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PubMed2003

Chemical modification of chitosan. Part 15: synthesis of novel chitosan derivatives by substitution of hydrophilic amine using N-carboxyethylchitosan ethyl ester as an intermediate.

The Michael type reaction of chitosan with ethyl acrylate has been investigated. Although this reaction was quite slow in the case of chitosan, the reiteration of the reaction was an effective means for increasing the degree of substitution (DS) of ethyl ester. The N-carboxyethylchitosan ethyl ester as an intermediate was successfully substituted with various hydrophilic amines, although the simultaneous hydrolysis of the ester to carboxylic acid also occurred. Water-soluble chitosan derivatives were obtained by substitution with hydroxyalkylamines and diamines.

Acrylates↗
PubMedDate not supplied

Synthesis of chitosan-stabilized polymer dispersions, capsules, and chitosan grafting products via miniemulsion.

The potential of chitosan as an emulsion stabilizer is combined with the miniemulsion technique to generate oil droplets, hollow capsules, and latex particles in the diameter range of 100-300 nm carrying a functional biopolymer surface. It turned out that chitosan alone, independent of its molecular weight, is just moderately efficient, which is speculatively attributed to its stiff polysaccharide structure. The addition of biocompatible costabilizers with higher flexibility either to the oil phase or to the water phase, such as Jeffamine or Gluadin (a peptide), eliminates these deficiencies, and very small nanocapsules made of biopolymer hybrids can be obtained. NMR analysis shows that the costabilizer is effectively grafted/cross-linked to the chitosan which makes the miniemulsion route also effective for the modification of hard-to-handle, amphiphilic biopolymers either from the water or from the oil phase.

Biocompatible Materials↗
PubMedDate not supplied

Protective immune responses to meningococcal C conjugate vaccine after intranasal immunization of mice with the LTK63 mutant plus chitosan or trimethyl chitosan chloride as novel delivery platform.

Chitosan and its derivative N-trimethyl chitosan chloride (TMC), given as microparticles or powder suspensions, and the non-toxic mucosal adjuvant LTK63, were evaluated for intranasal immunization with the group C meningococcal conjugated vaccine (CRM-MenC). Mice immunized intranasally with CRM-MenC formulated with chitosan or TMC and the LTK63 mutant, showed high titers of serum and mucosal antibodies specific for the MenC polysaccharide. Neither significant differences were observed between microparticle formulations and powder suspensions nor when LTK63 was pre-associated to the delivery system or not. The bactericidal activity measured in serum of mice immunized intranasally with the conjugated vaccine formulated with the delivery systems and the LT mutant was superior to the activity in serum of mice immunized sub-cutaneously. Importantly, intranasal but not parenteral immunization, induced bactericidal antibodies at the nasal level, when formulated with both delivery system and adjuvant.

Administration, Intranasal↗
PubMed1999

Biodisposition characteristics of N-succinyl-chitosan and glycol-chitosan in normal and tumor-bearing mice.

Two water-soluble chitosan derivatives, N-succinyl-chitosan (Suc-chi; average MW 3x10(5)) and glycol-chitosan (Gly-chi; average MW 1.5x10(5)), were examined concerning their biodisposition characteristics in order to evaluate their possible use as water-soluble drug carriers. Their body distribution and urinary excretion were investigated by i.v. administration of FITC-labeled Suc-chi (FTC-Suc-chi) and FITC-labeled Gly-chi (FTC-Gly-chi) to normal and Sarcoma 180 solid tumor-bearing mice. In normal mice, both polymers showed good retention in blood circulation; especially, FTC-Suc-chi exhibited a long half-life of 51 h, and its distribution to other tissues was very small. FTC-Gly-chi was distributed into the kidney to a relatively high extent. In tumor-bearing mice, FTC-Suc-chi and FTC-Gly-chi were eliminated faster from the blood circulation than in normal mice, that is, with half-lives of 11 and 7 h, respectively. FTC-Suc-chi was less partitioned to the tumor tissue but accumulated more easily into it compared with FTC-Gly-chi. This suggested the enhanced permeability and retention (EPR) effect of Suc-chi and explained the previous result that a water-soluble Suc-chi-mitomycin C conjugate injected intravenously exhibited a good effect against Sarcoma 180 solid tumor. FTC-Gly-chi showed greater distribution to the kidney than in normal mice. Urinary excretion studies indicated the faster excretion of both polymers in tumor-bearing mice. The molecular weight of the products excreted into urine indicated that both polymers should be pretty resistant to the hydrolytic enzyme, lysozyme. Taking toxicities into account, Suc-chi is considered to be available as a drug carrier showing long systemic retention and tumor accumulation.

Animals↗
PubMed2003

Fourth 3D structure of the chitosan molecule: conformation of chitosan in its salts with medical organic acids having a phenyl group.

Chitosan salts with two medical organic acids having phenyl groups (salicylic and gentisic acids) exhibited fiber diffraction patterns of a new type of crystal which does not compare with known types I and II. The crystals, called type III salts, showed a fiber repeat of 2.550 nm and a meridional reflection at the 5th layer line. These results coupled with a conformational analysis indicate the chain conformation of chitosan with the salts to be a 5/3 helix, this helix differing from those of type I (an extended two-fold helix) and type II (a relaxed two-fold helix or a 4/1 helix). The fiber patterns of all the type III salts were similar. This observation has also been found with type II salts and is an indication that the acid ions are not arranged in regular positions in the crystals. A comparison of solid-state 13C-NMR spectra of the gentisic acid salt and the aspirin salt, which could not be crystallized, suggests that, in the latter salt, the chitosan molecules also formed a 5/3 helix.

Acids↗
PubMed2004

Antimicrobial activity of a low-molecular-weight chitosan obtained from cellulase digestion of chitosan.

A water-soluble chitosan hydrolysate with high activity against Escherichia coli was obtained during cellulase digestion of chitosan for 18 h. This 18-h hydrolysate is composed of low-molecular-weight chitosan (LMWC), with a molecular weight of 12.0 kDa, and chitooligosaccharides, which are composed of sugars with a degree of polymerization of 1 to 8. LMWC has a strong activity at 100 ppm against many pathogens and yeast species, including Bacillus cereus, E. coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica serovar Typhi, and Saccharomyces cerevisiae, while the chitooligosaccharides have much weaker antimicrobial activity than does LMWC. Accordingly, the antimicrobial activity against E. coli in the 18-h hydrolysate proved to come mainly from the presence of LMWC.

Anti-Bacterial Agents↗
PubMedDate not supplied

Evaluation of microcrystalline chitosan properties as a drug carrier. Part II. The influence of microcrystalline chitosan on release rate of ketoprofen.

The effect of microcrystalline chitosan (MCCh) as hydrogel and dried gel (film) on the release of ketoprofen (KTA) was studied in vitro. Commercial ketoprofen gel (Profénid gel) was applied as a reference preparation for MCCh hydrogel, pure as well as in combination with methylcellulose (MC) and hydrophilising agents (1,2-propylene glycol and glycerol). The quantity of the released drug was determined by ultraviolet spectroscopy. IR spectroscopic analysis, proton magnetic resonance (1H NMR), powder X-ray diffraction, and differential scanning calorimetry (DSC) studies verified physical and chemical interactions between chitosan and ketoprofen. The influence of these interactions on the ketoprofen release from the hydrogel and film was analysed. It was found that microcrystalline chitosan may be used as a polymer drug carrier.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Synthesis of iron-crosslinked chitosan succinate and iron-crosslinked hydroxamated chitosan succinate and their in vitro evaluation as potential matrix materials for oral theophylline sustained-release beads.

Chitosan succinate (CS) and hydroxamated chitosan succinate (HCS) were prepared. The generated semisynthetic polymers were employed in the formation of drug-loaded, iron(III)-crosslinked polymeric beads. Infrared spectroscopy was employed to prove the crosslinking. The produced beads were evaluated in vitro as drug prolonging and potentially orally administered delivery system. Theophylline was used as the loaded model drug. The generated beads proved to be successful in prolonging drug release. Iron leaching from the generated beads was minimal (<2%), and it only took place under acidic conditions (pH 1).

Administration, Oral↗
PubMedDate not supplied

Study of the release mechanism of diltiazem hydrochloride from matrices based on chitosan-alginate and chitosan-carrageenan mixtures.

The aim of this work was to establish the diltiazem hydrochloride release mechanism from the chitosan-alginate matrix tablet (MCB/AS) and chitosan-carrageenan matrix tablet (MCS/CSI). The weight loss for MCS/CSI is mainly due to the weight loss of the matrix while for MCB/AS it is mainly due to the diltiazem hydrochloride released from the tablet. Using the Peppa's model the release order for MCS/CSI was n = 1.07 +/- 0.13 and for MCB/AS was n = 0.76 +/- 0.02. Thus, MCS/CSI has a transport mechanism, and for MCB/AS the drug release mechanism is a combined process of diffusion and relaxation. MCB/AS has an elastic modulus (G' = 10(5) Pa) one order of magnitude higher than MCS/CSI (G' = 10(4) Pa). MCB/AS is able to uptake solvent without disrupting the microstructure due to its high elastic modulus. Instead MCS/CSI showed a quick erosion process, which conducted to the tablet disintegration due to a fast solvent uptake process.

Alginates↗
PubMed2004

Chitosan-supported palladium catalyst. 5. Nitrophenol degradation using palladium supported on hollow chitosan fibers.

Hollow chitosan fibers were reacted with chloropalladate solutions and subsequently reduced by hydrogen produced in situ by reaction of sulfuric acid with zinc powder in order to manufacture palladium supported on catalytic hollow chitosan fibers (C2HF-Pd). This catalytic support was used to degrade 3-nitrophenol (3-NP) using two different hydrogen donors (hydrogen gas and sodium formate). The solution was flowed through the lumen of the fiber, while the sodium formate was recirculated round the outside of the fiber. In the case of hydrogen gas, the gas was maintained under controlled pressure outside the fiber. The influence of the pH, residence time (ca. flow velocity), nitrophenol concentration, and hydrogen-donor concentration (or pressure) was investigated for both systems in order to evaluate the limiting parameters. While the system using sodium formate was the most efficient for nitrophenol conversion, the system using hydrogen gas avoided the production of secondary waste solutions (formate solutions with traces of nitrophenol, which pass through the fiber membrane).

Catalysis↗
PubMedDate not supplied

Evaluation of properties microcrystalline chitosan as a drug carrier. Part 1. In vitro release of diclofenac from mictocrystalline chitosan hydrogel.

The influence of microcrystalline chitosan hydrogel, alone (MCCh) as well as in combination with methylcellulose (MC) or Carbopol (CP), on the release of diclofenac free acid (DA) and its salt (DS) was studied in vitro. Commercial Olfen gel (Mepha Ltd., Switzerland) was applied as a reference preparation. The influence of hydrophilizing agents (1,2-propylene glycol and glycerol) and methycellulose hydrogel on the rheological properties of the vehicle and on the release of drug from modified MCCh hydrogel was studied. The quantity of the released substance was determined by UV-spectroscopy. The results confirmed that release was dependent on the chemical character of the drug and on the type of vehicle. The process of diclofenac release from MCCh hydrogels as well as from Carbopol hydrogels runs in two phases. The first phase is characterised by rapid release whereas in the second phase the release is much slower. The most suitable basis for diclofenac is microcrystalline chitosan hydrogel with addition glycerol, 1,2-propylene glycol, and methylcellulose hydrogel.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

[Kinetics of in vitro drug release from chitosan and N-alkyl chitosan membranes].

By using the so-called "lag-time" method, we studied the effect of membrane thickness(h), initial drug concentration(Co) and flow rate(V) on the difusion coefficient(D) of model drug in membranes. The experiment indicates that D increases as h and v increase; D Keeps constant when C0 changes; Under the same condition, the D value of N-alkyl chitosan membrane is bigger than that of pure chitosan membrane.

Chitin↗
PubMed2004

[Studies on the insulin-liposomes double-coated by chitosan and chitosan-EDTA conjugates].

AIM: To evaluate the characteristics, the hypoglycemic efficacy and the pharmacokinetics of the insulin-liposomes double-coated by chitosan (CH) and chitosan-EDTA conjugates (CEC). METHODS: Insulin-liposomes were prepared by reversed-phase evaporation. The protection of insulin against peptic and tryptic digestion was studied with HPLC. The hypoglycemic effects of insulin-liposomes were investigated using the glucose oxidase method after oral administration to rats. Serum insulin concentration in rats were determined by radio-immunoassay, and were assessed by Pkanalyst computer program. RESULTS: The insulin-liposomes double-coated by CH and CEC was shown to protect insulin against digestion of pepsin, trypsin and gastrointestinal contents. In glucose tolerance test in normal rats, as compared with phosphate buffer solution control group, the insulin-liposomes coated by CH and CEC could reduce the glucose-induced peak of hyperglycemia. The reduction of the insulin-liposomes double-coated by CH and CEC was superior to that of other insulin-liposomes. When administered intragastrically to normal rats, the insulin-liposomes coated by CH and CEC could reduce glycemia measured after an overnight fast. The hypoglycemic effect the insulin-liposomes double-coated by CH and CEC was superior to that of other insulin-liposomes, and the dosage of 50 mu x kg(-1) decreased by 45.98% of initial blood glucose level at 1 h. As compared with subcutaneous injection, the relative pharmacological bioavailability was 17.02% calculated by area under the curve of glucose level versus time profile after oral administration of the insulin-liposomes double-coated by CH and CEC to rats. The serum insulin concentration-time curves were found to best fit the one-compartment open model. As compared with subcutaneous injection, the relative bioavailability was 8.91% calculated by the area under the curve of serum insulin concentration versus time profile after oral administration of the insulin-liposomes double-coated by CH and CEC to rats. CONCLUSION: The stability and absorption of insulin-liposomes double-coated by CH and CEC was superior to that of the insulin-liposomes coated either by CH, or by CEC respectively.

Administration, Oral↗
PubMed1999

Synthesis of chitosan succinate and chitosan phthalate and their evaluation as suggested matrices in orally administered, colon-specific drug delivery systems.

The naturally occurring polymer chitosan was reacted separately with succinic and phthalic anhydrides. The resulting semisynthetic polymers were assessed as potential matrices for colon-specific, orally administered drug delivery. Sodium diclofenac was used as the dispersed model drug. The prepared matrices were incorporated into tablets, which were evaluated in vitro. The evaluation included dissolution studies conducted under simulated gastrointestinal conditions of pH and transit times. The percentage fluid uptake was used to indicate the ability of the matrix to protect an embedded drug from gastric juices. The prepared matrices resisted dissolution under acidic conditions. On the other hand, improved drug release profiles were observed under basic conditions. Therefore, the results suggest the suitability of the prepared matrices in colon specific, orally administered drug delivery system. However, future in vivo testing is planned to fully establish the suitability of the prepared polymers for colon-specific drug delivery.

Chitin↗
PubMed2005

Novel polyelectrolyte carboxymethyl konjac glucomannan-chitosan nanoparticles for drug delivery. I. Physicochemical characterization of the carboxymethyl konjac glucomannan-chitosan nanoparticles.

Carboxymethyl konjac glucomannan-chitosan (CKGM-CS) nanoparticles, which are well dispersed and stable in aqueous solution, were spontaneously prepared under very mild conditions via polyelectrolyte complexation. The physicochemical properties of the nanoparticles were identified by Zetasizer 3000 and Fourier transform infrared. It was found that at various CKGM and CS concentrations the particles ranged in size from approximately 50 to 1200 nm, and the zeta potential from 15 to 45 mV. By changing pH value of the medium and increasing the concentration of salt, the mean size of the particles increased and the zeta potential decreased. Also, investigations on the encapsulation efficiency of the bovine serum albumin loaded CKGM-CS nanoparticles were also undertaken. This nanoparticulate system driven by complex formation shows potential as an advanced drug delivery system for water-soluble drugs.

Chitosan↗
PubMed1997

Prevention of postsurgical adhesions with N,O-carboxymethyl chitosan: examination of the most efficacious preparation and the effect of N,O-carboxymethyl chitosan on postsurgical healing.

BACKGROUND: Adhesion formation after operation can result in major complications. We have previously demonstrated that N,O-carboxymethyl chitosan (NOCC) is an effective inhibitor of postsurgical peritoneal adhesion formation. However, the optimal form of NOCC (i.e., cross-linked gel versus solution), as well as the best time of administration for optimal reduction in adhesion development, was not investigated. In addition, because adhesion formation and normal wound healing are related events and weakening of wound healing would be a serious drawback to the use of NOCC clinically, we wished to assess the effect of NOCC on the healing of surgical incisions. METHODS: Three surgical models were used: (1) an abdominal aortic anastomosis, (2) a large bowel anastomosis, and (3) an abdominal skin incision. In the first model Sprague-Dawley rats received an abdominal aortic transection and repair. NOCC solution or gel was administered at different time points throughout the procedure. Control and NOCC-treated animals were killed 14 days after operation. The condition of the anastomosed vessel was examined, and adhesion frequency and intensity in the abdomen were scored. In the second model Sprague-Dawley rats underwent large bowel transection and repair. Control and NOCC-treated animals were killed on postoperative days 4, 7, and 14, and strength of repair was assessed by removal of the large bowel and measurement of the bursting strength of the repaired incision. In the third model rats received an abdominal incision and were immediately closed. Control and NOCC-treated animals were killed 14 days after operation, and the skin tensile strength of the wound was measured with a tensiometer. RESULTS: In all three models studied, NOCC treatment did not adversely affect the strength of the repaired incision. NOCC solution administered before operation did not greatly reduce adhesion formation, whereas the delivery of both NOCC gel and solution after operation was most efficacious. CONCLUSIONS: The administration of both NOCC gel and solution after operation is most efficacious, and NOCC does not compromise postsurgical healing in rats at doses that prevent peritoneal adhesion formation.

Abdomen↗