The Kinetics of Chitosan Degradation in Organic Acid Solutions

Abstract

This paper presents a comparative study on chitosan degradation in organic acid solutions according to their different dissociation characteristics. More precisely, the aim of the study was to determine the kinetics of the degradation process depending on the different acid dissociation constants (pKa values). The scientists involved in chitosan to date have focused mainly on acetic acid solutions. Solutions of lactic, acetic, malic, and formic acids in concentrations of 3% wt. were used in this research. The progress of degradation was determined based on the intrinsic viscosity measurement, GPC/SEC chromatographic analysis, and their correlation. Changes in the viscosity parameters were performed at a temperature of 20 °C ± 1 °C and a timeframe of up to 168 h (7 days). The chemical structure and DDA of the initial chitosan were analyzed using 1H-NMR spectroscopy analysis. The results of this study can be considered of high importance for the purpose of electrospinning, production of micro- and nano-capsules for drug delivery, and other types of processing. Understanding the influence of the dissociation constant of the solvent on the kinetics of chitosan degradation will allow the selection of an appropriate medium, ensuring an effective and stable spinning process, in which the occurrence of polymer degradation is unfavorable.

Extraction, characterization, and kinetics of N-deacetylation of chitin obtained from mud crab shells

“…13 In this condition, the hydroxyl (OH − ) ions react with acetamide groups and generate a dianion intermediate species which converts into chitosan. 14 The structure of chitosan consists of randomly distributed β-(1→4)-N-acetyl-D-glucosamine and β-(1→4)-D-glucosamine residues. 12…”

“…13 In this condition, the hydroxyl (OH À ) ions react with acetamide groups and generate a dianion intermediate species which converts into chitosan. 14 The structure of chitosan consists of randomly distributed β-(1→4)-N-acetyl-D-glucosamine and β-(1→4)-D-glucosamine residues. 12 Although the deacetylation reaction can be controlled by several parameters, the conversion from acetyl to amine groups is difficult to complete, and repetitive deacetylation is often required in order to achieve high conversion from chitin to chitosan.…”

Biodegradable microneedle patch for delivery of meloxicam for managing pain in cattle

“…At one day after solution preparation, η 0 = 540 ± 30 Pa.s, and four days after solution preparation, η 0 = 320 ± 10 Pa.s, representing a reduction of approximately 40.7%. The drop in viscosity can be attributed to the degradation of the chitosan by hydrolysis, which occurs mainly under the influence of acids [ 24 , 25 ], such as acetic acid, affecting the degree of degradation and the molecular mass of oligochitosan [ 26 ]. Similarly, in Fig 2B the frequency sweep showed that the storage and loss moduli of the solution, which represent a measure of elastic and viscous response of a material, respectively, were lower when comparing both time points, one versus four days.…”

“…At one day after solution preparation, η 0 = 540 ± 30 Pa.s, and four days after solution preparation, η 0 = 320 ± 10 Pa.s, representing a reduction of approximately 40.7%. The drop in viscosity can be attributed to the degradation of the chitosan by hydrolysis, which occurs mainly under the influence of acids [24,25], such as acetic acid, affecting the degree of degradation and the molecular mass of oligochitosan [26].…”

A Novel Method of Endotoxins Removal from Chitosan Hydrogel as a Potential Bioink Component Obtained by CO2 Saturation

“…It is highly probable that the rate of CS degradation is mainly determined by the presence of acid in the environment and only by other factors such as concentration and molecular weight. The presence of acid in CS materials mainly causes the hydrolysis of the polymer to lower molecular weight without significantly affecting the degree of deacetylation and polydispersity [ 22 ]. We observed a similar phenomenon during the attempt to thermally degrade dry CS-poly(vinyl acid) composites, in which the elimination of the acid from the CS material significantly increases its stability during thermal treatment, even when it is used as a filler for thermoplastic materials [ 1 ].…”