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

Abstract

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...

Covalent immobilization of enzyme on aminated woven poly (lactic acid) via ammonia plasma: evaluation of the optimum immobilization conditions

“…36 The effects of different temperature were assessed by measuring the activity of free and immobilized trypsin in tris-HCI buffer (25 mM, pH 8.5) at a broad range of temperature (25–65℃) for 1 h. After incubation, the remaining activity of the free and immobilized trypsin was measured at room temperature using L-BAPNA as a substrate. 7,15,16 Thermal stability of free and immobilized trypsin was measured at 25℃ and 50℃ for 240 min, respectively. 37,38…”

“…GA, which is a protein crosslinking reagent, is more efficient than other aldehydes under a broad range of reaction conditions, as it forms a strong bond via an intense multi-point crosslink between the enzyme and the support, enabling an increase in enzyme stability. 8,14,15…”

“…17–20 Plasma treatment, which is one of the most effective techniques for the introduction of functional groups onto the surface of materials, has been shown to be able to control surface structure and energy, and to uniformly modify the surface without affecting bulk properties. 15,17 Moreover, plasma treatment is capable of introducing a large variety of reactive functionalities depending on the gases included in the plasma, for example, oxygen, helium, nitrogen, and ammonia. Plasma surface treatment with a variety of reactive functionalities has been utilized to synthesize PLA surfaces with various functional groups on the top layer.…”