Radiosensitizing performance of uncoated and citrate-coated SPIONs in cancerous and non-cancerous cells

Superparamagnetic iron oxide nanoparticles were shown to exhibit a high performance as X-ray dosage enhancer in tumor cells. The radio-enhancing potential of uncoated and citrate-coated SPIONs was comprehensively studied for tumor and healthy cells. Pristine and citrate-coated SPIONs drastically differ in their water dispersibility and adsorption affinity for proteins. The activities of antioxidant enzymes in the healthy cells were shown to be significantly distinct from those in the tumor cells as containing a much higher H2O2 concentration. Pristine SPIONs catalyzed the Fenton reaction of hydrogen peroxide to the highly reactive hydroxyl radical in all cell types. In contrast, intracellular citrate-stabilized SPIONs were shown t o be non-toxic and to do not affect the formation of reactive oxygen species. X-ray irradiation of citrate-stabilized SPIONs, when internalized by tumor cells, significantly boost the formation of hydroxyl radicals, whereas the healthy cells preserved their initial levels of reactive oxygen species.