ИСТИНА

The main reason for the application of chitosan for creating of drug, enzyme and nucleic acids carrier systems in the form of polyelectrolyte complex (PEC) are its important biological properties: biocompatibility, biodegradability, antioxidant and anticoagulant activity, mucoadhesiveness, antimicrobial activity, and synergistic/additive effects on microorganisms in combination with classical antibiotics. Chitosan/surfactant mixtures are prospective for usage in cosmetics, food, pharmaceuticals, and personal care products. However, a significant limitation for creating of these systems is a loss of chitosan solubility in neutral and weakly alkaline media, corresponding to the acidity of the main physiological fluids. This limitation makes the study of regularities of chitosan complexation in such media problematic. In our previous work [1], it was shown that partially N-reacetylated short-chain chitosan (Mw ≤ 20000) with an acetylation degree of about 25% are soluble in alkaline media in a wide pH range up to pH ≥ 9. The use of these chitosans allows us to overcome this limitation and to study the regularities of chitosan complexation in these media. Therefore, the aim of the present study is to elucidate the specific features of the behavior of a partially N-reacetylated short chain chitosan in the mixtures with a weak polyacid carboxymethylcellulose (CMC) and with an anionic surfactant sodium dodecyl sulphate (SDS) in weakly alkaline media using light scattering and isothermic titration calorimetry methods. It is shown that the formation of PEC with CMC can occur in pH range of 6 – 8, while this pair of polyelectrolytes loses the ability to complexation upon transition to a more alkaline medium. The revealed dependence of the observed enthalpy of interaction on the ionization enthalpy of the buffer indicates the participation of proton transfer from the buffer substance to chitosan and its additional ionization in the binding process. The interaction of chitosan with SDS in weakly alkaline media is found to be exothermic and cooperative, it is also coupled with proton transfer from the buffer substance to chitosan [2]. With an increase in pH > 8, the interaction mechanism changes from preliminary electrostatic to preliminary hydrophobic.