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PubMed2004

Enzymatic grafting of carboxyl groups on to chitosan--to confer on chitosan the property of a cationic dye adsorbent.

Chitosan (CTS) is a good adsorbent for dyes but lacks the ability to adsorb cationic dyes. In this study, chitosan was modified to possess the ability to adsorb cationic dyes from water. Four kinds of phenol derivatives: 4-hydroxybenzoic acid (BA), 3,4-dihydroxybenzoic acid (DBA), 3,4-dihydroxyphenyl-acetic acid (PA), hydrocaffeic acid (CA) were used individually as substrates of tyrosinase to graft onto chitosan. FTIR analysis provided supporting evidence of phenol derivatives being grafted. The grafting amounts of these phenol derivatives onto chitosan were examined by the adsorption of an anionic dye (amaranth) and reached a plateau value. The final contents of carboxyl groups in chitosan (mmol carboxyl groups per kg chitosan) were measured as 46.36 for BA, 70.32 for DBA, 106.44 for PA, and 113.15 for CA. These modified chitosans were used in experiments on uptake of the cationic dyes crystal violet (CV) and bismarck brown Y (BB) by a batch adsorption technique at pH 7 for CV and at pH 9 for BB and 30 degrees C. Langmuir type adsorption was found, and the maximum adsorption capacities for both dyes were increased with the following order CTS-CA>CTS-PA>CTS-DBA>CTS-BA.

Adsorption↗

PubMed2006

Visualization of the penetrative and mucoadhesive properties of chitosan and chitosan-coated liposomes through the rat intestine.

The objectives of this study were to observe the penetrative and mucoadhesive behavior of polymer-coated liposomes into the intestinal mucosa of rats. Chitosan (CS) and negatively charged liposomes were chosen as model polymer-coated liposomes. In order to observe their behavior, chitosan was labeled with Fluorescence Isothiocyanate (FITC) via chemical reaction at the isothiocyanate group of FITC and the primary amino group of chitosan; the liposomes (Lips) were marked by incorporation of DiI into the liposomal formulation. FITC-labeled chitosan (FITC-CS), Non-Lips, and FITC-labeled CS-coated Liposomes (FITC-CS-Lips) were intragastrically administered into male Wistar rats, and the behavior of the molecules was subsequently visualized by CLSM (Confocal Laser Scanning Microscopy). The results demonstrated that the chitosan molecules themselves, as well as the liposomes, could penetrate across the intestinal mucosa. Moreover, the CLSM images demonstrated a lack of separation of the chitosan molecules from the surface of the liposomes after the administration of chitosan-coated liposomes.

Adhesiveness↗

PubMedDate not supplied

Chitosan nanoparticles for plasmid DNA delivery: effect of chitosan molecular structure on formulation and release characteristics.

Chitosan can be useful as a nonviral vector for gene delivery. Although there are several reports to form chitosan-pDNA particles, the optimization and effect on transfection remain insufficient. The chitosan-pDNA nanoparticles were formulated using complex coacervation and solvent evaporation techniques. The important parameters for the encapsulation efficiency were investigated, including molecular weight and deacetylation degree of chitosan. We found that encapsulation efficiency of pDNA is directly proportional with deacetylation degree, but there is an inverse proportion with molecular weight of chitosan. DNA-nanoparticles in the size range of 450-820 nm depend on the formulation process. The surface charge of the nanoparticles prepared with complex coacervation method was slightly positive with a zeta potential of +9 to +18 mV; nevertheless, nanoparticles prepared with solvent evaporation method had a zeta potential approximately +30 mV. The pDNA-chitosan nanoparticles prepared by using high deacetylation degree chitosan having 92.7%, 98.0%, and 90.4% encapsulation efficiency protect the encapsulated pDNA from nuclease degradation as shown by electrophoretic mobility analysis. The release of pDNA from the formulation prepared by complex coacervation was completed in 24 hr whereas the formulation prepared by evaporation technique released pDNA in 96 hr, but these release profiles are not statistically significant compared with formulations with similar structure (p > .05). According to the results, we suggest nanoparticles have the potential to be used as a transfer vector in further studies.

Chemistry, Pharmaceutical↗

PubMed2004

Effects of a chitosan scaffold containing TGF-beta1 encapsulated chitosan microspheres on in vitro chondrocyte culture.

The objectives of this study were (1) to develop a three-dimensional chitosan scaffold in combination with transforming growth factor-beta1 (TGF-beta1)-loaded chitosan microspheres and (2) to evaluate the effect of the TGF-beta1 release on the chondrogenic potential of rabbit chondrocytes in the scaffolds. TGF-beta1 was loaded into chitosan microspheres using an emulsion-crosslinking method, resulting in spherical shapes with a size ranging from 0.3 to 1.5 microm. Controlled release of TGF-beta1, as measured by enzyme-linked immunosorbent assay (ELISA), was observed with chitosan microspheres over 7 days. Chitosan solutions (2% and 3%) were fabricated into two types of scaffolds with different pore morphologies and mechanical properties using a freeze-drying technique, with the result that scaffold with higher concentrations showed smaller pores and lower porosity, leading to a much stronger scaffold. The TGF-beta1 microspheres were incorporated into the scaffolds at a concentration of 10 ng TGF-beta1/scaffold and then chondrocytes seeded into each scaffold and incubated in vitro for 2 weeks. The 2% chitosan scaffolds showed higher cell attachment levels than the 3% chitosan scaffolds (P < 0.01), regardless of the TGF-beta1 microspheres. Both the proliferation rate and glycosaminoglycan (GAG) production were significantly higher for scaffolds incorporating TGF-beta1 microspheres than for the control scaffolds without microspheres 10 days after incubation. Extracellular matrix staining by Safranin O and immunohistochemistry for type II collagen both significantly increased in scaffolds containing TGF-beta1 microspheres. These results suggest that the TGF-beta1 microsphere incorporated in scaffolds have the potential to enhance cartilage formation.

Animals↗

PubMed2006

Effects of chitosan and a low-molecular-weight chitosan on Bacillus cereus and application in the preservation of cooked rice.

Shrimp chitosan with 95% deacetylation and low-molecular-weight chitosan (LMWC) isolated from chitosan hydrolysate were investigated for their effects on the growth of Bacillus cereus and for use in the preservation of cooked rice. Four strains of Bacillus cereus were used: standard strain BCRC 10603 and three isolates (nos. 1 through 3) from cooked rice. The antibacterial activity of chitosan against B. cereus was greatly decreased when the reaction pH was changed from 6.0 to 7.0, but LMWC activity was less affected by this pH change. The susceptibility of B. cereus cells to chitosan decreased with increasing of cell age, in accordance with the relative electronegativity of the cell surface. B. cereus spores were more sensitive to LMWC and chitosan than were vegetative cells. Addition of 80 ppm LMWC and chitosan in sterile saline (pH 7.0) greatly reduced the D-value for the tested four strains at 90 degrees C from 30.77 to 46.51 min to 7.47 to 10.17 min and 4.68 to 7.91 min, respectively, and at 100 degrees C from 1.95 to 2.56 min to 0.89 to 0.93 min and 0.72 to 0.80 min, respectively. Addition of 2,000 ppm LMWC to raw rice water before steam cooking effectively inhibited increases in total aerobic bacteria and B. cereus in cooked rice stored at 37 and 18 degrees C.

Bacillus cereus↗

PubMed2002

Adsorption behavior of mercury and precious metals on cross-linked chitosan and the removal of ultratrace amounts of mercury in concentrated hydrochloric acid by a column treatment with cross-linked chitosan.

Cross-linked chitosan was synthesized with chitosan and ethylene glycol diglycidyl ether. The adsorption behavior of trace amounts of metal ions on the cross-linked chitosan was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. The cross-linked chitosan adsorbed mercury and precious metals (Pd, Pt, and Au) at pH values from acidic to neutral. Especially, mercury in concentrated hydrochloric acids could be adsorbed on cross-linked chitosan quantitatively by an anion-exchange mechanism in the form of a stable chloride complex. This method was applied to the removal of mercury from commercially available hydrochloric acid; more than 97% of mercury was removed, and the residual mercury in the hydrochloric acid (Grade: for trace analysis) was found to be 0.15 ppb. Mercury adsorbed on the cross-linked chitosan could be easily desorbed with an eluent containing I M hydrochloric acid and 0.05 M thiourea. The thus-refreshed cross-linked chitosan could be repeatedly used for the removal of mercury in hydrochloric acid.

Journal Article↗

PubMed2005

Preparation of chitosan-g-polycaprolactone copolymers through ring-opening polymerization of epsilon-caprolactone onto phthaloyl-protected chitosan.

The new biodegradable chitosan graft copolymer, chitosan-g-polycaprolactone, was synthesized by the ring-opening graft copolymerization of epsilon-caprolactone onto phthaloyl-protected chitosan (PHCS) at the hydroxyl group in the presence of tin(II) 2-ethylhexanoate catalyst via a protection-graft-deprotection procedure. Toluene acted as a swelling agent in this heterogeneous system. The grafting reactions were conducted with various PHCS/monomer/toluene feed ratios to obtain chitosan-g-polycaprolactone copolymers with various polycaprolactone contents. The chemical structure of the chitosan-g-polycaprolactone was characterized by Fourier transform infrared and one- and two-dimensional NMR spectroscopy. After deprotection, the phthaloyl group was removed and the amino group was regenerated. Thus the obtained chitosan-g-polycaprolactone was an amphoteric hybrid with a large amount of free amino groups and hydrophobic polycaprolactone side chains. Some properties of the final product were also investigated, such as crystallinity, thermal property, and solubility.

Amino Acids↗

PubMed2006

Peritoneal application of chitosan and UV-cross-linkable chitosan.

The suitability of chitosan and UV-cross-linkable chitosan for intraperitoneal use, for example as a barrier device for preventing peritoneal adhesions or for drug delivery, was examined. In vitro experiments using two major cell types present in the peritoneal cavity (mesothelial cells and peritoneal macrophages) revealed neither attractive interactions between cross-linked chitosan gels and the cells nor a proliferative effect. However, the same UV-cross-linked chitosan applied in the peritoneal cavity of rabbits caused a granulomatous reaction with adhesion formation within two weeks in all animals, which persisted up to 4 weeks after exposure. Unmodified chitosan also caused adhesions, while UV irradiation did not. UV-cross-linkable chitosan induced significant elevations in MIP-2 and TNF-alpha from peritoneal macrophages, suggesting that soluble mediators could play a role in inducing adhesion formation. These results reinforce the view that the predictive value of in vitro cytotoxicity assays in matters of biocompatibility may not be sufficient, and suggest that other assays such as cytokine levels may be of value in predicting outcomes in situations involving multiple cell types (i.e. in vivo).

Animals↗

PubMed2005

Enhancement of bronchial octreotide absorption by chitosan and N-trimethyl chitosan shows linear in vitro/in vivo correlation.

Chitosan is a biocompatible polysaccharide of natural origin that can act as a permeation enhancer. In this study, we used an integral in vitro/in vivo correlation approach to: a) investigate polysaccharide-mediated absorption kinetics of the peptide drug octreotide across mammalian airway epithelium, b) assess formulation toxicity, c) correlate the mechanism of permeation enhancement. The 20% and 60% N-trimethylated chitosan derivatives (TMC20 and TMC60) were synthesized by alkaline methylation using chitosan as starting material. Octreotide was administered in control buffers or in 1.5% (w/v) gel-phase formulations of pH 5.5 for chitosan and pH 7.4 for TMCs. In vitro, reconstituted Calu-3 cell monolayers were used for trans-epithelial electrical resistance (TEER), transport and cytotoxicity assays. Intratracheal instillation in rats was used to determine octreotide kinetics and formulation toxicity in vivo. Chitosan, TMC20 and TMC60 decreased TEER significantly and enhanced octreotide permeation in vitro by 21-, 16- and 30-fold. In vivo, sustained release properties of the formulations were observed and the bio-availability was enhanced by 2.4-, 2.5- and 3.9-fold, respectively. Interestingly, we found a linear in vitro/in vivo correlation between calculated absorption rates (R2=0.93), suggesting that the permeation enhancement by polysaccharides, both in vitro and in vivo, proceeds via an analogous mechanism. Cell viability and histology studies showed that the TMCs are safer than chitosan and that Calu-3 cell monolayers are a valuable model for predicting paracellular transport kinetics in airway epithelia. Additionally, cationic polysaccharides are promising enhancers for peptide drug absorption with prospect for sustained-release formulations.

Absorption↗

PubMedDate not supplied

Influence of chitosan structure on the formation and stability of DNA-chitosan polyelectrolyte complexes.

The interactions between DNA and chitosans varying in fractional content of acetylated units (FA), degree of polymerization (DP), and degree of ionization were investigated by several techniques, including an ethidium bromide (EtBr) fluorescence assay, gel retardation, atomic force microscopy, and dynamic and electrophoretic light scattering. The charge density of the chitosan and the number of charges per chain were found to be the dominating factors for the structure and stability of DNA-chitosan complexes. All high molecular weight chitosans condensed DNA into physically stable polyplexes; however, the properties of the complexes were strongly dependent on FA, and thereby the charge density of chitosan. By employing fully charged oligomers of constant charge density, it was shown that the complexation of DNA and stability of the polyplexes is governed by the number of cationic residues per chain. A minimum of 6-9 positive charges appeared necessary to provide interaction strength comparable to that of polycations. In contrast, further increase in the number of charges above 9 did not increase the apparent binding affinity as judged from the EtBr displacement assay. The chitosan oligomers exhibited a pH-dependent interaction with DNA, reflecting the number of ionized amino groups. The complexation of DNA and the stability of oligomer-based polyplexes became reduced above pH 7.4. Such pH-dependent dissociation of polyplexes around the physiological pH is highly relevant in gene delivery applications and might be one of the reasons for the high transfection activity of oligomer-based polyplexes observed.

Animals↗

PubMed2004

Comparison of chitosan scaffold and chitosan-collagen scaffold: a preliminary study.

Chitosan has similar structure to glycosaminoglycans in the tissue, thus may be a good candidates as tissue engineering scaffold. However, to improve their cell attachment ability, we try to incorporate this natural polymer with collagen by combining it via cross-linking process. In this preliminary study we evaluate the cell attachment ability of chitosan-collagen scaffold versus chitosan scaffold alone. Chitosan and collagen were dissolved in 1% acetic acid and then were frozen for 24 hours before the lyophilizing process. Human skin fibroblasts were seeded into both scaffold and were cultured in F12: DMEM (1:1). Metabolic activity assay were used to evaluate cell attachment ability of scaffold for a period of 1, 3, 7 and 14 days. Scanning electron micrographs shows good cell morphology on chitosan-collagen hybrid scaffold. In conclusion, the incorporation of collagen to chitosan will enhance its cell attachment ability and will be a potential scaffold in tissue engineering.

Cell Adhesion↗

PubMed1989

Studies on chitosan: 2. Solution stability and reactivity of partially N-acetylated chitosan derivatives in aqueous media.

The stability of the solutions of partially N-acetylated chitosans was studied by two methods: (1) 1% solutions of the chitosan derivatives in 0.1 M aqueous acetic acid were added dropwise to buffer solutions with pH from 8.6 to 12 and to a 0.1 M NaOH solution; (2) to each 0.5% solution of the derivatives in 0.1 M acetic acid was added the desired amount of a 1 M NaOH solution. The stability data obtained were summarized with respect to the degree of N-acetylation. It was found that the solutions of the derivatives with more than 50% acetyl content were stable even in alkaline conditions and the gelation and precipitation of the solutions did not occur. The reactivity of the derivatives with the degree of N-acetylation of more than 50% was studied using methyl 4-azidobenzoimidate (MABI) and ethylene glycol diglycidyl ether in homogeneous states. It was found that MABI reacted with amino groups of the chitosans only at neutral pH and glycidyl groups reacted at neutral and alkaline pH. It seems that these unique properties of chitosans with a degree of N-acetylation of more than 50% will enable us to prepare new chitosan derivatives.

Acetylation↗

PubMed1993

Studies on chitosan: 6. Relationship between N-acetyl group distribution pattern and chitinase digestibility of partially N-acetylated chitosans.

The digestibility of partially N-acetylated chitosans by microbial chitinases was investigated in view of the distribution pattern of N-acetyl groups along the polysaccharide chain. Partially N-acetylated chitosans are classified into two groups; moderately N-deacetylated chitosans (MDC) with 10-30% acetyl content obtained by heterogeneous N-deacetylation of chitin and partially N-acetylated chitosans (PAC-H) with 20-70% acetyl content prepared by homogeneous N-acetylation of highly N-deacetylated chitosans (HDC). MDC have some blocks of N-acetyl-D-glucosamine (GlcNAc) sequences but PAC-H are random-type copolymers of GlcNAc and D-glucosamine. The apparent Km values of Streptomyces griseus chitinase were 0.14 g l-1 for 30% N-acetylated MDC and 0.16 g l-1 for 30% N-acetylated PAC-H. The Km values decreased with increased N-acetylation but the values for both MDC and PAC-H with similar acetyl content were almost the same. The chitinase from S. griseus could not distinguish the difference between block and random distributions of GlcNAc. The chitinases from Bacillus sp. and Bacillus sp. PI-7S also hydrolysed MDC and PAC-H in the same manner. From these results we conclude that sequences of GlcNAc are not necessary for recognition by these chitinases in contrast to lysozyme.

Acetylation↗

PubMed2006

Effect of chitosan type on protein and water recovery efficiency from surimi wash water treated with chitosan-alginate complexes.

Previous research has shown that soluble protein recovery by chitosan (Chi) complexes with polyanions such as alginate (Alg) is more effective than using chitosan alone. In this study, Chi-Alg complexes were used to recover soluble proteins from surimi wash water (SWW) slightly acidified to pH 6. Six Chi samples differing in molecular weight (MW) and degree of deacetylation (DD) were used at 20, 40 and 100mg/L SWW Chi-Alg complexes prepared with a Chi:Alg mixing ratio previously optimized (MR=0.2). FTIR analysis of the solids recovered revealed the three characteristic amide bands observed in the same region for untreated SWW confirming protein adsorption by Chi-Alg. The superior effectiveness of Chi complexes was confirmed but differences among chitosan types could not be correlated to MW and DD. Experimental Chi samples with 94%, 93%, 75% and 93% DD and 22, 47, 225 and 3404 x 10(3)Da, respectively, showed 73-76% protein adsorption while a commercial chitosan sample with 84% DD and 3832 x 10(3)Da had 74-83% protein adsorption. An experimental chitosan, SY-1000 with 94% DD and 1.5 x 10(6)Da, showed the highest protein adsorption (79-86%) and turbidity reduction (85-92%) when used at 20mg/L SWW.

Alginates↗

PubMed2006

Hydroxyl radicals scavenging activity of N-substituted chitosan and quaternized chitosan.

N-substituted chitosan and quaternized chitosan were synthesized and their antioxidant activity against hydroxyl radicals was assessed, respectively. Compared with the antioxidant activity of chitosan, the results indicated that the two kinds of chitosan derivatives had different scavenging ability on hydroxyl radicals, which should be related to the form of amido in the two kinds of chitosan derivatives.

Antioxidants↗

PubMed1992

Studies on chitosan: 4. Lysozymic hydrolysis of partially N-acetylated chitosans.

The lysozymic digestibility of partially N-acetylated chitosans was studied by measuring the reducing sugars produced and the molecular weights of their hydrolysates. Moderately N-deacetylated chitosans (MDC), obtained by N-deacetylation of chitin under heterogeneous conditions, were about four times more digestible at an early stage than partially N-acetylated chitosans (PAC-H) with similar acetyl content, prepared by N-acetylation of highly N-deacetylated chitosans under homogeneous conditions. The molecular weights of the hydrolysates of MDC decreased rapidly but gradually reached a constant value in contrast to the behaviour of PAC-H. The Km was 0.14 mM for 30% N-acetylated MDC and 0.12 mM for 65% N-acetylated PAC-H although the degree of N-acetylation of the latter was twice as much as the former. These differences were due to the different distribution patterns of N-acetyl groups in two types of the chitosans. MDC with 20-30% acetyl content have the sequences of more than three N-acetyl-D-glucosamine residues but PAC-H with about 30% acetyl content are random-type copolymers of N-acetyl-D-glucosamine and D-glucosamine units. PAC-H with more than 50% acetyl content have the sequences of more than three N-acetyl-D-glucosamine residues.

Acetylation↗

PubMedDate not supplied

Preparation and characterization of ampicillin loaded methylpyrrolidinone chitosan and chitosan microspheres.

Ampicillin was embedded in microparticles made of a new derivative of chitosan: methylpyrrolidinone chitosan. They were prepared using different drug-to-polymer weight ratios and by a spray-drying technique. Spray-dried drug-loaded chitosan microspheres were prepared for comparison. The microparticles were characterized by scanning electron microscopy (SEM), particle size analysis, differential scanning calorimetry (DSC) and in vitro drug release. Microbiological assay was performed using different bacterial strains. Spray-dried microspheres of almost spherical shape, smooth surface and narrow size distribution were always obtained. Ampicillin loaded into both polymer matrices showed amorphous behaviour as determined by DSC. Drug-loaded microspheres resulted to control the drug release in a 30-120 min range, depending on chitosan type. Thermal denaturation of the microspheres does not modify drug release rate. The results of the microbiological assay show that the loading of ampicillin into chitosans is able to maintain or improve the anti-bacterial activity of the drug.

Ampicillin↗

PubMed1998

Chitosan-chondroitin sulfate and chitosan-hyaluronate polyelectrolyte complexes: biological properties.

In this work, we compare some biological properties of a highly deacetylated chitosan to those obtained with the materials made from its polyelectrolyte complexes with various GAG's such as chondroitin-sulfates and hyaluronic acid. The hydrolysis of the complexes by means of the specific hydrolytic enzymes is studied. Cell-adhesion and cell-proliferation on these materials is compared to that obtained with a pure chitosan material. Finally, a series of in vivo experiments is performed to test the wound-healing properties of this kind of complexes. All the results agree to show that chitosan has a protective effect against GAG's hydrolysis by their specific enzymes but only at pH's different from the optimal pH of the enzyme considered. In addition, they also agree to confirm that a pure chitosan material gives the best results in connection with cell-attachment and cell-proliferation or wound healing. Nevertheless, whatever the case, no adverse effect was observed with the polyelectrolyte complexes GAG's-chitosan.

Animals↗