Hybrid nanocarriers with different densities of silver nanoparticles formation features and antimicrobial properties

This work presents the synthesis and characterization of silica/polyacrylamide hybrid carriers Hyb1 and Hyb2 containing different amounts and lengths of grafted PAAm chains, as well as the formation mechanism, structure, and antibacterial efficacy of their nanocomposites with silver nanoparticles (AgNPs). The main difference between Hyb1 and Hyb2 carriers, such as the thickness and permeability of the PAAm "corona", is highlighted. Using the methods of potentiometry, UV-Vis spectroscopy, TEM and viscometry, the influence of the hybrid structure and concentration of reagents on the two-stage process of reduction of Ag⁺ ions with sodium borohydride in Hyb1-2 aqueous solutions was established. A strong binding of Ag⁺ ions to both hybrid matrices at the first stage of reduction and a significant influence of the concentration of Ag-salt (and reducing agent) on the rate of accumulation and yield of AgNPs at the second stage were shown. The presence of two types of AgNPs (internal and external) in the resulting nanocomposites was revealed, resulting from the reduction process both in the internal space of the hybrid "corona" and on its surface. The average size of external AgNPs was larger than internal ones and increased with increasing concentration of Ag-salt (and reducing agent). The role of purification in creating more uniform AgNP/Hyb nanocomposites is demonstrated. High antibacterial effectiveness against S. aureus, E. coli, and P. aeruginosa was established using well diffusion and broth microdilution methods. The obtained MIC values ~ (1.25-2.5)·10^-3 kg/m³) are compared to those of potent antibiotics such as ciprofloxacin, ceftriaxone and tetracycline.