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

Abstract

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.

Keywords: antiradical activity; carrageenan; galactomannan; hydrogels; silver nanoparticles.

Figure 1

XRD diffractograms of AgNP composites based on GM (a–c) and κ-CG (d–f) with different percentages of silver nanoparticles.

Figure 2

Microphotographs (TEM) of AgNP composites based on GM (a–c) and κ-CG (d–f) with different percentages of silver.

Figure 3

Absorption spectra of 0.05% aqueous solutions of AgNP composites based on GM (a) and κ-CG (b) with different silver contents.

Figure 4

Intensity distribution of Rh particles in 0.1% aqueous solutions of κ-CG (a) and κ-CG-AgNPs composites with 2.5% and 7.0% Ag (b,c), respectively.

Figure 5

Radical-binding ability of GM-AgNPs (a) and κ-CG-AgNPs (b) composites against ABTS⁺·; dependence of the IC₅₀ parameter on the silver concentration in the GM and κ-CG-based nanocomposites (c). Error bars are hidden in the bar when not visible; data are mean ± SD, n ≥ 3.

Figure 6

Water-holding capacity of AgNP-containing hydrogels based on the GM-κ-CG system in the absence (a) and presence (b) of Ca²⁺ ions. Error bars are hidden in the bar when not visible; data are mean ± SD, n ≥ 3.

Figure 7

Effect of GM-AgNPs-κ-CG-AgNPs ratio on the stress–strain dependence of hydrogels (a) and their elastic modulus (b).

Figure 8

AgNPs release dynamics from hydrogels based on the GM-AgNPs/κ-CG-AgNPs system with different composite ratios in the absence (a) and presence of Ca²⁺ ions (b); Ag+ concentration dynamics in aqueous medium within the dissolution of hydrogels based on the GM-AgNPs/κ-CG-AgNPs system in the presence of Ca²⁺ ions with different composite ratios (c). Error bars are hidden in the bar when not visible; data are mean ± SD, n ≥ 3.