A comprehensive study was performed on the supramolecular ordering and optical properties of thin nanostructured glycerohydrogel sol-gel plates based on chitosan L- and D-aspartate and their individual components in the X-ray, UV, visible, and IR ranges. Our comparative analysis of chiroptical characteristics, optical collimated transmittance, the average cosine of the scattering angle, microrelief and surface asymmetry, and the level of structuring shows a significant influence of the wavelength range of electromagnetic radiation and the enantiomeric form of aspartic acid on the functional characteristics of the sol-gel materials. At the macrolevel of the supramolecular organization, a complex topography of the surface layer and a dense amorphous–crystalline ordering of polymeric substances were revealed, while at the nanolevel, there were two forms of voluminous scattering domains: nanospheres with diameters of 60–120 nm (L-) and 45–55 nm (D-), anisometric particles of lengths within ~100–160 (L-) and ~85–125 nm (D-), and widths within ~10–20 (L-) and ~20–30 nm (D-). The effect of optical clearing on glass coated with a thin layer of chitosan L-(D-)aspartate in the near-UV region was discovered (observed for the first time for chitosan-based materials). The resulting nanocomposite shape-stable glycerohydrogels seem promising for sensorics and photonics.

A comprehensive study of the structure, properties and biological functionality of salt chitosan complexes with L- and D-aspartic acid (AspA) was carried out. It has been established that these polymer salts differ in their spatial organization, chirooptic characteristics, surface charge and macrocoil size. In experiments in vitro on a wide range of biological objects (unicellular algae, planktonic crustaceans, aerobic bacterial microorganisms, cell cultures and test plants), it was found that the chitosan salt with D-AspA exhibited the best biological activity. The results obtained confirm our hypothesis that the biological homochiral hierarchy principles are most consistent with the chitosan (D-aminoglycan) derivatives with the D-antipode of the acid.

Glycerohydrogels based on silicon glycerolate, chitosan (CS) and polyvinyl alcohol (PVA) are widely studied for use in biomedical applications. In line with the general trend of replacing synthetic polymers with natural ones in such compositions, it would be of interest to replace PVA with the polysaccharide glucomannan (GM), as well as to introduce functional additives to impart the desired properties, including gelation time, to the final hydrogel. In this work, a comprehensive study of the preparation conditions and properties of glycerohydrogels based on silicon tetraglycerolate, chitosan hydrochloride (CS·HCl) and GM was carried out. Viscometry was used to assess the conformational state of CS·HCl and GM macromolecules, and their associates in solution before gelation. Gelation was studied using the vessel inversion method. The mucoadhesive and the dermoadhesive properties of the glycerohydrogels obtained were assessed using the tearing off method from the model substrates simulating mucous and dermal tissues. The conformational state of the individual polymers and their mixed associates in solution before gelation was estimated; the intrinsic viscosity and the hydrodynamic radius of the macromolecular coils were calculated. The influence of various factors (addition of ε-aminocaproic and hydrochloric acids, sodium chloride, hydroxide and tetraborate to vary the acidity and ionic strength of the medium, as well as temperature) and the molecular weight of chitosan on the gelation time was studied. The gelation time achieved was less than 2 min, which is promising in practical terms, i.e., for creating liquid plasters. Our best samples are not inferior to the commercial preparation “Metrogyl Denta”^® in terms of tearing force during mucoadhesion and dermoadhesion at short gelation times. Thus, the glycerohydrogels synthesized by us and based on silicon tetraglycerolate, CS·HCl and GM could find usage in new biopharmaceutical and biomedical applications.

In the traditional method of removing excess acid used to obtain the salt form of chitosan, not only a reaction with neutralizing bases proceeds, but also partial deprotonation of macrochains. Since charged amino groups are responsible for the biological activity of the aminopolysaccharide, it seems important to develop methods for optimizing the acid–base composition of a chitosan-containing system without proton elimination. The paper presents the results of our study on the removal of non-stoichiometric aspartic acid from an aqueous dispersion of chitosan aspartate nanoparticles obtained by in situ self-assembly during counterion association on charged polymer chains and stabilized by a polysiloxane shell coating using isohydric and isothermal crystallization approaches. It is shown that a temperature decrease in the range of 50–4°C in combination with water distillation by 50–85% leads to supersaturation of the nanodispersion and crystallization of the poorly soluble component of the dispersion medium with precipitation. The influence of the acid/polymer molar ratio (1.3–1.7 mol/mol of NH2) in the target substance of the dispersed phase, the cooling rate (10 and 30°C/h) and the dispersion concentration degree (50–85%), as well as the temperature (22±2 and 4°C) and holding time (1–200 days) on the morphostructure, chemical composition, crystalline ordering and quantitative yield of the solid phase has been estimated. The correspondence of the air-dry form of the isolated precipitate to crystals of the zwitterionic form of aspartic acid has been proven by IR spectroscopy, X-ray structural analysis, dialysis, potentiometry and gravimetry. It has been found that the most optimal option for preparative removal of non-stoichiometric double bipolar ions is the concentration of nanodispersion by 85% followed by supercooling from 50 down to 4°C at a rate of 10°C/h. The developed approach to combining isohydric and isothermal crystallization of non-stoichiometric aspartic acid has been successfully tested on moderately concentrated solutions of the complex salt of chitosan hydrochloride–aspartate.