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At least 19 recordsLinked to original sources

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↗

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↗

PubMed1996

In vivo drug release and antitumor characteristics of water-soluble conjugates of mitomycin C with glycol-chitosan and N-succinyl-chitosan.

The water-soluble conjugates of mitomycin C (MMC) with N-succinyl-chitosan (N-Suc-chitosan) and glycol-chitosan (Gly-chitosan), named N-Suc-chitosan-glu-MMC and Gly-chitosan-glu-MMC, respectively, were characterized mainly by the plasma concentration-time profiles of MMC after intraperitoneal administration and their in vivo antitumor effect against P388 leukemia and Sarcoma 180. Before in vivo evaluation, polymer-drug binding characteristics were checked by gel-chromatography. Gel-chromatographs proposed the covalent binding of 1a-(4-carboxybutyryl)-MMC (glu-MMC) with both the polymer supports. The plasma concentration of MMC showed that each conjugate released MMC in vivo at a similar rate. Kinetic analysis suggested that the in vivo drug release should be considerably faster than the in vitro release in the buffer, pH 7.4, alone. In the treatment against P388 leukemia inoculated intraperitoneally, Gly-chitosan-glu-MMC showed the highest increase in life span (ILS) at 10 mg MMC eq/kg. It was lethally toxic at the dose of 20 mg MMC eq/kg, while N-Suc-chitosan-glu-MMC gave the highest ILS value at this dose. Each conjugate exhibited a little larger ILS value than MMC. For the Sarcoma 180 solid tumor inoculated subcutaneously, the polymer characteristics affected the antitumor effect. Namely, with the intravenous injection, Gly-chitosan-glu-MMC hardly exhibited any tumor growth inhibition, but N-Suc-chitosan-glu-MMC showed significant tumor growth suppression. As to the intratumoral administration, the tendency to suppress tumor growth was observed in MMC and both the conjugates.

Animals↗

PubMed1997

Chitosan as a nasal delivery system: the effect of chitosan solutions on in vitro and in vivo mucociliary transport rates in human turbinates and volunteers.

In these studies, we examined the effect on mucociliary transport rates (MTR) of various 0.25% (w/v) chitosan solutions applied to human nasal tissue both ex vivo and in vivo. In the first study a range of chitosans with different molecular weights were applied to freshly amputated human nasal turbinates, and their effect on MTR was recorded. The transient inhibitory effect on turbinate MTR that was found for most of the chitosan preparations showed a marked dependence on the volume of chitosan solution applied and the molecular weight of the chitosan tested. The higher the molecular weight of the chitosan and the more chitosan applied, the longer the original MTR was depressed. A small scale human trial, investigating the effect of chitosan glutamate, on saccharin clearance times, was also undertaken. The study showed that a once daily application of a 0.25% solution of the chitosan for 7 days had no effect on either saccharin clearance times or nasal histology as examined by light microscopy.

Adult↗

PubMed1998

Chitosan-membrane interactions and their probable role in chitosan-mediated transfection.

Recent studies in our laboratory have shown that chitosan, a polycationic polymer of glucosamine, can facilitate the transfection of HeLa cells with a plasmid that codes for beta-galactosidase. Although chitosan can bind to DNA and other polyanions, the kinetics of complexation might differ depending on the polyanion tested. This evidence suggests that, in addition to ionic interactions, the carbohydrate backbone of chitosan might have an important role in the process of transfection. Beads prepared by the complexation of chitosan with polyphosphate were used to investigate the nature of cellular interactions with chitosan. HeLa cells bound to chitosan-polyphosphate beads could be readily displaced from the beads with methyl alpha-D-mannopyranoside but not with NaCl. Membrane proteins solubilized by CHAPS bound readily to chitosan-polyphosphate beads. A major fraction of the membrane proteins could be eluted from the beads with methyl alpha-D-mannopyranoside. These results suggest that non-ionic interactions between the carbohydrate backbone of chitosan and cell surface proteins might have an important role in the chitosan-mediated transfection of HeLa cells.

Biopolymers↗

PubMedDate not supplied

Release characteristics of chitosan treated alginate beads: I. Sustained release of a macromolecular drug from chitosan treated alginate beads.

Alginate and chitosan treated alginate beads were prepared and compared as an oral controlled release system for macromolecular drugs. Dextran (M.W. 70,000) was used as a model substance. The beads were prepared by the ionotropic gelation method and the effect of various factors (alginate, chitosan, drug and calcium chloride concentrations, the volume of external and internal phases and drying methods) on bead properties were investigated. The addition of chitosan increased the drug loading capacity of the beads, and larger beads were obtained in the presence of chitosan. On the other hand, addition of chitosan in the gel structure reduced the drug release from beads. The erosion of the beads was suppressed by chitosan treatment. The drying method was important to the properties of the chitosan-alginate beads. It is proposed that chitosan treated alginate beads may be used as a potential controlled release system of such macromolecules.

Alginates↗

PubMed1991

Studies on chitosan: 3. Evidence for the presence of random and block copolymer structures in partially N-acetylated chitosans.

The chemical structures of moderately N-deacetylated chitosans (MDC) derived from chitin under heterogeneous reaction conditions and partially N-acetylated chitosans (PAC) derived from highly N-deacetylated chitosans (HDC) under homogeneous reaction conditions were deduced from the data of the stability of their solutions in alkaline media, the swelling behaviour and X-ray diffraction patterns of their films in connection with the degree of N-acetylation of them. The solutions of PAC with more than 51% acetyl content, which were prepared from HDC by N-acetylation, were stable and remained clear and homogeneous by adding 1.2 equivalents of NaOH. On the contrary the solutions of PAC with more than 52% acetyl content, which were prepared from MDC, became turbid by neutralization with less than 1.15 equivalents of NaOH. The films of PAC prepared from HDC were highly swollen in water. The degree of swelling of the chitosan film with 51% acetyl content, prepared from the 6% acetyl content chitosan, was 121% while that of the 53% acetyl content chitosan, prepared from the 30% acetyl content chitosan, was 28%. From these data it was possible to set up a hypothesis that PAC prepared from HDC were considered as random-type copolymers of N-acetyl-glucosamine and glucosamine units whereas MDC were considered as block-type copolymers.

Acetylation↗

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↗

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↗

PubMed1999

Aging phenomena of chitosan and chitosan-diclofenac sodium system detected by low-frequency dielectric spectroscopy.

The use of natural polymers for design of dosage form has received considerable attention recently, especially from the safety point of view. Among these polymers, chitosan shows very interesting biological, chemical and physical properties which makes it possible to use chitosan for various pharmaceutical applications. Microcrystalline chitosan (MCCh) is a special multifunctional polymeric material existing in the form of either of gelatinous water dispersion or a powder. Thermal aging of chitosan and chitosan-diclofenac sodium mixture have been studied using low-frequency dielectric measurements. The aging was carried out by annealing in ambient atmosphere in the temperature range between 25 degrees C and 100 degrees C. The dielectric losses in the aged samples proved to decrease by about one order of magnitude. The additional measurements of molecular weight distribution and infrared absorption were also carried out for better understanding of nature of the ageing phenomena. Partial evacuation of water, cross-linking and improvement of structural order may be suggested to be a result of thermal aging of the investigated materials.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1998

Chitosan and depolymerized chitosan oligomers as condensing carriers for in vivo plasmid delivery.

Chitosan is a polysaccharide that demonstrates much potential as a gene delivery system. The ability of a commercially available chitosan and depolymerized chitosan oligomers to condense plasmid was determined using TEM and microtitration calorimetry, while the diameter and stability of the resultant complexes were measured using laser light scattering. Selected complexes were physically stable to challenge with both serum and salt solutions. Parameters such as chitosan molecular weight, plasmid concentration and charge ratio influenced such stability. The effect of including a pH-sensitive endosomolytic peptide on the physicochemical properties of the complex was determined. The presence of a pH-sensitive endosomolytic peptide enhanced the levels of reporter gene expression in Cos-1 cells 4-fold. A selected complex containing a lytic peptide was administered in the upper small intestine and colon of rabbits, and reporter gene expression was measured in defined intestinal tissues. Reporter gene expression was enhanced in defined intestinal tissues, although levels of expression remained low. The combination of strong complex stability and low in vivo expression levels suggest that uptake and/or decomplexation, but not endosomal release, may be the critical rate-limiting steps in the uptake process.

Amino Acid Sequence↗

PubMed1996

Preparation and drug release characteristics of the conjugates of mitomycin C with glycol-chitosan and N-succinyl-chitosan.

Mitomycin C (MMC) was covalently attached to glycol-chitosan (Gly-chitosan) and N-succinyl-chitosan (N-Suc-chitosan) through a spacer of the glutaryl group, and each conjugate was obtained as a water-soluble product. Stability of 1a-(4-carboxybutyryl)-MMC (Glu-MMC) in vitro was investigated by incubation in 1/15 M phosphate buffers of pH 5, 6, 7.4, 8 and 9 at 37 degrees C. The release rate of MMC from Glu-MMC was very slow at neutral pH, gradual at basic pH and relatively fast at acidic pH, but the quick decomposition of MMC proceeded simultaneously at acidic pH. Release of MMC from the conjugates in vitro was investigated by incubation in 1/15 M phosphate buffers of pH 5, 7.4 and 9 at 37 degrees C. The release rate of MMC from the conjugates was slight at acidic pH, accelerated at basic pH, and was gradual at pH 7.4. In a plasma-buffer (pH 7.4) mixture (1:1, v/v), the release rate of MMC from the conjugates was rather similar to that in only the buffer (pH 7.4).

Antibiotics, Antineoplastic↗

PubMed1981

SEM ultrastructure studies of N-acyl- and N-benzylidene-chitosan and chitosan membranes.

Fine ultrastructures of the cross sections of membranes, which are derived from chitosan and utilizable as artificial kidney, are examined by scanning electron microscopy (SEM). Three types of unique ultrastructure of the membrane cross sections are present: N-acylchitosan membranes [N-acetyl (1), N-propionyl (2), N-butyryl (3), N-pentanoyl (4), N-hexanoyl (5), N-octanoyl (6), and N-benzoyl (7)], N-benzylidenechitosan membranes (8) and chitosan membranes (9). The vertical cross sections of membranes 1-7 consist of orderly arranged layers that are formed by an assembly of particle units of fibrils. Neither fibrils nor layers are present and a smooth surface is characteristic of the cross sections of (8). On the other hand, the particle units of fibrils are absent and a nappy rough surface is characteristic of the cross sections of (9). N-Acetylation of (9) affords the article units of fibrils that are disorderly oriented. Low- and middle-molecular compounds (MW less than 2000) pass through small pores among these fibrils present in orderly arranged layers of the membranes. Properties of these N-acyl-chitosan membranes well meet the requirements of artificial kidney membranes.

Benzylidene Compounds↗