Multiple fold increase in activity of ferroxidase–apoferritin complex by silver and gold nanoparticles

The effect of silver (Ag) and gold (Au) nanoparticles on the ferroxidase activity of apoferritin showed a 110-fold increase in specific activity and a 9-fold increase over the control at the respective molar ratios of Au-apoferritin and Ag-apoferritin nanoparticles (NPs) of 500:1 and 1000:1. Typical color change, from pale yellow to brown, occurred when apoferritin was mixed with AgNO3 or AuCl3 followed by sodium borohydride to afford respective metal-apoferritin NP complexes in a ratio of between 250:1 and 4000:1. These complexes were characterized by ultraviolet-visible inductively coupled plasma–optical emission spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy. Transmission electron microscopy revealed that the size of NPs increased as the molar ratio of metal to apoferritin increased, with an average size of 3–6 nm generated with Au-to-apoferritin and/or Ag-to-apoferritin molar ratios of 250:1 to 4000:1. Fourier transform infrared spectrometry showed no structural changes of apoferritin when the NPs were attached to the protein.From the Clinical EditorIn this paper the utility of gold and silver nanoparticles in augmenting the activity of the ferroxidase-apoferritin complex is described. Both NPs dramatically increased the ferroxidase activity.

Graphical AbstractEncapsulation of the silver nanoparticles within the cavity of apoferritinnot only maintained the integrity and structure of the protein cage but enhanced its ferroxidaseactivity by 110 fold. This effect was both size dependent, [4 – 6 nm] of the nanoparticle, and concentration of the Ag:Apoferritin [1000:1]. Any major variation outside these limits afforded normal ferroxidase activity as that of the control. This has clinical implications in the treatment of diseases associated with poor iron absorption and a decrease in oxidative stress associated with the toxic levels of iron in biological systems.Figure optionsDownload high-quality image (277 K)Download as PowerPoint slide