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Merkovich, E. A.; Carruette, M.-L.; Babak, Valéry G.; Вихорева, Г. А.; Гальбрайх, Л. С.; Kim, V. E.

doi:10.1023/a:1016608630105

Cited by 17 publications

(3 citation statements)

References 7 publications

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“…This shear thinning became more pronounced for solutions of higher concentration. This behavior was already observed, for example, by Merkovich et al for solutions containing 2.4% (w/w) of chitosan with two different molecular weights equal to 330 000 and 550 000 g/mol 3 Variation of G ‘, G ‘ ‘, and the modulus of η* versus the frequency for a chitosan solution [DA = 5.2%, initial C polymer = 1.5% (w/w)]. …”

Section: Resultssupporting

confidence: 61%

“…This behavior was already observed, for example, by Merkovich et al for solutions containing 2.4% (w/w) of chitosan with two different molecular weights equal to 330 000 and 550 000 g/mol. 24 For the initial solutions, the values of the zero shear rate viscosity (η 0 ) were evaluated for low frequencies from the extrapolated Newtonian plateau on the curves of the variation of the dynamic viscosity (Figure 3). η 0 showed a typical variation with DA illustrated in Figure 4 (solutions concentrated at 1.5% (w/w)).…”

Section: Resultsmentioning

confidence: 99%

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Rheometric Study of the Gelation of Chitosan in Aqueous Solution without Cross-Linking Agent

2005

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A new process of formation of chitosan physical hydrogels in aqueous solution, without any organic solvent or cross-linking additive, was studied. The three conditions required for the physical gelation were an initial polymer concentration over C*, a critical value of the balance between hydrophilic and hydrophobic interactions, and a physicochemical perturbation responsible for a bidimensional percolating mechanism. The time necessary to reach the gel point was determined by rheometry, and gelations were compared according to different initial conditions. Thus, we investigated the influence of the polymer concentration and the degree of acetylation (DA) of chitosan on gelation. The number of junctions per unit volume at the gel point varied with the initial polymer concentration, i.e., the initial number of chain entanglements per unit volume or the number of gel precursors. The time to reach the gel point decreased with both higher DAs and concentrations. For a chitosan of DA = 36.7%, a second critical initial concentration close to 1.8% (w/w) was observed. Above this concentration, the decrease of the time to reach the gel point was higher and fewer additional junctions had to be formed to induce gelation. To optimize these physical hydrogels, to be used for cartilage regeneration, their final rheological properties were studied as a function of their degree of acetylation and their polymer concentration. Our results allowed us to define the most appropriate gel for the targeted application corresponding to a final concentration of chitosan in the gel of near 1.5% (w/w) and a DA close to 40%.

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Rheometric Study of the Gelation of Chitosan in Aqueous Solution without Cross-Linking Agent

2005

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“…Kinetics of the change in the modulus of elasticity of chitosan gels crosslinked with GA at pH 4.1 (1-3), 5.6 (4, 5), GA/NH 2 ratio of 0.415 (4), 1.049(2,3,5), and 2.517 mole/mole (1) and concentration of chitosan of 1.31 (1, 2, 4, 5) and 1.62%(3).…”

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confidence: 99%

Crosslinking in solutions of chitosan in the presence of a crosslinking reagent for production of fibre biocatalysts

2006

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541.64:547.458 and N. R. Kildeeva Gelation in soltuion sof chitosan in the prfesence of a bifunctional crosslinking reagent of glutaraldehyde and protein was investigated. It was shown that the gelation rate, strength, and equilibrium moisture absorption fo the gel formed are determined by the conditions of crosslinking the chitosan (MW of chitosan, pH, and GA/NH 2 ratio). The systems studied were used in fabrication of fibre biocvatalysts by pformation of an enzyme-containing gel membrane on the surface of coarse calico.Of the natural polysaccharides, chitosan is in second place after cellulose with respect to distribution and industrial use. The increased interest in this aminopolysaccharide is due to its properties: biocompatibility, susceptibility to enzymatic hydrolysis, intrinsic physiological activity combined with nontoxicity, ability to bind some organic compounds, heavy metal ions, etc. For these reasons, chitosan is used in medicine, agriculture, the food industry, and manufacture of cosmetics [1].The features of the chemical structure of chitosan are responsible for its solubility in acid aqueous media, which significantly reduces the environmental stress in manufacture and facilitates its processing into different polymer forms: films, fibres, membranes, and capsules. At the same time, the solubility of the finished articles made from chitosan, films in particular, is frequently a drawback, so that these articles are heated or treated with modifying reagents: diisocyanates, sulfuric acid, glutaraldehyde (GA), etc., to increase resistance to dissolution. Glutaraldehyde is a very common crosslinking reagent long used for immobilizing proteins [2]. In addition to reducing the solubility of chitosan, intermolecular crosslinking at amino groups [3, 4] allows covalently adding proteins to chitosan, enzymes in particular, to obtain heterogeneous biocatalysts.Chitosan manufactured by Bioprogress Closed Joint-Stock Company (Shchelkovo) with a molecular weight (MW) of 170 and 840 kDa and degree of deacetylation of 0.92 in the form of 2% solutions in 2% acetic acid was used to study the features of crosslinking of chitosan by GA; the pH of freshly prepared solutions of chitosan was 4.1. To establish the effect of the pH on the features of gelation, potentiometric titration of a solution of chitosan with MW of 170 kDa was conducted with a concentrated solution of NaOH to pH 5.6, which is 0.1 less than the cloud point. The reaction of chitosan and GA was studied at a 1.31% concentration of chitosan in the reaction mixture, and the GA/NH 2 ratio was adjusted by varying the concentration of the GA solution (Merck). The kinetics of the change in the viscosity of the solution was investigated on a Rheotest 2 flow viscometer using a coneplane measuring device which allowed giving the shear rate and fixing the stresses that develop in the system with low consumption of reagents. The kinetics of the change in the modulus of elasticity of crosslinked chitosan gels was investigated with penetration of a spherical ind...

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A novel thermally-activated crosslinking agent for chitosan in aqueous solution: a rheological investigation

Johnson

Dunstan

Franks

2004

Colloid & Polymer Science

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Untitled

Cited by 17 publications

References 7 publications

Rheometric Study of the Gelation of Chitosan in Aqueous Solution without Cross-Linking Agent

Rheometric Study of the Gelation of Chitosan in Aqueous Solution without Cross-Linking Agent

Crosslinking in solutions of chitosan in the presence of a crosslinking reagent for production of fibre biocatalysts

A novel thermally-activated crosslinking agent for chitosan in aqueous solution: a rheological investigation

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