Molecular Mass Of Chitosan Research Articles

Reasons for unstable viscous properties of chitosan solutions in acetic acid

A decrease in the molecular mass of chitosan as a result of polymer degradation during storage of its acetic acid solutions has been simulated by means of mixing of chitosan fractions with different molecular masses. It has been shown that a decline in the polymer molecular mass is responsible for a reduction in the dynamic viscosity of chitosan solutions in acetic acid during their storage.

Nanocomposites based on modified chitosan and titanium oxide

The effect of primary amino groups and molecular mass of chitosan on the stability of suspensions based on nanoscale TiO2 dispersions in acidic solutions of various concentrations at pH 2.5 was studied. In the case of chitosan prepared according to a commercialized process, the stability of TiO2 suspensions was low and depended on the concentration of the polymer solution. Solutions of low-molecular-mass highly deacetylated chitosan prepared by solid-phase synthesis stabilized a dispersion of nanosized TiO2 particles for a very long time. Nanocomposites based on a chitosan-PVA graft copolymer and TiO2 were prepared, in which the initial filler dispersion is retained up to very high filling ratios. A potential use of these nanocomposites in photocatalytic processes is discussed. The results of this study can be used for refining engineering procedures and processes for the manufacture of new biocompatible, bioactive, and biodegradable functional composite materials based on chitosan and synthetic polymers.

Progress in Research of Chitosan as a Non-viral Gene Delivery Vector

Efficiency of non-viral gene delivery based on chitosan and chitosan derivatives as DNA condensing carrier is dependent on a series of factors, such as complex size, the charge ratio of chitosan/DNA, molecular mass of chitosan, the degree of chitosan deacetylation, pH and serum concentration of the transfection medium. Through modifying the chitosan in a certain extent, we can change the efficiency of transfection. Studies on transfection condition, efficiency and mechanism using chitosan and chitosan derivatives as transfection agents are reviewed.

Water soluble chitosan conjugates with plant antioxidants and polyelectrolyte complexes on their basis

Water soluble conjugates of trimethyl chitosan (ChTM) and the low molecular mass chitosan (Ch 30 ) with plant antioxidants – quercetin (Q) or dihydroquercetin (DHQ) – were synthesized. The carbodiimide-assisted reaction was used to couple Q or DHQ (previously modified by succinic anhydride) to the primary amino group of Ch 30 or ChTM. The in vitro free-radical scavenging activity of conjugates derived was tested by their capacity to bleach the stable 1,1-diphenyl-2-picrylhydrazyl radical. All conjugates showed an antiradical activity higher than that of phenoxane, the known efficient antioxidant (sterically hindered phenol). The microparticles of complexes of the conjugates and Ch sulfate were proposed for pH-sensitive controlled release of antioxidants. The properties of the polyelectrolyte complexes with plant antioxidants would appear promising for per oral administration.

Characterization of chito-oligosaccharides prepared by chitosanolysis with the aid of papain and Pronase, and their bactericidal action against Bacillus cereus and Escherichia coli.

Papain (from papaya latex; EC 3.4.22.2) and Pronase (from Streptomyces griseus; EC 3.4.24.31) caused optimum depolymerization of chitosan at pH 3.5 and 37 degrees C, resulting in LMMC (low molecular mass chitosan) and chito-oligomeric-monomeric mixture. The yield of the latter was 14-16% and 14-19% respectively for papain- and Pronase-catalysed reactions, depending on the reaction time (1-5 h). HPLC revealed the presence of monomer(s) and oligomers of DP (degree of polymerization) 2-6, which was also confirmed by matrix-assisted laser-desorption ionization-time-of-flight MS. Along with the chito-oligomers, the appearance of only GlcNAc (N-acetylglucosamine) in Pronase-catalysed chitosanolysis was indicative of its different action pattern compared with papain. Fourier-transform infrared, liquid-state 13C-NMR spectra and CD analyses of chito-oligomeric-monomeric mixture indicated the release of GlcNAc/GlcNAc-rich oligomers. The monomeric sequence at the non-reducing ends of chito-oligomers was elucidated using N-acetylglucosaminidase. The chito-oligomeric-monomeric mixture showed better growth inhibitory activity towards Bacillus cereus and Escherichia coli compared with native chitosan. Optimum growth inhibition was observed with chito-oligomers of higher DP having low degree of acetylation. The latter caused pore formation and permeabilization of the cell wall of B. cereus, whereas blockage of nutrient flow due to the aggregation of chito-oligomers-monomers was responsible for the growth inhibition and lysis of E. coli, which were evidenced by scanning electron microscopy analysis. The spillage of cytoplasmic enzymes and native PAGE of the cell-free supernatant of B. cereus treated with chito-oligomeric-monomeric mixture further confirmed bactericidal activity of the latter. Use of papain and Pronase, which are inexpensive and easily available, for chitosanolysis, is of commercial importance, as the products released are of considerable biomedical value.

Mucoadhesive thiolated chitosans as platforms for oral controlled drug delivery: synthesis and in vitro evaluation

The aim of the present study was to evaluate the influence of the degree of modification and the polymer chain length on the mucoadhesive properties and the swelling behavior of thiolated chitosan derivatives obtained via a simple one-step reaction between the polymer and 2-iminothiolane. The conjugates differing in molecular mass of the polymer backbone and in the amount of immobilized thiol groups were compressed into tablets. They were investigated for their mucoadhesive properties on freshly excised porcine mucosa via tensile studies and the rotating cylinder method. Moreover, the swelling behavior of these tablets in aqueous solutions was studied by a simple gravimetric method. The obtained results demonstrated that the total work of adhesion of chitosan-TBA (=4-thio-butyl-amidine) conjugates can be improved by an increasing number of covalently attached thiol groups; a 100-fold increase compared to unmodified chitosan was observed for a medium molecular mass chitosan–TBA conjugate exhibiting 264 μM thiol groups per gram polymer. Also, the polymer chain length had an influence on the mucoadhesive properties of the polymer. The medium molecular mass polymer displayed a fourfold improved adhesion on the rotating cylinder compared to the derivative of low molecular mass. These results contribute to the development of new delivery systems exhibiting improved mucoadhesive properties.

Effect of molecular mass and degree of deacetylation of chitosan on adsorption of Streptococcus sobrinus 6715 to saliva treated hydroxyapatite.

We evaluated the influence of molecular mass and degree of deacetylation of chitosan on the adsorption of Streptococcus sobrinus 6715 to saliva-treated hydroxyapatite (S-HA) by measuring the optical density of the bacterial cell suspensions released from saliva-treated hydroxyapatite. Twenty-five chitosan samples with different molecular masses (0.8-6 kDa) and degrees of deacetylation (10-95%) were prepared for the study. We found that the inhibition of adsorption of S. sobrinus 6715 to S-HA correlated positively with the molecular mass of chitosan (R = 0.876) and that the optimal degree of deacetylation was 50-60% for maximum inhibition of bacterial binding to S-HA. We also examined the effect of chitosan on zeta potentials of the oral bacteria and their surface hydrophobicities. It was observed that chitosan reduced the magnitude of the zeta potential and surface hydrophobicities of the oral bacteria. Thus, the results demonstrated that chitosan with a molecular mass of 5-6 kDa and a degree of deacetylation of 50-60% might have the potential to act as an effective anti-plaque agent because of its polycationic properties.

Factors affecting protein release from alginate–chitosan coacervate microcapsules during production and gastric/intestinal simulation

A series of experiments was performed to evaluate the influence of a number of physico–chemical factors on the diffusion of a model protein, bovine serum albumin (BSA), from dried chitosan-coated alginate microcapsules. Diffusion of BSA was quantified during the microcapsule manufacture processes (gelation, washing, rinsing) and during incubation in conditions simulating the pH encountered during the gastric (0.1 N HCl; pH 1.5) and intestinal (200 mM Tris–HCl; pH 7.5) phases of digestion. Factors tested included alginate and chitosan concentration, calcium chloride (CaCl 2) concentration in the gelation medium, loading rate, chitosan molecular mass and pH of the gelation medium. Microcapsule size and gelation time were altered in order to determine their effects on protein retention. Alginate and chitosan concentration significantly influenced BSA retention during microcapsule manufacture and acid incubation, as did calcium chloride concentration in the gelation medium ( P<0.05). BSA retention during manufacture was not significantly altered by protein loading rate or pH of the encapsulation medium, however, protein retention during acid incubation decreased significantly with increasing protein loading rate and encapsulation medium pH ( P<0.05). Microcapsules that were washed with acetone following manufacture demonstrated significantly increased protein retention during acid incubation ( P<0.05). In microcapsules that had been acetone-dried to a point whereby their mass was reduced to 10% of that immediately following encapsulation, protein retention was over 80% following 24-h acid incubation vs. only 20% protein retention from non acetone-dried microcapsules. The presence of calcium in the neutral buffer medium significantly reduced BSA diffusion in a concentration-dependent manner ( P<0.05).

Mechanism of cell transfection with plasmid/chitosan complexes

Chitosan is useful as a non-viral vector for gene delivery. Although there are several reports supporting the use of chitosan for gene delivery, studies regarding effects on transfection and the chitosan-specific transfection mechanism remain insufficient. In this report, the level of expression with plasmid/chitosan was observed to be no less than that with plasmid/lipofectin complexes in SOJ cells. The transfection mechanism of plasmid/chitosan complexes as well as the relationship between transfection activity and cell uptake was analyzed by using fluorescein isothiocyanate-labeled plasmid and Texas Red-labeled chitosan. In regard to effects on transfection, there were several factors to affect transfection activity and cell uptake, for example: the molecular mass of chitosan, stoichiometry of complex, as well as serum concentration and pH of transfection medium. The level of transfection with plasmid/chitosan complexes was found to be highest when the molecular mass of chitosan was 40 or 84 kDa, ratio of chitosan nitrogen to DNA phosphate (N/P ratio) was 5, and transfection medium contained 10% serum at pH 7.0. We also investigated the transfection mechanism, and found that plasmid/chitosan complexes most likely condense to form large aggregates (5–8 μm), which absorb to the cell surface. After this, plasmid/chitosan complexes are endocytosed, and possibly released from endosomes due to swelling of lysosomal in addition to swelling of plasmid/chitosan complex, causing the endosome to rupture. Finally, complexes were also observed to accumulate in the nucleus using a confocal laser scanning microscope.

In vitro gene delivery mediated by chitosan. Effect of pH, serum, and molecular mass of chitosan on the transfection efficiency

Aminopolysaccharides such as chitosan and polygalactosamine (pGalN) were used to transfer luciferase plasmid into tumor cells. Chitosan largely enhanced the transfection efficiency of luciferase plasmid (pGL3), while pGalN did not at all. Transfection efficiencies of the pGL3/chitosan complexes were dependent on pH of culture medium, stoicheometry of pGL3 : chitosan, serum, and molecular mass of chitosan. Transfection efficiency at pH 6.9 was higher than that at pH7.6. Optimum charge ratio of the pGL3 : chitosan was 1 : 5. Chitosan polymer of 15 and 52 kDa largely promoted luciferase activities. Transfection efficiency mediated by chitosan of >100 kDa was less than that by chitosan of 15 and 52 kDa. Heptamer (1.3 kDa) did not show any gene expression. Cationic liposome (lipofectin)-associated gene expression was inhibited by serum, while chitosan showed resistance to serum.

Effective Deacetylation of Chitin under Conditions of 15 psi/121 °C

Deacetylation of chitin under autoclaving conditions (15 psi/121 degrees C) was evaluated for the preparation of chitosan under different NaOH concentrations and reaction times. Deacetylation was effectively achieved by treatment of chitin under elevated temperature and pressure with 45% NaOH for 30 min and a solids/solvent ratio of 1:15. Treated chitosan showed similar nitrogen content (7.42%), degree of deacetylation (90.4%), and molecular mass (1560 kDa) but significantly higher viscosity values (2025 cP) compared with those (7.40%, 87.6%, 1304 kDa, and 143 cP, respectively) of a commercial chitosan. Reduction of the solids/solvent ratio from 1:15 to 1:10 did not affect degree of deacetylation, viscosity, and molecular mass of chitosan.

Potential of low molecular mass chitosan as a DNA delivery system: biocompatibility, body distribution and ability to complex and protect DNA

Cationic polymers have the potential for DNA complexation and it is recognised that they may be useful as non-viral vectors for gene delivery. Highly purified chitosan fractions of <5000 Da (N1), 5000–10 000 Da (N2) and >10 000 Daltons (N3) were prepared and characterised in respect of their cytotoxicity, ability to cause haemolysis, ability to complex DNA as well as to protect DNA from nuclease degradation. Also the biodistribution of 125I-labelled chitosans was followed at 5 and 60 min after intravenous injection into male Wistar rats. All chitosan fractions displayed little cytotoxicity against CCRF-CEM and L132 cells (IC 50>1 mg/ml), and they were not haemolytic (<15% lysis after 1 and 5 h). Chitosan–DNA interaction at a charge ration of 1:1 was much greater than seen for poly( l-lysine) and complexation resulted in inhibition of DNA degradation by DNase II: 99.9±0.1, 99.1±1.5 and 98.5±2.0% for N1, N2 and N3, respectively. After intravenous injection, all the chitosans showed rapid blood clearance, the plasma levels at 1 h being 32.2±10.5% of recovered dose for N1 and 2.6±0.5% of recovered dose for N3. Liver accumulation was molecular mass dependent, being 26.5±4.9% of the recovered dose for N1 and 82.7±1.9% of the recovered dose for N3. The observations that the highly purified chitosan fractions used were neither toxic nor haemolytic, that they have the ability to complex DNA and protect against nuclease degradation and that low molecular weight chitosan can be administered intravenously without liver accumulation suggest there is potential to investigate further low molecular weight chitosans as components of a synthetic gene delivery system.