Cerium Dioxide-Dextran Nanocomposites in the Development of a Medical Product for Wound Healing: Physical, Chemical and Biomedical Characteristics.

PURPOSE OF THE STUDY: the creation of a dextran coating on cerium oxide crystals using different ratios of cerium and dextran to synthesize nanocomposites, and the selection of the best nanocomposite to develop a nanodrug that accelerates quality wound healing with a new type of antimicrobial effect. MATERIALS AND METHODS: Nanocomposites were synthesized using cerium nitrate and dextran polysaccharide (6000 Da) at four different initial ratios of Ce(NO3)3x6H2O to dextran (by weight)-1:0.5 (Ce0.5D); 1:1 (Ce1D); 1:2 (Ce2D); and 1:3 (Ce3D). A series of physicochemical experiments were performed to characterize the created nanocomposites: UV-spectroscopy; X-ray phase analysis; transmission electron microscopy; dynamic light scattering and IR-spectroscopy. The biomedical effects of nanocomposites were studied on human fibroblast cell culture with an evaluation of their effect on the metabolic and proliferative activity of cells using an MTT test and direct cell counting. Antimicrobial activity was studied by mass spectrometry using gas chromatography-mass spectrometry against E. coli after 24 h and 48 h of co-incubation. RESULTS: According to the physicochemical studies, nanocrystals less than 5 nm in size with diffraction peaks characteristic of cerium dioxide were identified in all synthesized nanocomposites. With increasing polysaccharide concentration, the particle size of cerium dioxide decreased, and the smallest nanoparticles (<2 nm) were in Ce2D and Ce3D composites. The results of cell experiments showed a high level of safety of dextran nanoceria, while the absence of cytotoxicity (100% cell survival rate) was established for Ce2D and C3D sols. At a nanoceria concentration of 10-2 M, the proliferative activity of fibroblasts was statistically significantly enhanced only when co-cultured with Ce2D, but decreased with Ce3D. The metabolic activity of fibroblasts after 72 h of co-cultivation with nano composites increased with increasing dextran concentration, and the highest level was registered in Ce3D; from the dextran group, differences were registered in Ce2D and Ce3D sols. As a result of the microbiological study, the best antimicrobial activity (bacteriostatic effect) was found for Ce0.5D and Ce2D, which significantly inhibited the multiplication of E. coli after 24 h by an average of 22-27%, and after 48 h, all nanocomposites suppressed the multiplication of E. coli by 58-77%, which was the most pronounced for Ce0.5D, Ce1D, and Ce2D. CONCLUSIONS: The necessary physical characteristics of nanoceria-dextran nanocomposites that provide the best wound healing biological effects were determined. Ce2D at a concentration of 10-3 M, which stimulates cell proliferation and metabolism up to 2.5 times and allows a reduction in the rate of microorganism multiplication by three to four times, was selected for subsequent nanodrug creation.

ACTH(6-9)-Pro-Gly-Pro ameliorates anxiety-like and depressive-like behaviour and gut mucosal microbiota composition in rats under conditions of chronic restraint stress.

The effects of the peptide ACTH(6-9)-Pro-Gly-Pro at doses of 5; 50; 500 µg/kg on the Wistar rats' behaviour and gut mucosal microbiota composition under conditions of chronic immobilization stress (CRS) were studied. CRS increased anxiety-like and depressive-like behaviour, disturbances in locomotor activity and gut dysbiosis. Administration of ACTH(6-9)-Pro-Gly-Pro showed many phenotypic results. Peptide demonstrated anti-depressant activity at doses of 5 and 500 µg/kg by a decrease in the total immobile time in the FST. ACTH(6-9)-Pro-Gly-Pro administered at a dose of 50 µg/kg resulted in an anxiolytic effect which is shown by an increase in the time in the open arms of EPM (p < 0.05) and a decrease in the time in the closed arms (p < 0.05). Moreover, the peptide led to a decrease in alpha- and beta-diversity of the gut microbiota (p < 0.01). Correlation and linear regression analysis demonstrated central mechanisms of ACTH(6-9)-Pro-Gly-Pro anxiolytic activity and both central and peripheral ones in an anti-depressant effect. In this way, peptide ACTH(6-9)-Pro-Gly-Pro could prevent the development of behavioural disturbances and gut dysbiosis caused by chronic restraint stress.