The targeted antibacterial and antifungal properties of magnetic nanocomposite of iron oxide and silver nanoparticles

Two types of magnetic binary nanocomposites, Ag@Fe3O4 and γ-Fe2O3@Ag, were synthesized and characterized and their antibacterial activities were tested. As a magnetic component, Fe3O4 (magnetite) nanoparticles with an average size of about 70 nm and monodisperse γ-Fe2O3 (maghemite) nanoparticles with an average size of 5 nm were used. Nanocomposites were prepared via in situ chemical reduction of silver ions by maltose in the presence of particular magnetic phase and molecules of polyacrylate serving as a spacer among iron oxide and silver nanoparticles. In the case of the Ag@Fe3O4 nanocomposite, silver nanoparticles, caught at the surfaces of Fe3O4 nanocrystals, were around 5 nm in a size. On the contrary, in the case of the γ-Fe2O3@Ag nanocomposite, ultrafine γ-Fe2O3 nanoparticles surrounded silver nanoparticles ranging in a size between 20 and 40 nm. In addition, the molecules of polyacrylate in this nanocomposite type suppress considerably interparticle magnetic interactions as proved by magnetization measurements. Both synthesized nanocomposites exhibited very significant antibacterial and antifungal activities against ten tested bacterial strains (minimum inhibition concentrations (MIC) from 15.6 mg/L to 125 mg/L) and four candida species (MIC from 1.9 mg/L to 31.3 mg/L). Moreover, acute nanocomposite cytotoxicity against mice embryonal fibroblasts was observed at concentrations of higher than 430 mg/L (Ag@Fe3O4) and 292 mg/L (γ-Fe2O3@Ag). With respect to the non-cytotoxic nature of the polyacrylate linker, both kinds of silver nanocomposites are well applicable for a targeted magnetic delivery of silver nanoparticles in medicinal and disinfection applications.