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PROCEDURE FOR DETERMINATION OF THE MOLECULAR WEIGHT OF CHITOSAN BY VISCOMETRY

100%
Czechowska-Biskup R., Wach R. A., Rosiak J. M., Ulański P.
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vol. 23
45 - 54
EN
The aim of this publication is to facilitate the estimation of chitosan molecular weight (MW) in laboratories with no access to sophisticated analytical instruments, by applying the easily accessible and economical capillary viscometry. The procedure of viscosity-average molecular weight (Mv) determination is described in details. The examples provided encompass testing of the experimental procedure for determination of the Mv of chitosan with a low-molecular weight of 7.7 kDa and 88 kDa, after verification with a high-molecular weight polymer (477 kDa). The experimental work demonstrated the importance of the initial concentration of low-MW chitosan for the accurate determination of intrinsic viscosity and, as a consequence, the viscosity-average molecular weight.
2
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PREPARATION OF GOLD NANOPARTICLES STABILIZED BY CHITOSAN USING IRRADIATION AND SONICATION METHODS

100%
Czechowska-Biskup R., Rokita B., Ulański P., Rosiak J. M.
Progress on Chemistry and Application of Chitin and its Derivatives
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2015
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vol. 20
18-33
EN
Gold nanoparticles (AuNPs) were synthesized, in the absence of any reducing agent, using ionizing radiation or ultrasound in aqueous solutions of chloroauric acid (HAuCl4). Chitosan (average molecular weight 158 kDa, degree of deacetylation 90 %) was used as a stabilizing agent. Both techniques yielded AuNPs which were stable in solution at RT for at least 3 months after synthesis. UV-Vis spectroscopy was used to follow substrate decay, nanoparticles formation, size of the gold core and particles stability. Hydrodynamic radii and polydispersion of the chitozan-stabilized AuNPs (i.e. the whole core-shell nanoparticles) were determined by dynamic light scattering. Zeta potential measurements were performed to assess the surface charge and stability of the particles. Influence of synthesis parameters and presence of isopropanol on the formation and properties of the products have been described and reaction mechanisms have been discussed. Radiation and sonochemical methods are demonstrated to be very efficient, fast and easy-to-control methods of synthesizing gold nanoparticles, leaving behind no unreacted reducing agent or unwanted side products, while stabilization by chitosan provides AuNPs with excellent stability and long shelf life.
3
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DETERMINATION OF DEGREE OF DEACETYLATION OF CHITOSAN - COMPARISION OF METHODS

88%
Czechowska-Biskup R., Jarosińska D., Rokita B., Ulański P., Rosiak J. M.
Progress on Chemistry and Application of Chitin and its Derivatives
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2012
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vol. 17
5 - 20
EN
Degree of deacetylation (DD) is one of the main parameters characterizing chitosan. The most precise measurements of DD require sophisticated equipment (NMR spectrometer), not available at many laboratories worldwide working on chitosan. There is a need for low-cost, simple, yet sturdy and reliable methods and procedures for DD determination. The aim of this work was to test and compare – on the same set of chitosan samples - a few of the existing analytical techniques and provide recommendation for selecting DD determination methods. Tests were performed on four chitosans of nominal DD in the range 70 - 95%. Three different methods of titration, two different methods of spectroscopy UV / Vis and infrared spectroscopy using various calculation approaches were used. The results are summarized and compared with values obtained by 1H NMR, considered as the reference method. Moreover, evaluation of the ease of performance and availability of reagents in the given methods was performed. On that basis, recommendations for selection of DD determination methods were formulated.
4
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SYNTHESIS OF CHITOSAN AND CARBOXYMETHYL CHITOSAN HYDROGELS BY ELECTRON BEAM IRRADIATION

76%
Czechowska-Biskup R., Wach R., Stojek P., Kamińska M., Rosiak J. M., Ulański P.
Progress on Chemistry and Application of Chitin and its Derivatives
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2016
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vol. 21
27-45
EN
Solutions of chitosan (CS) and carboxymethyl chitosan (CMCS) were subjected to irradiation by electron beam in presence of a crosslinking agent (poly(ethylene glycol) diacrylate - PEGDA) in order to produce carboxymethyl chitosan- and chitosan-based hydrogels. PEGDA macromonomer itself undergoes simultaneous polymerization and crosslinking either in neutral water or in acidic medium. Acidic solutions of chitosan of 0.5, 1 and 2% can be effectively crosslinked with PEGDA to form a gel. Although CMCS undergoes radiation-initiated crosslinking only at high concentration in water (over 10%), the presence of PEGDA in solution facilitated hydrogel formation even at lower concentration of CMCS. Formation of CS and CMCS hydrogels required irradiation doses lower than those needed for sterilization, i.e. 25 kGy, in some cases even as low as 200 Gy. Sol-gel analysis revealed relatively high gel fraction of obtained hydrogels, up to 80%, and good swelling ability. Both parameters can be easily controlled by composition of the initial solution and irradiation dose. Possible mechanisms of crosslinking reactions were proposed, involving addition of the polysaccharide macroradicals to a terminal double bond of PEGDA.
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