Silver-Decorated and Silica-Capped Magnetite Nanoparticles with Effective Antibacterial Activity and Reusability

Abstract

Fruits are safe, toxin-free, and biomolecule-rich raw materials that may be utilized to decrease metal ions and stabilize nanoparticles. Here, we demonstrate the green synthesis of magnetite nanoparticles which were first capped with a layer of silica, followed by the decoration of silver nanoparticles, termed Ag@SiO2@Fe3O4, by using lemon fruit extract as the reducing agent in a size range of ∼90 nm. The effect of the green stabilizer on the characteristics of nanoparticles was examined via different spectroscopy techniques, and the elemental composition of the multilayer-coated structures was verified. The saturation magnetization of bare Fe3O4 nanoparticles at room temperature was recorded as 78.5 emu/g, whereas it decreased to 56.4 and 43.8 emu/g for silica coating and subsequent decoration with silver nanoparticles. All nanoparticles displayed superparamagnetic behavior with almost zero coercivity. While magnetization decreased with further coating processes, the specific surface area increased with silica coating from 67 to 180 m2 g–1 and decreased after the addition of silver and reached 98 m2 g–1, which can be explained by the organization of silver nanoparticles in an island-like model. Zeta potential values also decreased from −18 to −34 mV with coating, indicating an enhanced stabilization effect of the addition of silica and silver. The antibacterial tests against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) revealed that the bare Fe3O4 and SiO2@Fe3O4 did not show sufficient effect, while Ag@SiO2@Fe3O4, even at low concentrations (≤ 200 μg/mL), displayed high antibacterial activity due to the existence of silver atoms on the surface of nanoparticles. Furthermore, the in vitro cytotoxicity assay revealed that Ag@SiO2@Fe3O4 nanoparticles were not toxic to HSF-1184 cells at 200 μg/mL concentration. Antibacterial activity during consecutive magnetic separation and recycling steps was also investigated, and nanoparticles offered a high antibacterial effect for more than 10 cycles of recycling, making them potentially useful in biomedical fields.

Zeolite-Copper Ferrite Nanocomposites with Improved Antibacterial Activity and Reusability for Biomedical Applications

“…6 Scientists have given significant attention to effective antibacterial NPs recently. 7 Inorganic NPs with resistance to heat, radiation, and mechanical stress have become essential antibacterial agents for biomedical and biological applications. 8 Nanostructures have remarkable physicochemical properties, huge surface area, simple and inexpensive production processes, environmental friendliness, and structural composition flexibility.…”

“…Moreover, the problems associated with the use of conventional chemical-based antibiotics stimulate the demand for novel, effective, and ecologically friendly bactericidal agents . Scientists have given significant attention to effective antibacterial NPs recently . Inorganic NPs with resistance to heat, radiation, and mechanical stress have become essential antibacterial agents for biomedical and biological applications .…”

Charge-transfer-driven enhanced room-temperature ferromagnetism in BiFeO3/Ag nanocomposite

“…This is, as well, necessary for making the structure bio-compatible. In fact, attempts are being made [5][6][7][8] to cap or functionalize magnetic nanoparticles by Au or Ag for different biomedical applications. Such structures, however, more often than not exhibit decrease in magnetization because of the capping or functionalization [9].…”