Interfacial properties of chitosan lactate at the liquid/air interface

The interfacial properties (dynamic and equilibrium surface tension, viscosity and elasticity moduli) of chitosan lactate have been studied at the liquid/air interface by the oscillating drop shape method. Isotherms of dynamic surface tension of chitosan lactate are similar to dependences for other polyelectrolyte solutions, in particular for proteins. Chitosan is a weak cationic polyelectrolyte which can change its conformation from a linear rod to a chaotic and compacted coil. Therefore, the experimental dependence of the equilibrium surface tension on concentration of chitosan lactate was analyzed with the adsorption model proposed earlier for proteins. This model accounts the possibility of polyelectrolyte molecules existence in surface layer in n states with different molar surface varying from the maximum value at very low surface coverage by polyelectrolyte molecules to a minimum value at high surface coverage. Good agreement between the calculated and experimental values of surface tension was observed. The dependences of the elasticity and viscosity moduli of chitosan lactate solutions on the drop oscillations frequency are conditioned by the influence of exchange processes both between the surface layer and the bulk solution and in the surface layer itself. An increase of the solution concentration intensifies the exchange processes, and an increase of the oscillation frequency suppresses them. It is shown that the dependence of the surface viscoelasticity modulus of chitosan lactate is extreme in nature with a pronounced maximum. The reason for such behavior is the possibility of changing the molar surface area of the polyelectrolyte at the interface dependent on the amount of adsorption and its structural properties. Attempt of theoretical description of the viscoelasticity modulus within the framework of model accounting mono- or bilayer adsorption did not lead to a satisfactory result, possibly due to barrier adsorption mechanism of chitosan. But bilayer model provide qualitative description of extreme behavior of surface viscoelasticity on concentration. The values of the surface viscoelasticity modulus of chitosan lactate occupy an intermediate position in comparison with the data available in the literature for globular and flexible-chain proteins, that is consistent with their molecular structure. In addition, the work shows the applicability of the adsorption model, developed earlier for proteins in the framework of a nonideal two-dimensional solution theory, for describing the surface properties of other polyelectrolytes. This makes it possible to obtain qualitative and quantitative information about the processes occurring in the systems under study.

Physico-Chemical Properties and Biocompatibility of Thermosensitive Chitosan Lactate and Chitosan Chloride Hydrogels Developed for Tissue Engineering Application

Recently, the modification of the initial structure of biopolymers, mainly chitosan, has been gaining importance with a view to obtain functional forms with increased practicality and specific properties enabling their use in tissue engineering. Therefore, in this article, the properties (structural and biological) of thermosensitive hydrogels obtained from chitosan lactate/chloride and two types of crosslinking agents (β-glycerol phosphate disodium salt pentahydrate and uridine 5′-monophosphate disodium salt) are discussed. The aim of the research is to identify changes in the structure of the biomaterials during conditioning in water. Structural investigations were carried out by FTIR spectroscopy. The crystallinity of gels was determined by X-ray diffraction analysis. The biocompatibility (evaluation of cytotoxicity and genotoxicity) of chitosan hydrogels was investigated by contact with human colon adenocarcinoma cell line for 48 h. The cytotoxicity was verified based on the colorimetric resazurin assay, and the genotoxicity was checked by the comet assay (percentage of DNA in the comet tail). The conducted research showed that the analyzed types of chitosan hydrogels are non-cytotoxic and non-genotoxic materials. The good biocompatibility of chitosan hydrogels surfaces makes them interesting scaffolds with clinical potential in tissue regeneration engineering.

Cytotoxicity of amorphous calcium phosphate multifunctional composite coatings on titanium obtained by in situ anodization/anaphoretic deposition

Cytotoxicity of amorphous calcium phosphate (ACP) and chitosan lactate (ChOL) multifunctional and hybrid composite coatings on MRC-5 human lung fibroblast cell line is elucidated. ACP/TiO2 and ACP/TiO2/ChOL are deposited onto Ti by novel in situ anodization/anaphoretic process at constant voltage. Cytotoxicity tests showed that there was no significant decrease in the survival of healthy MRC-5 cells eposed to composite samples without chitosan lactate, while there was an increase in the number of viable cells in the sample containing ChOL. The findings show that there is improved cell proliferation, differentiation and cell viability in the ChOL-containing sample, which makes ACP/TiO2/ChOL coating a good candidate for the applications in medicine and stomatology.

ADSORPTION AND DILATIONAL RHEOLOGICAL PROPERTIES OF CHITOSAN LACTATE AT THE LIQUID-GAS INTERFACE

Методом формы осциллирующей капли исследованы адсорбционные и дилатационные реологические характеристики (модуль упругости и вязкости) лактата хитозана на границе раздела жидкость - газ. Определены зависимости динамического и равновесного поверхностного натяжения от концентрации лактата хитозана в растворе. Установлено, что полученные зависимости сходны с таковыми для поверхностноактивных высокомолекулярных соединений. Изучены зависимости поверхностных упругости и вязкости лактата хитозана от частоты осцилляций и концентрации. Показано, что лактат хитозана способен образовывать упругие адсорбционные слои со значениями модуля вязкоупругости сопоставимыми для биополимеров белковой природы. The adsorption and dilatational rheological characteristics (the elasticity and viscosity modulus) of chitosan lactate at the liquid-gas interface are investigated by the oscillating drop shape method. The dependences of the dynamic and equilibrium surface tension on the concentration of chitosan lactate in solution have been determined. It was found that the dependences obtained are similar to those for surface-active high-molecular weight compounds. The dependences of the surface elasticity and viscosity of chitosan lactate on the oscillation frequency and concentration have been studied. It has been shown that chitosan lactate is capable of forming elastic adsorption layers with the values of the viscoelastic modulus comparable to that of protein biopolymers.