Protective Role of Gold Nanoparticles against Radiation-induced Oxidative Damage in Bovine Serum Albumin

Gold nanoparticles (AuNPs) are increasingly recognized as theranostic agents in radiation oncology. Hence, the interaction of these nanoparticles with biomolecules viz DNA, RNA, and proteins needs to be investigated. In this study, the potential radioprotective role of AuNPs in preventing free radical-induced changes in bovine serum albumin (BSA) was investigated using ultraviolet–visible (UV–Vis) spectroscopy, fluorescence, Fourier-transform infrared (FTIR) spectroscopy, circular dichroism (CD), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 5,5'-Dithiobis-(2-nitrobenzoic acid) (DTNB) assay. γ-irradiation of the protein disrupts the ordered structure of the protein. AuNPs reduced the •OH-induced oxidation of tryptophan (Trp) to nearly half of that without the AuNPs. CD studies revealed that the % α helix of BSA post-irradiation in the presence of AuNPs was higher (62%) than that without AuNPs (53%). DTNB assay results showed that, following irradiation of BSA, 25% of the thiol content was retained in the presence of AuNPs, indicating that the thiol group was substantially protected with a retained thiol content of ~ 70%. This suggested that AuNPs protected the protein from degradation by scavenging the free radicals generated during radiation-induced oxidation.