A ferritin photochemical synthesis of monodispersed silver nanoparticles that possess antimicrobial properties

Abstract

We previously reported that ferritin acts as a photocatalyst to form monodispersed gold nanoparticles. Because silver possesses a favorable reduction potential (+0.80 V), we postulated that the ferritin photochemical method could be used to reduce Ag(I) to Ag(0). Additionally, we postulated that similar to gold, the reduced silver should nucleate and form silver nanoparticles (AgNPs) on the external surface of ferritin. This study reports that Ag(I) can function as an electron acceptor to form monodispersed AgNPs using the ferritin photocatalytic method. The formation and growth of the AgNPs were monitored by following the surface plasmon resonance (SPR) peak at 420 nm by spectrophotometry. The resulting monodispersed AgNPs were analyzed by transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDX). Gel filtration chromatography demonstrated that the AgNPs comigrated with ferritin through the column suggesting a strong association with ferritin. AgNPs are known to possess antimicrobial properties. The antimicrobial properties of Ferritin-AgNPs were compared to commercially available AgNPs by testing the minimal growth inhibition of Staphylococcus aureus. Commercially available AgNPs inhibited bacterial growth at 5 ppm AgNPs, and Ferritin-AgNPs inhibited growth at 20 ppm Ferritin-AgNPs.