared from Chitosan-Alginate coacervates.

Chitosan-alginate polyelectrolyte complex (PEC) have been prepared in situ in beads and microspheres. This study examines the preparation of suitable chitosan-alginate coacervates for casting into homogeneous PEC films for potential applications in packaging, controlled release systems and wound dressings. Coacervation between chitosan and alginate was rapid, but the rate may be controlled with the addition of water miscible organic solvents. Compared with ethanol and PEG200, acetone was the more promising solvent moderator. Suspensions of fine, uniformly dispersed coacervates were produced by a dropwise addition of 0.25% w/v chitosan solution (solvent: 1: 1 v/v of 2% acetic acid and acetone) into 0.25% w/v sodium alginate solution in water under rapid agitation. The PEC films were transparent and flexible. They exhibited high permeability to water vapor, but resisted complete dissolution in 0.1 M HCI, distilled water and pH 7.4 phosphate buffer solution. Microscopic heterogeneity in the films could be reduced by immersion in aqueous media, but this was accompanied by modifications in the thickness, permeability and mechanical property of the films.