Modulation of the peroxidase-like activity of iron oxide nanoparticles by surface functionalization with polysaccharides and its application for the detection of glutathione

Here, we employed three polysaccharides, such as dextran, hyaluronic acid, and chitosan, for surface modification of iron oxide nanoparticles (IONPs) and carried out in-depth investigation to elucidate the effect of surface functionalities on the peroxidase (POD) like activity of IONPs. The affinity of substrates to the catalytic site of IONPs was found to be determined by the surface functional groups and hydration layer of polysaccharide coating on the surface of IONPs. The role of hydration layer was further confirmed by the results that the POD-like activity of IONPs coated with a certain polysaccharide having higher water holding capacity was significantly enhanced by salting-out reagent, such as ammonium chloride that is known to reduce the thickness of hydration layer. Moreover, the excellent catalytic activity of dextran-coated IONPs was successfully applied to develop a highly sensitive sensing system for the detection of glutathione (GSH) with a limit of detection of 2.3 nM.