Chitosan: a unique polysaccharide for drug delivery

Physicochemical and cell adhesion properties of chitosan films prepared from sugar and phosphate-containing solutions

This work was aimed at investigating a series of chitosan films obtained from chitosan, chitosan-phosphate, chitosan-phosphate-D-(+)raffinose or chitosan-phosphate-D-(+)sucrose solutions to preliminarily select a suitable biomaterial for developing a cell substrate for tissue engineering. The prepared films were characterized in terms of physicochemical properties (FT-IR, XRD, optical microscopy, wettability, water absorption, and tensile stress) and effects on proliferation of different types of human cells (endothelial, HUVEC; fibroblast, WI-38). The obtained results indicated that the presence of sucrose or raffinose at high concentration along with phosphate salts in the chitosan film-forming solution affords smooth, amorphous and highly hydrophilic materials in the form of soft and elastic film with optimal cytocompatibility. Owing to improved physicochemical and mechanical properties as well as affinity for differentiated human cells, these novel chitosan films appear as promising candidate biomaterials for tissue regeneration and repair. The major finding is the possibility to improve the biocompatibility of chitosan films by simply modifying their solid state characteristics.

Influence of chitosan type on the properties of extruded pellets with low amount of microcrystalline cellulose

The purpose of this research was to study the influence of type of chitosan with different molecular weights, ie, 190 and 419 kDa, on properties of pellets prepared by extrusion/spheronization. The formulations, consisting of acetaminophen as model drug, chitosan, microcrystalline cellulose (MCC), and dibasic calcium phosphate dihydrate with/without sodium alginate, were extruded using a twin-screw extruder and water as the granulating liquid. With 30% wt/wt MCC and no added sodium alginate, spherical pellets were produced containing low and high molecular weight chitosan at a maximum amount of 60% and 40% wt/wt, respectively. With sodium alginate (2.5% wt/wt), pellets with either type of chitosan (60% wt/wt), MCC (17.5% wt/wt), and acetaminophen (20% wt/wt) could be produced indicating an improved pellet-forming ability. Type and amount of chitosan and added sodium alginate affected physical properties of pellets including size, roundness, crushing force, and drug release. Low molecular weight chitosan produced pellets with higher mean diameter, sphericity, and crushing force. Additionally, the pellets made of low molecular weight chitosan and added sodium alginate showed faster drug release in 0.1 N HCl but had slower drug release in pH 7.4 phosphate buffer. This indicated that drug release from pellets could be modified by the molecular weight of chitosan. In conclusion, the molecular weight of chitosan had a major influence on formation, physical properties, and drug release from the obtained pellets.

Enzybiotics: A Look to the Future, Recalling the Past

The discovery and development of antibiotics was one of the greatest successes of Medicine in the 20th century and allowed the control of many diseases caused by microorganisms. Nevertheless, it is necessary to search constantly for new therapeutic tools in the continuing fight against disease-causing microorganisms and this probably leads us to today's concept of enzybiotics. Although microorganism-degrading enzymes have been known since the beginning of the last century, their use was soon forgotten because of the widespread use of antibiotics. The term enzybiotic is a hybrid word from "enzyme" and "antibiotic" and refers to phages: that is, viruses that attack and lyse bacteria and that can potentially help us to fight bacterial diseases. If the concept of enzybiotic is extended to antifungal enzymes, an enormous potential in the struggle against microorganism-due diseases may become available in the foreseeable future.

Effect of oppositely charged polymer and dissolution medium on swelling, erosion, and drug release from chitosan matrices

The reasons for retarded release of naproxen sodium from the chitosan matrices at different pH include poor aqueous solubility of drug, the formation of a rate-limiting polymer gel barrier along the periphery of matrices, the interaction of naproxen sodium with protonated amino groups of chitosan, and the interaction of ionized amino groups of chitosan with ionized sulfate groups of kappa-carrageenan.

In vitroantioxidative activities of three marine oligosaccharides

The antioxidant activities of three marine oligosaccharides, alginate oligosaccharides (AOs), chitosan oligosaccharides (COs), and fucoidan oligosaccharides (FOs), were investigated in vitro by several antioxidant assays, including hydroxyl radical scavenging, superoxide radical scavenging, erythrocyte hemolysis inhibiting, metal chelating activities, and anti-lipid peroxidation. The results show that these oligosaccharides exhibited different activities in various assays. AOs had the highest scavenging hydroxyl radical activity than FOs and COs at all the tested amounts. COs had the highest scavenging superoxide radical and inhibiting erythrocyte hemolysis activity than AOs and FOs at all the tested amounts. In the assay of chelating Fe2+, COs and FOs indicated good chelation while AOs hardly had any activity. In the assay of anti-lipid peroxidation, only COs had significantly high antioxidant activity.

Atomistic simulations to compute surface properties of poly(N-vinyl-2-pyrrolidone) (PVP) and blends of PVP/chitosan

Atomistic simulations were performed on poly(N-vinyl-2-pyrrolidone) (PVP) and its blends with chitosan (CS) in different ratios using molecular mechanics (MM) and molecular dynamics (MD) simulations in three-dimensionally periodic and effective two-dimensionally periodic condensed phases. Four independent microstructures were generated to analyze their surface properties. The calculated surface-energy values for PVP compared quite well with the experimental data reported in the literature. The density profile was analyzed, and the structure of the films showed an interior region of the bulk density. Various components of the energetic interactions (torsional, van der Waals, etc.) were examined to gain deeper insight into the nature of regular and anomalous interactions between the bulk and the surface films. Surface energies of PVP/CS blends were computed by MD simulations using the bulk pressure-volume-temperature (PVT) parameters. Bulk properties such as the cohesive energy density (CED) and solubility parameter (delta) were calculated using MM and MD simulations in the NVT ensemble under periodic boundary conditions. The Flory equation of state was used to compute the thermal expansion coefficient as well as PVT parameters. These surface-energy values agreed well with the surface-energy data calculated using the Zisman equation, which were also in accordance with the experimental observations. The results from this study suggest that computer simulations would provide valuable information on polymers and polymer-blend surfaces.

Evaluation and modification of N-trimethyl chitosan chloride nanoparticles as protein carriers

N-Trimethyl chitosan chloride (TMC) nanoparticles were prepared by ionic crosslinking of TMC with tripolyphosphate (TPP). Two model proteins with different pI values, bovine serum albumin (BSA, pI=4.8) and bovine hemoglobin (BHb, pI=6.8), were used to investigate the loading and release features of the TMC nanoparticles. TMC samples with different degrees of quaternization were synthesized to evaluate its influence on the physicochemical properties and release profiles of the nanoparticles. Sodium alginate was used to modify the TMC nanoparticles to reduce burst release. The results indicated that the TMC nanoparticles had a high loading efficiency (95%) for BSA but a low one (30%) for BHb. The particle size and zeta potential were significantly affected by the BSA concentration but not by the BHb concentration. Nanoparticles of TMC with a lower degree of quaternization showed an increase in particle size, a decrease in zeta potential and a slower drug-release profile. As for the alginate-modified nanoparticles, a smaller size and lower zeta potential were observed and the burst release of BSA was reduced. These studies demonstrated that TMC nanoparticles are potential protein carriers, and that their physicochemical properties and release profile could be optimized by means of various modifications.

Chitosan reduced gold nanoparticles as novel carriers for transmucosal delivery of insulin

PURPOSE

Colloidal metallic systems have been recently investigated in the area of nanomedicine. Gold nanoparticles have found themselves useful for diagnostic and drug delivery applications. Herein we have reported a novel method for synthesis of gold nanoparticles using a natural, biocompatible and biodegradable polymer; chitosan. Use of chitosan serves dual purpose by acting as a reducing agent in the synthesis of gold nanoparticles and also promotes the penetration and uptake of peptide hormone insulin across the mucosa. To demonstrate the use of chitosan reduced gold nanoparticles as carriers for drug delivery, we report herein the transmucosal delivery of insulin loaded gold nanoparticles.

MATERIALS AND METHODS

Gold nanoparticles were prepared using different concentrations of chitosan (from 0.01% w/v up to 1% w/v). The gold nanoparticles were characterized for surface plasmon band, zeta potential, surface morphology, in vitro diffusion studies and fluorescence spectroscopy. The in vivo studies in diabetic male Wistar rats were carried out using insulin loaded chitosan reduced gold nanoparticles.

RESULTS

Varying concentrations of chitosan used for the synthesis of gold nanoparticles demonstrated that the nanoparticles obtained at higher chitosan concentrations (>0.1% w/v) were stable showing no signs of aggregation. The nanoparticles also showed long term stability in terms of aggregation for about 6 months. Insulin loading of 53% was obtained and found to be stable after loading. Blood glucose lowering at the end of 2 h following administration of insulin loaded gold nanoparticles to diabetic rats was found to be 30.41 and 20.27% for oral (50 IU/kg) and nasal (10 IU/kg), respectively. Serum gold level studies have demonstrated significant improvement in the uptake of chitosan reduced gold nanoparticles.

CONCLUSIONS

The synthesis of gold nanoparticles using a biocompatible polymer, chitosan would improve its surface properties for binding of biomolecules. Our studies indicate that oral and nasal administration of insulin loaded chitosan reduced gold nanoparticles has led to improved pharmacodynamic activity. Thus, chitosan reduced gold nanoparticles loaded with insulin prove to be promising in controlling the postprandial hyperglycemia.

Antidiabetic effects of chitooligosaccharides on pancreatic islet cells in streptozotocin-induced diabetic rats

AIM: To investigate the effect of chitooligosaccharides on proliferation of pancreatic islet cells, release of insulin and 2 h plasma glucose in streptozotocin-induced diabetic rats.

METHODS: In vitro, the effect of chitooligosaccharides on proliferation of pancreatic islet cells and release of insulin was detected with optical microscopy, colorimetric assay, and radioimmunoassay respectively. In vivo, the general clinical symptoms, 2 h plasma glucose, urine glucose, oral glucose tolerance were examined after sixty days of feeding study to determine the effect of chitooligosaccharides in streptozotocin-induced diabetic rats.

RESULTS: Chitooligosaccharides could effectively accelerate the proliferation of pancreatic islet cells. Chitooligosaccharides (100 mg/L) had direct and prominent effect on pancreastic β cells and insulin release from islet cells. All concentrations of chitooligosaccharides could improve the general clinical symptoms of diabetic rats, decrease the 2 h plasma glucose and urine glucose, and normalize the disorders of glucose tolerance.

CONCLUSION: Chitooligosaccharides possess various biological activities and can be used in the treatment of diabetes mellitus.

Induction of lymphocytes activated marker CD69 following exposure to chitosan and alginate biopolymers

CD69 is a very early cell activation antigen expressed on the surface of activated immune cells. It can appear within 1-2h of activation and exhibits maximal expression levels between 18 and 24h after stimulation. In this work, the expression profile of CD69 in mice splenocytes was evaluated following exposure to the biopolymers, chitosan or alginate and the immunostimulatory factors, CpG ODN 1826 or concanavalin A. We have shown that both polymers are able to upregulate expression of CD69 on B cells and CD4+ T-lymphocytes, with alginate as the least potent stimulus. Moreover, the expression of the CD69 molecule on CD8+ T-lymphocytes was observed only in splenocytes cultured with chitosan. However, activation of lymphocytes did not result in cell proliferation. On the other hand, CpG ODN proved to be a potent B cell stimulator, as evidenced by the upregulation of CD69, but had less effect on T-cells. These results, together with previous discoveries reported in scientific literature, may contribute to the clarification of the adjuvant effect, which has been attributed to chitosan and alginate formulations or to the biopolymers itself.

Drug–polymer microparticles produced by supercritical assisted atomization

The supercritical assisted atomization (SAA) was proposed as a new technique to produce composite microparticles for drug controlled release. Ampicillin trihydrate and chitosan were selected as model drug and carrier, respectively, and 1% v/v acetic acid aqueous solution was used as solvent. The effect of the polymer/drug ratio on particle morphology and drug release rate was evaluated. SEM analysis indicated that non-coalescing spherical microparticles formed by chitosan/ampicillin were produced by SAA. All coprecipitates produced have a sharp particle distribution, with diameters ranging between about 0.1 and 6 microm. SAA composite microparticles were characterized by X-ray, DSC, EDX and UV-vis analysis. A solid solution of the chitosan and ampicillin was produced and a stabilizing effect of the polymer on the drug has resulted that protects ampicillin from thermal degradation. A prolonged release from SAA coprecipitates with respect to raw drug and physical mixtures of chitosan and ampicillin was obtained; moreover, the polymer/drug ratio has revealed to be a controlling parameter for drug release. Drug release mechanisms characteristic of swelling-controlled systems were observed, with ampicillin release depending on both relaxation and diffusive mechanisms. An empirical binomial equation was used to describe experimental data, showing a fair good agreement with ampicillin release data if both the relaxational and the diffusional parameters are function of the polymer/drug ratio.

Application of chitosan gel in the treatment of chronic periodontitis

Local administration of antibiotics in periodontal therapy can be provided with an appropriate delivery system. The purpose of this study was to evaluate the clinical effectiveness of chitosan, both as a carrier in gel form and as an active agent in the treatment of chronic periodontitis (CP). The chitosan gel (1% w/w) incorporated with or without 15% metronidazole was prepared and applied adjunctive to scaling and root planing (SRP) in comparison to SRP alone (control group-C), in CP patients. The clinical parameters such as probing depth (PD), clinical attachment level, the amount of gingival recession, plaque index, gingival index, and gingival bleeding time index were recorded at baseline and at weeks 6, 12, and 24. In all groups, significant improvements were observed in clinical parameters between baseline and week 24 (p < 0.05). The reductions in PD values were 1.21 mm for Ch, 1.48 mm for Ch + M, and 0.94 mm for C groups. No complications related to the chitosan were observed in patients throughout the study period. It is suggested that chitosan itself is effective as well as its combination with metronidazole in CP treatment due to its antimicrobial properties.

N-Trimethyl chitosan (TMC) nanoparticles loaded with influenza subunit antigen for intranasal vaccination: Biological properties and immunogenicity in a mouse model

In this study, the potential of N-trimethyl chitosan (TMC) nanoparticles as a carrier system for the nasal delivery of a monovalent influenza subunit vaccine was investigated. The antigen-loaded nanoparticles were prepared by mixing a solution containing TMC and monovalent influenza A subunit H3N2 with a tripolyphosphate (TPP) solution, at ambient temperature and pH 7.4 while stirring. The nanoparticles had an average size of about 800 nm with a narrow size distribution and a positive surface charge. The nanoparticles showed a loading efficiency of 78% and a loading capacity of 13% (w/w). It was shown that more than 75% of the protein remained associated with the TMC nanoparticles upon incubation of the particles in PBS for 3h. The molecular weight and antigenicity of the entrapped hemagglutinin was maintained as shown by polyacrylamide gel electrophoresis and Western blotting, respectively. Single i.n. or i.m. immunization with antigen-loaded TMC nanoparticles resulted in strong hemagglutination inhibition and total IgG responses. These responses were significantly higher than those achieved after i.m. administration of the subunit antigen, whereas the IgG1/IgG2a profile did not change substantially. The i.n. administered antigen-TMC nanoparticles induced higher immune responses compared to the other i.n. antigen formulations, and these responses were enhanced by i.n. booster vaccinations. Moreover, among the tested formulations only i.n. administered antigen-containing TMC nanoparticles induced significant IgA levels in nasal washes of all mice. In conclusion, these findings demonstrate that TMC nanoparticles are a potent new delivery system for i.n. administered influenza antigens.

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. verticillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.

Assembly of multilayer microcapsules on CacO3 particles from biocompatible polysaccharides

Multilayer microcapsules were fabricated by layer-by-layer (LbL) assembly of natural polysaccharides onto CaCO3 particles, following with core removal. The micron-sized CaCO3 particles were synthesized by reaction between Ca(NO3)2 and Na2CO3 solutions in the existence of carboxylmethyl cellulose (CMC). The incorporated amount of CMC in the CaCO3 particles was found to be 5.3 wt% by thermogravimetric analysis. Two biocompatible polysaccharides, chitosan and sodium alginate were alternately deposited onto the CaCO3(CMC) templates to obtain hollow microcapsules. Regular oscillation of surface charge as detected by zeta potential demonstrated that the assembly proceeded surely in a LbL manner. The stability of the microcapsules was effectively improved by cross-linking of chitosan with glutaraldehyde. The chemical reaction was verified by infrared spectroscopy. The microcapsules thus fabricated could be spontaneously filled with positively charged low molecular weight substances such as rhodamine 6G and showed good biocompatibility, as detected by in vitro cell culture.

Polysaccharide-based polymer blends: Methods of their production

The existing methods of preparing polymer blends of cellulose, chitin and chitosan with natural and synthetic polymers and their applications are reviewed. The methods of solid-phase blending of these polymers under conditions of joint action of high pressure and shear deformation are discussed. Normally, under these conditions the processes of dispersion of polymer particles, amorphization, mixing at different levels, depolymerization as well as a chemical interaction resulting in formation of branched and crosslinked structures can take place. The probability and intensity of these processes depend in many respects on the type and magnitude of the external force, but the properties of the polymers are of higher importance. The advantages of the method of joint action of high pressure and shear deformation compared to the conventional techniques of polysaccharides mixtures production are shown.

Evaluation of powder and tableting properties of chitosan

The aim of this study was to analyze the process of tablet formation and the properties of the resulting tablets for 3 N-deacetylated chitosans, with a degree of deacetylation of 80%, 85%, or 90%. Material properties, such as water content, particle size and morphology, glass transition temperature, and molecular weight were studied. The process of tablet formation was analyzed by 3-D modeling, Heckel analysis, the pressure time function, and energy calculations in combination with elastic recovery dependent on maximum relative density and time. The crushing force and the morphology of the final tablets were analyzed. Chitosans sorb twice as much water as microcrystalline cellulose (MCC), the particle size is comparable to Avicel PH 200, a special type of MCC, the particles look like shells, and the edges are bent. Molecular weight ranges from 80,000 to 210,000 kDa, the glass transition temperature (Tg) was not dependent on molecular weight. The chitosans deform ductilely as MCC; however, plastic deformation with regard to time and also pressure plasticity are higher than for MCC, especially for Chit 85, which has the lowest crystallinity and molecular weight. At high densification, fast elastic decompression is higher. 3-D modeling allowed the most precise analysis. Elastic recovery after tableting is higher than for MCC tablets and continues for some time after tableting. The crushing force of the resulting tablets is high owing to a reversible exceeding of Tg in the amorphous parts of the material. However, the crushing force is lower compared with MCC, since the crystallinity and the Tg of the chitosans are higher than for MCC. In summation, chitosans show plastic deformation during compression combined with high elasticity after tableting. Highly mechanically stable tablets result.

Preparation of polylactic acid-O-carboxymethylated chitosan nanoparticles and their influences on the cultured porcine hepatocytes

AIM: To prepare polylactic acid-O-carboxyme-thylated chitosan (PLA-O-CMC) nanoparticles and evaluate their influences on the morphology and functions of cultured porcine hepatocytes.

METHODS: PLA-O-CMC nanoparticles were prepared from PLA and O-CMC by ultrasonic method. The nanoparticles were characterized by atomic force microscopy and X-ray photoelectron spectrometry. Isolated porcine hepatocytes were divided into two groups: commonly culturing group and nanomaterial group (co-culturing hepatocytes with PLA-O-CMC nanoparticles). The morphology and functions of the cultured hepatocytes were observed within 1 wk.

RESULTS: PLA-O-CMC nanoparticles were successfully prepared, and the diameter was 300-500 nm under atomic force microscope. X-ray photoelectron spectrometry showed that the proportions of C, O, and N element were 72.51%, 23.69%, and 3.80%, respectively. The hepatocytes lost their features of polygons after common culture for 48 h. However, after co-culture with PLA-O-CMC nanoparticles, the hepatocytes clustered into conglobulations, and most of them restored their cell polarities, shaping as typical polygons. After culture for 1, 3, and 5 d, the content of albumin (ALB) was significantly higher in nanomaterial group than that in commonly culturing group (3.53 ± 0.052, 3.48 ± 0.075, 3.57 ± 0.137 g/L vs 3.10 ± 0.179, 3.17 ± 0.186, 3.10 ± 0.219 g/L, all P < 0.05), while on day 3, 5 and 7, the level of alanine aminotransferase (ALT) was markedly lower (15.33 ± 13.05, 8.84 ± 8.87, 7.00 ± 5.22 nkat/L vs 24.17 ± 20.35, 16.17 ± 27.49, 15.50 ± 11.95 nkat/L, all P < 0.05). From day 3 to 7, the content of supernant blood urea nitrogen (BUN) was higher in nanomaterial group than that in commonly culturing group, but there was no significant difference (P > 0.05).

CONCLUSION: PLA-O-CMC nanoparticles are successfully prepared, and can be used in the culture of hepatocytes.

Preparation and characterization of protein-loaded N-trimethyl chitosan nanoparticles as nasal delivery system

In this study, the potential of N-trimethyl chitosan (TMC) nanoparticles as a carrier system for the nasal delivery of proteins was investigated. TMC nanoparticles were prepared by ionic crosslinking of TMC solution (with or without ovalbumin) with tripolyphosphate, at ambient temperature while stirring. The size, zeta-potential and morphology of the nanoparticles were investigated as a function of the preparation conditions. Protein loading, protein integrity and protein release were studied. The toxicity of the TMC nanoparticles was tested by ciliary beat frequency measurements of chicken embryo trachea and in vitro cytotoxicity assays. The in vivo uptake of FITC-albumin-loaded TMC nanoparticles by nasal epithelia tissue in rats was studied by confocal laser scanning microscopy. The nanoparticles had an average size of about 350 nm and a positive zeta-potential. They showed a loading efficiency up to 95% and a loading capacity up to 50% (w/w). The integrity of the entrapped ovalbumin was preserved. Release studies showed that more than 70% of the protein remained associated with the TMC nanoparticles for at least 3 h on incubation in PBS (pH 7.4) at 37 degrees C. Cytotoxicity tests with Calu-3 cells showed no toxic effects of the nanoparticles, whereas a partially reversible cilio-inhibiting effect on the ciliary beat frequency of chicken trachea was observed. In vivo uptake studies indicated the transport of FITC-albumin-associated TMC nanoparticles across the nasal mucosa. In conclusion, TMC nanoparticles are a potential new delivery system for transport of proteins through the nasal mucosa.

Preparation, Characterization and in Vitro Dissolution Studies of Solid Systems of Valdecoxib with Chitosan

In the present study, the solubilizing and amorphizing properties of Valdecoxib (a poorly water soluble anti inflammatory drug) with low molecular weight chitosan (a polymer), have been investigated. Binary systems of varying drug/polymer ratios were prepared using different techniques (physical mixing, co-grinding, kneading) and were tested for dissolution. Drug carrier interactions were investigated in both the liquid and solid state, by phase solubility analysis, differential scanning calorimetry, powder X-ray diffractrometry, FT-IR spectroscopy and scanning electron microscopy. The solubility of the drug increased with increasing polymer concentration showing A(N) type phase solubility diagram. Differential scanning calorimetry, powder X-ray diffractrometry and scanning electron microscopic studies of binary systems suggested generation of amorphous form of drug (in kneading and co ground mixtures). IR spectroscopy revealed the presence of hydrogen bonding in kneading and co ground mixtures. Drug dissolution was improved with increasing the polymer concentration in the mixture (Kneaded>co ground>physical mixture), which was attributed to the amorphonization and/or decreased drug crystallinity, size and polymer wetting effect. Enhanced dissolution combined with its direct compression feasibility and anti ulcerogenic action results in low molecular weight chitosan for developing fast release oral solid dosage forms of valdecoxib.

Permeability of Pig Urinary Bladder Wall: Time and Concentration Dependent Effect of Chitosan

Chitosan in 0.5% w/v concentration enhanced the permeability of the isolated pig urinary bladder wall by desquamation of the urothelium as ascertained in our previous study. The aim of the present work was to determine the time and concentration dependence of chitosan's effect on the permeation of a model drug into the bladder wall and to establish if the mechanism of permeation enhancement depends on the concentration of chitosan used. In the permeability studies performed by the use of diffusion cells, transport of a model drug moxifloxacin into the isolated pig urinary bladder wall was determined. For morphological observations of the urothelium in response to chitosan treatment scanning and transmission electron microscopy were applied. Within 90 min the effect of chitosan on the tissue amounts of moxifloxacin gradually increased and approached its plateau. In one hour even 0.0005% w/v dispersion of chitosan significantly enhanced the permeability of the pig urinary bladder wall for the model drug and at 0.001% w/v concentration the maximal effect on the tissue permeability was achieved. All concentrations of chitosan that significantly enhanced the permeability of the bladder wall triggered necrosis of superficial cells or desquamation of the urothelium. However, at lower concentrations and shorter exposure times the damage of the urothelium was limited to the changes in tight junctions. Chitosan was ascertained to increase the permeation of moxifloxacin into the urinary bladder wall in a time and concentration dependent manner.

Diethyl methyl chitosan as an intestinal paracellular enhancer: ex vivo and in vivo studies

Chitosan exhibits favorable biological properties such as no toxicity, biocompatibility and biodegradability; therefore, it has attracted great attention in both pharmaceutical and biomedical fields. Chitosan exhibits poor solubility at pH values above 6 that prevents enhancing effects at the sites of absorption of drugs. In the present work, N-diethyl methyl chitosan (DEMC) was prepared and the enhancing effect of this polymer was investigated. Ex vivo studies have shown a significant increase in absorption of brilliant blue in the presence of diethyl methyl chitosan in comparison with chitosan. DEMC with positive charges is able to interact with tight junctions of colon epithelial cells and hence increases permeability of brilliant blue across the tight junctions. In vivo investigations have exhibited the absorption enhancer effects of DEMC on the colon absorption of insulin in normal and diabetic rats. The insulin absorption from the rat's colon was evaluated by its hypoglycemic effect. A significant decrease in blood glucose was observed, when mixture of insulin and DEMC was introduced in ascending colon of rats.

Cross-linked cationic polymer microparticles: effect of N-trimethyl chitosan chloride on the release and permeation of ibuprofen

Microparticles made by cross-linking hydrophilic polymers, such as chitosan, have been used to modify the release rate of a loaded drug. In this study a polymer with fixed positive charges, N-trimethyl chitosan chloride (TMC), was used in combination with chitosan to formulate microparticles to investigate its effects on drug release rate and transport across intestinal epithelial cells. The microparticles were prepared by cross-linking these cationic polymer(s) using sodium citrate as the ionic cross-linker. This process was done under homogenization and ultrasonication to control the size of the particles. The addition of TMC to the chitosan microparticles resulted in an increase in particle size of the microparticles and an increase in ibuprofen release rate as compared to the microparticles containing chitosan alone. Permeation of ibuprofen across Caco-2 cell monolayers, after administration of a suspension of the microparticles to the apical side, was not significantly different for the microparticles containing TMC as compared to those consisting of chitosan alone. It was concluded that release of TMC molecules from the microparticles was probably not sufficient to interact with the intestinal epithelial cells in order to change the permeation of the released drug.

Mechanisms and kinetics of trisodium 2-hydroxy-1,1′-azonaphthalene-3,4′,6-trisulfonate adsorption onto chitosan

Chitosan, a naturally abundant biopolymer, has widely been studied for metal adsorption from various solutions, but the extension of chitosan as an adsorbent to remove organic substances from water and wastewater has seldom been explored. In this study, the adsorption of an azo dye, trisodium 2-hydroxy-1,1'-azonaphthalene-3,4',6-trisulfonate (1), from aqueous solution onto the various degrees of deacetylated chitosan has been investigated. Equilibrium studies have been carried out to determine the capacity of chitosan for dye. The experimental data were analyzed using two isotherm correlations, namely, Langmuir and Freundlich equations. The linear correlation coefficients were determined for each isotherm and the Langmuir provided the best fit. The experimental adsorption isotherms were perfectly reproduced in the simulated data obtained from numerical analysis on the basis of the Langmuir model and the isotherm constants. Adsorption of (1) onto the chitosan flakes was found to be strongly depending on degrees of deacetylation in chitosan and temperatures. Significant amounts of (1) were adsorbed by chitosan 8B (higher degree of deacetylated chitosan), but the adsorption capacity was reduced remarkably with increasing solution temperatures. Thermodynamic parameters such as change in free energy (DeltaG), enthalpy (DeltaH), and entropy (DeltaS) were also determined. In addition, kinetic study indicated that the adsorption process mechanisms were both transport- and attachment-limited.

Permeability of pig urinary bladder wall: the effect of chitosan and the role of calcium

Chitosan is a cationic polysaccharide widely employed as an absorption enhancer. The aim of this work was to examine the effect of chitosan on the permeability of isolated pig urinary bladder wall as well as to determine the role of calcium ions in this process. Besides permeability studies, scanning electron microscopy and fluorescent microscopy were applied to get an insight into the mechanism by which chitosan increases the permeability of urinary bladder wall. Additionally, the obtained findings were compared to the mechanism proposed for Caco-2 cells. The results show that 0.5% (w/v) chitosan increases the permeability of urinary bladder wall by causing the desquamation of the urothelium. Calcium ions, when applied to the luminal surface of the urinary bladder at the same time as chitosan, decreases the effect of chitosan on permeation of the model drug moxifloxacin into the bladder wall in concentration dependent way. The desquamation of urothelium cells caused by chitosan was reduced in the presence of calcium, but not to such extent as it would be expected from the permeability studies. When present, calcium obviously interferes directly in the interactions between chitosan and the surface of urothelium.

Chitosan nanoparticles as a novel delivery system for ammonium glycyrrhizinate

The ammonium glycyrrhizinate-loaded chitosan nanoparticles were prepared by ionic gelation of chitosan with tripolyphosphate anions (TPP). The particle size and zeta potential of nanoparticles were determined, respectively, by dynamic light scattering (DLS) and a zeta potential analyzer. The effects, including chitosan molecular weight, chitosan concentration, ammonium glycyrrhizinate concentration and polyethylene glycol (PEG) on the physicochemical properties of the nanoparticles were studied. These nanoparticles have ammonium glycyrrhizinate loading efficiency. The encapsulation efficiency decreased with the increase of ammonium glycyrrhizinate concentration and chitosan concentration. The introduction of PEG can decrease significantly the positive charge of particle surface. These studies showed that chitosan can complex TPP to form stable cationic nanoparticles for subsequent ammonium glycyrrhizinate loading.

Synthesis of chitosan-stabilized gold nanoparticles in the absence/presence of tripolyphosphate

Gold nanoparticles were prepared by reducing gold salt with a polysaccharide, chitosan, in the absence/presence of tripolyphosphate (TPP). Here, chitosan acted as a reducing/stabilizing agent. The obtained gold nanoparticles were characterized with UV--vis spectroscopy and transmission electron microscopy. The results indicated that the shape and size distribution of gold nanoparticles changed with the molecular weight and concentration of chitosan. More interestingly, the gelation of chitosan upon contacting with polyanion (TPP) can also affect the shape and size distribution of gold nanoparticles. By adding TPP to chitosan solution before the reduction of gold salt, gold nanoparticles have a bimodal size distribution, and at the same time, polygonal gold particles were obtained in addition to spherical gold nanoparticles.

QENS investigation of the dynamics of starch saccharides

We present here quasi-elastic neutron scattering results on D20 hydrated samples of amylose, one of the main saccharide components of starch. Two different sample hydrations (h = 0.5 and 1.0 g D2O (g dry amylose)-1 have been investigated in the temperature range 170 to 350 K. Below 260 K only an elastic contribution is present in the spectra, while a quasi-elastic component shows up above this temperature. The elastic incoherent structure factor (EISF) associated with this component changes considerably with increasing temperature. For the sample with hydration h = 0.5 the confinement volume increases by a factor of four in going from 300 to 350 K, and the proportion of hydrogen involved in the confined diffusion motion increases as well from 30 to 55%. Similar effects are observed at the higher hydration investigated. The observed dynamics can be associated with the known plasticising role of water in polysaccharides.

Recent advances on chitosan-based micro- and nanoparticles in drug delivery

Considerable research efforts have been directed towards developing safe and efficient chitosan-based particulate drug delivery systems. The present review outlines the major new findings on the pharmaceutical applications of chitosan-based micro/nanoparticulate drug delivery systems published over the past decade. Methods of their preparation, drug loading, release characteristics, and applications are covered. Chemically modified chitosan or its derivatives used in drug delivery research are discussed critically to evaluate the usefulness of these systems in delivering the bioactive molecules. From a literature survey, it is realized that research activities on chitosan micro/nanoparticulate systems containing various drugs for different therapeutic applications have increased at the rapid rate. Hence, the present review is timely.

Low molecular weight chitosan nanoparticles as new carriers for nasal vaccine delivery in mice

High molecular weight (Mw) chitosan (CS) solutions have already been proposed as vehicles for nasal immunization. The aim of the present work was to investigate the potential utility of low Mw CS in the form of nanoparticles as new long-term nasal vaccine delivery vehicles. For this purpose, CS of low Mws (23 and 38 kDa) was obtained previously by a depolymerization process of the commercially available CS (70 kDa). Tetanus toxoid (TT), used as a model antigen, was entrapped within CS nanoparticles by an ionic cross-linking technique. TT-loaded nanoparticles were first characterized for their size, electrical charge, loading efficiency and in vitro release of antigenically active toxoid. The nanoparticles were then administered intranasally to conscious mice in order to study their feasibility as vaccine carriers. CS nanoparticles were also labeled with FITC-BSA and their interaction with the rat nasal mucosa examined by confocal laser scanning microcopy (CLSM). Irrespective of the CS Mw, the nanoparticles were in the 350 nm size range, and exhibited a positive electrical charge (+40 mV) and associated TT quite efficiently (loading efficiency: 50-60%). In vitro release studies showed an initial burst followed by an extended release of antigenically active toxoid. Following intranasal administration, TT-loaded nanoparticles elicited an increasing and long-lasting humoral immune response (IgG concentrations) as compared to the fluid vaccine. Similarly, the mucosal response (IgA levels) at 6 months post-administration of TT-loaded CS nanoparticles was significantly higher than that obtained for the fluid vaccine. The CLSM images indicated that CS nanoparticles can cross the nasal epithelia and, hence, transport the associated antigen. Interestingly, the ability of these nanoparticles to provide improved access to the associated antigen to the immune system was not significantly affected by the CS Mw. Indeed, high and long-lasting responses could be obtained using low Mw CS molecules. Furthermore, the response was not influenced by the CS dose (70-200 microg), achieving a significant response for a very low CS dose. In conclusion, nanoparticles made of low Mw CS are promising carriers for nasal vaccine delivery.

Thiolated chitosans

The derivatization of the primary amino groups of chitosan with coupling reagents bearing thiol functions leads to the formation of thiolated chitosans. So far, three types of thiolated chitosans have been generated: chitosan-cysteine conjugates, chitosan-thioglycolic acid conjugates and chitosan-4-thio-butyl-amidine conjugates. Various properties of chitosan are improved by this immobilization of thiol groups. Due to the formation of disulfide bonds with mucus glycoproteins, the mucoadhesiveness is 6--100-fold augmented (I). The permeation of paracellular markers through intestinal mucosa can be enhanced 1.6--3-fold utilizing thiolated instead of unmodified chitosan (II). Moreover, thiolated chitosans display in situ-gelling features, due to the pH-dependent formation of inter- as well as intra-molecular disulfide bonds (III). This latter process provides a strong cohesion and stability of carrier matrices being based on thiolated chitosans (IV). Consequently, thiolated chitosans can guarantee a prolonged controlled release of embedded therapeutic ingredients (V). The potential of thiolated chitosans has meanwhile also been demonstrated in vivo. A significant pharmacological efficacy of 1.3% of orally given salmon calcitonin, for instance, could be achieved utilizing thiolated chitosan as polymeric drug carrier matrix, while no effect was reached using unmodified chitosan. According to these results thiolated chitosans represent a promising new category of polymeric excipients in particular for the non-invasive administration of hydrophilic macromolecules. Further applications such as their use as scaffold materials in tissue engineering or as coating material for stents seem feasible.