Insulin Conformation Changes in Hybrid Alginate-Gelatin Hydrogel Particles.

There is a strong need to develop an insulin delivery system suitable for oral administration and preserving natural (α-helix) insulin conformation. In this work, we fabricated alginate-gelatin hydrogel beads for insulin encapsulation. Altering matrix composition and crosslinking agents has resulted in various surface morphologies and internal spatial organization. The structures of the insulin-loaded matrices were studied using optical and field emission electronic microscopy. We use FTIR spectroscopy to identify insulin conformation changes as affected by the hydrogel matrices. It was found that blended alginate-gelatin matrices demonstrate better encapsulation efficiency and stronger swelling resistance to a simulated gastric environment than sodium alginate beads crosslinked with the CaCl2. FTIR measurements reveal conformation changes in insulin. It is also confirmed that in the presence of gelatin, the process of insulin fibrinogenesis ceases due to intermolecular interaction with the gelatin. Performed molecular modeling shows that dipole-dipole interactions are the dominating mechanism that determines insulin behavior within the fabricated matrix.

Peculiarities of adsorption of Cr (VI) ions on the surface of Chlorella vulgaris ZBS1 algae cells.

Cr (VI) compounds are the most dangerous for human health and the environment, therefore, the study of their adsorption features is of great interest. A comprehensive study of the adsorption of Cr (VI) ions on the surface of Chlorella vulgaris ZBS1 algae cells was carried out evaluating the effect of the pH of the medium on the degree of removal of Cr (VI) ions from solutions and on the zeta potential of the cell surface was. The highest values of the degree of removal of Cr (VI) ions equal to 94.6-95.4% are achieved in the pH range of 1-2, being the result of the electrostatic attraction of HCrO4 - groups to protonated amino groups of the cell surface and the possibility of reducing Cr (VI) ions to Cr (III) in an acidic medium, followed by the formation of Cr (III) ions of coordination bonds with amine and carboxyl groups of algae cells. The adsorption data were processed within the framework of Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. It was shown that the maximum Langmuir adsorption value was 74.63 mg/g. The values of the adsorption parameters 1/n and K f in the Freundlich model were equal to 0.713 and 2.82 mg/g. In the Dubinin-Radushkevich model, the maximum adsorption capacity (qm) and free energy (E) were equal to 39.73 mg/g and 2.604 kJ/mol, respectively. Whereas, according to the Temkin model, the constant A was equal to 18.215 L/mg, and bT was equal to 0.023 kJ/mol. Taking into account the low values of free energy, it is concluded that adsorption is caused by non-covalent interactions. The study of adsorption kinetics showed that the adsorption of Cr (VI) ions on the surface of Chlorella vulgaris ZBS1 algae cells is described in the framework of the pseudo-second order model. The kinetic behavior of the process is discussed in the framework of the IPDM and ELM models. With increasing temperature, the constant of intraparticle diffusion of Cr (VI) ions decreases, which is explained with increasing of hydrophobic interactions between nonpolar sites of protein macromolecules and polysaccharides in the composition of algae cells. The increase in the adsorption of Cr (VI) ions at pH 8.62 in the temperature range of 298-353 K is justified by the shrinkage of the biosorbent volume, which leads to the blocking of a part of the anionic groups on the surface of algae cells. Therefore, the decrease in the electrostatic repulsion between the negatively charged surface of the adsorbent and Cr (VI) oxyanions is observed.