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Characteristics of physicochemical and rheological properties of chitosan hydrogels based on selected hydroxy acids

Zavyalova Olga, Gajewska Sandra, Dąbrowska-Wisłocka Dominika, Sionkowska Alina

Engineering of Biomaterials

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2021

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Vol. 24, no. 161

2--7

EN

Chitosan is a natural cationic polymer that dissolves in an acidic environment and forms gels. Its properties depend on the degree of deacetylation and molecular weight. It is a bioactive compound with antibacterial and film-forming properties that allow to increase the regenerative capacity of the skin. Moreover, it is biodegradable, biocompatible, non-toxic, and stable. In this research, chitosan was combined with mandelic and lactobionic acids which are characterized by biological activity and low toxicity. This combination not only has a positive effect on the chitosan solubility, but it also allows to obtain new biomaterials whose positive features of the base ingredients are enhanced by their synergistic effect. The obtained hydrogels were assessed regarding the interaction of chitosan and hydroxy acid molecules, and the stability of the resulting structures was examined. The research was performed by using rheological methods and IR spectroscopy. Chitosan hydrogels made with mandelic acid are characterized by higher viscosity values, as compared to hydrogels containing lactobionic acid. The samples of the obtained hydrogels stored for 7 days showed no signs of degradation and their viscosity values were constantly increasing, which proves the ongoing process of creating new bonds between hydroxy acid molecules and chitosan chains. After this time, the hydrogels with mandelic acid revealed higher viscosity values in comparison to hydrogels made with lactobionic acid. Based on the obtained IR spectra, the shifts of the characteristic chitosan bands as a result of interaction with the tested hydroxy acids were analyzed.

2

Condensation oscillations in the condensation of mandelic acid

Sajewicz M., Gontarska M., Kronenbach D., Berry E, Kowalska T.

Acta Chromatographica

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2012

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Vol. 24, no. 1

1--13

EN

In our earlier studies, we were the first to discover a spontaneous chiral conversion of the low-molecular-weight carboxylic acids dissolved in aqueous media, running in vitro. The investigated chiral carboxylic acids belong to the classes of profen drugs, amino acids, and hydroxy acids. Then, the spontaneous chiral conversion running in vitro and accompanied by the spontaneous condensation of the discussed compounds was discovered. From the literature, we learnt that spontaneous condensation of certain chiral compounds sometimes can be oscillatory in nature. Thus, we considered it noteworthy to check if spontaneous condensation of the chiral low-molecular-weight carboxylic acids follows a linear or a nonlinear dynamic pattern. In this paper, we present the results of our studies on the dynamics of condensation of S-, R-, and rac-mandelic acid, carried out with the aid of the high-performance liquid chromatography with the diode-array detection (HPLC-DAD), and with the aid of mass spectrometry (MS). The obtained data furnish reliable evidence that condensation of mandelic acid is oscillatory in nature. Finally, a theoretical model is recalled, which jointly describes the oscillatory chiral conversion and the oscillatory condensation with S-, R-, and rac-mandelic acid.

3

Kinetyczny rozdział enancjomerów kwasu migdałowego w reaktorze kolumnowym

Dąbkowska K., Szewczyk K. W., Piasecka A.

Inżynieria i Aparatura Chemiczna

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2009

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Nr 3

40-41

PL

Kinetyczny rozdział enancjomerów kwasu migdałowego prowadzono na drodze transestryfikacji octanem winylu katalizowanej przez lipa-zę z Burkholderia cepacia. Proces realizowano w sposób ciągły w reaktorze kolumnowym wypełnionym enzymem. Przebieg reakcji opisano modelem Bi Bi Ping Pong z inhibicją substratem i produktem.

EN

Racemic mandelic acid was separated in a column reactor using tran-sesterification with vinyl acetate catalyzed by Burkholderia cepacia li-pase. The Bi Bi Ping Pong mechanism with inhibition by both substrate and product was used in reaction rate modeling.

4

On the spontaneous condensation of selected hydroxy acids

Sajewicz M., Matlengiewicz M., Kronenbach D., Gontarska M., Kowalska T.

Acta Chromatographica

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2009

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Vol. 21, no. 2

259--271

EN

In a previous study we provided thin-layer chromatographic, polarimetric, and other experimental evidence that phenylglycine can undergo easy spontaneous peptidization in abiotic aqueous media. From our unpublished results it is apparent that this behaviour is also characteristic of some other amino acids (e.g., alanine and phenylalanine). It seems highly probable that this abiotic peptidization of amino acids dissolved in aqueous media is directly linked to their ability to undergo spontaneous oscillatory chiral conversion. In our earlier research it was also shown that spontaneous oscillatory chiral conversion was characteristic not only of amino acids but also of several other classes of carboxylic acid, including profen drugs and hydroxy acids. We therefore decided to check whether selected chiral hydroxy acids — lactic acid and mandelic acid — previously recognized for their ability to undergo spontaneous oscillatory chiral conversion, could also furnish the respective polyacids. Condensation of hydroxy acids can be viewed as a reaction fully analogous with peptidization of amino acids and, hence, it seemed to us highly probable that it also can be triggered by oscillatory chiral conversion. In our study, we used thin-layer chromatography and 13 C NMR spectroscopy to check whether formation of polylactic acid and polymandelic acid occurred in stored solutions of lactic and mandelic acids. By means of polarimetry with continuous recording we provided experimental evidence that all three hydroxy acids investigated (i.e. L -(+)-lactic acid, S -(+)-mandelic acid, and R -(−)-mandelic acid) undergo continuous chiral conversion. From the thin-layer chromatographic results obtained it was apparent that — similar to the spontaneous and instantaneous peptidization of amino acids — the hydroxy acids investigated also undergo easy condensation to form the respective polyacids. 13 C NMR spectroscopy provided additional experimental confirmation of this.

5

Mathematical modelling of enzymatic transesterification of mandelic acid with vinyl acetate

Dąbkowska K., Szewczyk K.

Chemical and Process Engineering

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2007

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Vol. 28, z. 3

795-802

EN

Racemic mandelic acid was resolved by transesterification with vinyl acetate catalysed by Pseudo-monas cepacia lipase. A high enantiomeric excess (>99%) of both unreacted substrate and acylated product was obtained at 25 C degrees using diisopropyl ether as the reaction medium. The Ping-Pong Bi-Bi mechanism and second order kinetics have been used to model the reaction rate. The best estimation has been obtained for the Ping-Pong Bi-Bi model without inhibition. Values of kinetic parameters were estimated.

PL

Przeprowadzono efektywny, kinetyczny rozdział enancjomerów kwasu migdałowego na drodze transestryfikacji octanem winylu, katalizowanej przez lipazę z Pseudomonas cepacia. Prowadząc reakcję w środowisku eteru diizopropylowego w 25 stopni C, uzyskano duży nadmiar enancjomeryczny (>99%) zarówno substratu, jak i produktu reakcji. Do opisu przebiegu reakcji zastosowano model reakcji drugiego rzędu oraz model Ping-Pong. Najlepszą zgodność obliczeń modelowych z danymi doświadczalnymi uzyskano dla modelu Bi-Bi Ping-Pong bez inhibicji żadnym z reagentów.