Determining the Rate of ROS Generation from Composite Magnetic Nanoparticle Hydrogels in an Alternating Magnetic Field

The surfaces of superparamagnetic iron oxide nanoparticles (IONPs) can generate reactive oxygen species (ROS) in the presence of hydrogen peroxide via the Fenton and Haber-Weiss reactions. The ROS were used in an advanced oxidative process (AOP), where the radicals degrade methylene blue, a commonly used model dye for an environmental pollutant. Previous research showed that when exposed to an alternating magnetic field (AMF), free IONPs in dispersion were able to enhance ROS production; however, as the exposure time and IONP concentration increased, the enhancement decreased. This was attributed to possible AMF-induced nanoparticle aggregation, which reduced the amount of surface area available for reaction. Here, IONPs were synthesized and entrapped in the crosslinked network of a poly(ethylene) glycol (PEG)-based hydrogel. It was hypothesized that immobilized IONPs would not aggregate under the AMF and would thus be able to sustain enhancement of ROS production. It was found that ROS production using immobilized IONPs under an AMF was indeed enhanced to a much higher degree than for free IONPs in dispersion, but the enhancement was still seen to decrease as exposure time increased. This may have been due to a change in oxidation state of the surface iron ions or hydrogen peroxide degradation under high local temperatures. Though a decrease in enhancement was observed, this result was promising in that the enhancement factor did not drop to 1 (no enhancement) even after 30 min of AMF exposure.