Radioprotective effect of nanoceria and magnetic flower-like iron oxide microparticles on gamma radiation-induced damage in BSA protein: Running Title: Radioprotective Effect of Nanostructures on BSA

Purpose: Gamma radiation at therapeutic doses can cause conformation changes in proteins and consequently damage cells/tissues associated with the initiation of several pathological disorders. In this study, serum albumin, the most abundant protein in plasma, was chosen as the protein sample. Methods and Materials: Bovine serum albumin (BSA) was exposed to gamma radiation at a therapeutic dose (3 Gy) in the absence and presence of Ceria nanoparticles (CNPs) and flower-like Fe3O4 microparticles (FIOMPs). The conformational changes in BSA including primary, secondary, tertiary structures were then studied by UV-Vis, circular dichroism (CD), and fluorescence spectroscopy, respectively. Results: The primary structure of gamma-irradiated BSA (IR-BSA) was conserved, whereas the secondary and tertiary structures were considerably changed. IR-BSA showed a-helix to P-sheet and random coil structure transition along with reduced fluorescence emission intensity compared to non-irradiated native BSA. Both CNPs and FIOMPs could inhibit the secondary and tertiary structural changes in IR-BSA by scavenging the reactive oxygen species produced during the radiolysis of water. Conclusions: The radioprotective property of CNPs arises from enzyme mimetic activities (catalase, superoxide dismutase, and peroxidase) and their antioxidant capability against hydroxyl radicals. In case of FIOMPs, the radioprotective property is attributed to catalase mimetic activity (CAT), and a porous structure leading to increased ROS recombination with each other in the same radiolytic track, and subsequently decreased encounters with BSA. The latter mechanism of restricting ROS migration seems to be more dominant for FIOMPs. Both CNPs/FIOMPs themselves at low concentrations do not show a significant effect on the native protein conformation. These findings indicate that the proposed NPs/MPs can be good candidates for developing strong nano-radioprotectors.