The Use of AgNP-Containing Nanocomposites Based on Galactomannan and κ-Carrageenan for the Creation of Hydrogels with Antiradical Activity

Series of composites containing 2.5-17.0% Ag and consisting of spherical silver nanoparticles with sizes ranging from 5.1 to 18.3 nm and from 6.4 to 21.8 nm for GM- and κ-CG-based composites, respectively, were prepared using the reducing and stabilizing ability of the natural polysaccharides galactomannan (GM) and κ-carrageenan (κ-CG). The antiradical activity of the obtained composites was evaluated using the decolorization of ABTS+^· solution. It was found that the IC₅₀ value of a composite's aqueous solution depends on the type of stabilizing ligand, the amount of inorganic phases, and the average size of AgNPs, and varies in the range of 0.015-0.08 mg·mL^-1 and 0.03-0.59 mg·mL^-1 for GM-AgNPs - κ-CG-AgNPs composites, respectively. GM-AgNPs - κ-CG-AgNPs hydrogels were successfully prepared and characterized on the basis of composites containing 2.5% Ag (demonstrating the most pronounced antiradical activity in terms of IC₅₀ values per mole amount of Ag). It was found that the optimal ratio of composites that provided the best water-holding capacity and prolonged complete release of AgNPs from the hydrogel composition was 1:1. The influence of Ca²⁺ cations on the co-gel formation of the GM-AgNPs - κ-CG-AgNPs system, as well as the expression of their water-holding capacity and the rate of AgNPs release from the hydrogel carrier, was evaluated.